Showing 1–50 of 65 results for author: Fusillo, N P G

The Twentieth Data Release of the Sloan Digital Sky Survey: First All-Sky BOSS Spectra, eROSITA-SDSS-V Mapper Coordinated Observations, and a Preview of the Local Volume Mapper

Authors: SDSS Collaboration, Mojgan Aghakhanloo, David Aguilar, James Aird, Andrés Almeida, Bella Abigail Sanabria Alonso, Hillary Diane Andales, Scott F. Anderson, Stefan Arseneau, Consuelo González Ávila, Shir Aviram, Catarina Aydar, Carles Badenes, Carolina Andonie, Jorge K. Barrera-Ballesteros, Franz E. Bauer, Chad Bender, Michelle A. Berg, F. Besser, Binod Bhattarai, Christian Moni Bidin, Jonathan C. Bird, Dmitry Bizyaev, Guillermo A. Blanc, Alexandra Bonkoski , et al. (251 additional authors not shown)

Abstract: This paper presents the twentieth data release (DR20) from the Sloan Digital Sky Survey, the third data release of its fifth generation (SDSS-V). SDSS-V is a panoptic spectroscopy survey that is mapping the stars, gas, and galaxies through three scientific programs: the Milky Way Mapper (MWM), the Local Volume Mapper (LVM), and the Black Hole Mapper (BHM). DR20 presents the first optical (BOSS) SD… ▽ More This paper presents the twentieth data release (DR20) from the Sloan Digital Sky Survey, the third data release of its fifth generation (SDSS-V). SDSS-V is a panoptic spectroscopy survey that is mapping the stars, gas, and galaxies through three scientific programs: the Milky Way Mapper (MWM), the Local Volume Mapper (LVM), and the Black Hole Mapper (BHM). DR20 presents the first optical (BOSS) SDSS-V spectra from southern hemisphere for the MWM and BHM surveys; new optical MWM and BHM data from the northern hemisphere are also available, for a total over 3 million spectra of 1.5 million stars and half a million galaxies and quasars, with galactic and extragalactic x-ray targets coordinate with eROSITA DR2. DR20 includes integral field spectroscopy maps from LVM of six targets and 169 tiles, spanning Galactic HII regions, planetary nebulae, and nearby galaxies. Additionally, eighteen value added catalogs are also released with DR20, based on SDSS-V MWM and BHM data, and we present a new LVM visualization tool including an RGB HiPS map as a value added product. △ Less

Submitted 28 July, 2026; originally announced July 2026.

Comments: 81 pages, 13 figures, 8 tables

I Can Do It With A Broken Planetesimal: Characterising the planetary debris in heavily polluted cool white dwarfs

Authors: Anna-Maria Cutolo, Boris T. Gänsicke, Andrew Swan, Andrew M. Buchan, Jamie T. Williams, Detlev Koester, Paula Izquierdo, Mark A. Hollands, James A. Blake, Nicola P. Gentile Fusillo

Abstract: We present the analysis of four cool and strongly metal-polluted H-atmosphere white dwarfs observed with X-shooter. We compared their atmospheric parameters obtained from spectroscopy, photometry and a hybrid method, finding a difference of up to $\simeq160$ K in $T_\mathrm{eff}$, and $\simeq0.3$ dex in $\log g$, between the three analyses. We adopt the $T_\mathrm{eff}$ and $\log g$ from the photo… ▽ More We present the analysis of four cool and strongly metal-polluted H-atmosphere white dwarfs observed with X-shooter. We compared their atmospheric parameters obtained from spectroscopy, photometry and a hybrid method, finding a difference of up to $\simeq160$ K in $T_\mathrm{eff}$, and $\simeq0.3$ dex in $\log g$, between the three analyses. We adopt the $T_\mathrm{eff}$ and $\log g$ from the photometric analysis, and subsequently measured the metal abundances of the photospheric elements from spectroscopic modelling, analysing their compositions. We identified from five to eleven unique metals in the photospheres of the four white dwarfs, with total accretion rates ranging from $10^{8}$ to $10^{9}$ $\mathrm{g~s^{-1}}$. The compositional analysis of WD J035826.49$+$215726.16 suggests an accreted planetesimal akin to a core-rich differentiated body, with a core mass fraction of 70 per cent, placing it among the most core-rich objects known to be accreted by white dwarfs. The parent body accreted by WD J042643.98$-$415341.44 shows an enhancement in Na compared to that of the Earth, making it most similar to primitive chondrites. The photosphere of WD J013222.88$+$052923.71 is greatly depleted in core-like material, and its composition resembles that of pure crust/mantle material. WD J232428.21$-$021643.65 has accreted the most Fe-rich planetesimal, with an Fe mass fraction of 67 per cent. We compare these results to other published studies and conclude that these white dwarfs are among the most heavily polluted cool DAZs studied to date, increasing the sample of cool H-dominated white dwarfs with five or more metals by 50 per cent. △ Less

Submitted 13 July, 2026; originally announced July 2026.

Comments: 21 pages, 15 figures, accepted by MNRAS

Journal ref: Mon Not R Astron Soc (2026)

The Future of Evolved Planetary Systems

Authors: Roberto Raddi, Anna F. Pala, Alberto Rebassa-Mansergas, Boris T. Gänsicke, Lientur Celedon, Tim Cunningham, Camila Damia Rincón, Aina Ferrer i Burjachs, Enrique García-Zamora, Nicola Pietro Gentile Fusillo, Joaquim Meza, Evelyn Puebla, Pablo Rodríguez-Gil, Snehalata Sahu, Alejandro Santos-García, Odette Toloza, Santiago Torres, Pier-Emmanuel Tremblay, Jan van Roestel, Murat Uzundag, Dimitri Veras, Jamie Williams

Abstract: Understanding the formation, evolution, and chemical diversity of exoplanets are now central areas of astrophysics research. White dwarfs provide a uniquely sensitive laboratory for studying the end stages of planetary-system evolution and for probing the bulk composition of both rocky and volatile-rich exoplanetary material. In the 2030s new facilities will transform our ability to carry out \tex… ▽ More Understanding the formation, evolution, and chemical diversity of exoplanets are now central areas of astrophysics research. White dwarfs provide a uniquely sensitive laboratory for studying the end stages of planetary-system evolution and for probing the bulk composition of both rocky and volatile-rich exoplanetary material. In the 2030s new facilities will transform our ability to carry out \textit{``industrial-scale''} astrophysics, leading to fundamental results and new challenges for the next decade. By combining the volume of data surveyed by the ESA {\em Gaia} mission and Vera C. Rubin Observatory with the next-generation of spectroscopic facilities, the European Southern Observatory (ESO) community will be in a position to obtain an unbiased census of evolved planetary systems, constrain the composition of thousands of disrupted planetesimals, and connect these signatures to Galactic populations and stellar birth environments. Thus, it is now the time for assessing those challenges and preparing for the future. This white paper outlines key science opportunities arising in the next decade and the technological requirements of future ESO facilities in enabling transformative discoveries in the 2040s. These future facilities will have to combine a number of features that are crucial for studying evolved planetary systems at white dwarfs, such as broad optical to near-infrared coverage, a high sensitivity at blue wavelengths, multi-resolution capability, massive multi-plexing, and time-domain reactivity. △ Less

Submitted 16 December, 2025; originally announced December 2025.

Comments: White paper submitted to the ESO call for the Expanding Horizons initiative: "Transforming Astronomy in the 2040s (5 pages, 2 figures)

Discovery of an icy and nitrogen-rich extrasolar planetesimal

Authors: Snehalata Sahu, Boris T. Gänsicke, Jamie T. Williams, Detlev G. Koester, Jay Farihi, Steven J. Desch, Nicola Pietro Gentile Fusillo, Dimitri Veras, Sean N. Raymond, Maria Teresa Belmonte

Abstract: White dwarfs accreting planetary debris provide detailed insight into the bulk composition of rocky exo-planetesimals. However, only one Kuiper-Belt analogue has been identified in that way so far. Here, we report the accretion of an icy extra-solar planetesimal onto white dwarf WD 1647+375 using ultraviolet spectroscopy from the Hubble Space Telescope. The accreted material is rich in the volatil… ▽ More White dwarfs accreting planetary debris provide detailed insight into the bulk composition of rocky exo-planetesimals. However, only one Kuiper-Belt analogue has been identified in that way so far. Here, we report the accretion of an icy extra-solar planetesimal onto white dwarf WD 1647+375 using ultraviolet spectroscopy from the Hubble Space Telescope. The accreted material is rich in the volatiles carbon, nitrogen, and sulphur, with a chemical composition analogous to Kuiper-belt objects (KBOs) in our solar system. It has a high nitrogen mass fraction ($5.1\pm1.6$ per cent) and large oxygen excess ($84\pm7$ per cent), indicating that the accreted planetesimal is water-rich (a water-to-rock ratio of $\simeq2.45$), corroborating a cometary- or dwarf planet-like composition. The white dwarf has been accreting at a rate of $\approx 2\times10^{8}$ g s$^{-1}$ for the past 13 years, implying a minimum mass of $\sim10^{17}$ g for the icy parent body. The actual mass could be several orders of magnitude larger if the accretion phase lasts $\sim10^5$ yr as estimated in the literature from debris disc studies. We argue that the accreted body is most likely a fragment of a KBO dwarf planet based on its nitrogen-rich composition. However, based on the chemical composition alone, it is difficult to discern whether this icy body is intrinsic to this planetary system, or may have an interstellar origin. △ Less

Submitted 16 September, 2025; originally announced September 2025.

Comments: Published in MNRAS on 18th September 2025, see https://academic.oup.com/mnras/article-lookup/doi/10.1093/mnras/staf1424

Double White Dwarf Binaries in SDSS-V DR19 : A catalog of DA white dwarf binaries and constraints on the binary population

Authors: Gautham Adamane Pallathadka, Vedant Chandra, Nadia L. Zakamska, Nicole R. Crumpler, Stefan M. Arseneau, Kareem El-Badry, Boris T. Gäensicke, Yossef Zenati, J. J. Hermes, Axel D. Schwope, Carles Badenes, Nicola Pietro Gentile Fusillo, Sean Morrison, Tim Cunningham, Priyanka Chakraborty, Gagik Tovmasian, Dmitry Bizyaev, Kaike Pan, Scott F. Anderson, Sebastian Demasi

Abstract: The fifth-generation Sloan Digital Sky Survey (SDSS-V) includes the first large-scale spectroscopic survey of white dwarfs (WDs) in the era of Gaia parallaxes. SDSS-V collects multiple exposures per target, making it ideal for binary detection. We present a search for hydrogen atmosphere (DA) double white dwarf (DWD) binaries in this rich dataset. We quantify radial velocity variations between sub… ▽ More The fifth-generation Sloan Digital Sky Survey (SDSS-V) includes the first large-scale spectroscopic survey of white dwarfs (WDs) in the era of Gaia parallaxes. SDSS-V collects multiple exposures per target, making it ideal for binary detection. We present a search for hydrogen atmosphere (DA) double white dwarf (DWD) binaries in this rich dataset. We quantify radial velocity variations between sub-exposures to identify binary candidates, and also measure the orbital period for a subset of DWD binary candidates. We find 63 DWD binary candidates, of which 43 are new discoveries, and we provide tentative periods for 10 binary systems. Using these measurements, we place constraints on the binary fraction of the Galactic WD population with $< 0.4$ AU separations $f_{\mathrm{bin,0.4}} = 9\%$, and the power-law index of the initial separation distribution $α= -0.62$. Using the simulated binary population, we estimate that $\leq 10$ super-Chandrasekhar binaries that merge within a Hubble time are expected in our sample. We predict that $\leq 5$ systems in our sample should be detectable via gravitational waves by LISA (Laser Interferometer Space Antenna), one of which has already been identified as a LISA verification source. We also estimate a total of about 10,000 - 20,000 LISA-detectable DWD binaries in the galaxy. Our catalog of WD+WD binary candidates in SDSS-V is now public, and promises to uncover a large number of exciting DWD systems. △ Less

Submitted 2 September, 2025; originally announced September 2025.

Comments: Submitted to AAS journals

Faint southern spectrophotometric standard stars

Authors: N. P. Gentile Fusillo, S. Moehler, N. Przybilla, A. K. Elms, P. -E. Tremblay, W. Kausch, F. Kerber

Abstract: Context. The advent of the Extremely Large Telescope (ELT) will increase the collecting area by more than an order of magnitude compared to the individual Unit Telescopes of the Very Large Telescope (VLT). Fainter spectrophotometric standard stars than those currently available in the V = 11 to 13 mag (K = 12 to 14 mag) range are required for spectroscopic observations with instruments such as the… ▽ More Context. The advent of the Extremely Large Telescope (ELT) will increase the collecting area by more than an order of magnitude compared to the individual Unit Telescopes of the Very Large Telescope (VLT). Fainter spectrophotometric standard stars than those currently available in the V = 11 to 13 mag (K = 12 to 14 mag) range are required for spectroscopic observations with instruments such as the Multi-AO Imaging Camera for Deep Observations (MICADO) on the ELT, notably in the near-infrared wavelength regime. Aims. We identify suitable spectrophotometric standard stars among white dwarfs with hydrogen atmospheres (DA white dwarfs) in the magnitude range K =14 to 16 mag and provide reference data based on stellar model atmospheres. Methods. We observed 24 candidate DA white dwarfs with the X-shooter instrument on the VLT, covering the wavelength range 300 nm to 2480 nm in three arms. We took care to include stars at latitudes below and above -25 degrees to allow observations for all wind directions at the location of the ELT. The spectra were analysed using model fluxes from 3D pure-hydrogen local thermodynamic equilibrium model atmospheres and multi-band photometry. From the sample of observed targets, we selected 14 reliable flux calibrators. For these targets, the residuals from the match between the model best-fit models and the observed spectra across the full wavelength range are < 3%, with the exception of the UV regions affected by the ozone Huggins bands (300 nm - 340 nm) and regions contaminated by telluric lines. Results. We have identified and fully characterised 14 DA white dwarfs that can be used as spectrophotometric standard stars for the MICADO instrument as well as any other future instrument with similar requirements in the brightness range, K = 14 to 16 mag (Vegamag), and provide reference fluxes △ Less

Submitted 7 August, 2025; originally announced August 2025.

Comments: 8 pages, 6 figure, 2 tables. Appendix 8 pages, 13 figures. Accepted for publication in A&A

The Nineteenth Data Release of the Sloan Digital Sky Survey

Authors: SDSS Collaboration, Gautham Adamane Pallathadka, Mojgan Aghakhanloo, James Aird, Andrés Almeida, Singh Amrita, Friedrich Anders, Scott F. Anderson, Stefan Arseneau, Consuelo González Avila, Shir Aviram, Catarina Aydar, Carles Badenes, Jorge K. Barrera-Ballesteros, Franz E. Bauer, Aida Behmard, Michelle Berg, F. Besser, Christian Moni Bidin, Dmitry Bizyaev, Guillermo Blanc, Michael R. Blanton, Jo Bovy, William Nielsen Brandt, Joel R. Brownstein , et al. (187 additional authors not shown)

Abstract: Mapping the local and distant Universe is key to our understanding of it. For decades, the Sloan Digital Sky Survey (SDSS) has made a concerted effort to map millions of celestial objects to constrain the physical processes that govern our Universe. The most recent and fifth generation of SDSS (SDSS-V) is organized into three scientific ``mappers". Milky Way Mapper (MWM) that aims to chart the var… ▽ More Mapping the local and distant Universe is key to our understanding of it. For decades, the Sloan Digital Sky Survey (SDSS) has made a concerted effort to map millions of celestial objects to constrain the physical processes that govern our Universe. The most recent and fifth generation of SDSS (SDSS-V) is organized into three scientific ``mappers". Milky Way Mapper (MWM) that aims to chart the various components of the Milky Way and constrain its formation and assembly, Black Hole Mapper (BHM), which focuses on understanding supermassive black holes in distant galaxies across the Universe, and Local Volume Mapper (LVM), which uses integral field spectroscopy to map the ionized interstellar medium in the local group. This paper describes and outlines the scope and content for the nineteenth data release (DR19) of SDSS and the most substantial to date in SDSS-V. DR19 is the first to contain data from all three mappers. Additionally, we also describe nine value added catalogs (VACs) that enhance the science that can be conducted with the SDSS-V data. Finally, we discuss how to access SDSS DR19 and provide illustrative examples and tutorials. △ Less

Submitted 9 July, 2025; originally announced July 2025.

Comments: Submitted to AASJournals. 56 Pages, 9 Tables, 11 Figures

Sloan Digital Sky Survey-V: Pioneering Panoptic Spectroscopy

Authors: Juna A. Kollmeier, Hans-Walter Rix, Conny Aerts, James Aird, Pablo Vera Alfaro, Andrés Almeida, Scott F. Anderson, Óscar Jiménez Arranz, Stefan M. Arseneau, Roberto Assef, Shir Aviram, Catarina Aydar, Carles Badenes, Avrajit Bandyopadhyay, Kat Barger, Robert H. Barkhouser, Franz E. Bauer, Chad Bender, Felipe Besser, Binod Bhattarai, Pavaman Bilgi, Jonathan Bird, Dmitry Bizyaev, Guillermo A. Blanc, Michael R. Blanton , et al. (195 additional authors not shown)

Abstract: The Sloan Digital Sky Survey-V (SDSS-V) is pioneering panoptic spectroscopy: it is the first all-sky, multi-epoch, optical-to-infrared spectroscopic survey. SDSS-V is mapping the sky with multi-object spectroscopy (MOS) at telescopes in both hemispheres (the 2.5-m Sloan Foundation Telescope at Apache Point Observatory and the 100-inch du Pont Telescope at Las Campanas Observatory), where 500 zonal… ▽ More The Sloan Digital Sky Survey-V (SDSS-V) is pioneering panoptic spectroscopy: it is the first all-sky, multi-epoch, optical-to-infrared spectroscopic survey. SDSS-V is mapping the sky with multi-object spectroscopy (MOS) at telescopes in both hemispheres (the 2.5-m Sloan Foundation Telescope at Apache Point Observatory and the 100-inch du Pont Telescope at Las Campanas Observatory), where 500 zonal robotic fiber positioners feed light from a wide-field focal plane to an optical (R$\sim 2000$, 500 fibers) and a near-infrared (R$\sim 22,000$, 300 fibers) spectrograph. In addition to these MOS capabilities, the survey is pioneering ultra wide-field ($\sim$ 4000~deg$^2$) integral field spectroscopy enabled by a new dedicated facility (LVM-I) at Las Campanas Observatory, where an integral field spectrograph (IFS) with 1801 lenslet-coupled fibers arranged in a 0.5 degree diameter hexagon feeds multiple R$\sim$4000 optical spectrographs that cover 3600-9800 angstroms. SDSS-V's hardware and multi-year survey strategy are designed to decode the chemo-dynamical history of the Milky Way Galaxy and tackle fundamental open issues in stellar physics in its Milky Way Mapper program, trace the growth physics of supermassive black holes in its Black Hole Mapper program, and understand the self-regulation mechanisms and the chemical enrichment of galactic ecosystems at the energy-injection scale in its Local Volume Mapper program. The survey is well-timed to multiply the scientific output from major all-sky space missions. The SDSS-V MOS programs began robotic operations in 2021; IFS observations began in 2023 with the completion of the LVM-I facility. SDSS-V builds upon decades of heritage of SDSS's pioneering advances in data analysis, collaboration spirit, infrastructure, and product deliverables in astronomy. △ Less

Submitted 9 July, 2025; originally announced July 2025.

Comments: 76 pages, submitted to the Astronomical Journal

A network of cooler white dwarfs as infrared standards for flux calibration

Authors: Abbigail K. Elms, Nicola Pietro Gentile Fusillo, Pier-Emmanuel Tremblay, Ralph C. Bohlin, Mark A. Hollands, Snehalata Sahu, Mairi W. O'Brien, Susana Deustua, Tim Cunningham

Abstract: The accurate flux calibration of observational data is vital for astrophysics and cosmology because absolute flux uncertainties of stellar standards propagate into scientific results. With the ever higher precision achieved by telescopic missions (e.g. JWST) in the infrared (IR), suitable calibrators are required for this regime. The basis of the Hubble Space Telescope (HST) flux scale is defined… ▽ More The accurate flux calibration of observational data is vital for astrophysics and cosmology because absolute flux uncertainties of stellar standards propagate into scientific results. With the ever higher precision achieved by telescopic missions (e.g. JWST) in the infrared (IR), suitable calibrators are required for this regime. The basis of the Hubble Space Telescope (HST) flux scale is defined by model fits of three hot (Teff > 30000 K) hydrogen-atmosphere (DA) white dwarfs, which achieve an accuracy better than 1 per cent at optical wavelengths but falls below this level in the IR range. We present a network of 17 cooler DA white dwarfs with Teff < 20000 K as spectrophotometric flux standards that are equally, if not more, accurate at IR wavelengths. Cooler white dwarfs do not suffer from non-local thermal equilibrium (NLTE) effects in continuum flux or from UV metal line blanketing, have a larger sky density, are generally closer to Earth with little or negligible interstellar reddening, and have energy distributions peaking in the optical or near-IR. Using the latest grid of DA LTE atmosphere models with three-dimensional (3D) convection, the observed Space Telescope Imaging Spectrometer (STIS) and Wide Field Camera three (WFC3) fluxes of our network are accurate to 3 per cent over most of the range 1450 - 16000 AA, with a median standard deviation of 1.41 per cent. Fitting the HST STIS and WFC3 white dwarf SEDs and Balmer lines independently yields SEDs that agree within 3$σ$, which demonstrates the precision of the models for our network. △ Less

Submitted 16 October, 2024; v1 submitted 9 October, 2024; originally announced October 2024.

Comments: 24 pages, 18 figures. Published by MNRAS

Journal ref: 2024, MNRAS, 534, 2758

Constraints on Remnant Planetary Systems as a Function of Main-Sequence Mass with HST/COS

Authors: Lou Baya Ould Rouis, J. J. Hermes, Boris T. Gänsicke, Snehalata Sahu, Detlev Koester, P. -E. Tremblay, Dimitri Veras, Jay Farihi, Tyler M. Heintz, Nicola Pietro Gentile Fusillo, Seth Redfield

Abstract: As the descendants of stars with masses less than 8 M$_{\odot}$ on the main sequence, white dwarfs provide a unique way to constrain planetary occurrence around intermediate-mass stars (spectral types BAF) that are otherwise difficult to measure with radial-velocity or transit surveys. We update the analysis of more than 250 ultraviolet spectra of hot ($13{,}000$ K $< T_{\mathrm{eff}} <$… ▽ More As the descendants of stars with masses less than 8 M$_{\odot}$ on the main sequence, white dwarfs provide a unique way to constrain planetary occurrence around intermediate-mass stars (spectral types BAF) that are otherwise difficult to measure with radial-velocity or transit surveys. We update the analysis of more than 250 ultraviolet spectra of hot ($13{,}000$ K $< T_{\mathrm{eff}} <$ $30{,}000$ K), young (less than $800$ Myr) white dwarfs collected by the Hubble Space Telescope, which reveals that more than 40% of all white dwarfs show photospheric silicon and sometimes carbon, signpost for the presence of remnant planetary systems. However, the fraction of white dwarfs with metals significantly decreases for massive white dwarfs (M$_{\rm WD}~>$ 0.8 M$_{\odot}$), descendants of stars with masses greater than 3.5 M$_{\odot}$ on the main sequence, as just $11^{+6}_{-4}$% exhibit metal pollution. In contrast, $44\pm6$% of a subset of white dwarfs (M$\rm _{WD}~<$ 0.7 M$_{\odot}$) unbiased by the effects of radiative levitation are actively accreting planetary debris. While the population of massive white dwarfs is expected to be influenced by the outcome of binary evolution, we do not find merger remnants to broadly affect our sample. We connect our measured occurrence rates of metal pollution on massive white dwarfs to empirical constraints into planetary formation and survival around stars with masses greater than 3.5 M$_{\odot}$ on the main sequence. △ Less

Submitted 8 October, 2024; originally announced October 2024.

Comments: 21 pages, 5 figures, accepted to The Astrophysical Journal (ApJ)

J-PLUS: The fraction of calcium white dwarfs along the cooling sequence

Authors: C. López-Sanjuan, P. -E. Tremblay, M. W. O'Brien, D. Spinoso, A. Ederoclite, H. Vázquez Ramió, A. J. Cenarro, A. Marín-Franch, T. Civera, J. M. Carrasco, B. T. Gänsicke, N. P. Gentile Fusillo, A. Hernán-Caballero, M. A. Hollands, A. del Pino, H. Domínguez Sánchez, J. A. Fernández-Ontiveros, F. M. Jiménez-Esteban, A. Rebassa-Mansergas, L. Schmidtobreick, R. E. Angulo, D. Cristòbal-Hornillos, R. A. Dupke, C. Hernández-Monteagudo, M. Moles , et al. (2 additional authors not shown)

Abstract: We used the Javalambre Photometric Local Universe Survey (J-PLUS) DR2 photometry in twelve optical bands over 2176 deg2 to estimate the fraction of white dwarfs with presence of CaII H+K absorption along the cooling sequence. We compared the J-PLUS photometry against metal-free theoretical models to estimate the equivalent width in the J0395 passband of 10 nm centered at 395 nm (EW_J0395), a proxy… ▽ More We used the Javalambre Photometric Local Universe Survey (J-PLUS) DR2 photometry in twelve optical bands over 2176 deg2 to estimate the fraction of white dwarfs with presence of CaII H+K absorption along the cooling sequence. We compared the J-PLUS photometry against metal-free theoretical models to estimate the equivalent width in the J0395 passband of 10 nm centered at 395 nm (EW_J0395), a proxy to detect calcium absorption. A total of 4399 white dwarfs within 30000 > Teff > 5500 K and mass M > 0.45 Msun were analyzed. Their EW_J0395 distribution was modeled using two populations, corresponding to polluted and non-polluted systems, to estimate the fraction of calcium white dwarfs (f_Ca) as a function of Teff. The probability for each individual white dwarf of presenting calcium absorption, pca, was also computed. The comparison with both the measured Ca/He abundance and the metal pollution from spectroscopy shows that EW_J0395 correlates with the presence of calcium. The fraction of calcium white dwarfs increases from f_Ca = 0 at Teff = 13500 K to f_Ca = 0.15 at Teff = 5500 K. We compare our results with the fractions derived from the 40 pc spectroscopic sample and from SDSS spectra. The trend found in J-PLUS observations is also present in the 40 pc sample, however SDSS shows a deficit of metal-polluted objects at Teff < 12000 K. Finally, we found 39 white dwarfs with pca > 0.99. Twenty of them have spectra presented in previous studies, whereas we observed six additional targets. These 26 objects were all confirmed as metal-polluted systems. The J-PLUS optical data provide a robust statistical measurement for the presence of CaII H+K absorption in white dwarfs. We find a 15 +- 3 % increase in the fraction of calcium white dwarfs from Teff = 13500 K to 5500 K, which reflects their selection function in the optical from the total population of metal-polluted systems. △ Less

Submitted 23 June, 2024; originally announced June 2024.

Comments: Submitted to Astronomy and Astrophysics. Comments are welcome

Journal ref: A&A 691, A211 (2024)

The DESI Early Data Release White Dwarf Catalogue

Authors: Christopher J. Manser, Paula Izquierdo, Boris T. Gänsicke, Andrew Swan, Detlev Koester, Akshay Robert, Siyi Xu, Keith Inight, Ben Amroota, N. P. Gentile Fusillo, Sergey E. Koposov, Bokyoung Kim, Arjun Dey, Carlos Allende Prieto, J. Aguilar, S. Ahlen, R. Blum, D. Brooks, T. Claybaugh, A. P. Cooper, K. Dawson, A. de la Macorra, P. Doel, J. E. Forero-Romero, E. Gaztañaga , et al. (29 additional authors not shown)

Abstract: The Early Data Release (EDR) of the Dark Energy Spectroscopic Instrument (DESI) comprises spectroscopy obtained from 2020 December 14 to 2021 June 10. White dwarfs were targeted by DESI both as calibration sources and as science targets and were selected based on Gaia photometry and astrometry. Here we present the DESI EDR white dwarf catalogue, which includes 2706 spectroscopically confirmed whit… ▽ More The Early Data Release (EDR) of the Dark Energy Spectroscopic Instrument (DESI) comprises spectroscopy obtained from 2020 December 14 to 2021 June 10. White dwarfs were targeted by DESI both as calibration sources and as science targets and were selected based on Gaia photometry and astrometry. Here we present the DESI EDR white dwarf catalogue, which includes 2706 spectroscopically confirmed white dwarfs of which approximately 1630 (roughly 60 per cent) have been spectroscopically observed for the first time, as well as 66 white dwarf binary systems. We provide spectral classifications for all white dwarfs, and discuss their distribution within the Gaia Hertzsprung-Russell diagram. We provide atmospheric parameters derived from spectroscopic and photometric fits for white dwarfs with pure hydrogen or helium photospheres, a mixture of those two, and white dwarfs displaying carbon features in their spectra. We also discuss the less abundant systems in the sample, such as those with magnetic fields, and cataclysmic variables. The DESI EDR white dwarf sample is significantly less biased than the sample observed by the Sloan Digital Sky Survey, which is skewed to bluer and therefore hotter white dwarfs, making DESI more complete and suitable for performing statistical studies of white dwarfs. △ Less

Submitted 28 February, 2024; originally announced February 2024.

Comments: 19 pages, 17 figures, not including appendix. Submitting to MNRAS. Comments and suggestions welcome

The Gaia white dwarf revolution

Authors: Pier-Emmanuel Tremblay, Antoine Bédard, Mairi W. O'Brien, James Munday, Abbigail K. Elms, Nicola Pietro Gentillo Fusillo, Snehalata Sahu

Abstract: This review highlights the role of the Gaia space mission in transforming white dwarf research. These stellar remnants constitute 5-7% of the local stellar population in volume, yet before Gaia the lack of trigonometric parallaxes hindered their identification. The mission's Data Release 2 in 2018 provided the first unbiased colour-absolute magnitude diagram of the local stellar population, identi… ▽ More This review highlights the role of the Gaia space mission in transforming white dwarf research. These stellar remnants constitute 5-7% of the local stellar population in volume, yet before Gaia the lack of trigonometric parallaxes hindered their identification. The mission's Data Release 2 in 2018 provided the first unbiased colour-absolute magnitude diagram of the local stellar population, identifying 260,000 white dwarfs, with the number later increasing to over 355,000 in Data Release 3. Since then, more than 400 white dwarf studies have made critical use of Gaia data, establishing it as a fundamental resource for white dwarf identification, fundamental parameter determination and more recently spectral type characterisation. The review underscores the routine reliance on Gaia parallaxes and extensive use of its photometry in white dwarf surveys. We also discuss recent discoveries firmly grounded in Gaia data, including white dwarf mergers, exotic compact binaries and evolved planetary systems. △ Less

Submitted 5 June, 2024; v1 submitted 22 February, 2024; originally announced February 2024.

Comments: Accepted to New Astronomy Reviews (Special Issue "Gaia, the first crop of discoveries")

The 40 pc sample of white dwarfs from Gaia

Authors: Mairi W. O'Brien, P. -E. Tremblay, B. L. Klein, D. Koester, C. Melis, A. Bédard, E. Cukanovaite, T. Cunningham, A. E. Doyle, B. T. Gänsicke, N. P. Gentile Fusillo, M. A. Hollands, J. McCleery, I. Pelisoli, S. Toonen, A. J. Weinberger, B. Zuckerman

Abstract: We present a comprehensive overview of a volume-complete sample of white dwarfs located within 40 pc of the Sun, a significant proportion of which were detected in Gaia Data Release 3 (DR3). Our DR3 sample contains 1076 spectroscopically confirmed white dwarfs, with just five candidates within the volume remaining unconfirmed (more than 99 per cent spectroscopic completeness). Additionally, 28 whi… ▽ More We present a comprehensive overview of a volume-complete sample of white dwarfs located within 40 pc of the Sun, a significant proportion of which were detected in Gaia Data Release 3 (DR3). Our DR3 sample contains 1076 spectroscopically confirmed white dwarfs, with just five candidates within the volume remaining unconfirmed (more than 99 per cent spectroscopic completeness). Additionally, 28 white dwarfs were not in our initial selection from Gaia DR3, most of which are in unresolved binaries. We use Gaia DR3 photometry and astrometry to determine a uniform set of white dwarf parameters, including mass, effective temperature, and cooling age. We assess the demographics of the 40 pc sample, specifically magnetic fields, binarity, space density and mass distributions. △ Less

Submitted 4 January, 2024; v1 submitted 5 December, 2023; originally announced December 2023.

Comments: Accepted for publication in MNRAS. 24 pages, 25 figures

Journal ref: MNRAS 527, 3 (2024) 8687-8705

Cataclysmic Variables from Sloan Digital Sky Survey V -- the search for period bouncers continues

Authors: K. Inight, Boris T. Gänsicke, A. Schwope, S. F. Anderson, C. Badenes, E. Breedt, V. Chandra, B. D. R. Davies, N. P. Gentile Fusillo, M. J. Green, J. J. Hermes, I. Achaica Huamani, H. Hwang, K. Knauff, J. Kurpas, K. S. Long, V. Malanushenko, S. Morrison, I. J. Quiroz C., G. N. Aichele Ramos, A. Roman-Lopes, M. R. Schreiber, A. Standke, L. Stütz, J. R. Thorstensen , et al. (3 additional authors not shown)

Abstract: SDSS-V is carrying out a dedicated survey for white dwarfs, single and in binaries, and we report the analysis of the spectroscopy of cataclysmic variables (CVs) and CV candidates obtained during the final plug plate observations of SDSS. We identify eight new CVs, spectroscopically confirm 53 and refute eleven published CV candidates, and we report 21 new or improved orbital periods. Combined wit… ▽ More SDSS-V is carrying out a dedicated survey for white dwarfs, single and in binaries, and we report the analysis of the spectroscopy of cataclysmic variables (CVs) and CV candidates obtained during the final plug plate observations of SDSS. We identify eight new CVs, spectroscopically confirm 53 and refute eleven published CV candidates, and we report 21 new or improved orbital periods. Combined with previously published data, the orbital period distribution of the SDSS-V CVs does not clearly exhibit a period gap. This is consistent with previous findings that spectroscopically identified CVs have a larger proportion of short-period systems compared to samples identified from photometric variability. Remarkably, despite a systematic search, we find very few period bouncers. We estimate the space density of period bouncers to be $\simeq0.2\times10^{-6}\,\mathrm{pc}^{-3}$, i.e. they represent only a few per cent of the total CV population. This suggests that during their final phase of evolution, CVs either destroy the donor, e.g. via a merger, or that they become detached and cease mass transfer. △ Less

Submitted 11 September, 2023; v1 submitted 22 May, 2023; originally announced May 2023.

Comments: Accepted by MNRAS. Includes machine readable list of CVs

Journal ref: 2023MNRAS.525.3597I

Systematic uncertainties in the characterisation of helium-dominated metal-polluted white dwarf atmospheres

Authors: Paula Izquierdo, Boris T. Gänsicke, Pablo Rodríguez-Gil, Detlev Koester, Odette Toloza, Nicola P. Gentile Fusillo, Anna F. Pala, Pier-Emmanuel Tremblay

Abstract: White dwarf photospheric parameters are usually obtained by means of spectroscopic or photometric analysis. These results are not always consistent with each other, with the published values often including just the statistical uncertainties. The differences are more dramatic for white dwarfs with helium-dominated photospheres, so to obtain realistic uncertainties we have analysed a sample of 13 o… ▽ More White dwarf photospheric parameters are usually obtained by means of spectroscopic or photometric analysis. These results are not always consistent with each other, with the published values often including just the statistical uncertainties. The differences are more dramatic for white dwarfs with helium-dominated photospheres, so to obtain realistic uncertainties we have analysed a sample of 13 of these white dwarfs, applying both techniques to up to three different spectroscopic and photometric data sets for each star. We found mean standard deviations of < $σT_{\mathrm{eff}}$ > = 524 K, < $σ\log g$ > = 0.27 dex and < $σ\log(\mathrm{H/He})$ > = 0.31 dex for the effective temperature, surface gravity and relative hydrogen abundance, respectively, when modelling diverse spectroscopic data. The photometric fits provided mean standard deviations up to < $σT_{\mathrm{eff}}$ > = 1210 K and < $σ\log g$ > = 0.13 dex. We suggest these values to be adopted as realistic lower limits to the published uncertainties in parameters derived from spectroscopic and photometric fits for white dwarfs with similar characteristics. In addition, we investigate the effect of fitting the observational data adopting three different photospheric chemical compositions. In general, pure helium model spectra result in larger $T_{\mathrm{eff}}$ compared to those derived from models with traces of hydrogen. The $\log g$ shows opposite trends: smaller spectroscopic values and larger photometric ones when compared to models with hydrogen. The addition of metals to the models also affects the derived atmospheric parameters, but a clear trend is not found. △ Less

Submitted 23 January, 2023; originally announced January 2023.

Comments: 25 pages, 16 figures, submitted to MNRAS

Pulsating H-deficient WDs and pre-WDs observed with TESS: V. Discovery of two new DBV pulsators, WD J152738.4-450207.4 and WD 1708-871, and asteroseismology of the already known DBV stars PG 1351+489, EC 20058-5234, and EC 04207-4748

Authors: Alejandro H. Córsico, Murat Uzundag, S. O. Kepler, Leandro G. Althaus, Roberto Silvotti, Paul A. Bradley, Andrzej S. Baran, Detlev Koester, Keaton J. Bell, Alejandra D. Romero, J. J. Hermes, Nicola P. Gentile Fusillo

Abstract: The {\sl TESS} space mission has recently demonstrated its great potential to discover new pulsating white dwarf and pre-white dwarf stars, and to detect periodicities with high precision in already known white-dwarf pulsators. We report the discovery of two new pulsating He-rich atmosphere white dwarfs (DBVs) and present a detailed asteroseismological analysis of three already known DBV stars emp… ▽ More The {\sl TESS} space mission has recently demonstrated its great potential to discover new pulsating white dwarf and pre-white dwarf stars, and to detect periodicities with high precision in already known white-dwarf pulsators. We report the discovery of two new pulsating He-rich atmosphere white dwarfs (DBVs) and present a detailed asteroseismological analysis of three already known DBV stars employing observations collected by the {\sl TESS} mission along with ground-based data. We extracted frequencies from the {\sl TESS} light curves of these DBV stars using a standard pre-whitening procedure to derive the potential pulsation frequencies. All the oscillation frequencies that we found are associated with $g$-mode pulsations with periods spanning from $\sim 190$ s to $\sim 936$ s. We find hints of rotation from frequency triplets in some of the targets, including the two new DBVs. For three targets, we find constant period spacings, which allowed us to infer their stellar masses and constrain the harmonic degree $\ell$ of the modes. We also performed period-to-period fit analyses and found an asteroseismological model for three targets, with stellar masses generally compatible with the spectroscopic masses. Obtaining seismological models allowed us to estimate the seismological distances and compare them with the precise astrometric distances measured with {\it Gaia}. We find a good agreement between the seismic and the astrometric distances for three stars (PG~1351+489, EC~20058$-$5234, and EC~04207$-$4748), although for the other two stars (WD~J152738.4$-$50207 and WD~1708$-$871), the discrepancies are substantial. The high-quality data from the {\sl TESS} mission continue to provide important clues to determine the internal structure of pulsating pre-white dwarf and white dwarf stars through the tools of asteroseismology. △ Less

Submitted 11 October, 2022; originally announced October 2022.

Comments: 22 pages, 27 figures, 21 tables. To be published in Astronomy & Astrophysics

$\textit{Gaia}$ white dwarfs within 40 pc III: spectroscopic observations of new candidates in the southern hemisphere

Authors: Mairi W. O'Brien, P. -E. Tremblay, N. P. Gentile Fusillo, M. A. Hollands, B. T. Gaensicke, D. Koester, I. Pelisoli, E. Cukanovaite, T. Cunningham, A. E. Doyle, A. Elms, J. Farihi, J. J. Hermes, J. Holberg, S. Jordan, B. L. Klein, S. J. Kleinman, C. J. Manser, D. De Martino, T. R. Marsh, J. McCleery, C. Melis, A. Nitta, S. G. Parsons, R. Raddi , et al. (9 additional authors not shown)

Abstract: We present a spectroscopic survey of 248 white dwarf candidates within 40 pc of the Sun; of these 244 are in the southern hemisphere. Observations were performed mostly with the Very Large Telescope (X-Shooter) and Southern Astrophysical Research Telescope. Almost all candidates were selected from $\textit{Gaia}$ Data Release 3 (DR3). We find a total of 246 confirmed white dwarfs, 209 of which had… ▽ More We present a spectroscopic survey of 248 white dwarf candidates within 40 pc of the Sun; of these 244 are in the southern hemisphere. Observations were performed mostly with the Very Large Telescope (X-Shooter) and Southern Astrophysical Research Telescope. Almost all candidates were selected from $\textit{Gaia}$ Data Release 3 (DR3). We find a total of 246 confirmed white dwarfs, 209 of which had no previously published spectra, and two main-sequence star contaminants. Of these, 100 white dwarfs display hydrogen Balmer lines, 69 have featureless spectra, and two show only neutral helium lines. Additionally, 14 white dwarfs display traces of carbon, while 37 have traces of other elements that are heavier than helium. We observe 36 magnetic white dwarfs through the detection of Zeeman splitting of their hydrogen Balmer or metal spectral lines. High spectroscopic completeness (> 97 per cent) has now been reached, such that we have 1058 confirmed $\textit{Gaia}$ DR3 white dwarfs out of 1083 candidates within 40 pc of the Sun at all declinations. △ Less

Submitted 9 November, 2022; v1 submitted 4 October, 2022; originally announced October 2022.

Comments: 49 pages, 19 figures. Accepted by MNRAS on 8 November, 2022

Spectral analysis of ultra-cool white dwarfs polluted by planetary debris

Authors: Abbigail K. Elms, Pier-Emmanuel Tremblay, Boris T. Gänsicke, Detlev Koester, Mark A. Hollands, Nicola P. Gentile Fusillo, Tim Cunningham, Kevin Apps

Abstract: We identify two ultra-cool ($T_\mathrm{eff} < 4000$ K) metal-polluted (DZ) white dwarfs WDJ2147$-$4035 and WDJ1922$+$0233 as the coolest and second coolest DZ stars known to date with $T_\mathrm{eff} \approx 3050$ K and $T_\mathrm{eff} \approx 3340$ K, respectively. Strong atmospheric collision-induced absorption (CIA) causes the suppression of red optical and infra-red flux in WDJ1922$+$0233, res… ▽ More We identify two ultra-cool ($T_\mathrm{eff} < 4000$ K) metal-polluted (DZ) white dwarfs WDJ2147$-$4035 and WDJ1922$+$0233 as the coolest and second coolest DZ stars known to date with $T_\mathrm{eff} \approx 3050$ K and $T_\mathrm{eff} \approx 3340$ K, respectively. Strong atmospheric collision-induced absorption (CIA) causes the suppression of red optical and infra-red flux in WDJ1922$+$0233, resulting in an unusually blue colour given its low temperature. WDJ2147$-$4035 has moderate infra-red CIA yet has the reddest optical colours known for a DZ white dwarf. Microphysics improvements to the non-ideal effects and CIA opacities in our model atmosphere code yields reasonable solutions to observations of these ultra-cool stars. WDJ2147$-$4035 has a cooling age of over 10 Gyr which is the largest known for a DZ white dwarf, whereas WDJ1922$+$0233 is slightly younger with a cooling age of 9 Gyr. Galactic kinematics calculations from precise Gaia EDR3 astrometry reveal these ultra-cool DZ stars as likely members of the Galactic disc thus they could be pivotal objects in future studies constraining an upper age limit for the disc of the Milky Way. We present intermediate-resolution spectroscopy for both objects, which provides the first spectroscopic observations of WDJ2147$-$4035. Detections of sodium and potassium are made in both white dwarfs, in addition to calcium in WDJ1922$+$0233 and lithium in WDJ2147$-$4035. We identify the magnetic nature of WDJ2147$-$4035 from Zeeman splitting in the lithium line and also make a tentative detection of carbon, so we classify this star as DZQH. WDJ1922$+$0233 likely accreted planetary crust debris, while the debris composition that polluted WDJ2147$-$4035 remains unconstrained. △ Less

Submitted 7 October, 2022; v1 submitted 10 June, 2022; originally announced June 2022.

Comments: 18 pages, 8 figures. Accepted by MNRAS

Kinematic properties of white dwarfs. Galactic orbital parameters and age-velocity dispersion relation

Authors: R. Raddi, S. Torres, A. Rebassa-Mansergas, J. Maldonado, M. E. Camisassa, D. Koester, N. P. Gentile Fusillo, P. -E. Tremblay, M. Dimpel, U. Heber, T. Cunningham, J. -J. Ren

Abstract: We present the first detailed 3D kinematic analysis of a sample of 3133 white dwarfs that use Gaia astrometry plus radial velocities, which were measured either by Gaia or by ground based spectroscopic observations. The sample includes either isolated white dwarfs that have direct radial velocity measurements, or white dwarfs that belong to common proper motion pairs that contain nondegenerate com… ▽ More We present the first detailed 3D kinematic analysis of a sample of 3133 white dwarfs that use Gaia astrometry plus radial velocities, which were measured either by Gaia or by ground based spectroscopic observations. The sample includes either isolated white dwarfs that have direct radial velocity measurements, or white dwarfs that belong to common proper motion pairs that contain nondegenerate companions with available radial velocities. A subset of common proper motion pairs also have metal abundances that have been measured by large scale spectroscopic surveys or by our own follow-up observations. We used the white dwarfs as astrophysical clocks, by determining their masses and total ages via interpolation with dedicated evolutionary models. We also used the nondegenerate companions in common proper motions to chemically tag of the population. Combining accurate radial velocities with Gaia astrometry and proper motions, we derived the velocity components of our sample in the Galactic rest frame and their Galactic orbital parameters. The sample is mostly located within ~300 pc from the Sun. It contains predominantly (90-95%) thin-disk stars with close-to-circular Galactic orbits, while the remaining 5-10% of stars have more eccentric trajectories and belong to the thick disk. We identified seven isolated white dwarfs and two common proper motion pairs as halo members. We determined the age - velocity dispersion relation for the thin-disk members, which shows signatures of dynamical heating and saturation after 4-6 Gyr. We observed a mild anti-correlation between [Fe/H] and the radial component of the average - velocity dispersion, showing that dynamical mixing of populations takes place in the Galactic disk, as was detected via the analysis of other samples of FGK stars. [Abridged] △ Less

Submitted 28 January, 2022; v1 submitted 1 November, 2021; originally announced November 2021.

Comments: Accepted for publication (Raddi et al. 2022, A&A, 658, A22). 16 pages, 14 figures, 9 tables. Tables 2, 4, 5, 6, and 7 are available as pdf files and in electronic form via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/658/A22

Journal ref: A&A 658, A22 (2022)

J-PLUS: Spectral evolution of white dwarfs by PDF analysis

Authors: C. López-Sanjuan, P. -E. Tremblay, A. Ederoclite, H. Vázquez Ramió, J. M. Carrasco, J. Varela, A. J. Cenarro, A. Marín-Franch, T. Civera, S. Daflon, B. T. Gänsicke, N. P. Gentile Fusillo, F. M. Jiménez-Esteban, J. Alcaniz, R. E. Angulo, D. Cristóbal-Hornillos, R. A. Dupke, C. Hernández-Monteagudo, M. Moles, L. Sodré Jr

Abstract: We estimated the spectral evolution of white dwarfs with effective temperature using the Javalambre Photometric Local Universe Survey (J-PLUS) second data release (DR2), that provides twelve photometric optical passbands over 2176 deg2. We analysed 5926 white dwarfs with r <= 19.5 mag in common between a white dwarf catalog defined from Gaia EDR3 and J-PLUS DR2. We performed a Bayesian analysis by… ▽ More We estimated the spectral evolution of white dwarfs with effective temperature using the Javalambre Photometric Local Universe Survey (J-PLUS) second data release (DR2), that provides twelve photometric optical passbands over 2176 deg2. We analysed 5926 white dwarfs with r <= 19.5 mag in common between a white dwarf catalog defined from Gaia EDR3 and J-PLUS DR2. We performed a Bayesian analysis by comparing the observed J-PLUS photometry with theoretical models of hydrogen (H) and helium (He) dominated atmospheres. We estimated the PDF for effective temperature (Teff), surface gravity, parallax, and spectral type; and the probability of having a H-dominated atmosphere (pH) for each source. We applied a prior in parallax, using Gaia EDR3 measurements as reference, and derived a self-consistent prior for the atmospheric composition as a function of Teff. We described the fraction of He-dominated atmosphere white dwarfs (fHe) with a linear function of Teff at 5000 < Teff < 30000 K. We found fHe = 0.24 +- 0.01 at Teff = 10000 K, a change rate along the cooling sequence of 0.14 +- 0.02 per 10 kK, and a minimum He-dominated fraction of 0.08 +- 0.02 at the high-temperature end. We tested the obtained pH by comparison with spectroscopic classifications, finding that it is reliable. We estimated the mass distribution for the 351 sources with distance d < 100 pc, mass M > 0.45 Msun, and Teff > 6000 K. The result for H-dominated white dwarfs agrees with previous work, with a dominant M = 0.59 Msun peak and the presence of an excess at M ~ 0.8 Msun. This high-mass excess is absent in the He-dominated distribution, which presents a single peak. The J-PLUS optical data provides a reliable statistical classification of white dwarfs into H- and He-dominated atmospheres. We find a 21 +- 3 % increase in the fraction of He-dominated white dwarfs from Teff = 20000 K to Teff = 5000 K. △ Less

Submitted 24 March, 2022; v1 submitted 27 October, 2021; originally announced October 2021.

Comments: Published in Astronomy and Astrophysics. 18 pages, 15 figures, 4 tables

Journal ref: A&A 658, A79 (2022)

Velocity-imaging the rapidly precessing planetary disc around the white dwarf HE 1349-2305 using Doppler tomography

Authors: Christopher J. Manser, Erik Dennihy, Boris T. Gänsicke, John H. Debes, Nicola P. Gentile Fusillo, J. J. Hermes, Mark Hollands, Paula Izquierdo, B. C. Kaiser, T. R. Marsh, Joshua S. Reding, Pablo Rodríguez-Gil, Dimitri Veras, David J. Wilson

Abstract: The presence of planetary material in white dwarf atmospheres, thought to be accreted from a dusty debris disc produced via the tidal disruption of a planetesimal, is common. Approximately five per cent of these discs host a co-orbital gaseous component detectable via emission from atomic transitions - usually the 8600 Angstrom CaII triplet. These emission profiles can be highly variable in both m… ▽ More The presence of planetary material in white dwarf atmospheres, thought to be accreted from a dusty debris disc produced via the tidal disruption of a planetesimal, is common. Approximately five per cent of these discs host a co-orbital gaseous component detectable via emission from atomic transitions - usually the 8600 Angstrom CaII triplet. These emission profiles can be highly variable in both morphology and strength. Furthermore, the morphological variations in a few systems have been shown to be periodic, likely produced by an apsidally precessing asymmetric disc. Of the known gaseous debris discs, that around HE1349-2305 has the most rapidly evolving emission line morphology, and we present updated spectroscopy of the CaII triplet of this system. The additional observations show that the emission line morphologies vary periodically and consistently, and we constrain the period to two aliases of 459$\pm$3d and 502$\pm$3d. We produce images of the CaII triplet emission from the disc in velocity space using Doppler tomography - only the second such imaging of a white dwarf debris disc. We suggest that the asymmetric nature of these velocity images is generated by gas moving on eccentric orbits with radially-dependent excitation conditions via photo-ionisation from the white dwarf. We also obtained short-cadence (~ 4 min) spectroscopy to search for variability on the time-scale of the disc's orbital period (~ hours) due to the presence of a planetesimal, and rule out variability at a level of ~ 1.4 per cent. △ Less

Submitted 11 October, 2021; originally announced October 2021.

Comments: 14 Pages, 10 Figures, accepted for publication in MNRAS

A catalogue of white dwarfs in Gaia EDR3

Authors: N. P. Gentile Fusillo, P. -E. Tremblay, E. Cukanovaite, A. Vorontseva, R. Lallement, M. Hollands, B. T. Gänsicke, K. B. Burdge, J. McCleery, S. Jordan

Abstract: We present a catalogue of white dwarf candidates selected from Gaia early data release three (EDR3). We applied several selection criteria in absolute magnitude, colour, and Gaia quality flags to remove objects with unreliable measurements while preserving most stars compatible with the white dwarf locus in the Hertzsprung-Russell diagram. We then used a sample of over 30 000 spectroscopically con… ▽ More We present a catalogue of white dwarf candidates selected from Gaia early data release three (EDR3). We applied several selection criteria in absolute magnitude, colour, and Gaia quality flags to remove objects with unreliable measurements while preserving most stars compatible with the white dwarf locus in the Hertzsprung-Russell diagram. We then used a sample of over 30 000 spectroscopically confirmed white dwarfs and contaminants from the Sloan Digital Sky Survey (SDSS) to map the distribution of these objects in the Gaia absolute magnitude-colour space. Finally, we adopt the same method presented in our previous Gaia DR2 work to calculate a probability of being a white dwarf (Pwd) for $\simeq$1.3 million sources which passed our quality selection. The Pwd values can be used to select a sample of $\simeq$359 000 high-confidence white dwarf candidates in the magnitude range 8< G <21. We calculated stellar parameters (effective temperature, surface gravity, and mass) for all these stars by fitting Gaia astrometry and photometry with synthetic models. We estimate an upper limit of 93 per cent for the overall completeness of our catalogue for white dwarfs with G $\leq$20 mag and effective temperature (Teff)>7000K, at high Galactic latitudes (|b|>20°). Alongside the main catalogue we include a reduced-proper-motion extension containing $\simeq$10 200 white dwarf candidates with unreliable parallax measurements which could, however be identified on the basis of their proper motion. We also performed a cross-match of our catalogues with SDSS DR16 spectroscopy and provide spectral classification based on visual inspection for all resulting matches. △ Less

Submitted 28 September, 2021; v1 submitted 14 June, 2021; originally announced June 2021.

Comments: Minor text revisions. 20 pages,14 figures. Accepted in MNRAS. Catalogues can be downloaded at https://warwick.ac.uk/fac/sci/physics/research/astro/research/catalogues/gaiaedr3_wd_main.fits.gz ; https://warwick.ac.uk//fac/sci/physics/research/astro/research/catalogues/gaiaedr3_wd_rpm_ext.fits.gz ; https://warwick.ac.uk//fac/sci/physics/research/astro/research/catalogues/gaiaedr3_wd_sdssspec.fits.gz

First detection of a disk free of volatile elements around a young A-type star: A sign of collisions between rocky planets?

Authors: M. E. van den Ancker, N. P. Gentile Fusillo, T. J. Haworth, C. F. Manara, P. A. Miles-Páez, R. D. Oudmaijer, O. Panic, D. J. M. Petit dit de la Roche, M. G. Petr-Gotzens, M. Vioque

Abstract: Aims. We present the first detailed analysis of the astrophysical parameters of the poorly studied Sco-Cen member HD 152384 and its circumstellar environment. Methods. We analyze newly obtained optical-near-IR XSHOOTER spectra, as well as archival TESS data, of HD 152384. In addition, we use literature photometric data to construct a detailed spectral energy distribution (SED) of the star. Results… ▽ More Aims. We present the first detailed analysis of the astrophysical parameters of the poorly studied Sco-Cen member HD 152384 and its circumstellar environment. Methods. We analyze newly obtained optical-near-IR XSHOOTER spectra, as well as archival TESS data, of HD 152384. In addition, we use literature photometric data to construct a detailed spectral energy distribution (SED) of the star. Results. The photospheric absorption lines in the spectrum of HD 152384 are characteristic of a A0 V star, for which we derive a stellar mass of 2.1 +/- 0.1 M_sun and a stellar age > 4.5 Myr. Superimposed on the photospheric absorption, the optical spectrum also displays double-peaked emission lines of Ca II, Fe I, Mg I and Si I, typical of circumstellar disks. Notably, all Hydrogen and Helium lines appear strictly in absorption. A toy model shows that the observed emission line profiles can be reproduced by emission from a compact (radius < 0.3 au) disk seen at an inclination of ~24 degrees. Further evidence for the presence of circumstellar material comes from the detection of a moderate infrared excess in the SED, similar to those found in extreme debris disk systems. Conclusions. We conclude that HD 152384 is surrounded by a tenuous circumstellar disk which, although rich in refractory elements, is highly depleted of volatile elements. To the best of our knowledge such a disk is unique within the group of young stars. However, it is reminiscent of the disks seen in some white dwarfs, which have been attributed to the disruption of rocky planets. We suggest that the disk around HD 152384 may have a similar origin and may be due to collisions in a newly formed planetary system. △ Less

Submitted 25 May, 2021; v1 submitted 18 May, 2021; originally announced May 2021.

Comments: 5 pages, 5 figures, accepted for publication in A&A Letters

Journal ref: A&A 651, L11 (2021)

White dwarfs with planetary remnants in the era of Gaia I: six emission line systems

Authors: N. P. Gentile Fusillo, C. J. Manser, Boris T. Gänsicke, O. Toloza, D. Koester, E. Dennihy, W. R. Brown, J. Farihi, M. A. Hollands, M. J. Hoskin, P. Izquierdo, T. Kinnear, T. R. Marsh, A. Santamaria-Miranda, A. F. Pala, S. Redfield, P. Rodriguez-Gil, M. R. Schreiber, D. Veras, D. J. Wilson

Abstract: White dwarfs with emission lines from gaseous debris discs are among the rarest examples of planetary remnant hosts, but at the same time they are key objects for studying the final evolutionary stage of planetary systems. Making use of the large number of white dwarfs identified in Gaia DR2, we are conducting a survey of planetary remnants and here we present the first results of our search: six… ▽ More White dwarfs with emission lines from gaseous debris discs are among the rarest examples of planetary remnant hosts, but at the same time they are key objects for studying the final evolutionary stage of planetary systems. Making use of the large number of white dwarfs identified in Gaia DR2, we are conducting a survey of planetary remnants and here we present the first results of our search: six white dwarfs with gaseous debris discs. This first publication focuses on the main observational properties of these objects and highlights their most unique features. Three systems in particular stand out: WDJ084602.47+570328.64 displays an exceptionally strong infrared excess which defies the standard model of a geometrically-thin, optically-thick dusty debris disc; WDJ213350.72+242805.93 is the hottest gaseous debris disc host known with Teff=29282 K; and WDJ052914.32-340108.11, in which we identify a record number of 51 emission lines from five elements. These discoveries shed light on the underlying diversity in gaseous debris disc systems and bring the total number of these objects to 21. With these numbers we can now start looking at the properties of these systems as a class of objects rather than on a case-by-case basis. △ Less

Submitted 18 May, 2021; v1 submitted 26 October, 2020; originally announced October 2020.

Comments: 20 pages, 11 figures, accepted for publication in MNRAS. V2 replaced Fig.10 and minor changes to sections 4 and 7

Journal ref: 2021, MNRAS, 504, 2707

Five New Post-Main-Sequence Debris Disks with Gaseous Emission

Authors: Erik Dennihy, Siyi Xu, Samuel Lai, Amy Bonsor, J. C. Clemens, Patrick Dufour, Boris T. Gansicke, Nicola Pietro Gentile Fusillo, Francois Hardy, R. J. Hegedus, J. J. Hermes, B. C. Kaiser, Markus Kissler-Patig, Beth Klein, Christopher J. Manser, Joshua S. Reding

Abstract: Observations of debris disks, the products of the collisional evolution of rocky planetesimals, can be used to trace planetary activity across a wide range of stellar types. The most common end points of stellar evolution are no exception as debris disks have been observed around several dozen white dwarf stars. But instead of planetary formation, post-main-sequence debris disks are a signpost of… ▽ More Observations of debris disks, the products of the collisional evolution of rocky planetesimals, can be used to trace planetary activity across a wide range of stellar types. The most common end points of stellar evolution are no exception as debris disks have been observed around several dozen white dwarf stars. But instead of planetary formation, post-main-sequence debris disks are a signpost of planetary destruction, resulting in compact debris disks from the tidal disruption of remnant planetesimals. In this work, we present the discovery of five new debris disks around white dwarf stars with gaseous debris in emission. All five systems exhibit excess infrared radiation from dusty debris, emission lines from gaseous debris, and atmospheric absorption features indicating on-going accretion of metal-rich debris. In four of the systems, we detect multiple metal species in emission, some of which occur at strengths and transitions previously unseen in debris disks around white dwarf stars. Our first year of spectroscopic follow-up hints at strong variability in the emission lines that can be studied in the future, expanding the range of phenomena these post-main-sequence debris disks exhibit. △ Less

Submitted 19 October, 2020; v1 submitted 7 October, 2020; originally announced October 2020.

Comments: Accepted to ApJ, 22 pages, 14 figures. This replacement includes correction to erroneous systemic velocity values given in Table 1

Single magnetic white dwarfs with Balmer emission lines: A small class with consistent physical characteristics as possible signposts for close-in planetary companions

Authors: Boris T. Gaensicke, Pablo Rodriguez-Gil, Nicola P. Gentile Fusillo, Keith Inight, Matthias R. Schreiber, Anna F. Pala, Pier-Emmanuel Tremblay

Abstract: We report the identification of SDSS J121929.45+471522.8 as the third apparently isolated magnetic (B~18.5+/-1.0,MG) white dwarf exhibiting Zeeman-split Balmer emission lines. The star shows coherent variability at optical wavelengths with an amplitude of ~0.03mag and a period of 15.26h, which we interpret as the spin period of the white dwarf. Modelling the spectral energy distribution and Gaia p… ▽ More We report the identification of SDSS J121929.45+471522.8 as the third apparently isolated magnetic (B~18.5+/-1.0,MG) white dwarf exhibiting Zeeman-split Balmer emission lines. The star shows coherent variability at optical wavelengths with an amplitude of ~0.03mag and a period of 15.26h, which we interpret as the spin period of the white dwarf. Modelling the spectral energy distribution and Gaia parallax, we derive a white dwarf temperature of 7500+/-148K, a mass of 0.649+/-0.022Msun, and a cooling age of 1.5+/-0.1Gyr, as well as an upper limit on the temperature of a sub-stellar or giant planet companion of ~250K. The physical properties of this white dwarf match very closely those of the other two magnetic white dwarfs showing Balmer emission lines: GD356 and SDSS J125230.93$-$023417.7. We argue that, considering the growing evidence for planets and planetesimals on close orbits around white dwarfs, the unipolar inductor model provides a plausible scenario to explain the characteristics of this small class of stars. The tight clustering of the three stars in cooling age suggests a common mechanism switching the unipolar inductor on and off. Whereas Lorentz drift naturally limits the lifetime of the inductor phase, the relatively late onset of the line emission along the white dwarf cooling sequence remains unexplained. △ Less

Submitted 24 September, 2020; originally announced September 2020.

Comments: Accepted for publication in MNRAS, 10 pages, 6 figues

$\textit{Gaia}$ white dwarfs within 40 pc I: spectroscopic observations of new candidates

Authors: P. -E. Tremblay, M. A. Hollands, N. P. Gentile Fusillo, J. McCleery, P. Izquierdo, B. T. Gänsicke, E. Cukanovaite, D. Koester, W. R. Brown, S. Charpinet, T. Cunningham, J. Farihi, N. Giammichele, V. van Grootel, J. J. Hermes, M. J. Hoskin, S. Jordan, S. O. Kepler, S. J. Kleinman, C. J. Manser, T. R. Marsh, D. de Martino, A. Nitta, S. G. Parsons, I. Pelisoli , et al. (8 additional authors not shown)

Abstract: We present a spectroscopic survey of 230 white dwarf candidates within 40 pc of the Sun from the William Herschel Telescope and Gran Telescopio Canarias. All candidates were selected from $\textit{Gaia}$ Data Release 2 (DR2) and in almost all cases had no prior spectroscopic classifications. We find a total of 191 confirmed white dwarfs and 39 main-sequence star contaminants. The majority of stell… ▽ More We present a spectroscopic survey of 230 white dwarf candidates within 40 pc of the Sun from the William Herschel Telescope and Gran Telescopio Canarias. All candidates were selected from $\textit{Gaia}$ Data Release 2 (DR2) and in almost all cases had no prior spectroscopic classifications. We find a total of 191 confirmed white dwarfs and 39 main-sequence star contaminants. The majority of stellar remnants in the sample are relatively cool ($\langle T_{\rm eff} \rangle$ = 6200 K), showing either hydrogen Balmer lines or a featureless spectrum, corresponding to 89 DA and 76 DC white dwarfs, respectively. We also recover two DBA white dwarfs and 9--10 magnetic remnants. We find two carbon-bearing DQ stars and 14 new metal-rich white dwarfs. This includes the possible detection of the first ultra-cool white dwarf with metal lines. We describe three DZ stars for which we find at least four different metal species, including one which is strongly Fe- and Ni-rich, indicative of the accretion of a planetesimal with core-Earth composition. We find one extremely massive (1.31 $\pm$ 0.01 M$_{\odot}$) DA white dwarf showing weak Balmer lines, possibly indicating stellar magnetism. Another white dwarf shows strong Balmer line emission but no infrared excess, suggesting a low-mass sub-stellar companion. High spectroscopic completeness ($>$99%) has now been reached for $\textit{Gaia}$ DR2 sources within 40 pc sample, in the northern hemisphere ($δ>$ 0 deg) and located on the white dwarf cooling track in the Hertzsprung-Russell diagram. A statistical study of the full northern sample is presented in a companion paper. △ Less

Submitted 26 June, 2020; v1 submitted 1 June, 2020; originally announced June 2020.

Comments: 37 pages, 25 figures. Accepted for publication in MNRAS

$Gaia$ white dwarfs within 40 pc II: the volume-limited northern hemisphere sample

Authors: Jack McCleery, Pier-Emmanuel Tremblay, Nicola Pietro Gentile Fusillo, Mark A. Hollands, Boris T. Gänsicke, Paula Izquierdo, Silvia Toonen, Tim Cunningham, Alberto Rebassa-Mansergas

Abstract: We present an overview of the sample of northern hemisphere white dwarfs within 40 pc of the Sun detected from $Gaia$ Data Release 2 (DR2). We find that 521 sources are spectroscopically confirmed degenerate stars, 111 of which were first identified as white dwarf candidates from $Gaia$ DR2 and followed-up recently with the William Herschel Telescope and Gran Telescopio Canarias. Three additional… ▽ More We present an overview of the sample of northern hemisphere white dwarfs within 40 pc of the Sun detected from $Gaia$ Data Release 2 (DR2). We find that 521 sources are spectroscopically confirmed degenerate stars, 111 of which were first identified as white dwarf candidates from $Gaia$ DR2 and followed-up recently with the William Herschel Telescope and Gran Telescopio Canarias. Three additional white dwarf candidates remain spectroscopically unobserved and six unresolved binaries are known to include a white dwarf but were not in our initial selection of white dwarfs in the $Gaia$ DR2 Hertzsprung-Russell diagram (HRD). Atmospheric parameters are calculated from $Gaia$ and Pan-STARRS photometry for all objects in the sample, confirming most of the trends previously observed in the much smaller 20 pc sample. Local white dwarfs are overwhelmingly consistent with Galactic disc kinematics, with only four halo candidates. We find that DAZ white dwarfs are significantly less massive than the overall DA population ($\overline{M}_\mathrm{DAZ} = 0.59\,\mathrm{M}_\odot$, $\overline{M}_\mathrm{DA} = 0.66\,\mathrm{M}_\odot$). It may suggest that planet formation is less efficient at higher mass stars, producing more massive white dwarfs. We detect a sequence of crystallised white dwarfs in the mass range from $0.6\ \lesssim M/\mathrm{M}_\odot \lesssim\ 1.0\,$ and find that the vast majority of objects on the sequence have standard kinematic properties that correspond to the average of the sample, suggesting that their nature can be explained by crystallisation alone. We also detect 56 wide binaries including a white dwarf and 26 double degenerates. △ Less

Submitted 7 July, 2020; v1 submitted 1 June, 2020; originally announced June 2020.

Comments: 20 pages, 14 figures. Accepted for publication in MNRAS. Online tables available at http://deneb.astro.warwick.ac.uk/phrgwr/40pcTables/index.html

Spectroscopic and Photometric Periods of Six Ultracompact Accreting Binaries

Authors: Matthew J. Green, Thomas R. Marsh, Philip J. Carter, Danny Steeghs, Elmé Breedt, V. S. Dhillon, S. P. Littlefair, Steven G. Parsons, Paul Kerry, Nicola P. Gentile Fusillo, R. P. Ashley, Madelon C. P. Bours, Tim Cunningham, Martin J. Dyer, Boris T. Gänsicke, Paula Izquierdo, Anna F. Pala, Chuangwit Pattama, Sabrina Outmani, David I. Sahman, Boonchoo Sukaum, James Wild

Abstract: Ultracompact accreting binary systems each consist of a stellar remnant accreting helium-enriched material from a compact donor star. Such binaries include two related sub-classes, AM CVn-type binaries and helium cataclysmic variables, in both of which the central star is a white dwarf. We present a spectroscopic and photometric study of six accreting binaries with orbital periods in the range of… ▽ More Ultracompact accreting binary systems each consist of a stellar remnant accreting helium-enriched material from a compact donor star. Such binaries include two related sub-classes, AM CVn-type binaries and helium cataclysmic variables, in both of which the central star is a white dwarf. We present a spectroscopic and photometric study of six accreting binaries with orbital periods in the range of 40--70 min, including phase-resolved VLT spectroscopy and high-speed ULTRACAM photometry. Four of these are AM CVn systems and two are helium cataclysmic variables. For four of these binaries we are able to identify orbital periods (of which three are spectroscopic). SDSS J1505+0659 has an orbital period of 67.8 min, significantly longer than previously believed, and longer than any other known AM CVn binary. We identify a WISE infrared excess in SDSS J1505+0659 that we believe to be the first direct detection of an AM CVn donor star in a non-direct impacting binary. The mass ratio of SDSS J1505+0659 is consistent with a white dwarf donor. CRTS J1028-0819 has an orbital period of 52.1 min, the shortest period of any helium cataclysmic variable. MOA 2010-BLG-087 is co-aligned with a K-class star that dominates its spectrum. ASASSN-14ei and ASASSN-14mv both show a remarkable number of echo outbursts following superoutbursts (13 and 10 echo outbursts respectively). ASASSN-14ei shows an increased outburst rate over the years following its superoutburst, perhaps resulting from an increased accretion rate. △ Less

Submitted 26 May, 2020; originally announced May 2020.

Comments: 22 pages, 21 figures. Accepted for publication by MNRAS

The frequency of gaseous debris discs around white dwarfs

Authors: Christopher J. Manser, Boris T. Gänsicke, Nicola Pietro Gentile Fusillo, Richard Ashley, Elmé Breedt, Mark Hollands, Paula Izquierdo, Ingrid Pelisoli

Abstract: 1-3 per cent of white dwarfs are orbited by planetary dusty debris detectable as infrared emission in excess above the white dwarf flux. In a rare subset of these systems, a gaseous disc component is also detected via emission lines of the Ca II 8600Å triplet, broadened by the Keplerian velocity of the disc. We present the first statistical study of the fraction of debris discs containing detectab… ▽ More 1-3 per cent of white dwarfs are orbited by planetary dusty debris detectable as infrared emission in excess above the white dwarf flux. In a rare subset of these systems, a gaseous disc component is also detected via emission lines of the Ca II 8600Å triplet, broadened by the Keplerian velocity of the disc. We present the first statistical study of the fraction of debris discs containing detectable amounts of gas in emission at white dwarfs within a magnitude and signal-to-noise limited sample. We select 7705 single white dwarfs spectroscopically observed by the Sloan Digital Sky Survey (SDSS) and $Gaia$ with magnitudes $g$ $\leq$ 19. We identify five gaseous disc hosts, all of which have been previously discovered. We calculate the occurrence rate of a white dwarf hosting a debris disc detectable via Ca II emission lines as 0.067$\pm$$_{0.025}^{0.042}$ per cent. This corresponds to an occurrence rate for a dusty debris disc to have an observable gaseous component in emission as 4$\pm$$_{2}^{4}$ per cent. Given that variability is a common feature of the emission profiles of gaseous debris discs, and the recent detection of a planetesimal orbiting within the disc of SDSSJ122859.93+104032.9, we propose that gaseous components are tracers for the presence of planetesimals embedded in the discs and outline a qualitative model. We also present spectroscopy of the Ca II triplet 8600Å region for 20 white dwarfs hosting dusty debris discs in an attempt to identify gaseous emission. We do not detect any gaseous components in these 20 systems, consistent with the occurrence rate that we calculated. △ Less

Submitted 5 February, 2020; originally announced February 2020.

Comments: 13 pages, 6 Figures, accepted for publication in MNRAS

A Word to the WISE: Confusion is Unavoidable for WISE-selected Infrared Excesses

Authors: Erik Dennihy, Jay Farihi, Nicola Pietro Gentile Fusillo, John H. Debes

Abstract: Stars with excess infrared radiation from circumstellar dust are invaluable for studies of exoplanetary systems, informing our understanding on processes of planet formation and destruction alike. All-sky photometric surveys have made the identification of dusty infrared excess candidates trivial, however, samples that rely on data from WISE are plagued with source confusion, leading to high false… ▽ More Stars with excess infrared radiation from circumstellar dust are invaluable for studies of exoplanetary systems, informing our understanding on processes of planet formation and destruction alike. All-sky photometric surveys have made the identification of dusty infrared excess candidates trivial, however, samples that rely on data from WISE are plagued with source confusion, leading to high false positive rates. Techniques to limit its contribution to WISE-selected samples have been developed, and their effectiveness is even more important as we near the end-of-life of Spitzer, the only facility capable of confirming the excess. Here, we present a Spitzer follow-up of a sample of 22 WISE-selected infrared excess candidates near the faint-end of the WISE detection limits. Eight of the 22 excesses are deemed the result of source confusion, with the remaining candidates all confirmed by the Spitzer data. We consider the efficacy of ground-based near-infrared imaging and astrometric filtering of samples to limit confusion among the sample. We find that both techniques are worthwhile for vetting candidates, but fail to identify all of the confused excesses, indicating that they cannot be used to confirm WISE-selected infrared excess candidates, but only to rule them out. This result confirms the expectation that WISE-selected infrared excess samples will always suffer from appreciable levels of contamination, and that care should be taken in their interpretation regardless of the filters applied. △ Less

Submitted 3 February, 2020; originally announced February 2020.

Comments: 13 pages, 4 Figures; Accepted for publication in ApJ

Accretion of a giant planet onto a white dwarf

Authors: Boris T. Gaensicke, Matthias R. Schreiber, Odette Toloza, Nicola P. Gentile Fusillo, Detlev Koester, Christopher J. Manser

Abstract: The detection of a dust disc around G29-38 and transits from debris orbiting WD1145+017 confirmed that the photospheric trace metals found in many white dwarfs arise from the accretion of tidally disrupted planetesimals. The composition of these planetesimals is similar to that of rocky bodies in the inner solar system. Gravitationally scattering planetesimals towards the white dwarf requires the… ▽ More The detection of a dust disc around G29-38 and transits from debris orbiting WD1145+017 confirmed that the photospheric trace metals found in many white dwarfs arise from the accretion of tidally disrupted planetesimals. The composition of these planetesimals is similar to that of rocky bodies in the inner solar system. Gravitationally scattering planetesimals towards the white dwarf requires the presence of more massive bodies, yet no planet has so far been detected at a white dwarf. Here we report optical spectroscopy of a $\simeq27\,750$K hot white dwarf that is accreting from a circumstellar gaseous disc composed of hydrogen, oxygen, and sulphur at a rate of $\simeq3.3\times10^9\,\mathrm{g\,s^{-1}}$. The composition of this disc is unlike all other known planetary debris around white dwarfs, but resembles predictions for the makeup of deeper atmospheric layers of icy giant planets, with H$_2$O and H$_2$S being major constituents. A giant planet orbiting a hot white dwarf with a semi-major axis of $\simeq15$ solar radii will undergo significant evaporation with expected mass loss rates comparable to the accretion rate onto the white dwarf. The orbit of the planet is most likely the result of gravitational interactions, indicating the presence of additional planets in the system. We infer an occurrence rate of spectroscopically detectable giant planets in close orbits around white dwarfs of $\simeq10^{-4}$. △ Less

Submitted 3 December, 2019; originally announced December 2019.

Comments: Nature, December 5 issue

From Hydrogen to Helium: The Spectral Evolution of White Dwarfs as Evidence for Convective Mixing

Authors: Tim Cunningham, Pier-Emmanuel Tremblay, Nicola Pietro Gentile Fusillo, Mark Hollands, Elena Cukanovaite

Abstract: We present a study of the hypothesis that white dwarfs undergo a spectral change from hydrogen- to helium-dominated atmospheres using a volume-limited photometric sample drawn from the $Gaia$ DR2 catalogue, the Sloan Digital Sky Survey (SDSS) and the $Galaxy~Evolution~Explorer$ (GALEX). We exploit the strength of the Balmer jump in hydrogen-atmosphere DA white dwarfs to separate them from helium-d… ▽ More We present a study of the hypothesis that white dwarfs undergo a spectral change from hydrogen- to helium-dominated atmospheres using a volume-limited photometric sample drawn from the $Gaia$ DR2 catalogue, the Sloan Digital Sky Survey (SDSS) and the $Galaxy~Evolution~Explorer$ (GALEX). We exploit the strength of the Balmer jump in hydrogen-atmosphere DA white dwarfs to separate them from helium-dominated objects in SDSS colour space. Across the effective temperature range from 20000K to 9000K we find that 22% of white dwarfs will undergo a spectral change, with no spectral evolution being ruled out at 5$σ$. The most likely explanation is that the increase in He-rich objects is caused by the convective mixing of DA stars with thin hydrogen layers, in which helium is dredged up from deeper layers by a surface hydrogen convection zone. The rate of change in the fraction of He-rich objects as a function of temperature, coupled with a recent grid of 3D radiation-hydrodynamic simulations of convective DA white dwarfs - which include the full overshoot region - lead to a discussion on the distribution of total hydrogen mass in white dwarfs. We find that 60% of white dwarfs must have a hydrogen mass larger than $M_{\rm H}/M_{\rm WD} = 10^{-10}$, another 25% have masses in the range $M_{\rm H}/M_{\rm WD} = 10^{-14}-10^{-10}$, and 15% have less hydrogen than $M_{\rm H}/M_{\rm WD} = 10^{-14}$. These results have implications for white dwarf asteroseismology, stellar evolution through the asymptotic giant branch (AGB) and accretion of planetesimals onto white dwarfs. △ Less

Submitted 21 January, 2020; v1 submitted 31 October, 2019; originally announced November 2019.

Comments: 14 pages, 13 figures, accepted for publication in MNRAS

Orbital Decay in a 20 Minute Orbital Period Detached Binary with a Hydrogen Poor Low Mass White Dwarf

Authors: Kevin B Burdge, Jim Fuller, E. Sterl Phinney, Jan van Roestel, Antonio Claret, Elena Cukanovaite, Nicola Pietro Gentile Fusillo, Michael W. Coughlin, David L. Kaplan, Thomas Kupfer, Pier-Emmanuel Tremblay, Richard G. Dekany, Dmitry A. Duev, Michael Feeney, Reed Riddle, S. R. Kulkarni, Thomas A. Prince

Abstract: We report the discovery of a detached double white dwarf binary with an orbital period of $\approx20.6\,\rm minutes$, PTF J053332.05+020911.6. The visible object in this binary, PTF J0533+0209B, is a $\approx 0.17\,M_\odot$ mass white dwarf with a helium-dominated atmosphere containing traces of hydrogen (DBA). This object exhibits ellipsoidal variations due to tidal deformation, and is the visibl… ▽ More We report the discovery of a detached double white dwarf binary with an orbital period of $\approx20.6\,\rm minutes$, PTF J053332.05+020911.6. The visible object in this binary, PTF J0533+0209B, is a $\approx 0.17\,M_\odot$ mass white dwarf with a helium-dominated atmosphere containing traces of hydrogen (DBA). This object exhibits ellipsoidal variations due to tidal deformation, and is the visible component in a single-lined spectroscopic binary with a velocity semi-amplitude of $K_B=618.7\pm6.9 \, \rm km \, s^{-1}$. We have detected significant orbital decay due to the emission of gravitational radiation, and we expect that the Laser Interferometer Space Antenna (LISA) will detect this system with a signal to noise of $8.4^{+4.2}_{-3.0}$ after four years of operation. Because this system already has a well determined orbital period, radial velocity semi-amplitude, temperature, atmospheric composition, surface gravity, and orbital decay rate, a LISA signal will help fully constrain the properties of this system by providing a direct measurement of its inclination. Thus, this binary demonstrates the synergy between electromagnetic and gravitational radiation for constraining the physical properties of an astrophysical object. △ Less

Submitted 15 November, 2019; v1 submitted 24 October, 2019; originally announced October 2019.

Comments: 12 pages, 9 figures, 3 tables. Published online by the Astrophysical Journal Letters November 15, 2019

Journal ref: ApJL 886 L12 (2019)

Cool white dwarfs as standards for infrared observations

Authors: Nicola Pietro Gentile Fusillo, Pier-Emmanuel Tremblay, Ralph C. Bohlin, Susana E. Deustua, Jason S. Kalirai

Abstract: In the era of modern digital sky surveys, uncertainties in the flux of stellar standards are commonly the dominant systematic error in photometric calibration and can often affect the results of higher-level experiments. The Hubble Space Telescope (HST) spectrophotometry, which is based on computed model atmospheres for three hot (Teff > 30,000 K) pure-hydrogen (DA) white dwarfs, is currently cons… ▽ More In the era of modern digital sky surveys, uncertainties in the flux of stellar standards are commonly the dominant systematic error in photometric calibration and can often affect the results of higher-level experiments. The Hubble Space Telescope (HST) spectrophotometry, which is based on computed model atmospheres for three hot (Teff > 30,000 K) pure-hydrogen (DA) white dwarfs, is currently considered the most reliable and internally consistent flux calibration. However many next generation facilities (e.g. Harmoni on E-ELT, Euclid and JWST) will focus on IR observations, a regime in which white dwarf calibration has not yet been robustly tested. Cool DA white dwarfs have energy distributions that peak close to the optical or near-IR, do not have shortcomings from UV metal line blanketing, and have a reasonably large sky density ($\simeq$ 4 deg$^{-2}$ at G < 20), making them, potentially, excellent calibrators. Here we present a pilot study based on STIS+WFC3 observations of two bright DA white dwarfs to test whether targets cooler than current hot primary standards (Teff < 20,000 K) are consistent with the HST flux scale. We also test the robustness of white dwarf models in the IR regime from an X-shooter analysis of Paschen lines and by cross-matching our previously derived Gaia white dwarf catalogue with observations obtained with 2MASS, UKIDSS, VHS, and WISE. △ Less

Submitted 17 October, 2019; originally announced October 2019.

Comments: 12 pages, 8 figures, 2 tables. Accepted for publication in MNRAS. The best fitting models to the two white dwarfs analyzed are available from \<http://deneb.astro.warwick.ac.uk/phrhcc/WD_models.tar>

Core crystallization and pile-up in the cooling sequence of evolving white dwarfs

Authors: Pier-Emmanuel Tremblay, Gilles Fontaine, Nicola Pietro Gentile Fusillo, Bart H. Dunlap, Boris T. Gänsicke, Mark A. Hollands, J. J. Hermes, Thomas R. Marsh, Elena Cukanovaite, Tim Cunningham

Abstract: White dwarfs are stellar embers depleted of nuclear energy sources that cool over billions of years. These stars, which are supported by electron degeneracy pressure, reach densities of 1e7 grams per cubic centimetre in their cores. It has been predicted that a first-order phase transition occurs during white-dwarf cooling, leading to the crystallization of the non-degenerate carbon and oxygen ion… ▽ More White dwarfs are stellar embers depleted of nuclear energy sources that cool over billions of years. These stars, which are supported by electron degeneracy pressure, reach densities of 1e7 grams per cubic centimetre in their cores. It has been predicted that a first-order phase transition occurs during white-dwarf cooling, leading to the crystallization of the non-degenerate carbon and oxygen ions in the core, which releases a considerable amount of latent heat and delays the cooling process by about one billion years. However, no direct observational evidence of this effect has been reported so far. Here we report the presence of a pile-up in the cooling sequence of evolving white dwarfs within 100 parsecs of the Sun, determined using photometry and parallax data from the Gaia satellite. Using modelling, we infer that this pile-up arises from the release of latent heat as the cores of the white dwarfs crystallize. In addition to the release of latent heat, we find strong evidence that cooling is further slowed by the liberation of gravitational energy from element sedimentation in the crystallizing cores. Our results describe the energy released by crystallization in strongly coupled Coulomb plasmas, and the measured cooling delays could help to improve the accuracy of methods used to determine the age of stellar populations from white dwarfs. △ Less

Submitted 1 August, 2019; originally announced August 2019.

Comments: 17 pages, author accepted version. Published in Nature 9 January 2019

Journal ref: Nature, Volume 565, Issue 7738, 2019, p. 202-205

A Volume Limited Sample of Cataclysmic Variables from $\mathit{Gaia}$ DR2: Space Density and Population Properties

Authors: A. F. Pala, B. T. Gänsicke, E. Breedt, C. Knigge, J. J. Hermes, N. P. Gentile Fusillo, M. A. Hollands, T. Naylor, I. Pelisoli, M. R. Schreiber, S. Toonen, A. Aungwerojwit, E. Cukanovaite, E. Dennihy, C. J. Manser, M. L. Pretorius, S. Scaringi, O. Toloza

Abstract: We present the first volume-limited sample of cataclysmic variables (CVs), selected using the accurate parallaxes provided by the second data release (DR2) of the ESA $\mathit{Gaia}$ space mission. The sample is composed of 42 CVs within $150\,$pc, including two new systems discovered using the $\mathit{Gaia}$ data, and is $(77 \pm 10)\,$per cent complete. We use this sample to study the intrinsic… ▽ More We present the first volume-limited sample of cataclysmic variables (CVs), selected using the accurate parallaxes provided by the second data release (DR2) of the ESA $\mathit{Gaia}$ space mission. The sample is composed of 42 CVs within $150\,$pc, including two new systems discovered using the $\mathit{Gaia}$ data, and is $(77 \pm 10)\,$per cent complete. We use this sample to study the intrinsic properties of the Galactic CV population. In particular, the CV space density we derive, $ρ=(4.8^{+0.6}_{-0.8}) \times10^{-6}\,\mathrm{pc}^{-3}$, is lower than predicted by most binary population synthesis studies. We also find a low fraction of period bounce CVs, seven per cent, and an average white dwarf mass of $\langle M_\mathrm{WD} \rangle = (0.83 \pm 0.17)\,\mathrm{M}_\odot$. Both findings confirm previous results, ruling out the presence of observational biases affecting these measurements, as has been suggested in the past. The observed fraction of period bounce CVs falls well below theoretical predictions, by at least a factor of five, and remains one of the open problems in the current understanding of CV evolution. Conversely, the average white dwarf mass supports the presence of additional mechanisms of angular momentum loss that have been accounted for in the latest evolutionary models. The fraction of magnetic CVs in the $150\,$pc sample is remarkably high at $36\,$per cent. This is in striking contrast with the absence of magnetic white dwarfs in the detached population of CV progenitors, and underlines that the evolution of magnetic systems has to be included in the next generation of population models. △ Less

Submitted 6 May, 2020; v1 submitted 30 July, 2019; originally announced July 2019.

Comments: Published in MNRAS. Definitive version. A typo in Table 6 (space density of novalikes) has been corrected

Partly burnt runaway stellar remnants from peculiar thermonuclear supernovae

Authors: R. Raddi, M. A. Hollands, D. Koester, J. J. Hermes, B. T. Gaensicke, U. Heber, K. J. Shen, D. M. Townsley, A. F. Pala, J. S. Reding, O. F. Toloza, I. Pelisoli, S. Geier, N. P. Gentile Fusillo, U. Munari, J. Strader

Abstract: We report the discovery of three stars that, along with the prototype LP40-365, form a distinct class of chemically peculiar runaway stars that are the survivors of thermonuclear explosions. Spectroscopy of the four confirmed LP 40-365 stars finds ONe-dominated atmospheres enriched with remarkably similar amounts of nuclear ashes of partial O- and Si-burning. Kinematic evidence is consistent with… ▽ More We report the discovery of three stars that, along with the prototype LP40-365, form a distinct class of chemically peculiar runaway stars that are the survivors of thermonuclear explosions. Spectroscopy of the four confirmed LP 40-365 stars finds ONe-dominated atmospheres enriched with remarkably similar amounts of nuclear ashes of partial O- and Si-burning. Kinematic evidence is consistent with ejection from a binary supernova progenitor; at least two stars have rest-frame velocities indicating they are unbound to the Galaxy. With masses and radii ranging between 0.20-0.28 Msun and 0.16-0.60 Rsun, respectively, we speculate these inflated white dwarfs are the partly burnt remnants of either peculiar Type Iax or electron-capture supernovae. Adopting supernova rates from the literature, we estimate that ~20 LP40-365 stars brighter than 19 mag should be detectable within 2 kpc from the Sun at the end of the Gaia mission. We suggest that as they cool, these stars will evolve in their spectroscopic appearance, and eventually become peculiar O-rich white dwarfs. Finally, we stress that the discovery of new LP40-365 stars will be useful to further constrain their evolution, supplying key boundary conditions to the modelling of explosion mechanisms, supernova rates, and nucleosynthetic yields of peculiar thermonuclear explosions. △ Less

Submitted 7 June, 2019; v1 submitted 13 February, 2019; originally announced February 2019.

Comments: 22 pages, 14 figures, 6 tables. Accepted for publication on MNRAS

Discovery of the first resolved triple white dwarf

Authors: M. Perpinyà-Vallès, A. Rebassa-Mansergas, B. T. Gänsicke, S. Toonen, J. J. Hermes, N. P. Gentile Fusillo, P. -E. Tremblay

Abstract: We report the discovery of J1953-1019, the first resolved triple white dwarf system. The triplet consists of an inner white dwarf binary and a wider companion. Using Gaia DR2 photometry and astrometry combined with our follow-up spectroscopy, we derive effective temperatures, surface gravities, masses and cooling ages of the three components. All three white dwarfs have pure-hydrogen (DA) atmosphe… ▽ More We report the discovery of J1953-1019, the first resolved triple white dwarf system. The triplet consists of an inner white dwarf binary and a wider companion. Using Gaia DR2 photometry and astrometry combined with our follow-up spectroscopy, we derive effective temperatures, surface gravities, masses and cooling ages of the three components. All three white dwarfs have pure-hydrogen (DA) atmospheres, masses of 0.60-0.63 Msun and cooling ages of 40-290 Myr. We adopt eight initial-to-final mass relations to estimate the main sequence progenitor masses (which we find to be similar for the three components, 1.6-2.6 Msun) and lifetimes. The differences between the derived cooling times and main sequence lifetimes agree for most of the adopted initial-to-final mass relations, hence the three white dwarfs in J1953-1019 are consistent with coeval evolution. Furthermore, we calculate the projected orbital separations of the inner white dwarf binary (303.25 +- 0.01 au) and of the centre of mass of the inner binary and the outer companion (6398.97 +- 0.09 au). From these values, and taking into account a wide range of possible configurations for the triplet to be currently dynamically stable, we analyse the future evolution of the system. We find that a collision between the two inner white dwarfs due to Lidov-Kozai oscillations is unlikely, though if it occurs it could result in a sub-Chandrasekhar Type Ia supernova explosion. △ Less

Submitted 19 November, 2018; originally announced November 2018.

Comments: accepted for publication by MNRAS

Fundamental parameter accuracy of DA and DB white dwarfs in Gaia Data Release 2

Authors: P. -E. Tremblay, E. Cukanovaite, N. P. Gentile Fusillo, T. Cunningham, M. Hollands

Abstract: We report on a comparison of spectroscopic analyses for hydrogen (DA) and helium atmosphere (DB) white dwarfs with Gaia Data Release 2 (DR2) parallaxes and photometry. We assume a reddening law and a mass-radius relation to connect the effective temperatures (Teff) and surface gravities (log g) to masses and radii. This allows the comparison of two largely independent sets of fundamental parameter… ▽ More We report on a comparison of spectroscopic analyses for hydrogen (DA) and helium atmosphere (DB) white dwarfs with Gaia Data Release 2 (DR2) parallaxes and photometry. We assume a reddening law and a mass-radius relation to connect the effective temperatures (Teff) and surface gravities (log g) to masses and radii. This allows the comparison of two largely independent sets of fundamental parameters for 7039 DA and 521 DB stars with high-quality observations. This subset of the Gaia white dwarf sample is large enough to detect systematic trends in the derived parameters. We find that spectroscopic and photometric parameters generally agree within uncertainties when the expectation of a single star is verified. Gaia allows the identification of a small systematic offset in the temperature scale between the two techniques, as well as confirming a small residual high-mass bump in the DA mass distribution around 11,000-13,000 K. This assessment of the accuracy of white dwarf fundamental parameters derived from Gaia is a first step in understanding systematic effects in related astrophysical applications such as the derivation of the local stellar formation history, initial-to-final mass relation, and statistics of evolved planetary systems. △ Less

Submitted 7 November, 2018; originally announced November 2018.

Comments: 13 pages, 13 figures, accepted for publication in MNRAS

The population of hot subdwarf stars studied with Gaia II. The Gaia DR2 catalogue of hot subluminous stars

Authors: S. Geier, R. Raddi, N. P. Gentile Fusillo, T. R. Marsh

Abstract: Based on data from the ESA Gaia Data Release 2 (DR2) and several ground-based, multi-band photometry surveys we compiled an all-sky catalogue of $39\,800$ hot subluminous star candidates selected in Gaia DR2 by means of colour, absolute magnitude and reduced proper motion cuts. We expect the majority of the candidates to be hot subdwarf stars of spectral type B and O, followed by blue horizontal b… ▽ More Based on data from the ESA Gaia Data Release 2 (DR2) and several ground-based, multi-band photometry surveys we compiled an all-sky catalogue of $39\,800$ hot subluminous star candidates selected in Gaia DR2 by means of colour, absolute magnitude and reduced proper motion cuts. We expect the majority of the candidates to be hot subdwarf stars of spectral type B and O, followed by blue horizontal branch stars of late B-type (HBB), hot post-AGB stars, and central stars of planetary nebulae. The contamination by cooler stars should be about $10\%$. The catalogue is magnitude limited to Gaia $G<19\,{\rm mag}$ and covers the whole sky. Except within the Galactic plane and LMC/SMC regions, we expect the catalogue to be almost complete up to about $1.5\,{\rm kpc}$. The main purpose of this catalogue is to serve as input target list for the large-scale photometric and spectroscopic surveys which are ongoing or scheduled to start in the coming years. In the long run, securing a statistically significant sample of spectroscopically confirmed hot subluminous stars is key to advance towards a more detailed understanding of the latest stages of stellar evolution for single and binary stars. △ Less

Submitted 22 October, 2018; originally announced October 2018.

Comments: 13 pages, A&A, accepted

A $Gaia$ Data Release 2 catalogue of white dwarfs and a comparison with SDSS

Authors: Nicola Pietro Gentile Fusillo, Pier-Emmanuel Tremblay, Boris T. Gänsicke, Christopher J. Manser, Tim Cunningham, Elena Cukanovaite, Mark Hollands, Thomas Marsh, Roberto Raddi, Stefan Jordan, Silvia Toonen, Stephan Geier, Martin Barstow, Jeffrey D. Cummings

Abstract: We present a catalogue of white dwarf candidates selected from the second data release of $Gaia$ (DR2). We used a sample of spectroscopically confirmed white dwarfs from the Sloan Digital Sky Survey (SDSS) to map the entire space spanned by these objects in the $Gaia$ Hertzsprung-Russell diagram. We then defined a set of cuts in absolute magnitude, colour, and a number of $Gaia$ quality flags to r… ▽ More We present a catalogue of white dwarf candidates selected from the second data release of $Gaia$ (DR2). We used a sample of spectroscopically confirmed white dwarfs from the Sloan Digital Sky Survey (SDSS) to map the entire space spanned by these objects in the $Gaia$ Hertzsprung-Russell diagram. We then defined a set of cuts in absolute magnitude, colour, and a number of $Gaia$ quality flags to remove the majority of contaminating objects. Finally, we adopt a method analogous to the one presented in our earlier SDSS photometric catalogues to calculate a probability of being a white dwarf ($P_{\mathrm{WD}}$) for all $Gaia$ sources which passed the initial selection. The final catalogue is composed of $486\,641$ stars with calculated $P_{\mathrm{WD}}$ from which it is possible to select a sample of $\simeq 260\,000$ high-confidence white dwarf candidates in the magnitude range $8<G<21$. By comparing this catalogue with a sample of SDSS white dwarf candidates we estimate an upper limit in completeness of $85$ per cent for white dwarfs with $G \leq 20$ mag and $T_{\mathrm{eff}} > 7000$ K, at high Galactic latitudes ($|b|>20^{\circ}$). However, the completeness drops at low Galactic latitudes, and the magnitude limit of the catalogue varies significantly across the sky as a function of $Gaia$'s scanning law. We also provide the list of objects within our sample with available SDSS spectroscopy. We use this spectroscopic sample to characterise the observed structure of the white dwarf distribution in the H-R diagram. △ Less

Submitted 5 November, 2018; v1 submitted 9 July, 2018; originally announced July 2018.

Comments: 23 pages, 21 figures, 4 tables. Accepted for publication in MNRAS. Version 3 accepted. Gaia DR2 catalogue of white dwarf candidates available <https://warwick.ac.uk/fac/sci/physics/research/astro/research/catalogues/gaia_dr2_white_dwarf_candidates_v2.csv>. SDSS spectra sample available <https://warwick.ac.uk/fac/sci/physics/research/astro/research/catalogues/gaia-sdss_white_dwarf_catalogue_v2.csv>

Anatomy of the hyper-runaway star LP 40-365 with Gaia

Authors: R. Raddi, M. A. Hollands, B. T. Gaensicke, D. M. Townsley, J. J. Hermes, N. P. Gentile Fusillo, D. Koester

Abstract: LP 40-365 (aka GD 492) is a nearby low-luminosity hyper-runaway star with an extremely unusual atmospheric composition, which has been proposed as the remnant of a white dwarf that survived a subluminous Type Ia supernova (SN Ia) in a single-degenerate scenario. Adopting the Gaia Data Release (DR2) parallax, 1.58 +/- 0.03 mas, we estimate a radius of 0.18 +/- 0.01 Rsun, confirming LP 40-365 as a s… ▽ More LP 40-365 (aka GD 492) is a nearby low-luminosity hyper-runaway star with an extremely unusual atmospheric composition, which has been proposed as the remnant of a white dwarf that survived a subluminous Type Ia supernova (SN Ia) in a single-degenerate scenario. Adopting the Gaia Data Release (DR2) parallax, 1.58 +/- 0.03 mas, we estimate a radius of 0.18 +/- 0.01 Rsun, confirming LP 40-365 as a subluminous star that is ~ 15 times larger than a typical white dwarf and is compatible with the SN Ia remnant scenario. We present an updated kinematic analysis, making use of the Gaia parallax and proper motion, and confirm that Lp 40-365 is leaving the Milky Way at about 1.5 times the escape velocity of the Solar neighbourhood with a rest-frame velocity of 852 +/- 10 km/s. Integrating the past trajectories of LP 40-365, we confirm it crossed the Galactic disc 5.0 +/- 0.3 Myr ago in the direction of Carina, likely coming from beneath the plane. Finally, we estimate that LP 40-365 was ejected from its progenitor binary with a velocity of at least 600 km/s, which is compatible with theoretical predictions for close binaries containing a white dwarf and a helium-star donor. △ Less

Submitted 8 June, 2018; v1 submitted 25 April, 2018; originally announced April 2018.

Comments: 6 pages, 4 figures, 1 table. Accepted for publication on MNRAS

A 15.7-Minute AM CVn Binary Discovered in K2

Authors: M. J. Green, J. J. Hermes, T. R. Marsh, D. T. H. Steeghs, Keaton J. Bell, S. P. Littlefair, S. G. Parsons, E. Dennihy, J. T. Fuchs, J. S. Reding, B. C. Kaiser, R. P. Ashley, E. Breedt, V. S. Dhillon, N. P. Gentile Fusillo, P. Kerry, D. I. Sahman

Abstract: We present the discovery of SDSS J135154.46-064309.0, a short-period variable observed using 30-minute cadence photometry in K2 Campaign 6. Follow-up spectroscopy and high-speed photometry support a classification as a new member of the rare class of ultracompact accreting binaries known as AM CVn stars. The spectroscopic orbital period of $15.65 \pm 0.12$\,minutes makes this system the fourth-sho… ▽ More We present the discovery of SDSS J135154.46-064309.0, a short-period variable observed using 30-minute cadence photometry in K2 Campaign 6. Follow-up spectroscopy and high-speed photometry support a classification as a new member of the rare class of ultracompact accreting binaries known as AM CVn stars. The spectroscopic orbital period of $15.65 \pm 0.12$\,minutes makes this system the fourth-shortest period AM CVn known, and the second system of this type to be discovered by the Kepler spacecraft. The K2 data show photometric periods at $15.7306 \pm 0.0003$\,minutes, $16.1121 \pm 0.0004$\,minutes and $664.82 \pm 0.06$\,minutes, which we identify as the orbital period, superhump period, and disc precession period, respectively. From the superhump and orbital periods we estimate the binary mass ratio $q = M_2/M_1 = 0.111 \pm 0.005$, though this method of mass ratio determination may not be well calibrated for helium-dominated binaries. This system is likely to be a bright foreground source of gravitational waves in the frequency range detectable by LISA, and may be of use as a calibration source if future studies are able to constrain the masses of its stellar components. △ Less

Submitted 19 April, 2018; originally announced April 2018.

Comments: 13 pages, 11 figures

Meet the family - the catalog of known hot subdwarf stars

Authors: Stephan Geier, Roy H. Østensen, Peter Nemeth, Ulrich Heber, Nicola P. Gentile Fusillo, Boris T. Gänsicke, John H. Telting, Elizabeth M. Green, Johannes Schaffenroth

Abstract: In preparation for the upcoming all-sky data releases of the Gaia mission, we compiled a catalog of known hot subdwarf stars and candidates drawn from the literature and yet unpublished databases. The catalog contains 5613 unique sources and provides multi-band photometry from the ultraviolet to the far infrared, ground based proper motions, classifications based on spectroscopy and colors, publis… ▽ More In preparation for the upcoming all-sky data releases of the Gaia mission, we compiled a catalog of known hot subdwarf stars and candidates drawn from the literature and yet unpublished databases. The catalog contains 5613 unique sources and provides multi-band photometry from the ultraviolet to the far infrared, ground based proper motions, classifications based on spectroscopy and colors, published atmospheric parameters, radial velocities and light curve variability information. Using several different techniques, we removed outliers and misclassified objects. By matching this catalog with astrometric and photometric data from the Gaia mission, we will develop selection criteria to construct a homogeneous, magnitude-limited all-sky catalog of hot subdwarf stars based on Gaia data. As first application of the catalog data, we present the quantitative spectral analysis of 280 sdB and sdOB stars from the Sloan Digital Sky Survey Data Release 7. Combining our derived parameters with state-of-the-art proper motions, we performed a full kinematic analysis of our sample. This allowed us to separate the first significantly large sample of 78 sdBs and sdOBs belonging to the Galactic halo. Comparing the properties of hot subdwarfs from the disk and the halo with hot subdwarf samples from the globular clusters $ω$ Cen and NGC 2808, we found the fraction of intermediate He-sdOBs in the field halo population to be significantly smaller than in the globular clusters. △ Less

Submitted 6 November, 2017; originally announced November 2017.

Comments: 5 pages, to appear in the Proceedings of the 8th Meeting on Hot Subdwarf Stars and Related Objects, 9. to 15. July 2017, Cracow, Poland. Eds. A. Baran, A. E. Lynas-Gray, Open Astronomy, in press

Can magnetic fields suppress convection in the atmosphere of cool white dwarfs? A case study on WD2105-820

Authors: Nicola Pietro Gentile Fusillo, Pier-Emmanuel Tremblay, Stefan Jordan, Boris T. Gänsicke, Jason S. Kalirai, Jeffrey Cummings

Abstract: Around 10% of white dwarfs exhibit global magnetic structures with fields ranging from 1 kG to hundreds of MG. Recently, the first radiation magnetohydrodynamics simulations of the atmosphere of white dwarfs showed that convection should be suppressed in their photospheres for magnetic fields with strengths B $\gtrsim$ 50 kG. These predictions are in agreement with our knowledge of stellar physics… ▽ More Around 10% of white dwarfs exhibit global magnetic structures with fields ranging from 1 kG to hundreds of MG. Recently, the first radiation magnetohydrodynamics simulations of the atmosphere of white dwarfs showed that convection should be suppressed in their photospheres for magnetic fields with strengths B $\gtrsim$ 50 kG. These predictions are in agreement with our knowledge of stellar physics (e.g. energy transfer in strong magnetic field regions of the solar photosphere), but have yet to be directly confirmed from white dwarf observations. We obtained COS far-UV spectroscopy of the weakly magnetic, hydrogen-atmosphere, white dwarf WD2105-820 and of three additional non-magnetic, convective remnants (all in the $T_{\mathrm{eff}}$ range 9000-11,000 K). We fitted both the COS and the already available optical spectra with convective and radiative atmospheric models. As expected, we find that for two of the non-magnetic comparison stars only convective model fits predict consistent $T_{\mathrm{eff}}$ values from both the optical and the FUV spectra. In contrast, for WD2105-820 only the best fitting radiative model produced consistent results. △ Less

Submitted 5 October, 2017; originally announced October 2017.

Comments: 8 pages, 7 figures, 1 table, accepted for publication in MNRAS

White Dwarf Rotation as a Function of Mass and a Dichotomy of Mode Linewidths: Kepler Observations of 27 Pulsating DA White Dwarfs Through K2 Campaign 8

Authors: J. J. Hermes, B. T. Gaensicke, Steven D. Kawaler, S. Greiss, P. -E. Tremblay, Nicola Pietro Gentile Fusillo, R. Raddi, S. M. Fanale, Keaton J. Bell, E. Dennihy, J. T. Fuchs, B. H. Dunlap, J. C. Clemens, M. H. Montgomery, D. E. Winget, P. Chote, T. R. Marsh, S. Redfield

Abstract: We present photometry and spectroscopy for 27 pulsating hydrogen-atmosphere white dwarfs (DAVs, a.k.a. ZZ Ceti stars) observed by the Kepler space telescope up to K2 Campaign 8, an extensive compilation of observations with unprecedented duration (>75 days) and duty cycle (>90%). The space-based photometry reveals pulsation properties previously inaccessible to ground-based observations. We observ… ▽ More We present photometry and spectroscopy for 27 pulsating hydrogen-atmosphere white dwarfs (DAVs, a.k.a. ZZ Ceti stars) observed by the Kepler space telescope up to K2 Campaign 8, an extensive compilation of observations with unprecedented duration (>75 days) and duty cycle (>90%). The space-based photometry reveals pulsation properties previously inaccessible to ground-based observations. We observe a sharp dichotomy in oscillation mode linewidths at roughly 800 s, such that white dwarf pulsations with periods exceeding 800 s have substantially broader mode linewidths, more reminiscent of a damped harmonic oscillator than a heat-driven pulsator. Extended Kepler coverage also permits extensive mode identification: We identify the spherical degree of 61 out of 154 unique radial orders, providing direct constraints of the rotation period for 20 of these 27 DAVs, more than doubling the number of white dwarfs with rotation periods determined via asteroseismology. We also obtain spectroscopy from 4m-class telescopes for all DAVs with Kepler photometry. Using these homogeneously analyzed spectra we estimate the overall mass of all 27 DAVs, which allows us to measure white dwarf rotation as a function of mass, constraining the endpoints of angular momentum in low- and intermediate-mass stars. We find that 0.51-to-0.73-solar-mass white dwarfs, which evolved from 1.7-to-3.0-solar-mass ZAMS progenitors, have a mean rotation period of 35 hr with a standard deviation of 28 hr, with notable exceptions for higher-mass white dwarfs. Finally, we announce an online repository for our Kepler data and follow-up spectroscopy, which we collect at http://www.k2wd.org. △ Less

Submitted 20 September, 2017; originally announced September 2017.

Comments: 33 pages, 31 figures, 5 tables; accepted for publication in ApJS. All raw and reduced data are collected at http://www.k2wd.org

Multi-band photometry and spectroscopy of an all-sky sample of bright white dwarfs

Authors: R. Raddi, N. P. Gentile Fusillo, A. F. Pala, J. J. Hermes, B. T. Gaensicke, P. Chote, M. A. Hollands, A. Henden, S. Catalán, S. Geier, D. Koester, U. Munari, R. Napiwotzki, P. -E. Tremblay

Abstract: The upcoming NASA Transiting Exoplanet Survey Satellite (TESS) will obtain space-based uninterrupted light curves for a large sample of bright white dwarfs distributed across the entire sky, providing a very rich resource for asteroseismological studies and the search for transits from planetary debris. We have compiled an all-sky catalogue of ultraviolet, optical, and infrared photometry as well… ▽ More The upcoming NASA Transiting Exoplanet Survey Satellite (TESS) will obtain space-based uninterrupted light curves for a large sample of bright white dwarfs distributed across the entire sky, providing a very rich resource for asteroseismological studies and the search for transits from planetary debris. We have compiled an all-sky catalogue of ultraviolet, optical, and infrared photometry as well as proper motions, which we propose as an essential tool for the preliminary identification and characterisation of potential targets. We present data for 1864 known white dwarfs and 305 high-probability white dwarf candidates brighter than 17 mag. We describe the spectroscopic follow-up of 135 stars, of which 82 are white dwarfs and 25 are hot subdwarfs. The new confirmed stars include six pulsating white dwarf candidates (ZZ Cetis), and nine white dwarf binaries with a cool main-sequence companion. We identify one star with a spectroscopic distance of only 25 pc from the Sun. Around the time TESS is launched, we foresee that all white dwarfs in this sample will have trigonometric parallaxes measured by the ESA Gaia mission next year. △ Less

Submitted 30 August, 2017; originally announced August 2017.

Comments: Accepted for publication on MNRAS. 21 pages, 8 tables. Machine readable tables, which will be made also available through VizieR, are also included

A catalogue of white dwarf candidates in VST ATLAS

Authors: Nicola Pietro Gentile Fusillo, Roberto Raddi, Boris T. Gänsicke, J. J. Hermes, Anna F. Pala, Joshua T. Fuchs, Ben Chehade, Nigel Metcalfe, Tom Shanks

Abstract: The Sloan Digital Sky Survey (SDSS) has created a knowledge gap between the Northern and the Southern hemispheres which is very marked for white dwarfs: only $\simeq 15$% of the known white dwarfs are south of the equator. Here we make use of the VST ATLAS survey, one of the first surveys obtaining deep, optical, multi-band photometry over a large area of the southern skies, to remedy this situati… ▽ More The Sloan Digital Sky Survey (SDSS) has created a knowledge gap between the Northern and the Southern hemispheres which is very marked for white dwarfs: only $\simeq 15$% of the known white dwarfs are south of the equator. Here we make use of the VST ATLAS survey, one of the first surveys obtaining deep, optical, multi-band photometry over a large area of the southern skies, to remedy this situation. Applying the colour and proper-motion selection developed in Gentile Fusillo et al. (2015a) to the most recent internal data release (2016 April 25) of VST ATLAS we created a catalogue of $\simeq 4200$ moderately bright ($g\leq19$), high-confidence southern white dwarf candidates, which can be followed up individually with both the large array of southern telescopes or in bulk with forthcoming multi-object spectrographs. △ Less

Submitted 28 March, 2017; originally announced March 2017.

Comments: Accepted for publication in MNRAS. 11 pages, 8 figures, 5 tables. The full catalogue presented in table 4 is available for download at http://www2.warwick.ac.uk/fac/sci/physics/research/astro/research/catalogues/ATLAS_WDcatalogue_submission.csv