Results 131 to 140 of about 63,914 (268)

On the Properties of X-Ray Corona in Seyfert 1 Galaxies

The Astrophysical Journal
We carried out a uniform and systematic analysis of a sample of 112 nearby bright Seyfert 1 type active galactic nuclei, the observations of which were carried out by the Nuclear Spectroscopic Telescope Array between 2013 August and 2022 May.
Indrani Pal, Anju A., H. Sreehari, Gitika Rameshan, C. S. Stalin, Claudio Ricci, S. Marchesi   +6 more
doaj   +1 more source

The nature of the infrared counterpart of IGR J19140+0951

, 2007
The INTEGRAL observatory has been (re-)discovering new X-ray sources since the beginning of nominal operations in early 2003. These sources include X-ray binaries, Active Galactic Nuclei, cataclysmic variables, etc.
Bird, Bodaghee, Bronfman, Charles, Corbet, Cox, D. C. Hannikainen, Hannikainen, Hannikainen, Hanson, Hanson, In 't Zand, J. Rodriguez, J. Schultz, Kuulkers, Lebrun, Liu, Lu, M. G. Rawlings, Nespoli, O. Vilhu, P. Muhli, Rawlings, Rodriguez, Rodriguez, Swank, Ubertini, Walter, Winkler   +28 more
core   +1 more source

The Constraint of Crewed Mars Missions Based on Current Radiation Dose Measurements

Space Weather, Volume 24, Issue 3, March 2026.
Abstract Crewed missions to Mars will be a milestone of future space exploration programs. However, the absence of Earth's magnetic field leaves astronauts directly exposed to unattenuated energetic particles in deep space, primarily galactic cosmic rays (GCRs), resulting in significantly higher radiation levels and enhanced health risks. Understanding
Chao Zhang, Weihao Liu, Jingnan Guo, Mikhail Dobynde, Robert F. Wimmer‐Schweingruber   +4 more
wiley   +1 more source

An Investigation of 5 yr Simultaneous X-Ray and Radio Light Curves of the Dwarf Seyfert Galaxy UGC 6728

The Astrophysical Journal
We present serendipitous simultaneous radio and X-ray light curves of the dwarf Seyfert galaxy UGC 6728 spanning 5 yr. The X-ray light curve exhibits a flaring period, followed by a gradual rise and decline.
Krista Lynne Smith, Macon Magno, Michael Koss   +2 more
doaj   +1 more source

X-ray variability observed with HEAO A-1 [PDF]

Results from the HEAO A-1 instrument which observed X-ray source variability over a wide range of accessible timescales are surveyed. The objects observed include quasars, BL Lacertae, and active galactic nuclei.
Friedman, H.
core   +1 more source

Identifying Compton-thick Active Galactic Nuclei with a Machine Learning Algorithm in Chandra Deep Field-South

The Astrophysical Journal
Compton-thick active galactic nuclei (CT-AGNs), which are defined by column density N _H ≥ 1.5 × 10 ^24 cm ^−2 , emit feeble X-ray radiation, even undetectable by X-ray instruments.
Rui Zhang, Xiaotong Guo, Qiusheng Gu, Guanwen Fang, Jun Xu, Hai-Cheng Feng, Yongyun Chen, Rui Li, Nan Ding, Hongtao Wang   +9 more
doaj   +1 more source

BASS. XLIX. Characterization of Highly Luminous and Obscured AGNs: Local X-Ray and [Ne V]λ3426 Emission in Comparison with the High-redshift Universe

The Astrophysical Journal
We present a detailed analysis of the most luminous and obscured active galactic nuclei (AGNs) detected in the ultra-hard X-ray band (14–195 kev) by the Swift/Burst Alert Telescope. Our sample comprises 21 X-ray luminous ( ${\mathrm{log}}\,{L}_{{\rm{X}}}/
Alessandro Peca, Michael J. Koss, Kyuseok Oh, Claudio Ricci, Benny Trakhtenbrot, Richard Mushotzky, Ezequiel Treister, C. Megan Urry, Andrealuna Pizzetti, Kohei Ichikawa, Alessia Tortosa, Federica Ricci, Matilde Signorini, Darshan Kakkad, Chin-Shin Chang, Giovanni Mazzolari, Turgay Caglar, Macon Magno, Ignacio del Moral-Castro, Peter G. Boorman, Tonima T. Ananna, Fiona Harrison, Daniel Stern, David Sanders   +23 more
doaj   +1 more source

X-ray astronomical spectroscopy [PDF]

The current status of the X-ray spectroscopy of celestial X-ray sources, ranging from nearby stars to distant quasars, is reviewed. Particular emphasis is placed on the role of such spectroscopy as a useful and unique tool in the elucidation of the ...
Holt, S. S.
core   +1 more source

X-Ray Polarization Variability of High Spectral Peak BL Lacertaes: Cases of 1ES 1959+650 and PKS 2155–304

The Astrophysical Journal Letters
The high-energy-peaked BL Lacertae objects (HBLs) are the main targets of the Imaging X-ray Polarimetry Explorer (IXPE) for investigating the mechanisms of radiation and particle acceleration in jets. In this Letter, we report the first IXPE observations
Xin-Ke Hu, Yu-Wei Yu, Jin Zhang, Tan-Zheng Wu, Ji-Shun Lian, Xiang-Gao Wang, Hai-Ming Zhang, En-Wei Liang   +7 more
doaj   +1 more source

A Long-term Study of Mrk 50: Appearance and Disappearance of Soft Excess

The Astrophysical Journal
We present an extensive temporal and spectral study of the Seyfert 1 AGN Mrk 50 using 15 yr (2007–2022) of multiwavelength observations from XMM-Newton, Swift, and NuSTAR for the first time.
Narendranath Layek, Prantik Nandi, Sachindra Naik, Arghajit Jana   +3 more
doaj   +1 more source