Showing 1–48 of 48 results for author: Pinchera, M

Mitigating half-wave plate systematics at the map-making level: calibration requirements for LiteBIRD

Authors: N. Raffuzzi, A. Carones, M. Monelli, S. Giardiello, L. Pagano, Y. Sakurai, H. Ishino, E. Allys, A. Anand, J. Aumont, A. J. Banday, G. Barbieri Ripamonti, R. B. Barreiro, N. Bartolo, S. Basak, A. Basyrov, A. Besnard, M. Bortolami, T. Brinckmann, F. Cacciotti, E. Calabrese, P. Campeti, F. Carralot, F. J. Casas, J. Chandran , et al. (79 additional authors not shown)

Abstract: Although half-wave plates (HWPs) are becoming a popular choice of polarization modulators for cosmic microwave background (CMB) experiments, their non-idealities can introduce systematic effects that should be carefully characterized and mitigated. One possible mitigation strategy is to incorporate information about the non-idealities at the map-making level, which helps to reduce the HWP-induced… ▽ More Although half-wave plates (HWPs) are becoming a popular choice of polarization modulators for cosmic microwave background (CMB) experiments, their non-idealities can introduce systematic effects that should be carefully characterized and mitigated. One possible mitigation strategy is to incorporate information about the non-idealities at the map-making level, which helps to reduce the HWP-induced distortions of the reconstructed CMB. Nevertheless, the non-idealities can only be known with finite precision. In this paper we investigate the consequences of discrepancies between their true frequency profiles and those assumed by the map-maker. We present an end-to-end framework, including a blind component-separation step, and use it to translate these discrepancies into a bias on the tensor-to-scalar ratio, $r$, for the LiteBIRD satellite mission. We subsequently derive realistic and conservative measurement requirements for accurately characterizing the HWP non-idealities to ensure they do not compromise LiteBIRD's ambitious scientific goals. We find that the obtained results are robust against sky models with varying complexity. △ Less

Submitted 2 February, 2026; originally announced February 2026.

First release of LiteBIRD simulations from an end-to-end pipeline

Authors: M. Bortolami, N. Raffuzzi, L. Pagano, G. Puglisi, A. Anand, A. J. Banday, P. Campeti, G. Galloni, A. I. Lonappan, M. Monelli, M. Tomasi, G. Weymann-Despres, D. Adak, E. Allys, J. Aumont, R. Aurvik, C. Baccigalupi, M. Ballardini, R. B. Barreiro, N. Bartolo, S. Basak, M. Bersanelli, A. Besnard, T. Brinckmann, E. Calabrese , et al. (85 additional authors not shown)

Abstract: The LiteBIRD satellite mission aims at detecting Cosmic Microwave Background $B$ modes with unprecedented precision, targeting a total error on the tensor-to-scalar ratio $r$ of $δr \sim 0.001$. Operating from the L2 Lagrangian point of the Sun-Earth system, LiteBIRD will survey the full sky across 15 frequency bands (34 to 448 GHz) for 3 years.The current LiteBIRD baseline configuration employs 4… ▽ More The LiteBIRD satellite mission aims at detecting Cosmic Microwave Background $B$ modes with unprecedented precision, targeting a total error on the tensor-to-scalar ratio $r$ of $δr \sim 0.001$. Operating from the L2 Lagrangian point of the Sun-Earth system, LiteBIRD will survey the full sky across 15 frequency bands (34 to 448 GHz) for 3 years.The current LiteBIRD baseline configuration employs 4508 detectors sampling at 19.1 Hz to achieve an effective polarization sensitivity of $ 2 μ\mathrm{K-arcmin}$ and an angular resolution of 31 arcmin (at 140 GHz).We describe the first release of the official LiteBIRD simulations, realized with a new simulation pipeline developed using the LiteBIRD Simulation Framework, see https://github.com/litebird/litebird_sim . This pipeline generates 500 full-sky simulated maps at a Healpix resolution of nside=512. The simulations include also one year of Time Ordered Data for approximately one-third of LiteBIRD's total detectors. △ Less

Submitted 5 November, 2025; v1 submitted 8 July, 2025; originally announced July 2025.

On the computational feasibility of Bayesian end-to-end analysis of LiteBIRD simulations within Cosmoglobe

Authors: R. Aurvik, M. Galloway, E. Gjerløw, U. Fuskeland, A. Basyrov, M. Bortolami, M. Brilenkov, P. Campeti, H. K. Eriksen, L. T. Hergt, D. Herman, M. Monelli, L. Pagano, G. Puglisi, N. Raffuzzi, N. -O. Stutzer, R. M. Sullivan, H. Thommesen, D. J. Watts, I. K. Wehus, D. Adak, E. Allys, A. Anand, J. Aumont, C. Baccigalupi , et al. (85 additional authors not shown)

Abstract: We assess the computational feasibility of end-to-end Bayesian analysis of the JAXA-led LiteBIRD experiment by analysing simulated time ordered data (TOD) for a subset of detectors through the Cosmoglobe and Commander3 framework. The data volume for the simulated TOD is 1.55 TB, or 470 GB after Huffman compression. From this we estimate a total data volume of 238 TB for the full three year mission… ▽ More We assess the computational feasibility of end-to-end Bayesian analysis of the JAXA-led LiteBIRD experiment by analysing simulated time ordered data (TOD) for a subset of detectors through the Cosmoglobe and Commander3 framework. The data volume for the simulated TOD is 1.55 TB, or 470 GB after Huffman compression. From this we estimate a total data volume of 238 TB for the full three year mission, or 70 TB after Huffman compression. We further estimate the running time for one Gibbs sample, from TOD to cosmological parameters, to be approximately 3000 CPU hours. The current simulations are based on an ideal instrument model, only including correlated 1/f noise. Future work will consider realistic systematics with full end-to-end error propagation. We conclude that these requirements are well within capabilities of future high-performance computing systems. △ Less

Submitted 19 December, 2025; v1 submitted 7 July, 2025; originally announced July 2025.

Comments: 18 pages, 4 figures, Published in JCAP

Journal ref: JCAP11(2025)041

A Simulation Framework for the LiteBIRD Instruments

Authors: M. Tomasi, L. Pagano, A. Anand, C. Baccigalupi, A. J. Banday, M. Bortolami, G. Galloni, M. Galloway, T. Ghigna, S. Giardiello, M. Gomes, E. Hivon, N. Krachmalnicoff, S. Micheli, M. Monelli, Y. Nagano, A. Novelli, G. Patanchon, D. Poletti, G. Puglisi, N. Raffuzzi, M. Reinecke, Y. Takase, G. Weymann-Despres, D. Adak , et al. (89 additional authors not shown)

Abstract: LiteBIRD, the Lite (Light) satellite for the study of $B$-mode polarization and Inflation from cosmic background Radiation Detection, is a space mission focused on primordial cosmology and fundamental physics. In this paper, we present the LiteBIRD Simulation Framework (LBS), a Python package designed for the implementation of pipelines that model the outputs of the data acquisition process from t… ▽ More LiteBIRD, the Lite (Light) satellite for the study of $B$-mode polarization and Inflation from cosmic background Radiation Detection, is a space mission focused on primordial cosmology and fundamental physics. In this paper, we present the LiteBIRD Simulation Framework (LBS), a Python package designed for the implementation of pipelines that model the outputs of the data acquisition process from the three instruments on the LiteBIRD spacecraft: LFT (Low-Frequency Telescope), MFT (Mid-Frequency Telescope), and HFT (High-Frequency Telescope). LBS provides several modules to simulate the scanning strategy of the telescopes, the measurement of realistic polarized radiation coming from the sky (including the Cosmic Microwave Background itself, the Solar and Kinematic dipole, and the diffuse foregrounds emitted by the Galaxy), the generation of instrumental noise and the effect of systematic errors, like pointing wobbling, non-idealities in the Half-Wave Plate, et cetera. Additionally, we present the implementation of a simple but complete pipeline that showcases the main features of LBS. We also discuss how we ensured that LBS lets people develop pipelines whose results are accurate and reproducible. A full end-to-end pipeline has been developed using LBS to characterize the scientific performance of the LiteBIRD experiment. This pipeline and the results of the first simulation run are presented in Puglisi et al. (2025). △ Less

Submitted 12 September, 2025; v1 submitted 7 July, 2025; originally announced July 2025.

Comments: 35 pages, 1 figure, to be submitted to JCAP

Requirements on bandpass resolution and measurement precision for LiteBIRD

Authors: S. Giardiello, A. Carones, T. Ghigna, L. Pagano, F. Piacentini, L. Montier, R. Takaku, E. Calabrese, D. Adak, E. Allys, A. Anand, J. Aumont, M. Ballardini, A. J. Banday, R. B. Barreiro, N. Bartolo, S. Basak, M. Bersanelli, A. Besnard, M. Bortolami, T. Brinckmann, F. J. Casas, K. Cheung, M. Citran, L. Clermont , et al. (73 additional authors not shown)

Abstract: In this work, we study the impact of an imperfect knowledge of the instrument bandpasses on the estimate of the tensor-to-scalar ratio $r$ in the context of the next-generation LiteBIRD satellite. We develop a pipeline to integrate over the bandpass transmission in both the time-ordered data (TOD) and the map-making processing steps. We introduce the systematic effect by having a mismatch between… ▽ More In this work, we study the impact of an imperfect knowledge of the instrument bandpasses on the estimate of the tensor-to-scalar ratio $r$ in the context of the next-generation LiteBIRD satellite. We develop a pipeline to integrate over the bandpass transmission in both the time-ordered data (TOD) and the map-making processing steps. We introduce the systematic effect by having a mismatch between the ``real'', high resolution bandpass $τ$, entering the TOD, and the estimated one $τ_s$, used in the map-making. We focus on two aspects: the effect of degrading the $τ_s$ resolution, and the addition of a Gaussian error $σ$ to $τ_s$. To reduce the computational load of the analysis, the two effects are explored separately, for three representative LiteBIRD channels (40 GHz, 140 GHz and 402 GHz) and for three bandpass shapes. Computing the amount of bias on $r$, $Δr$, caused by these effects on a single channel, we find that a resolution $\lesssim 1.5$ GHz and $σ\lesssim 0.0089$ do not exceed the LiteBIRD budget allocation per systematic effect, $Δr < 6.5 \times 10^{-6}$. We then check that propagating separately the uncertainties due to a resolution of 1 GHz and a measurement error with $σ= 0.0089$ in all LiteBIRD frequency channels, for the most pessimistic bandpass shape of the three considered, still produces a $Δr < 6.5 \times 10^{-6}$. This is done both with the simple deprojection approach and with a blind component separation technique, the Needlet Internal Linear Combination (NILC). Due to the effectiveness of NILC in cleaning the systematic residuals, we have tested that the requirement on $σ$ can be relaxed to $σ\lesssim 0.05$. (Abridged) △ Less

Submitted 8 October, 2025; v1 submitted 27 June, 2025; originally announced June 2025.

Comments: 20 pages, 7 figures

Journal ref: JCAP10(2025)038

The Telescope Calibration of the Imaging X-ray Polarimetry Explorer

Authors: Brian Ramsey, Jeffery Kolodziejczak, Wayne Baumgartner, Nicholas Thomas, Stephen Bongiorno, Phillip Kaaret, Stephen O'Dell, Allyn Tennant, Martin C. Weisskopf, Sergio Fabiani, Fabio Muleri, Paolo Soffitta, Enrico Costa, Alessandro Di Marco, Riccardo Ferrazzoli, Fabio La Monaca, John Rankin, Ajay Ratheesh, Alessio Trois, Luca Baldini, Ronaldo Bellazzini, Alessandro Brez, Luca Latronico, Leonardo Lucchesi, Alberto Manfreda , et al. (5 additional authors not shown)

Abstract: Fifty years after the very first sounding rocket measurement of cosmic X-ray polarization, the Imaging X-ray Polarimetry Explorer (IXPE) mission has effectively opened a new window into the X-ray sky. Prior to launch of IXPE, an extensive calibration campaign was carried out to fully characterize the response of this new type of instrument. Specifically, the polarization-sensitive detectors were i… ▽ More Fifty years after the very first sounding rocket measurement of cosmic X-ray polarization, the Imaging X-ray Polarimetry Explorer (IXPE) mission has effectively opened a new window into the X-ray sky. Prior to launch of IXPE, an extensive calibration campaign was carried out to fully characterize the response of this new type of instrument. Specifically, the polarization-sensitive detectors were intensively calibrated in Italy, where they were developed and built. The X-ray optics, which collect and focus X rays onto the detectors, were built and calibrated in the U.S. A key question was whether the telescope (optics + detectors) calibrations could be synthesized from the individual component calibrations, avoiding time consuming and costly end-to-end calibrations for a flight program with a fixed schedule. The data presented here are from a calibration of the flight spare telescope utilizing the flight spare detector and flight spare mirror assembly combined. These data show that the presence of the mirror module does not affect the polarization response of the detectors (within the required calibration accuracy) and that the angular resolution of the telescopes could be accurately determined. Thus, the original extensive stand-alone ground calibration data of all the flight detectors and all the flight optic can be utilized in full to derive the flight telescopes calibrations. △ Less

Submitted 1 May, 2025; originally announced May 2025.

Comments: Accepted for publication in AJ

Multi-dimensional optimisation of the scanning strategy for the LiteBIRD space mission

Authors: Y. Takase, L. Vacher, H. Ishino, G. Patanchon, L. Montier, S. L. Stever, K. Ishizaka, Y. Nagano, W. Wang, J. Aumont, K. Aizawa, A. Anand, C. Baccigalupi, M. Ballardini, A. J. Banday, R. B. Barreiro, N. Bartolo, S. Basak, M. Bersanelli, M. Bortolami, T. Brinckmann, E. Calabrese, P. Campeti, E. Carinos, A. Carones , et al. (83 additional authors not shown)

Abstract: Large angular scale surveys in the absence of atmosphere are essential for measuring the primordial $B$-mode power spectrum of the Cosmic Microwave Background (CMB). Since this proposed measurement is about three to four orders of magnitude fainter than the temperature anisotropies of the CMB, in-flight calibration of the instruments and active suppression of systematic effects are crucial. We inv… ▽ More Large angular scale surveys in the absence of atmosphere are essential for measuring the primordial $B$-mode power spectrum of the Cosmic Microwave Background (CMB). Since this proposed measurement is about three to four orders of magnitude fainter than the temperature anisotropies of the CMB, in-flight calibration of the instruments and active suppression of systematic effects are crucial. We investigate the effect of changing the parameters of the scanning strategy on the in-flight calibration effectiveness, the suppression of the systematic effects themselves, and the ability to distinguish systematic effects by null-tests. Next-generation missions such as LiteBIRD, modulated by a Half-Wave Plate (HWP), will be able to observe polarisation using a single detector, eliminating the need to combine several detectors to measure polarisation, as done in many previous experiments and hence avoiding the consequent systematic effects. While the HWP is expected to suppress many systematic effects, some of them will remain. We use an analytical approach to comprehensively address the mitigation of these systematic effects and identify the characteristics of scanning strategies that are the most effective for implementing a variety of calibration strategies in the multi-dimensional space of common spacecraft scan parameters. We also present Falcons, a fast spacecraft scanning simulator that we developed to investigate this scanning parameter space. △ Less

Submitted 15 November, 2024; v1 submitted 6 August, 2024; originally announced August 2024.

LiteBIRD Science Goals and Forecasts. Mapping the Hot Gas in the Universe

Authors: M. Remazeilles, M. Douspis, J. A. Rubiño-Martín, A. J. Banday, J. Chluba, P. de Bernardis, M. De Petris, C. Hernández-Monteagudo, G. Luzzi, J. Macias-Perez, S. Masi, T. Namikawa, L. Salvati, H. Tanimura, K. Aizawa, A. Anand, J. Aumont, C. Baccigalupi, M. Ballardini, R. B. Barreiro, N. Bartolo, S. Basak, M. Bersanelli, D. Blinov, M. Bortolami , et al. (82 additional authors not shown)

Abstract: We assess the capabilities of the LiteBIRD mission to map the hot gas distribution in the Universe through the thermal Sunyaev-Zeldovich (SZ) effect. Our analysis relies on comprehensive simulations incorporating various sources of Galactic and extragalactic foreground emission, while accounting for specific instrumental characteristics of LiteBIRD, such as detector sensitivities, frequency-depend… ▽ More We assess the capabilities of the LiteBIRD mission to map the hot gas distribution in the Universe through the thermal Sunyaev-Zeldovich (SZ) effect. Our analysis relies on comprehensive simulations incorporating various sources of Galactic and extragalactic foreground emission, while accounting for specific instrumental characteristics of LiteBIRD, such as detector sensitivities, frequency-dependent beam convolution, inhomogeneous sky scanning, and $1/f$ noise. We implement a tailored component-separation pipeline to map the thermal SZ Compton $y$-parameter over 98% of the sky. Despite lower angular resolution for galaxy cluster science, LiteBIRD provides full-sky coverage and, compared to the Planck satellite, enhanced sensitivity, as well as more frequency bands to enable the construction of an all-sky $y$-map, with reduced foreground contamination at large and intermediate angular scales. By combining LiteBIRD and Planck channels in the component-separation pipeline, we obtain an optimal $y$-map that leverages the advantages of both experiments, with the higher angular resolution of the Planck channels enabling the recovery of compact clusters beyond the LiteBIRD beam limitations, and the numerous sensitive LiteBIRD channels further mitigating foregrounds. The added value of LiteBIRD is highlighted through the examination of maps, power spectra, and one-point statistics of the various sky components. After component separation, the $1/f$ noise from LiteBIRD is effectively mitigated below the thermal SZ signal at all multipoles. Cosmological constraints on $S_8=σ_8\left(Ω_{\rm m}/0.3\right)^{0.5}$ obtained from the LiteBIRD-Planck combined $y$-map power spectrum exhibits a 15% reduction in uncertainty compared to constraints from Planck alone. This improvement can be attributed to the increased portion of uncontaminated sky available in the LiteBIRD-Planck combined $y$-map. △ Less

Submitted 23 October, 2024; v1 submitted 24 July, 2024; originally announced July 2024.

Comments: 38 pages, 13 figures, abstract shortened. Updated to match version accepted by JCAP

The LiteBIRD mission to explore cosmic inflation

Authors: T. Ghigna, A. Adler, K. Aizawa, H. Akamatsu, R. Akizawa, E. Allys, A. Anand, J. Aumont, J. Austermann, S. Azzoni, C. Baccigalupi, M. Ballardini, A. J. Banday, R. B. Barreiro, N. Bartolo, S. Basak, A. Basyrov, S. Beckman, M. Bersanelli, M. Bortolami, F. Bouchet, T. Brinckmann, P. Campeti, E. Carinos, A. Carones , et al. (134 additional authors not shown)

Abstract: LiteBIRD, the next-generation cosmic microwave background (CMB) experiment, aims for a launch in Japan's fiscal year 2032, marking a major advancement in the exploration of primordial cosmology and fundamental physics. Orbiting the Sun-Earth Lagrangian point L2, this JAXA-led strategic L-class mission will conduct a comprehensive mapping of the CMB polarization across the entire sky. During its 3-… ▽ More LiteBIRD, the next-generation cosmic microwave background (CMB) experiment, aims for a launch in Japan's fiscal year 2032, marking a major advancement in the exploration of primordial cosmology and fundamental physics. Orbiting the Sun-Earth Lagrangian point L2, this JAXA-led strategic L-class mission will conduct a comprehensive mapping of the CMB polarization across the entire sky. During its 3-year mission, LiteBIRD will employ three telescopes within 15 unique frequency bands (ranging from 34 through 448 GHz), targeting a sensitivity of 2.2\,$μ$K-arcmin and a resolution of 0.5$^\circ$ at 100\,GHz. Its primary goal is to measure the tensor-to-scalar ratio $r$ with an uncertainty $δr = 0.001$, including systematic errors and margin. If $r \geq 0.01$, LiteBIRD expects to achieve a $>5σ$ detection in the $\ell=$2-10 and $\ell=$11-200 ranges separately, providing crucial insight into the early Universe. We describe LiteBIRD's scientific objectives, the application of systems engineering to mission requirements, the anticipated scientific impact, and the operations and scanning strategies vital to minimizing systematic effects. We will also highlight LiteBIRD's synergies with concurrent CMB projects. △ Less

Submitted 4 June, 2024; originally announced June 2024.

Comments: 23 pages, 9 figures, 1 table, SPIE Astronomical Telescopes + Instrumentation 2024

LiteBIRD Science Goals and Forecasts: Improving Sensitivity to Inflationary Gravitational Waves with Multitracer Delensing

Authors: T. Namikawa, A. I. Lonappan, C. Baccigalupi, N. Bartolo, D. Beck, K. Benabed, A. Challinor, P. Diego-Palazuelos, J. Errard, S. Farrens, A. Gruppuso, N. Krachmalnicoff, M. Migliaccio, E. Martínez-González, V. Pettorino, G. Piccirilli, M. Ruiz-Granda, B. Sherwin, J. Starck, P. Vielva, R. Akizawa, A. Anand, J. Aumont, R. Aurlien, S. Azzoni , et al. (97 additional authors not shown)

Abstract: We estimate the efficiency of mitigating the lensing $B$-mode polarization, the so-called delensing, for the $LiteBIRD$ experiment with multiple external data sets of lensing-mass tracers. The current best bound on the tensor-to-scalar ratio, $r$, is limited by lensing rather than Galactic foregrounds. Delensing will be a critical step to improve sensitivity to $r$ as measurements of $r$ become mo… ▽ More We estimate the efficiency of mitigating the lensing $B$-mode polarization, the so-called delensing, for the $LiteBIRD$ experiment with multiple external data sets of lensing-mass tracers. The current best bound on the tensor-to-scalar ratio, $r$, is limited by lensing rather than Galactic foregrounds. Delensing will be a critical step to improve sensitivity to $r$ as measurements of $r$ become more and more limited by lensing. In this paper, we extend the analysis of the recent $LiteBIRD$ forecast paper to include multiple mass tracers, i.e., the CMB lensing maps from $LiteBIRD$ and CMB-S4-like experiment, cosmic infrared background, and galaxy number density from $Euclid$- and LSST-like survey. We find that multi-tracer delensing will further improve the constraint on $r$ by about $20\%$. In $LiteBIRD$, the residual Galactic foregrounds also significantly contribute to uncertainties of the $B$-modes, and delensing becomes more important if the residual foregrounds are further reduced by an improved component separation method. △ Less

Submitted 8 December, 2023; originally announced December 2023.

Comments: 21 pages, 7 figures

Journal ref: JCAP 06 (2024) 010

LiteBIRD Science Goals and Forecasts: A full-sky measurement of gravitational lensing of the CMB

Authors: A. I. Lonappan, T. Namikawa, G. Piccirilli, P. Diego-Palazuelos, M. Ruiz-Granda, M. Migliaccio, C. Baccigalupi, N. Bartolo, D. Beck, K. Benabed, A. Challinor, J. Errard, S. Farrens, A. Gruppuso, N. Krachmalnicoff, E. Martínez-González, V. Pettorino, B. Sherwin, J. Starck, P. Vielva, R. Akizawa, A. Anand, J. Aumont, R. Aurlien, S. Azzoni , et al. (97 additional authors not shown)

Abstract: We explore the capability of measuring lensing signals in $LiteBIRD$ full-sky polarization maps. With a $30$ arcmin beam width and an impressively low polarization noise of $2.16\,μ$K-arcmin, $LiteBIRD$ will be able to measure the full-sky polarization of the cosmic microwave background (CMB) very precisely. This unique sensitivity also enables the reconstruction of a nearly full-sky lensing map u… ▽ More We explore the capability of measuring lensing signals in $LiteBIRD$ full-sky polarization maps. With a $30$ arcmin beam width and an impressively low polarization noise of $2.16\,μ$K-arcmin, $LiteBIRD$ will be able to measure the full-sky polarization of the cosmic microwave background (CMB) very precisely. This unique sensitivity also enables the reconstruction of a nearly full-sky lensing map using only polarization data, even considering its limited capability to capture small-scale CMB anisotropies. In this paper, we investigate the ability to construct a full-sky lensing measurement in the presence of Galactic foregrounds, finding that several possible biases from Galactic foregrounds should be negligible after component separation by harmonic-space internal linear combination. We find that the signal-to-noise ratio of the lensing is approximately $40$ using only polarization data measured over $90\%$ of the sky. This achievement is comparable to $Planck$'s recent lensing measurement with both temperature and polarization and represents a four-fold improvement over $Planck$'s polarization-only lensing measurement. The $LiteBIRD$ lensing map will complement the $Planck$ lensing map and provide several opportunities for cross-correlation science, especially in the northern hemisphere. △ Less

Submitted 8 December, 2023; originally announced December 2023.

LiteBIRD Science Goals and Forecasts. A Case Study of the Origin of Primordial Gravitational Waves using Large-Scale CMB Polarization

Authors: P. Campeti, E. Komatsu, C. Baccigalupi, M. Ballardini, N. Bartolo, A. Carones, J. Errard, F. Finelli, R. Flauger, S. Galli, G. Galloni, S. Giardiello, M. Hazumi, S. Henrot-Versillé, L. T. Hergt, K. Kohri, C. Leloup, J. Lesgourgues, J. Macias-Perez, E. Martínez-González, S. Matarrese, T. Matsumura, L. Montier, T. Namikawa, D. Paoletti , et al. (85 additional authors not shown)

Abstract: We study the possibility of using the $LiteBIRD$ satellite $B$-mode survey to constrain models of inflation producing specific features in CMB angular power spectra. We explore a particular model example, i.e. spectator axion-SU(2) gauge field inflation. This model can source parity-violating gravitational waves from the amplification of gauge field fluctuations driven by a pseudoscalar "axionlike… ▽ More We study the possibility of using the $LiteBIRD$ satellite $B$-mode survey to constrain models of inflation producing specific features in CMB angular power spectra. We explore a particular model example, i.e. spectator axion-SU(2) gauge field inflation. This model can source parity-violating gravitational waves from the amplification of gauge field fluctuations driven by a pseudoscalar "axionlike" field, rolling for a few e-folds during inflation. The sourced gravitational waves can exceed the vacuum contribution at reionization bump scales by about an order of magnitude and can be comparable to the vacuum contribution at recombination bump scales. We argue that a satellite mission with full sky coverage and access to the reionization bump scales is necessary to understand the origin of the primordial gravitational wave signal and distinguish among two production mechanisms: quantum vacuum fluctuations of spacetime and matter sources during inflation. We present the expected constraints on model parameters from $LiteBIRD$ satellite simulations, which complement and expand previous studies in the literature. We find that $LiteBIRD$ will be able to exclude with high significance standard single-field slow-roll models, such as the Starobinsky model, if the true model is the axion-SU(2) model with a feature at CMB scales. We further investigate the possibility of using the parity-violating signature of the model, such as the $TB$ and $EB$ angular power spectra, to disentangle it from the standard single-field slow-roll scenario. We find that most of the discriminating power of $LiteBIRD$ will reside in $BB$ angular power spectra rather than in $TB$ and $EB$ correlations. △ Less

Submitted 23 March, 2025; v1 submitted 1 December, 2023; originally announced December 2023.

Comments: 22 pages, 13 figures. Published in JCAP 06 (2024) 008. Added comments at end of Sec. 6 reframing conclusions in more general way. Updated references

Journal ref: JCAP 06 (2024), 008

Polarization properties of X-ray tubes used for Imaging X-ray Polarimetry Explorer calibration

Authors: Ajay Ratheesh, John Rankin, Enrico Costa, Ettore Del Monte, Alessandro Di Marco, Sergio Fabiani, Fabio La Monaca, Fabio Muleri, Alda Rubini, Paolo Soffitta, Luca Baldini, Massimo Minuti, Michele Pinchera, Carmelo Sgrò

Abstract: In this work, we measured the polarization properties of the X-rays emitted from the X-ray tubes, which were used during the calibration of the instrument onboard Imaging X-ray Polarimetry Explorer (IXPE). X-ray tubes are used as a source of unpolarized X-rays to calibrate the response of the gas pixel detectors to unpolarized radiation. However, even though the characteristic fluorescent emission… ▽ More In this work, we measured the polarization properties of the X-rays emitted from the X-ray tubes, which were used during the calibration of the instrument onboard Imaging X-ray Polarimetry Explorer (IXPE). X-ray tubes are used as a source of unpolarized X-rays to calibrate the response of the gas pixel detectors to unpolarized radiation. However, even though the characteristic fluorescent emission lines are unpolarized, continuum bremsstrahlung emission can be polarized based on the geometry of the accelerated electrons and emitted photons. Hence, characterizing the contribution of polarized X-rays from bremsstrahlung emission is of interest, also for future measurements. We find that when accelerated electrons are parallel to the emitted photons, the bremsstrahlung emission is unpolarized, and when they are perpendicular, the polarization increases with energy, as expected from the theoretical predictions. A comparison with the theoretical predictions is also shown. △ Less

Submitted 27 July, 2023; originally announced July 2023.

Comments: 30 pages, 12 Figures and 6 tables. Published in Journal of Astronomical Telescopes, Instruments, and Systems (JATIS). DOI: 10.1117/1.JATIS.9.3.038002

Journal ref: J. Astron. Telesc. Instrum. Syst. 9(3), 038002 (2023)

X-ray Polarimetry of the accreting pulsar 1A~0535+262 in the supercritical state with PolarLight

Authors: Xiangyun Long, Hua Feng, Hong Li, Ling-Da Kong, Jeremy Heyl, Long Ji, Lian Tao, Fabio Muleri, Qiong Wu, Jiahuan Zhu, Jiahui Huang, Massimo Minuti, Weichun Jiang, Saverio Citraro, Hikmat Nasimi, Jiandong Yu, Ge Jin, Ming Zeng, Peng An, Luca Baldini, Ronaldo Bellazzini, Alessandro Brez, Luca Latronico, Carmelo Sgrò, Gloria Spandre , et al. (3 additional authors not shown)

Abstract: The X-ray pulsar 1A 0535+262 exhibited a giant outburst in 2020, offering us a unique opportunity for X-ray polarimetry of an accreting pulsar in the supercritical state. Measurement with PolarLight yielded a non-detection in 3-8 keV; the 99% upper limit of the polarization fraction (PF) is found to be 0.34 averaged over spin phases, or 0.51 based on the rotating vector model. No useful constraint… ▽ More The X-ray pulsar 1A 0535+262 exhibited a giant outburst in 2020, offering us a unique opportunity for X-ray polarimetry of an accreting pulsar in the supercritical state. Measurement with PolarLight yielded a non-detection in 3-8 keV; the 99% upper limit of the polarization fraction (PF) is found to be 0.34 averaged over spin phases, or 0.51 based on the rotating vector model. No useful constraint can be placed with phase resolved polarimetry. These upper limits are lower than a previous theoretical prediction of 0.6-0.8, but consistent with those found in other accreting pulsars, like Her X-1, Cen X-3, 4U 1626-67, and GRO J1008-57, which were in the subcritical state, or at least not confidently in the supercritical state, during the polarization measurements. Our results suggest that the relatively low PF seen in accreting pulsars cannot be attributed to the source not being in the supercritical state, but could be a general feature. △ Less

Submitted 26 April, 2023; originally announced April 2023.

Comments: accepted for publication in ApJ

XPOL-III: a New-Generation VLSI CMOS ASIC for High-Throughput X-ray Polarimetry

Authors: M. Minuti, L. Baldini, R. Bellazzini, A. Brez, M. Ceccanti, F. Krummenacher, L. Latronico, L. Lucchesi, A. Manfreda, L. Orsini, M. Pinchera, A. Profeti, C. Sgr`o, G. Spandre

Abstract: While the successful launch and operation in space of the Gas Pixel Detectors onboard the PolarLight cubesat and the Imaging X-ray Polarimetry Explorer demonstrate the viability and the technical soundness of this class of detectors for astronomical X-ray polarimetry, it is clear that the current state of the art is not ready to meet the challenges of the next generation of experiments, such as th… ▽ More While the successful launch and operation in space of the Gas Pixel Detectors onboard the PolarLight cubesat and the Imaging X-ray Polarimetry Explorer demonstrate the viability and the technical soundness of this class of detectors for astronomical X-ray polarimetry, it is clear that the current state of the art is not ready to meet the challenges of the next generation of experiments, such as the enhanced X-ray Timing and Polarimetry mission, designed to allow for a significantly larger data throughput. In this paper we describe the design and test of a new custom, self-triggering readout ASIC, dubbed XPOL-III, specifically conceived to address and overcome these limitations. While building upon the overall architecture of the previous generations, the new chip improves over its predecessors in several, different key areas: the sensitivity of the trigger electronics, the flexibility in the definition of the readout window, as well as the maximum speed for the serial event readout. These design improvements, when combined, allow for almost an order of magnitude smaller dead time per event with no measurable degradation of the polarimetric, spectral, imaging or timing capability of the detector, providing a good match for the next generation of X-ray missions. △ Less

Submitted 19 October, 2022; v1 submitted 30 August, 2022; originally announced August 2022.

Comments: accepted for publication at Nuclear Inst. and Methods in Physics Research Section A

Calibration of the IXPE focal plane X-ray polarimeters to polarized radiation

Authors: Alessandro Di Marco, Sergio Fabiani, Fabio La Monaca, Fabio Muleri, John Rankin, Paolo Soffitta, Fei Xie, Fabrizio Amici, Primo attinà, Matteo Bachetti, Luca Baldini, Mattia Barbanera, Wayne Baumgartner, Ronaldo Bellazzini, Fabio Borotto, Alessandro Brez, Daniele Brienza, Ciro Caporale, Claudia Cardelli, Rita Carpentiero, Simone Castellano, Marco Castronuovo, Luca Cavalli, Elisabetta Cavazzuti, Marco Ceccanti , et al. (58 additional authors not shown)

Abstract: IXPE (Imaging X-ray Polarimetry Explorer) is a NASA Small Explorer mission -- in partnership with the Italian Space Agency (ASI) -- dedicated to X-ray polarimetry in the 2--8 keV energy band. The IXPE telescope comprises three grazing incidence mirror modules coupled to three detector units hosting each one a Gas Pixel Detector (GPD), a gas detector that allows measuring the polarization degree by… ▽ More IXPE (Imaging X-ray Polarimetry Explorer) is a NASA Small Explorer mission -- in partnership with the Italian Space Agency (ASI) -- dedicated to X-ray polarimetry in the 2--8 keV energy band. The IXPE telescope comprises three grazing incidence mirror modules coupled to three detector units hosting each one a Gas Pixel Detector (GPD), a gas detector that allows measuring the polarization degree by using the photoelectric effect. A wide and accurate ground calibration was carried out on the IXPE Detector Units (DUs) at INAF-IAPS, in Italy, where a dedicated facility was set-up at this aim. In this paper, we present the results obtained from this calibration campaign to study the IXPE focal plane detector response to polarized radiation. In particular, we report on the modulation factor, which is the main parameter to estimate the sensitivity of a polarimeter. △ Less

Submitted 15 June, 2022; originally announced June 2022.

Comments: Accepted for publication on The Astronomical Journal

Journal ref: The Astronomical Journal 164 (2022) 103

A significant detection of X-ray Polarization in Sco X-1 with PolarLight and constraints on the corona geometry

Authors: Xiangyun Long, Hua Feng, Hong Li, Jiahuan Zhu, Qiong Wu, Jiahui Huang, Massimo Minuti, Weichun Jiang, Dongxin Yang, Saverio Citraro, Hikmat Nasimi, Jiandong Yu, Ge Jin, Ming Zeng, Peng An, Jiachen Jiang, Enrico Costa, Luca Baldini, Ronaldo Bellazzini, Alessandro Brez, Luca Latronico, Carmelo Sgro, Gloria Spandre, Michele Pinchera, Fabio Muleri , et al. (1 additional authors not shown)

Abstract: We report the detection of X-ray polarization in the neutron star low mass X-ray binary Scorpius (Sco) X-1 with PolarLight. The result is energy dependent, with a non-detection in 3-4 keV but a 4$σ$ detection in 4-8 keV; it is also flux dependent in the 4-8 keV band, with a non-detection when the source displays low fluxes but a 5$σ$ detection during high fluxes, in which case we obtain a polariza… ▽ More We report the detection of X-ray polarization in the neutron star low mass X-ray binary Scorpius (Sco) X-1 with PolarLight. The result is energy dependent, with a non-detection in 3-4 keV but a 4$σ$ detection in 4-8 keV; it is also flux dependent in the 4-8 keV band, with a non-detection when the source displays low fluxes but a 5$σ$ detection during high fluxes, in which case we obtain a polarization fraction of $0.043 \pm 0.008$ and a polarization angle of $52.6^\circ \pm 5.4^\circ$. This confirms a previous marginal detection with OSO-8 in the 1970s, and marks Sco X-1 the second astrophysical source with a significant polarization measurement in the keV band. The measured polarization angle is in line with the jet orientation of the source on the sky plane ($54^\circ$), which is supposedly the symmetric axis of the system. Combining previous spectral analysis, our measurements suggest that an optically thin corona is located in the transition layer under the highest accretion rates, and disfavor the extended accretion disk corona model. △ Less

Submitted 6 December, 2021; originally announced December 2021.

Comments: Submitted to AAS journals. We are grateful to some experts for useful comments

Journal ref: The Astrophysical Journal Letters, 924:L13 (5pp), 2022 January 1

The Imaging X-Ray Polarimetry Explorer (IXPE): Pre-Launch

Authors: Martin C. Weisskopf, Paolo Soffitta, Luca Baldini, Brian D. Ramsey, Stephen L. O'Dell, Roger W. Romani, Giorgio Matt, William D. Deininger, Wayne H. Baumgartner, Ronaldo Bellazzini, Enrico Costa, Jeffery J. Kolodziejczak, Luca Latronico, Herman L. Marshall, Fabio Muleri, Stephen D. Bongiorno, Allyn Tennant, Niccolo Bucciantini, Michal Dovciak, Frederic Marin, Alan Marscher, Juri Poutanen, Pat Slane, Roberto Turolla, William Kalinowski , et al. (133 additional authors not shown)

Abstract: Scheduled to launch in late 2021, the Imaging X-ray Polarimetry Explorer (IXPE) is a NASA Small Explorer Mission in collaboration with the Italian Space Agency (ASI). The mission will open a new window of investigation - imaging X-ray polarimetry. The observatory features 3 identical telescopes each consisting of a mirror module assembly with a polarization-sensitive imaging X-ray detector at the… ▽ More Scheduled to launch in late 2021, the Imaging X-ray Polarimetry Explorer (IXPE) is a NASA Small Explorer Mission in collaboration with the Italian Space Agency (ASI). The mission will open a new window of investigation - imaging X-ray polarimetry. The observatory features 3 identical telescopes each consisting of a mirror module assembly with a polarization-sensitive imaging X-ray detector at the focus. A coilable boom, deployed on orbit, provides the necessary 4-m focal length. The observatory utilizes a 3-axis-stabilized spacecraft which provides services such as power, attitude determination and control, commanding, and telemetry to the ground. During its 2-year baseline mission, IXPE will conduct precise polarimetry for samples of multiple categories of X-ray sources, with follow-on observations of selected targets. △ Less

Submitted 21 December, 2021; v1 submitted 2 December, 2021; originally announced December 2021.

The Instrument of the Imaging X-ray Polarimetry Explorer

Authors: Paolo Soffitta, Luca Baldini, Ronaldo Bellazzini, Enrico Costa, Luca Latronico, Fabio Muleri, Ettore Del Monte, Sergio Fabiani, Massimo Minuti, Michele Pinchera, Carmelo Sgrò, Gloria Spandre, Alessio Trois, Fabrizio Amici, Hans Andersson, Primo Attinà, Matteo Bachetti, Mattia Barbanera, Fabio Borotto, Alessandro Brez, Daniele Brienza, Ciro Caporale, Claudia Cardelli, Rita Carpentiero, Simone Castellano , et al. (56 additional authors not shown)

Abstract: While X-ray Spectroscopy, Timing and Imaging have improved verymuch since 1962, when the first astronomical non-solar source was discovered, especially with the launch of Newton/X-ray Multi-Mirror Mission, Rossi/X-ray Timing Explorer and Chandra/Advanced X-ray Astrophysics Facility, the progress of X-ray polarimetry has been meager. This is in part due to the lack of sensitive polarization detecto… ▽ More While X-ray Spectroscopy, Timing and Imaging have improved verymuch since 1962, when the first astronomical non-solar source was discovered, especially with the launch of Newton/X-ray Multi-Mirror Mission, Rossi/X-ray Timing Explorer and Chandra/Advanced X-ray Astrophysics Facility, the progress of X-ray polarimetry has been meager. This is in part due to the lack of sensitive polarization detectors, in part due to the fate of approved missions and in part because the celestial X-ray sources appeared less polarized than expected. Only one positive measurement has been available until now. Indeed the eight Orbiting Solar Observatory measured the polarization of the Crab nebula in the 70s. The advent of techniques of microelectronics allowed for designing a detector based on the photoelectric effect in gas in an energy range where the optics are efficient in focusing X-rays. Herewe describe the Instrument, which is the major contribution of the Italian collaboration to the SmallExplorer mission called IXPE, the Imaging X-ray Polarimetry Explorer, which will be flown in late 2021. The instrument, is composed of three Detector Units, based on this technique, and a Detector Service Unit. Three Mirror Modules provided by Marshall Space Flight Center focus X-rays onto the detectors. In the following we will show the technological choices, their scientific motivation and the results from the calibration of the Instrument. IXPE will perform imaging, timing and energy resolved polarimetry in the 2-8 keV energy band opening this window of X-ray astronomy to tens of celestial sources of almost all classes. △ Less

Submitted 31 July, 2021; originally announced August 2021.

Comments: 25 pages, 12 figures, 5 tables (accepted for publication in Astronomical Journal)

Design, Construction, and Test of the Gas Pixel Detectors for the IXPE Mission

Authors: L. Baldini, M. Barbanera, R. Bellazzini, R. Bonino, F. Borotto, A. Brez, C. Caporale, C. Cardelli, S. Castellano, M. Ceccanti, S. Citraro, N. Di Lalla, L. Latronico, L. Lucchesi, C. Magazzù, G. Magazzù, S. Maldera, A. Manfreda, M. Marengo, A. Marrocchesi, P. Mereu, M. Minuti, F. Mosti, H. Nasimi, A. Nuti , et al. (69 additional authors not shown)

Abstract: Due to be launched in late 2021, the Imaging X-Ray Polarimetry Explorer (IXPE) is a NASA Small Explorer mission designed to perform polarization measurements in the 2-8 keV band, complemented with imaging, spectroscopy and timing capabilities. At the heart of the focal plane is a set of three polarization-sensitive Gas Pixel Detectors (GPD), each based on a custom ASIC acting as a charge-collectin… ▽ More Due to be launched in late 2021, the Imaging X-Ray Polarimetry Explorer (IXPE) is a NASA Small Explorer mission designed to perform polarization measurements in the 2-8 keV band, complemented with imaging, spectroscopy and timing capabilities. At the heart of the focal plane is a set of three polarization-sensitive Gas Pixel Detectors (GPD), each based on a custom ASIC acting as a charge-collecting anode. In this paper we shall review the design, manufacturing, and test of the IXPE focal-plane detectors, with particular emphasis on the connection between the science drivers, the performance metrics and the operational aspects. We shall present a thorough characterization of the GPDs in terms of effective noise, trigger efficiency, dead time, uniformity of response, and spectral and polarimetric performance. In addition, we shall discuss in detail a number of instrumental effects that are relevant for high-level science analysis -- particularly as far as the response to unpolarized radiation and the stability in time are concerned. △ Less

Submitted 12 July, 2021; originally announced July 2021.

Comments: To be published in Astroparticle Physics

Fermi Large Area Telescope Performance After 10 Years Of Operation

Authors: The Fermi LAT Collaboration, M. Ajello, W. B. Atwood, M. Axelsson, R. Bagagli, M. Bagni, L. Baldini, D. Bastieri, F. Bellardi, R. Bellazzini, E. Bissaldi, E. D. Bloom, R. Bonino, J. Bregeon, A. Brez, P. Bruel, R. Buehler, S. Buson, R. A. Cameron, P. A. Caraveo, E. Cavazzuti, M. Ceccanti, S. Chen, C. C. Cheung, S. Ciprini , et al. (104 additional authors not shown)

Abstract: The Large Area Telescope (LAT), the primary instrument for the Fermi Gamma-ray Space Telescope (Fermi) mission, is an imaging, wide field-of-view, high-energy gamma-ray telescope, covering the energy range from 30 MeV to more than 300 GeV. We describe the performance of the instrument at the 10-year milestone. LAT performance remains well within the specifications defined during the planning phase… ▽ More The Large Area Telescope (LAT), the primary instrument for the Fermi Gamma-ray Space Telescope (Fermi) mission, is an imaging, wide field-of-view, high-energy gamma-ray telescope, covering the energy range from 30 MeV to more than 300 GeV. We describe the performance of the instrument at the 10-year milestone. LAT performance remains well within the specifications defined during the planning phase, validating the design choices and supporting the compelling case to extend the duration of the Fermi mission. The details provided here will be useful when designing the next generation of high-energy gamma-ray observatories. △ Less

Submitted 6 September, 2021; v1 submitted 23 June, 2021; originally announced June 2021.

Comments: 60 pages, 28 figures. Published in ApJS

Journal ref: ApJS 256 (2021) 12

X-ray polarimetry of the Crab nebula with PolarLight: polarization recovery after the glitch and a secular position angle variation

Authors: Xiangyun Long, Hua Feng, Hong Li, Jiahuan Zhu, Qiong Wu, Jiahui Huang, Massimo Minuti, Weichun Jiang, Weihua Wang, Renxin Xu, Enrico Costa, Dongxin Yang, Saverio Citraro, Hikmat Nasimi, Jiandong Yu, Ge Jin, Ming Zeng, Peng An, Luca Baldini, Ronaldo Bellazzini, Alessandro Brez, Luca Latronico, Carmelo Sgro, Gloria Spandre, Michele Pinchera , et al. (2 additional authors not shown)

Abstract: We report follow-up observations of the Crab nebula with the PolarLight X-ray polarimeter, which revealed a possible variation in polarization associated with a pulsar glitch in 2019. The new observations confirm that the polarization has recovered roughly 100 days after the glitch. With the new observations, we find that the polarization angle (PA) measured with PolarLight from the total nebular… ▽ More We report follow-up observations of the Crab nebula with the PolarLight X-ray polarimeter, which revealed a possible variation in polarization associated with a pulsar glitch in 2019. The new observations confirm that the polarization has recovered roughly 100 days after the glitch. With the new observations, we find that the polarization angle (PA) measured with PolarLight from the total nebular emission has a difference of 18.0 +- 4.6 (deg) from that measured 42 years ago with OSO-8, indicating a secular evolution of polarization with either the Crab nebula or pulsar. The long-term variation in PA could be a result of multiple glitches in the history, magnetic reconnection or movement of synchrotron emitting structures in the nebula, or secular evolution of the pulsar magnetic geometry. △ Less

Submitted 22 April, 2021; originally announced April 2021.

Comments: ApJ Letters to appear

Discrimination of background events in the PolarLight X-ray polarimeter

Authors: Jiahuan Zhu, Hong Li, Hua Feng, Jiahui Huang, Xiangyun Long, Qiong Wu, Weichun Jiang, Massimo Minuti, Saverio Citraro, Hikmat Nasimi, Dongxin Yang, Jiandong Yu, Ge Jin, Ming Zeng, Peng An, Luca Baldini, Ronaldo Bellazzini, Alessandro Brez, Luca Latronico, Carmelo Sgro, Gloria Spandre, Michele Pinchera, Fabio Muleri, Paolo Soffitta, Enrico Costa

Abstract: PolarLight is a space-borne X-ray polarimeter that measures the X-ray polarization via electron tracking in an ionization chamber. It is a collimated instrument and thus suffers from the background on the whole detector plane. The majority of background events are induced by high energy charged particles and show ionization morphologies distinct from those produced by X-rays of interest. Comparing… ▽ More PolarLight is a space-borne X-ray polarimeter that measures the X-ray polarization via electron tracking in an ionization chamber. It is a collimated instrument and thus suffers from the background on the whole detector plane. The majority of background events are induced by high energy charged particles and show ionization morphologies distinct from those produced by X-rays of interest. Comparing on-source and off-source observations, we find that the two datasets display different distributions on image properties. The boundaries between the source and background distributions are obtained and can be used for background discrimination. Such a means can remove over 70% of the background events measured with PolarLight. This approaches the theoretical upper limit of the background fraction that is removable and justifies its effectiveness. For observations with the Crab nebula, the background contamination decreases from 25% to 8% after discrimination, indicative of a polarimetric sensitivity of around 0.2 Crab for PolarLight. This work also provides insights into future X-ray polarimetric telescopes. △ Less

Submitted 13 May, 2021; v1 submitted 23 March, 2021; originally announced March 2021.

Comments: accepted for publication in Research in Astronomy and Astrophysics

Modeling the in-orbit background of PolarLight

Authors: Jiahui Huang, Hua Feng, Hong Li, Xiangyun Long, Dongxin Yang, Weihe Zeng, Qiong Wu, Weichun Jiang, Massimo Minuti, Enrico Costa, Fabio Muleri, Saverio Citraro, Hikmat Nasimi, Jiandong Yu, Ge Jin, Zhi Zeng, Ming Zeng, Peng An, Luca Baldini, Ronaldo Bellazzini, Alessandro Brez, Luca Latronico, Carmelo Sgro, Gloria Spandre, Michele Pinchera , et al. (1 additional authors not shown)

Abstract: PolarLight is a gas pixel X-ray polarimeter mounted on a CubeSat, which was launched into a Sun-synchronous orbit in October 2018. We build a mass model of the whole CubeSat with the Geant4 toolkit to simulate the background induced by the cosmic X-ray background (CXB) and high energy charged particles in the orbit. The simulated energy spectra and morphologies of event images both suggest that th… ▽ More PolarLight is a gas pixel X-ray polarimeter mounted on a CubeSat, which was launched into a Sun-synchronous orbit in October 2018. We build a mass model of the whole CubeSat with the Geant4 toolkit to simulate the background induced by the cosmic X-ray background (CXB) and high energy charged particles in the orbit. The simulated energy spectra and morphologies of event images both suggest that the measured background with PolarLight is dominated by high energy electrons, with a minor contribution from protons and the CXB. The simulation reveals that, in the energy range of 2-8 keV, there are roughly 28% of the background events are caused by energy deposit from a secondary electron with an energy of a few keV, in a physical process identical to the detection of X-rays. Thus, this fraction of background cannot be discriminated from X-ray events. The background distribution is uneven on the detector plane, with an enhancement near the edges. The edge effect is because high energy electrons tend to produce long tracks, which are discarded by the readout electronics unless they have partial energy deposits near the edges. The internal background rate is expected to be around 6 x 10^-3 counts/s/cm2 in 2-8 keV if an effective particle discrimination algorithm can be applied. This indicates that the internal background should be negligible for future focusing X-ray polarimeters with a focal size in the order of mm. △ Less

Submitted 17 January, 2021; originally announced January 2021.

Comments: accepted for publication in ApJ

Re-detection and a Possible Time Variation of Soft X-ray Polarisation from the Crab

Authors: Hua Feng, Hong Li, Xiangyun Long, Ronaldo Bellazzini, Enrico Costa, Qiong Wu, Jiahui Huang, Weichun Jiang, Massimo Minuti, Weihua Wang, Renxin Xu, Dongxin Yang, Luca Baldini, Saverio Citraro, Hikmat Nasimi, Paolo Soffitta, Fabio Muleri, Aera Jung, Jiandong Yu, Ge Jin, Ming Zeng, Peng An, Alessandro Brez, Luca Latronico, Carmelo Sgro , et al. (2 additional authors not shown)

Abstract: The Crab nebula is so far the only celestial object with a statistically significant detection in soft x-ray polarimetry, a window that has not been explored in astronomy since the 1970s. However, soft x-ray polarimetry is expected to be a sensitive probe of magnetic fields in high energy astrophysical objects including rotation-powered pulsars and pulsar wind nebulae. Here we report the re-detect… ▽ More The Crab nebula is so far the only celestial object with a statistically significant detection in soft x-ray polarimetry, a window that has not been explored in astronomy since the 1970s. However, soft x-ray polarimetry is expected to be a sensitive probe of magnetic fields in high energy astrophysical objects including rotation-powered pulsars and pulsar wind nebulae. Here we report the re-detection of soft x-ray polarisation after 40 years from the Crab nebula and pulsar with PolarLight, a miniature polarimeter utilising a novel technique onboard a CubeSat. The polarisation fraction of the Crab in the on-pulse phases was observed to decrease after a glitch of the Crab pulsar on July 23, 2019, while that of the pure nebular emission remained constant within uncertainty. The phenomenon may have lasted about 100 days. If the association between the glitch and polarisation change can be confirmed with future observations, it will place strong constraints on the physical mechanism of the high energy emission and glitch of pulsars. △ Less

Submitted 10 November, 2020; originally announced November 2020.

Comments: Authors' version of an article published in Nature Astronomy on 11 May 2020. Link to the paper: https://www.nature.com/articles/s41550-020-1088-1

Journal ref: Nature Astronomy 4, 511 (2020)

In-orbit Operation and Performance of the CubeSat Soft X-ray Polarimeter PolarLight

Authors: Hong Li, Xiangyun Long, Hua Feng, Qiong Wu, Jiahui Huang, Weichun Jiang, Massimo Minuti, Dongxin Yang, Saverio Citraro, Hikmat Nasimi, Jiandong Yu, Ge Jin, Ming Zeng, Peng An, Luca Baldini, Ronaldo Bellazzini, Alessandro Brez, Luca Latronico, Carmelo Sgro, Gloria Spandre, Michele Pinchera, Fabio Muleri, Paolo Soffitta, Enrico Costa

Abstract: PolarLight is a compact soft X-ray polarimeter onboard a CubeSat, which was launched into a low-Earth orbit on October 29, 2018. In March 2019, PolarLight started full operation, and since then, regular observations with the Crab nebula, Sco X-1, and background regions have been conducted. Here we report the operation, calibration, and performance of PolarLight in the orbit. Based on these, we dis… ▽ More PolarLight is a compact soft X-ray polarimeter onboard a CubeSat, which was launched into a low-Earth orbit on October 29, 2018. In March 2019, PolarLight started full operation, and since then, regular observations with the Crab nebula, Sco X-1, and background regions have been conducted. Here we report the operation, calibration, and performance of PolarLight in the orbit. Based on these, we discuss how one can run a low-cost, shared CubeSat for space astronomy, and how CubeSats can play a role in modern space astronomy for technical demonstration, science observations, and student training. △ Less

Submitted 2 September, 2020; originally announced September 2020.

Comments: accepted for publication in Advances in Space Research

PolarLight: a CubeSat X-ray Polarimeter based on the Gas Pixel Detector

Authors: Hua Feng, Weichun Jiang, Massimo Minuti, Qiong Wu, Aera Jung, Dongxin Yang, Saverio Citraro, Hikmat Nasimi, Jiandong Yu, Ge Jin, Jiahui Huang, Ming Zeng, Peng An, Luca Baldini, Ronaldo Bellazzini, Alessandro Brez, Luca Latronico, Carmelo Sgrò, Gloria Spandre, Michele Pinchera, Fabio Muleri, Paolo Soffitta, Enrico Costa

Abstract: The gas pixel detector (GPD) is designed and developed for high-sensitivity astronomical X-ray polarimetry, which is a new window about to open in a few years. Due to the small mass, low power, and compact geometry of the GPD, we propose a CubeSat mission Polarimeter Light (PolarLight) to demonstrate and test the technology directly in space. There is no optics but a collimator to constrain the fi… ▽ More The gas pixel detector (GPD) is designed and developed for high-sensitivity astronomical X-ray polarimetry, which is a new window about to open in a few years. Due to the small mass, low power, and compact geometry of the GPD, we propose a CubeSat mission Polarimeter Light (PolarLight) to demonstrate and test the technology directly in space. There is no optics but a collimator to constrain the field of view to 2.3 degrees. Filled with pure dimethyl ether (DME) at 0.8 atm and sealed by a beryllium window of 100 micron thick, with a sensitive area of about 1.4 mm by 1.4 mm, PolarLight allows us to observe the brightest X-ray sources on the sky, with a count rate of, e.g., ~0.2 counts/s from the Crab nebula. The PolarLight is 1U in size and mounted in a 6U CubeSat, which was launched into a low Earth Sun-synchronous orbit on October 29, 2018, and is currently under test. More launches with improved designs are planned in 2019. These tests will help increase the technology readiness for future missions such as the enhanced X-ray Timing and Polarimetry (eXTP), better understand the orbital background, and may help constrain the physics with observations of the brightest objects. △ Less

Submitted 4 March, 2019; originally announced March 2019.

Comments: Accepted for publication in Experimental Astronomy

eXTP -- enhanced X-ray Timing and Polarimetry Mission

Authors: S. N. Zhang, M. Feroci, A. Santangelo, Y. W. Dong, H. Feng, F. J. Lu, K. Nandra, Z. S. Wang, S. Zhang, E. Bozzo, S. Brandt, A. De Rosa, L. J. Gou, M. Hernanz, M. van der Klis, X. D. Li, Y. Liu, P. Orleanski, G. Pareschi, M. Pohl, J. Poutanen, J. L. Qu, S. Schanne, L. Stella, P. Uttley , et al. (160 additional authors not shown)

Abstract: eXTP is a science mission designed to study the state of matter under extreme conditions of density, gravity and magnetism. Primary targets include isolated and binary neutron stars, strong magnetic field systems like magnetars, and stellar-mass and supermassive black holes. The mission carries a unique and unprecedented suite of state-of-the-art scientific instruments enabling for the first time… ▽ More eXTP is a science mission designed to study the state of matter under extreme conditions of density, gravity and magnetism. Primary targets include isolated and binary neutron stars, strong magnetic field systems like magnetars, and stellar-mass and supermassive black holes. The mission carries a unique and unprecedented suite of state-of-the-art scientific instruments enabling for the first time ever the simultaneous spectral-timing-polarimetry studies of cosmic sources in the energy range from 0.5-30 keV (and beyond). Key elements of the payload are: the Spectroscopic Focusing Array (SFA) - a set of 11 X-ray optics for a total effective area of about 0.9 m^2 and 0.6 m^2 at 2 keV and 6 keV respectively, equipped with Silicon Drift Detectors offering <180 eV spectral resolution; the Large Area Detector (LAD) - a deployable set of 640 Silicon Drift Detectors, for a total effective area of about 3.4 m^2, between 6 and 10 keV, and spectral resolution <250 eV; the Polarimetry Focusing Array (PFA) - a set of 2 X-ray telescope, for a total effective area of 250 cm^2 at 2 keV, equipped with imaging gas pixel photoelectric polarimeters; the Wide Field Monitor (WFM) - a set of 3 coded mask wide field units, equipped with position-sensitive Silicon Drift Detectors, each covering a 90 degrees x 90 degrees FoV. The eXTP international consortium includes mostly major institutions of the Chinese Academy of Sciences and Universities in China, as well as major institutions in several European countries and the United States. The predecessor of eXTP, the XTP mission concept, has been selected and funded as one of the so-called background missions in the Strategic Priority Space Science Program of the Chinese Academy of Sciences since 2011. The strong European participation has significantly enhanced the scientific capabilities of eXTP. The planned launch date of the mission is earlier than 2025. △ Less

Submitted 29 July, 2016; originally announced July 2016.

Comments: 16 pages, 16 figures. Oral talk presented at SPIE Astronomical Telescopes and Instrumentation, June 26 to July 1, 2016, Edingurgh, UK

Journal ref: Science China Physics, Mechanics & Astronomy, 2019, Volume 62, Issue 2, article id. 29502, 25 pp

Assembly and Test of the Gas Pixel Detector for X-ray Polarimetry

Authors: H. Li, H. Feng, F. Muleri, R. Bellazzini, M. Minuti, P. Soffitta, A. Brez, G. Spandre, M. Pinchera, C. Sgro, L. Baldini, R. She, E. Costa

Abstract: The gas pixel detector (GPD) dedicated for photoelectric X-ray polarimetry is selected as the focal plane detector for the ESA medium-class mission concept X-ray Imaging and Polarimetry Explorer (XIPE). Here we show the design, assembly, and preliminary test results of a small GPD for the purpose of gas mixture optimization needed for the phase A study of XIPE. The detector is assembled in house a… ▽ More The gas pixel detector (GPD) dedicated for photoelectric X-ray polarimetry is selected as the focal plane detector for the ESA medium-class mission concept X-ray Imaging and Polarimetry Explorer (XIPE). Here we show the design, assembly, and preliminary test results of a small GPD for the purpose of gas mixture optimization needed for the phase A study of XIPE. The detector is assembled in house at Tsinghua University following a design by the INFN-Pisa group. The improved detector design results in a good uniformity for the electric field. Filled with pure dimethyl ether (DME) at 0.8 atm, the measured energy resolution is 18% at 6 keV and inversely scales with the square root of the X-ray energy. The measured modulation factor is well consistent with that from simulation, up to ~0.6 above 6 keV. The residual modulation is found to be 0.30% +/- 0.15% at 6 keV for the whole sensitive area, which can be translated into a systematic error of less than 1% for polarization measurement at a confidence level of 99%. The position resolution of the detector is about 80 um in FWHM, consistent with previous studies and sufficient for XIPE requirements. △ Less

Submitted 18 September, 2015; originally announced September 2015.

Comments: accepted for publication in Nuclear Instruments and Methods in Physics Research Section A (NIMA)

LAMP: a micro-satellite based soft X-ray polarimeter for astrophysics

Authors: Rui She, Hua Feng, Fabio Muleri, Paolo Soffitta, Renxin Xu, Hong Li, Ronaldo Bellazzini, Zhanshan Wang, Daniele Spiga, Massimo Minuti, Alessandro Brez, Gloria Spandre, Michele Pinchera, Carmelo Sgro, Luca Baldini, Mingwu Wen, Zhengxiang Shen, Giovanni Pareschi, Gianpiero Tagliaferri, Kashmira Tayabaly, Bianca Salmaso, Yafeng Zhan

Abstract: The Lightweight Asymmetry and Magnetism Probe (LAMP) is a micro-satellite mission concept dedicated for astronomical X-ray polarimetry and is currently under early phase study. It consists of segmented paraboloidal multilayer mirrors with a collecting area of about 1300 cm^2 to reflect and focus 250 eV X-rays, which will be detected by position sensitive detectors at the focal plane. The primary t… ▽ More The Lightweight Asymmetry and Magnetism Probe (LAMP) is a micro-satellite mission concept dedicated for astronomical X-ray polarimetry and is currently under early phase study. It consists of segmented paraboloidal multilayer mirrors with a collecting area of about 1300 cm^2 to reflect and focus 250 eV X-rays, which will be detected by position sensitive detectors at the focal plane. The primary targets of LAMP include the thermal emission from the surface of pulsars and synchrotron emission produced by relativistic jets in blazars. With the expected sensitivity, it will allow us to detect polarization or place a tight upper limit for about 10 pulsars and 20 blazars. In addition to measuring magnetic structures in these objects, LAMP will also enable us to discover bare quark stars if they exist, whose thermal emission is expected to be zero polarized, while the thermal emission from neutron stars is believed to be highly polarized due to plasma polarization and the quantum electrodynamics (QED) effect. Here we present an overview of the mission concept, its science objectives and simulated observational results. △ Less

Submitted 15 September, 2015; originally announced September 2015.

Journal ref: Proc. SPIE 9601, UV, X-Ray, and Gamma-Ray Space Instrumentation for Astronomy XIX, 96010I (August 24, 2015)

The imaging properties of the Gas Pixel Detector as a focal plane polarimeter

Authors: S. Fabiani, E. Costa, E. Del Monte, F. Muleri, P. Soffitta, A. Rubini, R. Bellazzini, A. Brez, L. de Ruvo, M. Minuti, M. Pinchera, C. Sgrò, G. Spandre, D. Spiga, G. Tagliaferri, G. Pareschi, S. Basso, O. Citterio, V. Burwitz, W. Burkert, B. Menz, G. Hartner

Abstract: X-rays are particularly suited to probe the physics of extreme objects. However, despite the enormous improvements of X-ray Astronomy in imaging, spectroscopy and timing, polarimetry remains largely unexplored. We propose the photoelectric polarimeter Gas Pixel Detector (GPD) as an instrument candidate to fill the gap of more than thirty years of lack of measurements. The GPD, in the focus of a te… ▽ More X-rays are particularly suited to probe the physics of extreme objects. However, despite the enormous improvements of X-ray Astronomy in imaging, spectroscopy and timing, polarimetry remains largely unexplored. We propose the photoelectric polarimeter Gas Pixel Detector (GPD) as an instrument candidate to fill the gap of more than thirty years of lack of measurements. The GPD, in the focus of a telescope, will increase the sensitivity of orders of magnitude. Moreover, since it can measure the energy, the position, the arrival time and the polarization angle of every single photon, allows to perform polarimetry of subsets of data singled out from the spectrum, the light curve or the image of source. The GPD has an intrinsic very fine imaging capability and in this work we report on the calibration campaign carried out in 2012 at the PANTER X-ray test facility of the Max-Planck-Institut für extraterrestrische Physik of Garching (Germany) in which, for the first time, we coupled it to a JET-X optics module with a focal length of 3.5 m and an angular resolution of 18 arcsec at 4.5 keV. This configuration was proposed in 2012 aboard the X-ray Imaging Polarimetry Explorer (XIPE) in response to the ESA call for a small mission. We derived the imaging and polarimetric performance for extended sources like Pulsar Wind Nebulae and Supernova Remnants as case studies for the XIPE configuration, discussing also possible improvements by coupling the detector with advanced optics, having finer angular resolution and larger effective area, to study with more details extended objects. △ Less

Submitted 27 March, 2014; originally announced March 2014.

Comments: Accepted for publication in The Astrophysical Journal Supplement

Re-testing the JET-X Flight Module No. 2 at the PANTER facility

Authors: Daniele Spiga, Gianpiero Tagliaferri, Paolo Soffitta, Oberto Citterio, Stefano Basso, Ronaldo Bellazzini, Alessandro Brez, Wolfgang Burkert, Vadim Burwitz, Enrico Costa, Luca de Ruvo, Ettore Del Monte, Sergio Fabiani, Gisela Hartner, Benedikt Menz, Massimo Minuti, Fabio Muleri, Giovanni Pareschi, Michele Pinchera, Alda Rubini, Carmelo Sgrò, Gloria Spandre

Abstract: The Joint European X-ray Telescope (JET-X) was the core instrument of the Russian Spectrum-X-gamma space observatory. It consisted of two identical soft X-ray (0.3 - 10 keV) telescopes with focusing optical modules having a measured angular resolution of nearly 15 arcsec. Soon after the payload completion, the mission was cancelled and the two optical flight modules (FM) were brought to the Brera… ▽ More The Joint European X-ray Telescope (JET-X) was the core instrument of the Russian Spectrum-X-gamma space observatory. It consisted of two identical soft X-ray (0.3 - 10 keV) telescopes with focusing optical modules having a measured angular resolution of nearly 15 arcsec. Soon after the payload completion, the mission was cancelled and the two optical flight modules (FM) were brought to the Brera Astronomical Observatory where they had been manufactured. After 16 years of storage, we have utilized the JET-X FM2 to test at the PANTER X-ray facility a prototype of a novel X-ray polarimetric telescope, using a Gas Pixel Detector (GPD) with polarimetric capabilities in the focal plane of the FM2. The GPD was developed by a collaboration between INFN-Pisa and INAF-IAPS. In the first phase of the test campaign, we have re-tested the FM2 at PANTER to have an up-to-date characterization in terms of angular resolution and effective area, while in the second part of the test the GPD has been placed in the focal plane of the FM2. In this paper we report the results of the tests of the sole FM2, using an unpolarized X-ray source, comparing the results with the calibration done in 1996. △ Less

Submitted 18 February, 2014; v1 submitted 9 November, 2013; originally announced November 2013.

Comments: Author's accepted manuscript posted to arXiv.org as permitted by Springer's Self-Archiving Policy. The final publication is available at http://rd.springer.com/article/10.1007%2Fs10686-013-9365-y

Journal ref: Experimental Astronomy, February 2014, Vol. 37(1), p. 37-53

XIPE: the X-ray Imaging Polarimetry Explorer

Authors: Paolo Soffitta, Xavier Barcons, Ronaldo Bellazzini, João Braga, Enrico Costa, George W. Fraser, Szymon Gburek, Juhani Huovelin, Giorgio Matt, Mark Pearce, Juri Poutanen, Victor Reglero, Andrea Santangelo, Rashid A. Sunyaev, Gianpiero Tagliaferri, Martin Weisskopf, Roberto Aloisio, Elena Amato, Primo Attiná, Magnus Axelsson, Luca Baldini, Stefano Basso, Stefano Bianchi, Pasquale Blasi, Johan Bregeon , et al. (74 additional authors not shown)

Abstract: X-ray polarimetry, sometimes alone, and sometimes coupled to spectral and temporal variability measurements and to imaging, allows a wealth of physical phenomena in astrophysics to be studied. X-ray polarimetry investigates the acceleration process, for example, including those typical of magnetic reconnection in solar flares, but also emission in the strong magnetic fields of neutron stars and wh… ▽ More X-ray polarimetry, sometimes alone, and sometimes coupled to spectral and temporal variability measurements and to imaging, allows a wealth of physical phenomena in astrophysics to be studied. X-ray polarimetry investigates the acceleration process, for example, including those typical of magnetic reconnection in solar flares, but also emission in the strong magnetic fields of neutron stars and white dwarfs. It detects scattering in asymmetric structures such as accretion disks and columns, and in the so-called molecular torus and ionization cones. In addition, it allows fundamental physics in regimes of gravity and of magnetic field intensity not accessible to experiments on the Earth to be probed. Finally, models that describe fundamental interactions (e.g. quantum gravity and the extension of the Standard Model) can be tested. We describe in this paper the X-ray Imaging Polarimetry Explorer (XIPE), proposed in June 2012 to the first ESA call for a small mission with a launch in 2017 but not selected. XIPE is composed of two out of the three existing JET-X telescopes with two Gas Pixel Detectors (GPD) filled with a He-DME mixture at their focus and two additional GPDs filled with pressurized Ar-DME facing the sun. The Minimum Detectable Polarization is 14 % at 1 mCrab in 10E5 s (2-10 keV) and 0.6 % for an X10 class flare. The Half Energy Width, measured at PANTER X-ray test facility (MPE, Germany) with JET-X optics is 24 arcsec. XIPE takes advantage of a low-earth equatorial orbit with Malindi as down-link station and of a Mission Operation Center (MOC) at INPE (Brazil). △ Less

Submitted 26 September, 2013; originally announced September 2013.

Comments: 49 pages, 14 figures, 6 tables. Paper published in Experimental Astronomy http://link.springer.com/journal/10686

Journal ref: Experimental Astronomy (Aug. 2013)

Chromatic X-Ray imaging with a fine pitch CdTe sensor coupled to a large area photon counting pixel ASIC

Authors: R. Bellazzini, G. Spandre, A. Brez, M. Minuti, M. Pinchera, P. Mozzo

Abstract: An innovative X-ray imaging sensor with intrinsic digital characteristics is presented. It is based on Chromatic Photon Counting technology. The detector is able to count individually the incident X-ray photons and to separate them according to their energy (two 'color' images per exposure). The energy selection occurs in real time and at radiographic imaging speed (GHz global counting rate). Phot… ▽ More An innovative X-ray imaging sensor with intrinsic digital characteristics is presented. It is based on Chromatic Photon Counting technology. The detector is able to count individually the incident X-ray photons and to separate them according to their energy (two 'color' images per exposure). The energy selection occurs in real time and at radiographic imaging speed (GHz global counting rate). Photon counting, color mode and a very high spatial resolution (more than 10 l.p./mm at MTF50) allow to obtain an optimal ratio between image quality and absorbed dose. The individual block of the imaging system is a two-side buttable semiconductor radiation detector made of a thin pixellated CdTe crystal (the sensor) coupled to a large area VLSI CMOS pixel ASIC. 1, 2, 4, 8 tile units have been built. The 8 tiles unit has 25cm x 2.5cm sensitive area. Results and images obtained from in depth testing of several configurations of the system are presented. The X-Ray imaging system is the technological platform of PIXIRAD Imaging Counters s.r.l., a recently constituted INFN spin-off company. △ Less

Submitted 5 October, 2012; v1 submitted 3 October, 2012; originally announced October 2012.

Comments: 8 pages, 5 figures, 3 tables

Measurement of the position resolution of the Gas Pixel Detector

Authors: Paolo Soffitta, Fabio Muleri, Sergio Fabiani, Enrico Costa, Ronaldo Bellazzini, Alessandro Brez, Massimo Minuti, Michele Pinchera, Gloria Spandre

Abstract: The Gas Pixel Detector was designed and built as a focal plane instrument for X-ray polarimetry of celestial sources, the last unexplored subtopics of X-ray astronomy. It promises to perform detailed and sensitive measurements resolving extended sources and detecting polarization in faint sources in crowded fields at the focus of telescopes of good angular resolution. Its polarimetric and spectral… ▽ More The Gas Pixel Detector was designed and built as a focal plane instrument for X-ray polarimetry of celestial sources, the last unexplored subtopics of X-ray astronomy. It promises to perform detailed and sensitive measurements resolving extended sources and detecting polarization in faint sources in crowded fields at the focus of telescopes of good angular resolution. Its polarimetric and spectral capability were already studied in earlier works. Here we investigate for the first time, with both laboratory measurements and Monte Carlo simulations, its imaging properties to confirm its unique capability to carry out imaging spectral-polarimetry in future X-ray missions. △ Less

Submitted 30 August, 2012; originally announced August 2012.

Comments: Submitted to Nuclear Instruments and Methods in Physics Research Section A; 15 figures, 3 tables

POLARIX: a pathfinder mission of X-ray polarimetry

Authors: Enrico Costa, Ronaldo Bellazzini, Gianpiero Tagliaferri, Giorgio Matt, Andrea Argan, Primo Attina', Luca Baldini, Stefano Basso, Alessandro Brez, Oberto Citterio, Sergio Di Cosimo, Vincenzo Cotroneo, Sergio Fabiani, Marco Feroci, Antonella Ferri, Luca Latronico, Francesco Lazzarotto, Massimo Minuti, Ennio Morelli, Fabio Muleri, Lucio Nicolini, Giovanni Pareschi, Giuseppe Di Persio, Michele Pinchera, Massimiliano Razzano , et al. (8 additional authors not shown)

Abstract: Since the birth of X-ray astronomy, spectral, spatial and timing observation improved dramatically, procuring a wealth of information on the majority of the classes of the celestial sources. Polarimetry, instead, remained basically unprobed. X-ray polarimetry promises to provide additional information procuring two new observable quantities, the degree and the angle of polarization. POLARIX is a m… ▽ More Since the birth of X-ray astronomy, spectral, spatial and timing observation improved dramatically, procuring a wealth of information on the majority of the classes of the celestial sources. Polarimetry, instead, remained basically unprobed. X-ray polarimetry promises to provide additional information procuring two new observable quantities, the degree and the angle of polarization. POLARIX is a mission dedicated to X-ray polarimetry. It exploits the polarimetric response of a Gas Pixel Detector, combined with position sensitivity, that, at the focus of a telescope, results in a huge increase of sensitivity. Three Gas Pixel Detectors are coupled with three X-ray optics which are the heritage of JET-X mission. POLARIX will measure time resolved X-ray polarization with an angular resolution of about 20 arcsec in a field of view of 15 arcmin $\times$ 15 arcmin and with an energy resolution of 20 % at 6 keV. The Minimum Detectable Polarization is 12 % for a source having a flux of 1 mCrab and 10^5 s of observing time. The satellite will be placed in an equatorial orbit of 505 km of altitude by a Vega launcher.The telemetry down-link station will be Malindi. The pointing of POLARIX satellite will be gyroless and it will perform a double pointing during the earth occultation of one source, so maximizing the scientific return. POLARIX data are for 75 % open to the community while 25 % + SVP (Science Verification Phase, 1 month of operation) is dedicated to a core program activity open to the contribution of associated scientists. The planned duration of the mission is one year plus three months of commissioning and SVP, suitable to perform most of the basic science within the reach of this instrument. △ Less

Submitted 3 May, 2011; originally announced May 2011.

Comments: 42 pages, 28 figures

Journal ref: Exper.Astron.28:137-183,2010

Spectral and polarimetric characterization of the Gas Pixel Detector filled with dimethyl ether

Authors: F. Muleri, P. Soffitta, L. Baldini, R. Bellazzini, A. Brez, E. Costa, S. Fabiani, F. Krummenacher, L. Latronico, F. Lazzarotto, M. Minuti, M. Pinchera, A. Rubini, C. Sgro, G. Spandre

Abstract: The Gas Pixel Detector belongs to the very limited class of gas detectors optimized for the measurement of X-ray polarization in the emission of astrophysical sources. The choice of the mixture in which X-ray photons are absorbed and photoelectrons propagate, deeply affects both the energy range of the instrument and its performance in terms of gain, track dimension and ultimately, polarimetric se… ▽ More The Gas Pixel Detector belongs to the very limited class of gas detectors optimized for the measurement of X-ray polarization in the emission of astrophysical sources. The choice of the mixture in which X-ray photons are absorbed and photoelectrons propagate, deeply affects both the energy range of the instrument and its performance in terms of gain, track dimension and ultimately, polarimetric sensitivity. Here we present the characterization of the Gas Pixel Detector with a 1 cm thick cell filled with dimethyl ether (DME) at 0.79 atm, selected among other mixtures for the very low diffusion coefficient. Almost completely polarized and monochromatic photons were produced at the calibration facility built at INAF/IASF-Rome exploiting Bragg diffraction at nearly 45 degrees. For the first time ever, we measured the modulation factor and the spectral capabilities of the instrument at energies as low as 2.0 keV, but also at 2.6 keV, 3.7 keV, 4.0 keV, 5.2 keV and 7.8 keV. These measurements cover almost completely the energy range of the instrument and allows to compare the sensitivity achieved with that of the standard mixture, composed of helium and DME. △ Less

Submitted 31 March, 2010; originally announced March 2010.

Comments: 20 pages, 11 figures, 5 tables. Accepted for publication by NIMA

X-ray polarimetry in Astrophysics with the Gas Pixel Detector

Authors: F. Muleri, R. Bellazzini, A. Brez, E. Costa, F. Lazzarotto, M. Minuti, M. Pinchera, A. Rubini, P. Soffitta, G. Spandre

Abstract: The Gas Pixel Detector, recently developed and continuously improved by Pisa INFN in collaboration with IASF-Roma of INAF, can visualize the tracks produced within a low Z gas by photoelectrons of few keV. By reconstructing the impact point and the original direction of the photoelectrons, the GPD can measure the linear polarization of X-rays, while preserving the information on the absorption p… ▽ More The Gas Pixel Detector, recently developed and continuously improved by Pisa INFN in collaboration with IASF-Roma of INAF, can visualize the tracks produced within a low Z gas by photoelectrons of few keV. By reconstructing the impact point and the original direction of the photoelectrons, the GPD can measure the linear polarization of X-rays, while preserving the information on the absorption point, the energy and the time of individual photons. Applied to X-ray Astrophysics, in the focus of grazing incidence telescopes, it can perform angular resolved polarimetry with a huge improvement of sensitivity, when compared with the conventional techniques of Bragg diffraction at 45 degrees and Compton scattering around 90 degrees. This configuration is the basis of POLARIX and HXMT, two pathfinder missions, and is included in the baseline design of IXO, the very large X-ray telescope under study by NASA, ESA and JAXA. △ Less

Submitted 30 November, 2009; originally announced November 2009.

Comments: Proceeding of MPGD2009 Conference, June 12-15, 2009 Kolympari, Crete, Greece; 10 pages, 6 figures and 1 table

Journal ref: JINST 4:11002,2009

XPOL: a photoelectric polarimeter onboard XEUS

Authors: Enrico Costa, Ronaldo Bellazzini, Jean Bregeon, Alessandro Brez, Massimo Frutti, Sergio Di Cosimo, Luca Latronicio, Francesco Lazzarotto, Giorgio Matt, Massimo Minuti, Ennio Morelli, Fabio Muleri, Michele Pinchera, Massimiliano Razzano, Alda Rubini, Paolo Soffitta, Gloria Spandre

Abstract: The XEUS mission incorporates two satellites: the Mirror Spacecraft with 5 m2 of collecting area at 1 keV and 2 m2 at 7 keV, and an imaging resolution of 5" HEW and the Payload Spacecraft which carries the focal plane instrumentation. XEUS was submitted to ESA Cosmic Vision and was selected for an advanced study as a large mission. The baseline design includes XPOL, a polarimeter based on the ph… ▽ More The XEUS mission incorporates two satellites: the Mirror Spacecraft with 5 m2 of collecting area at 1 keV and 2 m2 at 7 keV, and an imaging resolution of 5" HEW and the Payload Spacecraft which carries the focal plane instrumentation. XEUS was submitted to ESA Cosmic Vision and was selected for an advanced study as a large mission. The baseline design includes XPOL, a polarimeter based on the photoelectric effect, that takes advantage of the large effective area which permits the study of the faint sources and of the long focal length, resulting in a very good spatial resolution, which allows the study of spatial features in extended sources. We show how, with XEUS, Polarimetry becomes an efficient tool at disposition of the Astronomical community. △ Less

Submitted 15 October, 2008; originally announced October 2008.

Comments: 10 pages, 6 figures

Journal ref: Proceedings of SPIE Astronomical Instrumentation 2008 Conference, 23-28 June 2008 Marseille, France, vol. 7011-15

The Gas Pixel Detector as an X-ray photoelectric polarimeter with a large field of view

Authors: Fabio Muleri, Paolo Soffitta, Ronaldo Bellazzini, Alessandro Brez, Enrico Costa, Sergio Fabiani, Massimo Frutti, Massimo Minuti, Maria Barbara Negri, Michele Pinchera, Alda Rubini, Gloria Spandre

Abstract: The Gas Pixel Detector (GPD) is a new generation device which, thanks to its 50 um pixels, is capable of imaging the photoelectrons tracks produced by photoelectric absorption in a gas. Since the direction of emission of the photoelectrons is strongly correlated with the direction of polarization of the absorbed photons, this device has been proposed as a polarimeter for the study of astrophysic… ▽ More The Gas Pixel Detector (GPD) is a new generation device which, thanks to its 50 um pixels, is capable of imaging the photoelectrons tracks produced by photoelectric absorption in a gas. Since the direction of emission of the photoelectrons is strongly correlated with the direction of polarization of the absorbed photons, this device has been proposed as a polarimeter for the study of astrophysical sources, with a sensitivity far higher than the instruments flown to date. The GPD has been always regarded as a focal plane instrument and then it has been proposed to be included on the next generation space-borne missions together with a grazing incidence optics. Instead in this paper we explore the feasibility of a new kind of application of the GPD and of the photoelectric polarimeters in general, i.e. an instrument with a large field of view. By means of an analytical treatment and measurements, we verify if it is possible to preserve the sensitivity to the polarization for inclined beams, opening the way for the measurement of X-ray polarization for transient astrophysical sources. While severe systematic effects arise for inclination greater than about 20 degrees, methods and algorithms to control them are discussed. △ Less

Submitted 15 October, 2008; originally announced October 2008.

Comments: 11 pages, 8 figures

Journal ref: Proceedings of SPIE Astronomical Instrumentation 2008 Conference, 23-28 June 2008 Marseille, France, vol. 7011-88

A versatile facility for the calibration of X-ray polarimeters with polarized and unpolarized controlled beams

Authors: Fabio Muleri, Paolo Soffitta, Ronaldo Bellazzini, Alessandro Brez, Enrico Costa, Massimo Frutti, Marcello Mastropietro, Ennio Morelli, Michele Pinchera, Alda Rubini, Gloria Spandre

Abstract: We devised and built a versatile facility for the calibration of the next generation X-ray polarimeters with unpolarized and polarized radiation. The former is produced at 5.9 keV by means of a Fe55 radioactive source or by X-ray tubes, while the latter is obtained by Bragg diffraction at nearly 45 degrees. Crystals tuned with the emission lines of X-ray tubes with molybdenum, rhodium, calcium a… ▽ More We devised and built a versatile facility for the calibration of the next generation X-ray polarimeters with unpolarized and polarized radiation. The former is produced at 5.9 keV by means of a Fe55 radioactive source or by X-ray tubes, while the latter is obtained by Bragg diffraction at nearly 45 degrees. Crystals tuned with the emission lines of X-ray tubes with molybdenum, rhodium, calcium and titanium anodes are employed for the efficient production of highly polarized photons at 2.29, 2.69, 3.69 and 4.51 keV respectively. Moreover the continuum emission is exploited for the production of polarized photons at 1.65 keV and 2.04 keV and at energies corresponding to the higher orders of diffraction. The photons are collimated by means of interchangeable capillary plates and diaphragms, allowing a trade-off between collimation and high fluxes. The direction of the beam is accurately arranged by means of high precision motorized stages, controlled via computer so that long and automatic measurements can be done. Selecting the direction of polarization and the incidence point we can map the response of imaging devices to both polarized and unpolarized radiation. Changing the inclination of the beam we can study the systematic effects due to the focusing of grazing incidence optics and the feasibility of instruments with large field of view. △ Less

Submitted 15 October, 2008; originally announced October 2008.

Comments: 12 pages, 11 figures

Journal ref: Proceedings of SPIE Astronomical Instrumentation 2008 Conference, 23-28 June 2008 Marseille, France, vol. 7011-84

Low energy polarization sensitivity of the Gas Pixel Detector

Authors: F. Muleri, P. Soffitta, L. Baldini, R. Bellazzini, J. Bregeon, A. Brez, E. Costa, M. Frutti, L. Latronico, M. Minuti, M. B. Negri, N. Omodei, M. Pinchera, M. Pesce-Rollins, M. Razzano, A. Rubini, C. Sgro', G. Spandre

Abstract: An X-ray photoelectric polarimeter based on the Gas Pixel Detector has been proposed to be included in many upcoming space missions to fill the gap of about 30 years from the first (and to date only) positive measurement of polarized X-ray emission from an astrophysical source. The estimated sensitivity of the current prototype peaks at an energy of about 3 keV, but the lack of readily available… ▽ More An X-ray photoelectric polarimeter based on the Gas Pixel Detector has been proposed to be included in many upcoming space missions to fill the gap of about 30 years from the first (and to date only) positive measurement of polarized X-ray emission from an astrophysical source. The estimated sensitivity of the current prototype peaks at an energy of about 3 keV, but the lack of readily available polarized sources in this energy range has prevented the measurement of detector polarimetric performances. In this paper we present the measurement of the Gas Pixel Detector polarimetric sensitivity at energies of a few keV and the new, light, compact and transportable polarized source that was devised and built to this aim. Polarized photons are produced, from unpolarized radiation generated with an X-ray tube, by means of Bragg diffraction at nearly 45 degrees. The employment of mosaic graphite and flat aluminum crystals allow the production of nearly completely polarized photons at 2.6, 3.7 and 5.2 keV from the diffraction of unpolarized continuum or line emission. The measured modulation factor of the Gas Pixel Detector at these energies is in good agreement with the estimates derived from a Monte Carlo software, which was up to now employed for driving the development of the instrument and for estimating its low energy sensitivity. In this paper we present the excellent polarimetric performance of the Gas Pixel Detector at energies where the peak sensitivity is expected. These measurements not only support our previous claims of high sensitivity but confirm the feasibility of astrophysical X-ray photoelectric polarimetry. △ Less

Submitted 28 September, 2007; originally announced September 2007.

Comments: 15 pages, 12 figures. Accepted for publication in NIMA

Journal ref: Nucl.Instrum.Meth.A584:149-159,2008

Imaging with the invisible light

Authors: R. Bellazzini, G. Spandre, A. Brez, M. Minuti, L. Baldini, L. Latronico, M. M. Massai, N. Omodei, M. Pesce-Rollins, C Sgró, M. Razzano, M. Pinchera, J. Bregeon, M. Kuss, A. Braem

Abstract: We describe a UV photo-detector with single photon(electron) counting and imaging capability. It is based on a CsI photocathode, a GEM charge multiplier and a self triggering CMOS analog pixel chip with 105k pixels at 50 micron pitch. The single photoelectron produced by the absorption of a UV photon is drifted to and multiplied inside a single GEM hole. The coordinates of the GEM avalanche are… ▽ More We describe a UV photo-detector with single photon(electron) counting and imaging capability. It is based on a CsI photocathode, a GEM charge multiplier and a self triggering CMOS analog pixel chip with 105k pixels at 50 micron pitch. The single photoelectron produced by the absorption of a UV photon is drifted to and multiplied inside a single GEM hole. The coordinates of the GEM avalanche are reconstructed with high accuracy (4 micron rms) by the pixel chip. As a result the map of the GEM holes, arranged on a triangular pattern at 50micron pitch, is finely imaged. △ Less

Submitted 20 March, 2007; v1 submitted 19 March, 2007; originally announced March 2007.

Comments: 6 pages, 14 figures, presented at the 11th Vienna Conference on Instrumentation VIC 2007, submitted to Nuclear Instruments and Methods A

Journal ref: Nucl.Instrum.Meth.A581:246-253,2007; Erratum-ibid.A585:105,2008

A Sealed Gas Pixel Detector for X-ray Astronomy

Authors: R. Bellazzini, G. Spandre, M. Minuti, L. Baldini, A. Brez, L. Latronico, N. Omodei, M. Razzano, M. M. Massai, M. Pinchera, M. Pesce-Rollins, C. Sgro, E. Costa, P. Soffitta, H. Sipila, E. Lempinen

Abstract: We report on the results of a new, sealed, Gas Pixel Detector. The very compact design and the absence of the gas flow system, make this detector substantially ready for use as focal plane detector for future X-ray space telescopes. The instrument brings high sensitivity to X-ray polarimetry, which is the last unexplored field of X-ray astronomy. It derives the polarization information from the… ▽ More We report on the results of a new, sealed, Gas Pixel Detector. The very compact design and the absence of the gas flow system, make this detector substantially ready for use as focal plane detector for future X-ray space telescopes. The instrument brings high sensitivity to X-ray polarimetry, which is the last unexplored field of X-ray astronomy. It derives the polarization information from the track of the photoelectrons that are imaged by a high gain (>1000), fine pitch GEM that matches the pitch of a pixel ASIC which is the collecting anode of the GPD (105k, 50 micron wide, hexagonal cells). The device is able to simultaneously perform good imaging (50-60 micron), moderate spectroscopy (~15% at 6 keV) as well as fast, high rate timing in the 1-10keV range. Moreover, being truly 2D, it is non dispersive and does not require any rotation. The great improvement of sensitivity, at least two orders of magnitude with respect to traditional polarimeters (based on Bragg crystals or Thomson scattering), will allow the direct exploration of the most dramatic objects of the X-ray sky. At the focus of the large mirror area of the XEUS telescope it will be decisive in reaching many of the scientific goals of the mission. With integration times of the order of one day, polarimetry of Active Galactic Nuclei at the per cent level will be possible, making for a real breakthrough in high energy astrophysics. △ Less

Submitted 20 November, 2006; v1 submitted 16 November, 2006; originally announced November 2006.

Comments: 10 pages, 10 figures, Presented to the Sixth International "Hiroshima" Symposium on the Development and Application of Semiconductor Tracking Detectors (to be published on NIMA)

Journal ref: Nucl.Instrum.Meth.A579:853-858,2007

POLARIX: a small mission of x-ray polarimetry

Authors: Enrico Costa, Ronaldo Bellazzini, Paolo Soffitta, Fabio Muleri, Marco Feroci, Massimo Frutti, Marcello Mastropietro, Luigi Pacciani, Alda Rubini, Ennio Morelli, Luca Baldini, Francesco Bitti, Alessandro Brez, Francesco Cavalca, Luca Latronico, Marco Maria Massai, Nicola Omodei, Michele Pinchera, Carmelo Sgro', Gloria Spandre, Giorgio Matt, Giuseppe Cesare Perola, Guido Chincarini, Oberto Citterio, Gianpiero Tagliaferri , et al. (2 additional authors not shown)

Abstract: X-Ray Polarimetry can be now performed by using a Micro Pattern Gas Chamber in the focus of a telescope. It requires large area optics for most important scientific targets. But since the technique is additive a dedicated mission with a cluster of small telescopes can perform many important measurements and bridge the 40 year gap between OSO-8 data and future big telescopes such as XEUS. POLARIX… ▽ More X-Ray Polarimetry can be now performed by using a Micro Pattern Gas Chamber in the focus of a telescope. It requires large area optics for most important scientific targets. But since the technique is additive a dedicated mission with a cluster of small telescopes can perform many important measurements and bridge the 40 year gap between OSO-8 data and future big telescopes such as XEUS. POLARIX has been conceived as such a pathfinder. It is a Small Satellite based on the optics of JET-X. Two telescopes are available in flight configuration and three more can be easily produced starting from the available superpolished mandrels. We show the capabilities of such a cluster of telescopes each equipped with a focal plane photoelectric polarimeter and discuss a few alternative solutions. △ Less

Submitted 20 September, 2006; originally announced September 2006.

Comments: 9 pages, 5 figures

Journal ref: SPIE proceedings, Vol. 6266 0R-1, 24-31 May 2006, Orlando (Florida), M.J. Turner, G. Hasinger eds

An X-ray polarimeter for hard X-ray optics

Authors: Fabio Muleri, Ronaldo Bellazzini, Enrico Costa, Paolo Soffitta, Francesco Lazzarotto, Marco Feroci, Luigi Pacciani, Alda Rubini, Ennio Morelli, Luca Baldini, Francesco Bitti, Alessandro Brez, Francesco Cavalca, Luca Latronico, Marco Maria Massai, Nicola Omodei, Michele Pinchera, Carmelo Sgro', Gloria Spandre, Giorgio Matt, Giuseppe Cesare Perola, Oberto Citterio, Giovanni Pareschi, Vincenzo Cotroneo, Daniele Spiga , et al. (1 additional authors not shown)

Abstract: Development of multi-layer optics makes feasible the use of X-ray telescope at energy up to 60-80 keV: in this paper we discuss the extension of photoelectric polarimeter based on Micro Pattern Gas Chamber to high energy X-rays. We calculated the sensitivity with Neon and Argon based mixtures at high pressure with thick absorption gap: placing the MPGC at focus of a next generation multi-layer o… ▽ More Development of multi-layer optics makes feasible the use of X-ray telescope at energy up to 60-80 keV: in this paper we discuss the extension of photoelectric polarimeter based on Micro Pattern Gas Chamber to high energy X-rays. We calculated the sensitivity with Neon and Argon based mixtures at high pressure with thick absorption gap: placing the MPGC at focus of a next generation multi-layer optics, galatic and extragalactic X-ray polarimetry can be done up till 30 keV. △ Less

Submitted 20 September, 2006; originally announced September 2006.

Comments: 12 pages, 7 figures

Journal ref: SPIE proceedings, Vol. 6266 2X-1, 24-31 May 2006, Orlando (Florida), M.J. Turner, G. Hasinger eds

A photoelectric polarimeter for XEUS: a new window in x-ray sky

Authors: Ronaldo Bellazzini, Luca Baldini, Francesco Bitti, Alessandro Brez, Francesco Cavalca, Luca Latronico, Marco Maria Massai, Nicola Omodei, Michele Pinchera, Carmelo Sgro', Gloria Spandre, Enrico Costa, Paolo Soffitta, Giuseppe Di Persio, Marco Feroci, Fabio Muleri, Luigi Pacciani, Alda Rubini, Ennio Morelli, Giorgio Matt, Giuseppe Cesare Perola

Abstract: XEUS is a large area telescope aiming to rise X-ray Astronomy to the level of Optical Astronomy in terms of collecting areas. It will be based on two satellites, locked on a formation flight, one with the optics, one with the focal plane. The present design of the focal plane foresees, as an auxiliary instrument, the inclusion of a Polarimeter based on a Micropattern Chamber. We show how such a… ▽ More XEUS is a large area telescope aiming to rise X-ray Astronomy to the level of Optical Astronomy in terms of collecting areas. It will be based on two satellites, locked on a formation flight, one with the optics, one with the focal plane. The present design of the focal plane foresees, as an auxiliary instrument, the inclusion of a Polarimeter based on a Micropattern Chamber. We show how such a device is capable to solve open problems on many classes of High Energy Astrophysics objects and to use X-ray sources as a laboratory for a substantial progress on Fundamental Physics. △ Less

Submitted 20 September, 2006; originally announced September 2006.

Comments: 12 pages, 7 figures

Journal ref: Proc.SPIE Int.Soc.Opt.Eng. 6266 (2006) 24-31

Gas Pixel Detectors for X-ray Polarimetry applications

Authors: R. Bellazzini, F. Angelini, L. Baldini, F. Bitti, A. Brez, F. Cavalca, M. Del Prete, M. Kuss, L. Latronico, N. Omodei, M. Pinchera, M. M. Massai, M. Minuti, M. Razzano, C. Sgro, G. Spandre, A. Tenze, E. Costa, P. Soffitta

Abstract: We discuss a new class of Micro Pattern Gas Detectors, the Gas Pixel Detector (GPD), in which a complete integration between the gas amplification structure and the read-out electronics has been reached. An Application-Specific Integrated Circuit (ASIC) built in deep sub-micron technology has been developed to realize a monolithic device that is, at the same time, the pixelized charge collecting… ▽ More We discuss a new class of Micro Pattern Gas Detectors, the Gas Pixel Detector (GPD), in which a complete integration between the gas amplification structure and the read-out electronics has been reached. An Application-Specific Integrated Circuit (ASIC) built in deep sub-micron technology has been developed to realize a monolithic device that is, at the same time, the pixelized charge collecting electrode and the amplifying, shaping and charge measuring front-end electronics. The CMOS chip has the top metal layer patterned in a matrix of 80 micron pitch hexagonal pixels, each of them directly connected to the underneath electronics chain which has been realized in the remaining five layers of the 0.35 micron VLSI technology. Results from tests of a first prototype of such detector with 2k pixels and a full scale version with 22k pixels are presented. The application of this device for Astronomical X-Ray Polarimetry is discussed. The experimental detector response to polarized and unpolarized X-ray radiation is shown. Results from a full MonteCarlo simulation for two astronomical sources, the Crab Nebula and the Hercules X1, are also reported. △ Less

Submitted 8 February, 2006; v1 submitted 9 December, 2005; originally announced December 2005.

Comments: 16 pages, 20 figures, accepted for publication in Nuclear Instruments and Methods in Physics Research Section A

Journal ref: Nucl.Instrum.Meth.A560:425-434,2006