-
A parameterized equation of state for dark energy and Hubble Tension
Authors:
Jing-Ya Zhao,
Tong-Yu He,
Jia-Jun Yin,
Zhan-Wen Han,
Rong-Jia Yang
Abstract:
We propose a parameterized equation of state for dark energy and perform observational tests with the Hubble parameter measurements, the Pantheon supernova sample, baryon acoustic oscillations, and DESI DR2 data. We obtain the best-fit values for the parameters as: $H_0=73.96\pm 0.16$, $Ω_{\rm m}=0.2434\pm 0.0079$, and $α=-0.00049\pm 0.00092$, demonstrating that the model exhibits a high degree of…
▽ More
We propose a parameterized equation of state for dark energy and perform observational tests with the Hubble parameter measurements, the Pantheon supernova sample, baryon acoustic oscillations, and DESI DR2 data. We obtain the best-fit values for the parameters as: $H_0=73.96\pm 0.16$, $Ω_{\rm m}=0.2434\pm 0.0079$, and $α=-0.00049\pm 0.00092$, demonstrating that the model exhibits a high degree of consistency with astronomical observations and provides a promising parameterized method for addressing the Hubble tension.
△ Less
Submitted 14 December, 2025;
originally announced December 2025.
-
A New Algol-type Binary with an Accretion disk
Authors:
Tongyu He,
Jiao Li,
Xiaobin Zhang,
Mikhail Kovalev,
Zhibin Dai,
Zhenwei Li,
Hongwei Ge,
Shunyi Lan,
Jiangdan Li,
Dengkai Jiang,
Jianping Xiong,
Xuefei Chen,
Zhanwen Han
Abstract:
We present a comprehensive photometric and spectroscopic analysis of the Algol-type binary \textit{Gaia} DR3 1892576067672499328. We identified the system as a spectroscopic binary based on medium-resolution LAMOST spectra. Combined with \textit{TESS} photometry, we determine an orbital period of \( P = 2.47757 (1) \) days, a low mass ratio of \( q = 0.098 \pm 0.002 \), and an orbital inclination…
▽ More
We present a comprehensive photometric and spectroscopic analysis of the Algol-type binary \textit{Gaia} DR3 1892576067672499328. We identified the system as a spectroscopic binary based on medium-resolution LAMOST spectra. Combined with \textit{TESS} photometry, we determine an orbital period of \( P = 2.47757 (1) \) days, a low mass ratio of \( q = 0.098 \pm 0.002 \), and an orbital inclination of \( i = 46.934^{+2.613}_{-1.11} \) degrees. The orbit is consistent with being circular (\( e = 0 \)). The binary comprises a \( M_1 = 1.817 ^{ +0.106}_{-0.202} \,M_\odot \), \( R_1 = 1.265^{+0.121}_{-0.160}\,R_\odot \) A-type primary and a Roche-lobe-filling secondary of \( M_2 = 0.179 ^{ +0.011}_{-0.020} \,M_\odot \), \( R_2 = 1.994 ^{ +0.041}_{-0.077} \,R_\odot \). The double-peak H$α$ emission line indicates the possible existence of a Keplerian accretion disc. We established a simple standard accretion disc model and modeled the geometric and dynamical properties of the accretion disc. The obtained outer disc radius $R_{\mathrm{out}} \approx 3.36 \pm 0.43\,R_\odot$ is consistent with the values inferred from the emission velocity of H$α$. Systemic velocity variations observed over time suggest the possible presence of a tertiary companion, with a minimum mass of $M_3 > 0.369 \pm 0.024 \,M_\odot$. Given the low mass ratio, the secondary may evolve into a proto-helium white dwarf, forming an \text{EL CVn}-type system in the future. This system offers valuable insights into accretion dynamics and the formation of binaries.
△ Less
Submitted 8 October, 2025;
originally announced October 2025.
-
The enhanced X-ray Timing and Polarimetry mission -- eXTP for launch in 2030
Authors:
Shuang-Nan Zhang,
Andrea Santangelo,
Yupeng Xu,
Hua Feng,
Fangjun Lu,
Yong Chen,
Mingyu Ge,
Kirpal Nandra,
Xin Wu,
Marco Feroci,
Margarita Hernanz,
Congzhan Liu,
Huilin He,
Yusa Wang,
Weichun Jiang,
Weiwei Cui,
Yanji Yang,
Juan Wang,
Wei Li,
Xiaohua Liu,
Bin Meng,
Xiangyang Wen,
Aimei Zhang,
Jia Ma,
Maoshun Li
, et al. (136 additional authors not shown)
Abstract:
In this paper we present the current status of the enhanced X-ray Timing and Polarimetry mission, which has been fully approved for launch in 2030. eXTP is a space science mission designed to study fundamental physics under extreme conditions of matter density, gravity, and magnetism. The mission aims at determining the equation of state of matter at supra-nuclear density, measuring the effects of…
▽ More
In this paper we present the current status of the enhanced X-ray Timing and Polarimetry mission, which has been fully approved for launch in 2030. eXTP is a space science mission designed to study fundamental physics under extreme conditions of matter density, gravity, and magnetism. The mission aims at determining the equation of state of matter at supra-nuclear density, measuring the effects of quantum electro-dynamics, and understanding the dynamics of matter in strong-field gravity. In addition to investigating fundamental physics, the eXTP mission is poised to become a leading observatory for time-domain and multi-messenger astronomy in the 2030's, as well as providing observations of unprecedented quality on a variety of galactic and extragalactic objects. After briefly introducing the history and a summary of the scientific objectives of the eXTP mission, this paper presents a comprehensive overview of: 1) the cutting-edge technology, technical specifications, and anticipated performance of the mission's scientific instruments; 2) the full mission profile, encompassing spacecraft design, operational capabilities, and ground segment infrastructure.
△ Less
Submitted 8 September, 2025; v1 submitted 9 June, 2025;
originally announced June 2025.
-
Orbital Parameters of 665 Double-lined Spectroscopic Binaries in the LAMOST Medium-Resolution Survey
Authors:
Sufen Guo,
Mikhail Kovalev,
Jiao Li,
Guoliang Lu,
Shi Jia,
Zhenwei Li,
Jiangdan Li,
Jianping Xiong,
Mingkuan Yang,
Tongyu He,
Xuefei Chen,
Zhanwen Han
Abstract:
The period, mass ratio, eccentricity, and other orbital parameters are fundamental for investigating binary star evolution. However, the number of binaries with known orbital parameters remains limited. Utilizing the LAMOST-MRS survey, we derived orbital solutions for 665 SB2 binaries by fitting the radial velocities of 1119 SB2 systems with at least six observations, employing a modified version…
▽ More
The period, mass ratio, eccentricity, and other orbital parameters are fundamental for investigating binary star evolution. However, the number of binaries with known orbital parameters remains limited. Utilizing the LAMOST-MRS survey, we derived orbital solutions for 665 SB2 binaries by fitting the radial velocities of 1119 SB2 systems with at least six observations, employing a modified version of Thejoker optimized for SB2 binaries. To ensure the reliability of the results, four selection criteria were applied: reduced chi-square, normalized mean absolute error, maximum phase gap, and RV distribution metric. After applying these criteria, 665 reliable orbits were retained. Comparison with Kepler, TESS, and ZTF light curve data shows excellent agreement, with discrepancies in some cases attributed to shorter pulsation periods observed in light curves. Additionally, good consistency is found between our periods and those of SB1 systems in Gaia data. These orbital solutions contribute to understanding binary star evolution and the statistical properties of binary populations.
△ Less
Submitted 16 April, 2025;
originally announced April 2025.
-
Observational properties of black hole in quantum fluctuation modified gravity
Authors:
Jiajun Yin,
Tong-Yu He,
Ming Liu,
Hui-Min Fan,
Bohai Chen,
Zhan-Wen Han,
Rong-Jia Yang
Abstract:
This study investigates the properties of the thin accretion disk around a black hole in quantum fluctuation modified gravity (QFMGBH) using the Novikov-Thorne model. We restrict the parameter \( α\) characterizing the quantum fluctuation of metric and compute the ISCO radius, examining its effect on the energy flux, the radiation temperature, the luminosity spectrum, the energy efficiency, and th…
▽ More
This study investigates the properties of the thin accretion disk around a black hole in quantum fluctuation modified gravity (QFMGBH) using the Novikov-Thorne model. We restrict the parameter \( α\) characterizing the quantum fluctuation of metric and compute the ISCO radius, examining its effect on the energy flux, the radiation temperature, the luminosity spectrum, the energy efficiency, and the shadow size for various values of the parameter \( ω\) characterizing the matter around the black hole. Our findings show that the ISCO radius increases with \( α\) for \( ω= 1/3, 0, -2/3 \), but decreases for \( ω= -4/3 \). As \( α\) increases, the energy flux and the temperature show distinct trends, with changes in the luminosity spectrum and the efficiency. The shadow size increases for \( ω= 1/3, 0, -2/3 \), and decreases for \( ω= -4/3 \). The accretion disk around the QFMGBH is smaller, hotter, and brighter than that surrounded the Schwarzschild BH in GR, suggesting that the observable differences can potentially distinguish quantum fluctuation modified gravity from standard GR.
△ Less
Submitted 8 September, 2025; v1 submitted 1 March, 2025;
originally announced March 2025.
-
Identifying Hierarchically Triple Star Systems with Gaia DR3 and LAMOST
Authors:
Tongyu He,
Jiao Li,
Jiangdan Li,
Jianping Xiong,
Xiaobin Zhang,
Mikhail Kovalev,
Qiyuan Cheng,
Sufen Guo,
Mingkuan Yang,
Xuefei Chen,
Zhanwen Han
Abstract:
Triple star systems are critical for understanding stellar dynamics and compact objects in astrophysics, yet confirmed hierarchical triples identified via spectroscopy remain limited. In this study, we identified 23 triple systems by cross-matching the Gaia DR3 non-single star catalog with LAMOST DR10 spectroscopic data; 18 of them are new discoveries. For two well-observed triples, we performed r…
▽ More
Triple star systems are critical for understanding stellar dynamics and compact objects in astrophysics, yet confirmed hierarchical triples identified via spectroscopy remain limited. In this study, we identified 23 triple systems by cross-matching the Gaia DR3 non-single star catalog with LAMOST DR10 spectroscopic data; 18 of them are new discoveries. For two well-observed triples, we performed radial velocity curve fitting and light curve analysis to determine their orbital parameters, with inner and outer periods of 1.26 days and 656 days for one triple, and 3.42 days and 422 days for the other. We compared the results with other studies. We also analyzed the radial velocities (RVs) of these 23 triples, revealing a range of $V$ from approximately 40~km~s$^{-1}$ to 210~km~s$^{-1}$. Due to spectral resolution and detection limitations, velocity differences below 45~km~s$^{-1}$ in binaries and below 90~km~s$^{-1}$ in the inner binaries of triple systems are challenging to detect. Consequently, our detection range for inner orbital periods is restricted to 0.2--20 days, with the highest efficiency for periods under 10 days. These findings underscore the advantage of spectroscopic observations for identifying triple systems with short inner orbital periods.
△ Less
Submitted 3 December, 2024;
originally announced December 2024.
-
A new parametrization of Hubble function and Hubble tension
Authors:
Tong-Yu He,
Jia-Jun Yin,
Zhen-Yu Wang,
Zhan-Wen Han,
Rong-Jia Yang
Abstract:
We present a new Hubble parameterization method and employ observational data from Hubble, Pantheon, and Baryon Acoustic Oscillations to constrain model parameters. The proposed method is thoroughly validated against these datasets, demonstrating a robust fit to the observational data. The obtained best-fit values are $H_0 = 67.5^{+1.3}_{-1.6}$ $\text{km s}^{-1} \text{Mpc}^{-1}$,…
▽ More
We present a new Hubble parameterization method and employ observational data from Hubble, Pantheon, and Baryon Acoustic Oscillations to constrain model parameters. The proposed method is thoroughly validated against these datasets, demonstrating a robust fit to the observational data. The obtained best-fit values are $H_0 = 67.5^{+1.3}_{-1.6}$ $\text{km s}^{-1} \text{Mpc}^{-1}$, $Ω_{\rm{m0}} = 0.2764\pm{0.0094}$, and $α= 0.33\pm{0.22}$, consistent with the Planck 2018 results, highlighting the existence of Hubble tension.
△ Less
Submitted 17 September, 2024; v1 submitted 27 May, 2024;
originally announced May 2024.
-
Possible signatures of higher dimension in thin accretion disk around brane world black hole
Authors:
Ailin Liu,
Tong-Yu He,
Ming Liu,
Zhan-Wen Han,
Rong-Jia Yang
Abstract:
We probe deeply into the characteristics of thin accretion disk surrounding black hole within the brane world paradigm. We investigate how model parameters affect the physical properties of the disk. Our findings indicate that as the tidal charge parameter inherited from the higher dimension increases, the energy flux, the radiation temperature, the spectral cutoff frequency, the spectral luminosi…
▽ More
We probe deeply into the characteristics of thin accretion disk surrounding black hole within the brane world paradigm. We investigate how model parameters affect the physical properties of the disk. Our findings indicate that as the tidal charge parameter inherited from the higher dimension increases, the energy flux, the radiation temperature, the spectral cutoff frequency, the spectral luminosity, and the conversion efficiency of the disk all increase, but the radius of the innermost stable circular orbit decreases. Compared to cases of the Kerr and Schwarzschild black holes, the disk is hotter and more luminous for positive tidal charge parameter, while it is cooler and less luminous for negative tidal charge parameter, which suggests the potential for probing possible signatures of higher dimension.
△ Less
Submitted 1 September, 2024; v1 submitted 22 April, 2024;
originally announced April 2024.
-
Accretion of matter by a Charged dilaton black hole
Authors:
Yinan Jia,
Tong-Yu He,
Wen-Qian Wang,
Zhan-Wen Han,
Rong-Jia Yang
Abstract:
Considering accretion onto a charged dilaton black hole, the fundamental equations governing accretion, general analytic expressions for critical points, critical velocity, critical speed of sound, and ultimately the mass accretion rate are obtained. A new constraint on the dilation parameter coming from string theory is found and the case for polytropic gas is delved into a detailed discussion. I…
▽ More
Considering accretion onto a charged dilaton black hole, the fundamental equations governing accretion, general analytic expressions for critical points, critical velocity, critical speed of sound, and ultimately the mass accretion rate are obtained. A new constraint on the dilation parameter coming from string theory is found and the case for polytropic gas is delved into a detailed discussion. It is found that the dialtion and the adiabatic index of accreted material have deep effects on the accretion process.
△ Less
Submitted 18 May, 2024; v1 submitted 28 January, 2024;
originally announced January 2024.
-
Mass Ratio Distribution of Hierarchical Triple Systems from the LAMOST-MRS Survey
Authors:
Tongyu He,
Jiangdan Li,
Xuefei Chen,
Rong-jia Yang,
Lin Xiao,
Zhanwen Han
Abstract:
Hierarchical triple-star systems consists of three components organised into an inner binary ($M_{1}$,$M_{2}$) and a more distant outer tertiary ($M_{3}$) star. The LAMOST Medium-Resolution Spectroscopic Survey (LAMOST-MRS) has offered a great sample for the study of triple system populations. We used the Peak Amplitude Ratio (PAR) method to obtain the mass ratio ($q_\mathrm{in}$,…
▽ More
Hierarchical triple-star systems consists of three components organised into an inner binary ($M_{1}$,$M_{2}$) and a more distant outer tertiary ($M_{3}$) star. The LAMOST Medium-Resolution Spectroscopic Survey (LAMOST-MRS) has offered a great sample for the study of triple system populations. We used the Peak Amplitude Ratio (PAR) method to obtain the mass ratio ($q_\mathrm{in}$, $q_\mathrm{out}$) of a triple system from its normalised spectrum. By calculating Cross-Correlation Function (CCF), we determined the correlation between the mass ratio $q_\mathrm{out}$ ($M_{3}$/($M_{1}$+$M_{2}$)) and the amplitude ratio ($A_{3}$/($A_{1}$+$A_{2}$)). We derived $q_\mathrm{in}$ of $0.5-1.0$ and $q_\mathrm{out}$ between 0.2 and 0.8. By fitting a power-law function of the corrected $q_\mathrm{in}$ distribution, the $γ_\mathrm{in}$ are estimated to be $-0.654\pm2.915$, $4.304\pm1.125$ and $11.371\pm1.309$ for A, F and G type stars. The derived $γ_\mathrm{in}$-values increase as the mass decrease, indicating that less massive stars are more likely to have companion stars with similar masses. By fitting a power-law function of the corrected $q_\mathrm{out}$ distribution, the ${γ_\mathrm{out}}$ are estimated to be $-2.016\pm0.172$, $-1.962\pm0.853$ and $-1.238\pm0.141$ for G, F and A type stars, respectively. The ${γ_\mathrm{out}}$-values show a trend of growth toward lower primary star masses.
△ Less
Submitted 3 December, 2024; v1 submitted 13 November, 2023;
originally announced November 2023.
-
Observation of gamma rays up to 320 TeV from the middle-aged TeV pulsar wind nebula HESS J1849$-$000
Authors:
M. Amenomori,
S. Asano,
Y. W. Bao,
X. J. Bi,
D. Chen,
T. L. Chen,
W. Y. Chen,
Xu Chen,
Y. Chen,
Cirennima,
S. W. Cui,
Danzengluobu,
L. K. Ding,
J. H. Fang,
K. Fang,
C. F. Feng,
Zhaoyang Feng,
Z. Y. Feng,
Qi Gao,
A. Gomi,
Q. B. Gou,
Y. Q. Guo,
Y. Y. Guo,
Y. Hayashi,
H. H. He
, et al. (93 additional authors not shown)
Abstract:
Gamma rays from HESS J1849$-$000, a middle-aged TeV pulsar wind nebula (PWN), are observed by the Tibet air shower array and the muon detector array. The detection significance of gamma rays reaches $4.0\, σ$ and $4.4\, σ$ levels above 25 TeV and 100 TeV, respectively, in units of Gaussian standard deviation $σ$. The energy spectrum measured between $40\, {\rm TeV} < E < 320\, {\rm TeV}$ for the f…
▽ More
Gamma rays from HESS J1849$-$000, a middle-aged TeV pulsar wind nebula (PWN), are observed by the Tibet air shower array and the muon detector array. The detection significance of gamma rays reaches $4.0\, σ$ and $4.4\, σ$ levels above 25 TeV and 100 TeV, respectively, in units of Gaussian standard deviation $σ$. The energy spectrum measured between $40\, {\rm TeV} < E < 320\, {\rm TeV}$ for the first time is described with a simple power-law function of ${\rm d}N/{\rm d}E = (2.86 \pm 1.44) \times 10^{-16}(E/40\, {\rm TeV})^{-2.24 \pm 0.41}\, {\rm TeV}^{-1}\, {\rm cm}^{-2}\, {\rm s}^{-1}$. The gamma-ray energy spectrum from the sub-TeV ($E < 1\, {\rm TeV}$) to sub-PeV ($100\, {\rm TeV} < E < 1\, {\rm PeV}$) ranges including the results of previous studies can be modeled with the leptonic scenario, inverse Compton scattering by high-energy electrons accelerated by the PWN of PSR J1849$-$0001. On the other hand, the gamma-ray energy spectrum can also be modeled with the hadronic scenario in which gamma rays are generated from the decay of neutral pions produced by collisions between accelerated cosmic-ray protons and the ambient molecular cloud found in the gamma-ray emitting region. The cutoff energy of cosmic-ray protons $E_{\rm p\, cut}$, cut is estimated at ${\rm log}_{10}(E_{\rm p,\, cut}/{\rm TeV}) = 3.73^{+2.98}_{-0.66}$, suggesting that protons are accelerated up to the PeV energy range. Our study thus proposes that HESS J1849$-$000 should be further investigated as a new candidate for a Galactic PeV cosmic-ray accelerator, PeVatron.
△ Less
Submitted 26 August, 2023;
originally announced August 2023.
-
Measurement of the Gamma-Ray Energy Spectrum beyond 100 TeV from the HESS J1843$-$033 Region
Authors:
M. Amenomori,
S. Asano,
Y. W. Bao,
X. J. Bi,
D. Chen,
T. L. Chen,
W. Y. Chen,
Xu Chen,
Y. Chen,
Cirennima,
S. W. Cui,
Danzengluobu,
L. K. Ding,
J. H. Fang,
K. Fang,
C. F. Feng,
Zhaoyang Feng,
Z. Y. Feng,
Qi Gao,
A. Gomi,
Q. B. Gou,
Y. Q. Guo,
Y. Y. Guo,
H. H. He,
Z. T. He
, et al. (91 additional authors not shown)
Abstract:
HESS J1843$-$033 is a very-high-energy gamma-ray source whose origin remains unidentified. This work presents, for the first time, the energy spectrum of gamma rays beyond $100\, {\rm TeV}$ from the HESS J1843$-$033 region using the data recorded by the Tibet air shower array and its underground muon detector array. A gamma-ray source with an extension of $0.34^{\circ} \pm 0.12^{\circ}$ is success…
▽ More
HESS J1843$-$033 is a very-high-energy gamma-ray source whose origin remains unidentified. This work presents, for the first time, the energy spectrum of gamma rays beyond $100\, {\rm TeV}$ from the HESS J1843$-$033 region using the data recorded by the Tibet air shower array and its underground muon detector array. A gamma-ray source with an extension of $0.34^{\circ} \pm 0.12^{\circ}$ is successfully detected above $25\, {\rm TeV}$ at $(α,\, δ) = (281.09^{\circ}\pm 0.10^{\circ},\, -3.76^{\circ}\pm 0.09^{\circ})$ near HESS J1843$-$033 with a statistical significance of $6.2\, σ$, and the source is named TASG J1844$-$038. The position of TASG J1844$-$038 is consistent with those of HESS J1843$-$033, eHWC J1842$-$035, and LHAASO J1843$-$0338. The measured gamma-ray energy spectrum in $25\, {\rm TeV} < E < 130\, {\rm TeV}$ is described with ${\rm d}N/{\rm d}E = (9.70\pm 1.89)\times 10^{-16} (E/40\, {\rm TeV})^{-3.26\pm 0.30}\, {\rm TeV}^{-1} {\rm cm}^{-2} {\rm s}^{-1}$, and the spectral fit to the combined spectra of HESS J1843$-$033, LHAASO J1843$-$0338, and TASG J1844$-$038 implies the existence of a cutoff at $49.5\pm 9.0\, {\rm TeV}$. Associations of TASG J1844-038 with SNR G28.6$-$0.1 and PSR J1844-0346 are also discussed in detail for the first time.
△ Less
Submitted 26 August, 2023;
originally announced August 2023.
-
The Lobster Eye Imager for Astronomy Onboard the SATech-01 Satellite
Authors:
Z. X. Ling,
X. J. Sun,
C. Zhang,
S. L. Sun,
G. Jin,
S. N. Zhang,
X. F. Zhang,
J. B. Chang,
F. S. Chen,
Y. F. Chen,
Z. W. Cheng,
W. Fu,
Y. X. Han,
H. Li,
J. F. Li,
Y. Li,
Z. D. Li,
P. R. Liu,
Y. H. Lv,
X. H. Ma,
Y. J. Tang,
C. B. Wang,
R. J. Xie,
Y. L. Xue,
A. L. Yan
, et al. (101 additional authors not shown)
Abstract:
The Lobster Eye Imager for Astronomy (LEIA), a pathfinder of the Wide-field X-ray Telescope of the Einstein Probe (EP) mission, was successfully launched onboard the SATech-01 satellite of the Chinese Academy of Sciences on 27 July 2022. In this paper, we introduce the design and on-ground test results of the LEIA instrument. Using state-of-the-art Micro-Pore Optics (MPO), a wide field-of-view (Fo…
▽ More
The Lobster Eye Imager for Astronomy (LEIA), a pathfinder of the Wide-field X-ray Telescope of the Einstein Probe (EP) mission, was successfully launched onboard the SATech-01 satellite of the Chinese Academy of Sciences on 27 July 2022. In this paper, we introduce the design and on-ground test results of the LEIA instrument. Using state-of-the-art Micro-Pore Optics (MPO), a wide field-of-view (FoV) of 346 square degrees (18.6 degrees * 18.6 degrees) of the X-ray imager is realized. An optical assembly composed of 36 MPO chips is used to focus incident X-ray photons, and four large-format complementary metal-oxide semiconductor (CMOS) sensors, each of 6 cm * 6 cm, are used as the focal plane detectors. The instrument has an angular resolution of 4 - 8 arcmin (in FWHM) for the central focal spot of the point spread function, and an effective area of 2 - 3 cm2 at 1 keV in essentially all the directions within the field of view. The detection passband is 0.5 - 4 keV in the soft X-rays and the sensitivity is 2 - 3 * 10-11 erg s-1 cm-2 (about 1 mini-Crab) at 1,000 second observation. The total weight of LEIA is 56 kg and the power is 85 W. The satellite, with a design lifetime of 2 years, operates in a Sun-synchronous orbit of 500 km with an orbital period of 95 minutes. LEIA is paving the way for future missions by verifying in flight the technologies of both novel focusing imaging optics and CMOS sensors for X-ray observation, and by optimizing the working setups of the instrumental parameters. In addition, LEIA is able to carry out scientific observations to find new transients and to monitor known sources in the soft X-ray band, albeit limited useful observing time available.
△ Less
Submitted 24 May, 2023;
originally announced May 2023.
-
Thin accretion disks around a black hole in Einstein-Aether-scalar theory
Authors:
Tong-Yu He,
Ziqiang Cai,
Rong-Jia Yang
Abstract:
We consider the accretion process in the thin disk around a supermassive black hole in Einstein-aether-scalar theory. We probe the effects of the model parameter on the physical properties of the disk. The results show that with increasing value of the parameter, the energy flux, the radiation temperature, the spectra cut-off frequency, the spectra luminosity, and the conversion efficiency of the…
▽ More
We consider the accretion process in the thin disk around a supermassive black hole in Einstein-aether-scalar theory. We probe the effects of the model parameter on the physical properties of the disk. The results show that with increasing value of the parameter, the energy flux, the radiation temperature, the spectra cut-off frequency, the spectra luminosity, and the conversion efficiency of the disk decrease. The disk is hotter and more luminous than that in general relativity for negative parameter, while it is cooler and less luminous for positive parameter. We also find some values of the parameter allowed by the theory are excluded by the physical properties of the disk.
△ Less
Submitted 27 November, 2022; v1 submitted 7 August, 2022;
originally announced August 2022.
-
Potential PeVatron supernova remnant G106.3+2.7 seen in the highest-energy gamma rays
Authors:
M. Amenomori,
Y. W. Bao,
X. J. Bi,
D. Chen,
T. L. Chen,
W. Y. Chen,
Xu Chen,
Y. Chen,
Cirennima,
S. W. Cui,
Danzengluobu,
L. K. Ding,
J. H. Fang,
K. Fang,
C. F. Feng,
Zhaoyang Feng,
Z. Y. Feng,
Qi Gao,
Q. B. Gou,
Y. Q. Guo,
Y. Y. Guo,
H. H. He,
Z. T. He,
K. Hibino,
N. Hotta
, et al. (70 additional authors not shown)
Abstract:
Cosmic rays (protons and other atomic nuclei) are believed to gain energies of petaelectronvolts (PeV) and beyond at astrophysical particle accelerators called 'PeVatrons' inside our Galaxy. Although a characteristic feature of a PeVatron is expected to be a hard gamma-ray energy spectrum that extends beyond 100 teraelectronvolts (TeV) without a cutoff, none of the currently known sources exhibits…
▽ More
Cosmic rays (protons and other atomic nuclei) are believed to gain energies of petaelectronvolts (PeV) and beyond at astrophysical particle accelerators called 'PeVatrons' inside our Galaxy. Although a characteristic feature of a PeVatron is expected to be a hard gamma-ray energy spectrum that extends beyond 100 teraelectronvolts (TeV) without a cutoff, none of the currently known sources exhibits such a spectrum due to the low maximum energy of accelerated cosmic rays or insufficient detector sensitivity around 100 TeV. Here we report the observation of gamma-ray emission from the supernova remnant G106.3+2.7 above 10 TeV. This work provides flux data points up to and above 100 TeV and indicates that the very-high-energy gamma-ray emission above 10 TeV is well correlated with a molecular cloud rather than the pulsar PSR J2229+6114. Regarding the gamma-ray emission mechanism of G106.3+2.7, this morphological feature appears to favor a hadronic origin via the π0 decay caused by accelerated relativistic protons over a leptonic one via the inverse-Compton scattering by relativistic electrons. Furthermore, we point out that an X-ray flux upper limit on the synchrotron spectrum would provide important information to firmly establish the hadronic scenario as the mechanism of particle acceleration at the source.
△ Less
Submitted 7 September, 2021;
originally announced September 2021.
-
Gamma-ray Observation of the Cygnus Region in the 100 TeV Energy Region
Authors:
M. Amenomori,
Y. W. Bao,
X. J. Bi,
D. Chen,
T. L. Chen,
W. Y. Chen,
Xu Chen,
Y. Chen,
Cirennima,
S. W. Cui,
Danzengluobu,
L. K. Ding,
J. H. Fang,
K. Fang,
C. F. Feng,
Zhaoyang Feng,
Z. Y. Feng,
Qi Gao,
A. Gomi,
Q. B. Gou,
Y. Q. Guo,
Y. Y. Guo,
H. H. He,
Z. T. He,
K. Hibino
, et al. (88 additional authors not shown)
Abstract:
We report observations of gamma-ray emissions with energies in the 100 TeV energy region from the Cygnus region in our Galaxy. Two sources are significantly detected in the directions of the Cygnus OB1 and OB2 associations. Based on their positional coincidences, we associate one with a pulsar PSR J2032+4127 and the other mainly with a pulsar wind nebula PWN G75.2+0.1 with the pulsar moving away f…
▽ More
We report observations of gamma-ray emissions with energies in the 100 TeV energy region from the Cygnus region in our Galaxy. Two sources are significantly detected in the directions of the Cygnus OB1 and OB2 associations. Based on their positional coincidences, we associate one with a pulsar PSR J2032+4127 and the other mainly with a pulsar wind nebula PWN G75.2+0.1 with the pulsar moving away from its original birthplace situated around the centroid of the observed gamma-ray emission. This work would stimulate further studies of particle acceleration mechanisms at these gamma-ray sources.
△ Less
Submitted 2 July, 2021;
originally announced July 2021.
-
First Detection of sub-PeV Diffuse Gamma Rays from the Galactic Disk: Evidence for Ubiquitous Galactic Cosmic Rays beyond PeV Energies
Authors:
M. Amenomori,
Y. W. Bao,
X. J. Bi,
D. Chen,
T. L. Chen,
W. Y. Chen,
Xu Chen,
Y. Chen,
Cirennima,
S. W. Cui,
Danzengluobu,
L. K. Ding,
J. H. Fang,
K. Fang,
C. F. Feng,
Zhaoyang Feng,
Z. Y. Feng,
Qi Gao,
Q. B. Gou,
Y. Q. Guo,
Y. Y. Guo,
H. H. He,
Z. T. He,
K. Hibino,
N. Hotta
, et al. (70 additional authors not shown)
Abstract:
We report, for the first time, the long-awaited detection of diffuse gamma rays with energies between 100 TeV and 1 PeV in the Galactic disk. Particularly, all gamma rays above 398 TeV are observed apart from known TeV gamma-ray sources and compatible with expectations from the hadronic emission scenario in which gamma rays originate from the decay of $π^0$'s produced through the interaction of pr…
▽ More
We report, for the first time, the long-awaited detection of diffuse gamma rays with energies between 100 TeV and 1 PeV in the Galactic disk. Particularly, all gamma rays above 398 TeV are observed apart from known TeV gamma-ray sources and compatible with expectations from the hadronic emission scenario in which gamma rays originate from the decay of $π^0$'s produced through the interaction of protons with the interstellar medium in the Galaxy. This is strong evidence that cosmic rays are accelerated beyond PeV energies in our Galaxy and spread over the Galactic disk.
△ Less
Submitted 17 May, 2021; v1 submitted 11 April, 2021;
originally announced April 2021.
-
First Detection of Photons with Energy Beyond 100 TeV from an Astrophysical Source
Authors:
M. Amenomori,
Y. W. Bao,
X. J. Bi,
D. Chen,
T. L. Chen,
W. Y. Chen,
Xu Chen,
Y. Chen,
Cirennima,
S. W. Cui,
Danzengluobu,
L. K. Ding,
J. H. Fang,
K. Fang,
C. F. Feng,
Zhaoyang Feng,
Z. Y. Feng,
Qi Gao,
Q. B. Gou,
Y. Q. Guo,
H. H. He,
Z. T. He,
K. Hibino,
N. Hotta,
Haibing Hu
, et al. (66 additional authors not shown)
Abstract:
We report on the highest energy photons from the Crab Nebula observed by the Tibet air shower array with the underground water-Cherenkov-type muon detector array. Based on the criterion of muon number measured in an air shower, we successfully suppress 99.92% of the cosmic-ray background events with energies $E>100$ TeV. As a result, we observed 24 photon-like events with $E>100$ TeV against 5.5 b…
▽ More
We report on the highest energy photons from the Crab Nebula observed by the Tibet air shower array with the underground water-Cherenkov-type muon detector array. Based on the criterion of muon number measured in an air shower, we successfully suppress 99.92% of the cosmic-ray background events with energies $E>100$ TeV. As a result, we observed 24 photon-like events with $E>100$ TeV against 5.5 background events, which corresponds to 5.6$σ$ statistical significance. This is the first detection of photons with $E>100$ TeV from an astrophysical source.
△ Less
Submitted 13 June, 2019;
originally announced June 2019.
-
The baryon loading effect on relativistic astrophysical jet transport in the interstellar medium
Authors:
W. P. Yao,
B. Qiao,
Z. Xu,
H. Zhang,
Z. H. Zhao,
H. X. Chang,
C. T. Zhou,
S. P. Zhu,
X. T. He
Abstract:
The composition of the astrophysical relativistic jets remains uncertain. By kinetic particle-in-cell simulations, we show that the baryon component in the jet, or the so-called baryon loading effect (BLE), heavily affects relativistic jets transport dynamics in the interstellar medium. On the one hand, with the BLE, relativistic jets can transport in a much longer distance, because jet electrons…
▽ More
The composition of the astrophysical relativistic jets remains uncertain. By kinetic particle-in-cell simulations, we show that the baryon component in the jet, or the so-called baryon loading effect (BLE), heavily affects relativistic jets transport dynamics in the interstellar medium. On the one hand, with the BLE, relativistic jets can transport in a much longer distance, because jet electrons draw a significant amount of energy from jet baryons via the Buneman-induced electrostatic waves and the Weibel-mediated collisionless shock; on the other hand, the jet electron phase space distribution may transform from a bottom-wide-single-peak structure to a center-wide-multiple-peak one by increasing the BLE, which largely influences the observed jet morphology. Implications for related astrophysical studies are also discussed.
△ Less
Submitted 20 September, 2018;
originally announced September 2018.
-
Influence of Earth-Directed Coronal Mass Ejections on the Sun's Shadow Observed by the Tibet-III Air Shower Array
Authors:
M. Amenomori,
X. J. Bi,
D. Chen,
T. L. Chen,
W. Y. Chen,
S. W. Cui,
Danzengluobu,
L. K. Ding,
C. F. Feng,
Zhaoyang Feng,
Z. Y. Feng,
Q. B. Gou,
Y. Q. Guo,
H. H. He,
Z. T. He,
K. Hibino,
N. Hotta,
Haibing Hu,
H. B. Hu,
J. Huang,
H. Y. Jia,
L. Jiang,
F. Kajino,
K. Kasahara,
Y. Katayose
, et al. (56 additional authors not shown)
Abstract:
We examine the possible influence of Earth-directed coronal mass ejections (ECMEs) on the Sun's shadow in the 3~TeV cosmic-ray intensity observed by the Tibet-III air shower (AS) array. We confirm a clear solar-cycle variation of the intensity deficit in the Sun's shadow during ten years between 2000 and 2009. This solar-cycle variation is overall reproduced by our Monte Carlo (MC) simulations of…
▽ More
We examine the possible influence of Earth-directed coronal mass ejections (ECMEs) on the Sun's shadow in the 3~TeV cosmic-ray intensity observed by the Tibet-III air shower (AS) array. We confirm a clear solar-cycle variation of the intensity deficit in the Sun's shadow during ten years between 2000 and 2009. This solar-cycle variation is overall reproduced by our Monte Carlo (MC) simulations of the Sun's shadow based on the potential field model of the solar magnetic field averaged over each solar rotation period. We find, however, that the magnitude of the observed intensity deficit in the Sun's shadow is significantly less than that predicted by MC simulations, particularly during the period around solar maximum when a significant number of ECMEs is recorded. The $χ^2$ tests of the agreement between the observations and the MC simulations show that the difference is larger during the periods when the ECMEs occur, and the difference is reduced if the periods of ECMEs are excluded from the analysis. This suggests the first experimental evidence of the ECMEs affecting the Sun's shadow observed in the 3~TeV cosmic-ray intensity.
△ Less
Submitted 8 June, 2018;
originally announced June 2018.
-
Evaluation of the Interplanetary Magnetic Field Strength Using the Cosmic-Ray Shadow of the Sun
Authors:
M. Amenomori,
X. J. Bi,
D. Chen,
T. L. Chen,
W. Y. Chen,
S. W. Cui,
Danzengluobu,
L. K. Ding,
C. F. Feng,
Zhaoyang Feng,
Z. Y. Feng,
Q. B. Gou,
Y. Q. Guo,
H. H. He,
Z. T. He,
K. Hibino,
N. Hotta,
Haibing Hu,
H. B. Hu,
J. Huang,
H. Y. Jia,
L. Jiang,
F. Kajino,
K. Kasahara,
Y. Katayose
, et al. (58 additional authors not shown)
Abstract:
We analyze the Sun's shadow observed with the Tibet-III air shower array and find that the shadow's center deviates northward (southward) from the optical solar disc center in the "Away" ("Toward") IMF sector. By comparing with numerical simulations based on the solar magnetic field model, we find that the average IMF strength in the "Away" ("Toward") sector is…
▽ More
We analyze the Sun's shadow observed with the Tibet-III air shower array and find that the shadow's center deviates northward (southward) from the optical solar disc center in the "Away" ("Toward") IMF sector. By comparing with numerical simulations based on the solar magnetic field model, we find that the average IMF strength in the "Away" ("Toward") sector is $1.54 \pm 0.21_{\rm stat} \pm 0.20_{\rm syst}$ ($1.62 \pm 0.15_{\rm stat} \pm 0.22_{\rm syst}$) times larger than the model prediction. These demonstrate that the observed Sun's shadow is a useful tool for the quantitative evaluation of the average solar magnetic field.
△ Less
Submitted 21 January, 2018;
originally announced January 2018.
-
A Study of Fermi-LAT GeV gamma-ray Emission towards the Magnetar-harboring Supernova Remnant Kesteven 73 and Its Molecular Environment
Authors:
Bing Liu,
Yang Chen,
Xiao Zhang,
Qian-Cheng Liu,
Ting-Lan He,
Xin Zhou,
Ping Zhou,
Yang Su
Abstract:
We report our independent GeV gamma-ray study of the young shell-type supernova remnant (SNR) Kes 73 which harbors a central magnetar, and CO-line millimeter observations toward the SNR. Using 7.6 years of Fermi-LAT observation data, we detected an extended gamma-ray source ("source A") with the centroid on the west of the SNR, with a significance of 21.6 sigma in 0.1-300 GeV and an error circle o…
▽ More
We report our independent GeV gamma-ray study of the young shell-type supernova remnant (SNR) Kes 73 which harbors a central magnetar, and CO-line millimeter observations toward the SNR. Using 7.6 years of Fermi-LAT observation data, we detected an extended gamma-ray source ("source A") with the centroid on the west of the SNR, with a significance of 21.6 sigma in 0.1-300 GeV and an error circle of 5.4 arcminute in angular radius. The gamma-ray spectrum cannot be reproduced by a pure leptonic emission or a pure emission from the magnetar, and thus a hadronic emission component is needed. The CO-line observations reveal a molecular cloud (MC) at V_LSR~90 km/s, which demonstrates morphological correspondence with the western boundary of the SNR brightened in multiwavelength. The 12CO (J=2-1)/12CO (J=1-0) ratio in the left (blue) wing 85-88 km/s is prominently elevated to ~1.1 along the northwestern boundary, providing kinematic evidence of the SNR-MC interaction. This SNR-MC association yields a kinematic distance 9 kpc to Kes 73. The MC is shown to be capable of accounting for the hadronic gamma-ray emission component. The gamma-ray spectrum can be interpreted with a pure hadronic emission or a magnetar+hadronic hybrid emission. In the case of pure hadronic emission, the spectral index of the protons is 2.4, very similar to that of the radio-emitting electrons, essentially consistent with the diffusive shock acceleration theory. In the case of magnetar+hadronic hybrid emission, a magnetic field decay rate >= 10^36 erg/s is needed to power the magnetar's curvature radiation.
△ Less
Submitted 11 December, 2017; v1 submitted 1 November, 2017;
originally announced November 2017.
-
Probe of the Solar Magnetic Field Using the "Cosmic-Ray Shadow" of the Sun
Authors:
M. Amenomori,
X. J. Bi,
D. Chen,
T. L. Chen,
W. Y. Chen,
S. W. Cui,
Danzengluobu,
L. K. Ding,
C. F. Feng,
Zhaoyang Feng,
Z. Y. Feng,
Q. B. Gou,
Y. Q. Guo,
K. Hakamada,
H. H. He,
Z. T. He,
K. Hibino,
N. Hotta,
Haibing Hu,
H. B. Hu,
J. Huang,
H. Y. Jia,
L. Jiang,
F. Kajino,
K. Kasahara
, et al. (55 additional authors not shown)
Abstract:
We report on a clear solar-cycle variation of the Sun's shadow in the 10 TeV cosmic-ray flux observed by the Tibet air shower array during a full solar cycle from 1996 to 2009. In order to clarify the physical implications of the observed solar cycle variation, we develop numerical simulations of the Sun's shadow, using the Potential Field Source Surface (PFSS) model and the Current Sheet Source S…
▽ More
We report on a clear solar-cycle variation of the Sun's shadow in the 10 TeV cosmic-ray flux observed by the Tibet air shower array during a full solar cycle from 1996 to 2009. In order to clarify the physical implications of the observed solar cycle variation, we develop numerical simulations of the Sun's shadow, using the Potential Field Source Surface (PFSS) model and the Current Sheet Source Surface (CSSS) model for the coronal magnetic field. We find that the intensity deficit in the simulated Sun's shadow is very sensitive to the coronal magnetic field structure, and the observed variation of the Sun's shadow is better reproduced by the CSSS model. This is the first successful attempt to evaluate the coronal magnetic field models by using the Sun's shadow observed in the TeV cosmic-ray flux.
△ Less
Submitted 2 July, 2013; v1 submitted 12 June, 2013;
originally announced June 2013.
-
A Monte Carlo study to measure the energy spectra of the primary cosmic-ray components at the knee using a new Tibet AS core detector array
Authors:
The Tibet Asγ Collaboration,
:,
M. Amenomori,
X. J. Bi,
D. Chen,
W. Y. Chen,
S. W. Cui,
Danzengluobu,
L. K. Ding,
X. H. Ding,
C. F. Feng,
Zhaoyang Feng,
Z. Y. Feng,
Q. B. Gou,
H. W. Guo,
Y. Q. Guo,
H. H. He,
Z. T. He,
K. Hibino,
N. Hotta,
Haibing Hu,
H. B. Hu,
J. Huang,
W. J. Li,
H. Y. Jia
, et al. (54 additional authors not shown)
Abstract:
A new hybrid experiment has been started by ASγ experiment at Tibet, China, since August 2011, which consists of a low threshold burst-detector-grid (YAC-II, Yangbajing Air shower Core array), the Tibet air-shower array (Tibet-III) and a large underground water Cherenkov muon detector (MD). In this paper, the capability of the measurement of the chemical components (proton, helium and iron) with u…
▽ More
A new hybrid experiment has been started by ASγ experiment at Tibet, China, since August 2011, which consists of a low threshold burst-detector-grid (YAC-II, Yangbajing Air shower Core array), the Tibet air-shower array (Tibet-III) and a large underground water Cherenkov muon detector (MD). In this paper, the capability of the measurement of the chemical components (proton, helium and iron) with use of the (Tibet-III+YAC-II) is investigated by means of an extensive Monte Carlo simulation in which the secondary particles are propagated through the (Tibet-III+YAC-II) array and an artificial neural network (ANN) method is applied for the primary mass separation. Our simulation shows that the new installation is powerful to study the chemical compositions, in particular, to obtain the primary energy spectrum of the major component at the knee.
△ Less
Submitted 12 March, 2013;
originally announced March 2013.
-
Spectroscopic and Photometric Observations of Unidentified Ultraviolate Variable Objects in GUVV-2 Catalog
Authors:
Y. Li,
J. Wang,
J. Y. Wei,
X. T. He
Abstract:
An NUV-optical diagram made for sources from the secend Galaxy Evolution Explorer (GALEX) Ultraviolet Variability (GUVV-2) Catalog provide us a method to tentatively classify the unknown GUVV2 sources by their NUV-optical magnitudes. On the purpose of testing the correctness and generality of the method, we carry out a program on the spectroscopic observations of the unidentified GUVV2 sources. Th…
▽ More
An NUV-optical diagram made for sources from the secend Galaxy Evolution Explorer (GALEX) Ultraviolet Variability (GUVV-2) Catalog provide us a method to tentatively classify the unknown GUVV2 sources by their NUV-optical magnitudes. On the purpose of testing the correctness and generality of the method, we carry out a program on the spectroscopic observations of the unidentified GUVV2 sources. The spectroscopic identification for these 37 sources are 19 type -A to -F stars, 10 type -G to -K stars and 7 M dwarf stars together with an AGN. We also present the light curves in R-band for two RR Lyrae star candidates selected from the NUV-optical diagram, both of which perform cyclic variations. Combining there light curves and colors, we classify them as RR Lyrae stars. To confirm the results, we shows a color-color diagram for the 37 newly spectroscopically identified objects compared with the previously identified ones, which manifests good consistence with our former results, indicating that the ultroviolet variable sources can be initially classified by their NUV/optical color-color diagram.
△ Less
Submitted 30 March, 2011;
originally announced March 2011.
-
Gravity waves and the LHC: Towards high-scale inflation with low-energy SUSY
Authors:
Temple He,
Shamit Kachru,
Alexander Westphal
Abstract:
It has been argued that rather generic features of string-inspired inflationary theories with low-energy supersymmetry (SUSY) make it difficult to achieve inflation with a Hubble scale H > m_{3/2}, where m_{3/2} is the gravitino mass in the SUSY-breaking vacuum state. We present a class of string-inspired supergravity realizations of chaotic inflation where a simple, dynamical mechanism yields hie…
▽ More
It has been argued that rather generic features of string-inspired inflationary theories with low-energy supersymmetry (SUSY) make it difficult to achieve inflation with a Hubble scale H > m_{3/2}, where m_{3/2} is the gravitino mass in the SUSY-breaking vacuum state. We present a class of string-inspired supergravity realizations of chaotic inflation where a simple, dynamical mechanism yields hierarchically small scales of post-inflationary supersymmetry breaking. Within these toy models we can easily achieve small ratios between m_{3/2} and the Hubble scale of inflation. This is possible because the expectation value of the superpotential <W> relaxes from large to small values during the course of inflation. However, our toy models do not provide a reasonable fit to cosmological data if one sets the SUSY-breaking scale to m_{3/2} < TeV. Our work is a small step towards relieving the apparent tension between high-scale inflation and low-scale supersymmetry breaking in string compactifications.
△ Less
Submitted 26 May, 2010; v1 submitted 22 March, 2010;
originally announced March 2010.
-
A Sample of IRAS Infrared-Selected Seyfert 1.5 Galaxies: Infrared-Color $α(60,25)$ Dominated Eigenvector 1
Authors:
J. Wang,
J. Y. Wei,
X. T. He
Abstract:
The well-documented E1 relationships are first extended to infrared color $α(60,25)$ and flux ratio [OIII]/H$β_{\rm{n}}$ by comparing emission line properties to continuum properties in infrared wavelength. Both direct correlations and a principle component analysis are used in a sample of 50 IRAS IR-selected Seyfert 1.5 galaxies. In addition to confirm the correlations of E1 in Boroson & Green…
▽ More
The well-documented E1 relationships are first extended to infrared color $α(60,25)$ and flux ratio [OIII]/H$β_{\rm{n}}$ by comparing emission line properties to continuum properties in infrared wavelength. Both direct correlations and a principle component analysis are used in a sample of 50 IRAS IR-selected Seyfert 1.5 galaxies. In addition to confirm the correlations of E1 in Boroson & Green (1992), our Eigenvector 1 turns out to be dominated by mid-infrared color $α$(60,25), and most strongly effected by RFe, [OIII]/H$β_{\rm{n}}$, and EW(H$β_{\rm{b}}$). Our analysis indicate that the objects with large E1 tend to co-existent with relatively young nuclear stellar populations, which implies that the E1 is related with nuclear starformation history. The IR-dominated Eigenvector 1 can be, therefore, inferred to be interpreted as ``age'' of AGN. In confirmation of Xu et al. (2003), it is clear that the extreme Seyfert galaxies with both large RFe and large [OIII]/H$β_{\rm{n}}$ are rare in our Universe.
△ Less
Submitted 19 October, 2005;
originally announced October 2005.
-
Variability of Optical \ion{Fe}{ii} Complex in Narrow-Line Seyfert 1 Galaxy NGC 4051
Authors:
J. Wang,
J. Y. Wei,
X. T. He
Abstract:
The variability of optical FeII blends in NGC 4051 is examined from spectra extracted from the AGN Watch program.In our analysis, the FeII complex are subtracted and measured with the following results. Firstly, the FeII variations were detected in NGC 4051 during a 3-year period. The identified FeII variations followed the variations in continuum closely. Secondly, the EW of FeII is reported to…
▽ More
The variability of optical FeII blends in NGC 4051 is examined from spectra extracted from the AGN Watch program.In our analysis, the FeII complex are subtracted and measured with the following results. Firstly, the FeII variations were detected in NGC 4051 during a 3-year period. The identified FeII variations followed the variations in continuum closely. Secondly, the EW of FeII is reported to increase with the rising continuum flux, which is consistent with previous claims that there is no convincing Baldwin Effect in optical FeII. Thirdly, by comparing the variations of H$β$ and FeII, we find that RFe scales with continuum flux as $\rm{R_{Fe}\propto (5.0\pm0.8) \log(L/M)}$, which is significantly different from the theoretical expectations. Finally, in six selected Seyferts, four out of five Narrow-Line Seyfert 1 galaxies present positive correlation between RFe and the continuum flux. The negative correlations are identified in the remaindng two objects that have relatively broad profiles of H$β$ ($\rm{FWHM>1500 km\ s^{-1}}$).We argue that the difference of electron density of broad line clouds and/or variability behavior of incident high-energy radiation can explain the dichotomy in variability behavior of RFe.
△ Less
Submitted 5 April, 2005;
originally announced April 2005.
-
Variability of Broad and Blueshifted Component of [OIII]$λ$5007 in IZWI
Authors:
J. Wang,
J. Y. Wei,
X. T. He
Abstract:
Although the existence of asymmetrical profile of [OIII]$λ$5007 has been discovered for ages, its filiation and physics are poorly understood. Two new spectra of I ZWI taken on Nov 16, 2001 and on Dec 3, 2002 were compared with the spectra taken by BG92. Following results are obtained. 1)The certain variations of broad [OIII] during about 10 years separating the observations are identified. The…
▽ More
Although the existence of asymmetrical profile of [OIII]$λ$5007 has been discovered for ages, its filiation and physics are poorly understood. Two new spectra of I ZWI taken on Nov 16, 2001 and on Dec 3, 2002 were compared with the spectra taken by BG92. Following results are obtained. 1)The certain variations of broad [OIII] during about 10 years separating the observations are identified. The inferred length scale of broad [OIII] emitting region ranges from 0.3pc to 3pc. By assuming a Keplerian motion in emitting region, the material emitting broad [OIII] is likely to be located at transient emission line region, between BLR and NLR. 2)We find a positive relation between the FeII emission and flux of H$β$(or continuum). On the other hand, the parameter RFe decreases with ionizing continuum marginally. 3)We detect a low ionized NLR in I ZWI, because of the low flux ratios $\rm{[OIII]_{n}/Hβ_{n}}$($\sim1.7$).
△ Less
Submitted 4 April, 2005;
originally announced April 2005.
-
NIR Luminosity Function of Galaxies in Close Major-Merger Pairs and Mass Dependence of Merger Rate
Authors:
C. K. Xu,
Y. C. Sun,
X. T. He
Abstract:
A sample of close major-merger pairs (projected separation ${\rm 5 \leq r \leq 20 h^{-1}}$ kpc, ${\rm K_s}$ band magnitude difference $δ{\rm K_s} \leq 1$ mag) is selected from the matched 2MASS-2dFGRS catalog of Cole et al. (2001). The pair primaries are brighter than ${\rm K_s} = 12.5$ mag. After corrections for various biases, the comparison between counts in the paired galaxy sample and count…
▽ More
A sample of close major-merger pairs (projected separation ${\rm 5 \leq r \leq 20 h^{-1}}$ kpc, ${\rm K_s}$ band magnitude difference $δ{\rm K_s} \leq 1$ mag) is selected from the matched 2MASS-2dFGRS catalog of Cole et al. (2001). The pair primaries are brighter than ${\rm K_s} = 12.5$ mag. After corrections for various biases, the comparison between counts in the paired galaxy sample and counts in the parent sample shows that for the local `M* galaxies' sampled by flux limited surveys, the fraction of galaxies in the close major-merger pairs is 1.70$\pm 0.32%$. Using 38 paired galaxies in the sample, a ${\rm K_s}$ band luminosity function (LF) is calculated. This is the first unbiased LF for a sample of objectively defined interacting/merging galaxies in the local universe, while all previously determined LFs of paired galaxies are biased by mistreating paired galaxies as singles. A stellar mass function (MF) is translated from the LF. Compared to the LF/MF of 2MASS galaxies, a differential pair fraction function is derived. The results suggest a trend in the sense that less massive galaxies may have lower chance to be involved in close major-merger pairs than more massive galaxies. The algorithm presented in this paper can be easily applied to much larger samples of 2MASS galaxies with redshifts in near future.
△ Less
Submitted 7 February, 2004;
originally announced February 2004.