Search Publications
Missions
Journals
Publication Years
Perfecting Our Set of Spectrophotometric Standard DA White Dwarfs
Rest, Armin; Matheson, Thomas; Raddi, Roberto +17 more
We verified for photometric stability a set of DA white dwarfs with Hubble Space Telescope magnitudes from the near-ultraviolet to the near-infrared and ground-based spectroscopy by using time-spaced observations from the Las Cumbres Observatory network of telescopes. The initial list of 38 stars was whittled to 32 final ones, which comprise a hig…
Unbound Close Stellar Encounters in the Solar Neighborhood
Hansen, Bradley M. S.
We present a catalog of unbound stellar pairs, within 100 pc of the Sun, that are undergoing close, hyperbolic, encounters. The data are drawn from the GAIA EDR3 catalog, and the limiting factors are errors in the radial distance and unknown velocities along the line of sight. Such stellar pairs have been suggested to be possible events associated…
Exploring the Fundamental Mechanism in Driving Highest-Velocity Ionized Outflows in Radio AGNs
Xue, Yongquan; Woo, Jong-Hak; He, Zhicheng +4 more
We investigate the ionized gas kinematics relationship with X-ray, radio and accreting properties using a sample of 348 nearby (z<0.4) SDSS-FIRST-X-ray detected AGNs. X-ray properties of our sample are obtained from XMM-Newton, Swift and Chandra observations. We unveil the ionized gas outflows in our sample manifested by the non-gravitational b…
X-Ray and Radio Observations of Central Black Holes in Nearby Low-mass Early-type Galaxies: Preliminary Evidence for Low Eddington Fractions
Neumayer, Nadine; Strader, Jay; Seth, Anil C. +5 more
We present new radio and X-ray observations of two nearby (<4 Mpc) low-mass early-type galaxies with dynamically confirmed central black holes: NGC 5102 and NGC 205. NGC 5102 shows a weak nuclear X-ray source and has no core radio emission. However, for the first time we demonstrate that it shows luminous extended radio continuum emission in lo…
Relationship between gamma-ray loudness and X-ray spectra of radio galaxies
Fukazawa, Yasushi; Kayanoki, Taishu
The Fermi satellite has detected ~ 60 radio galaxies (RGs). In this study, we investigate the difference in the properties of X-ray spectra between GeV-loud RGs and GeV-quiet RGs. Our sample comprises 68 objects: 36 RGs detected with Fermi and 32 RGs not detected with gamma-rays. We analyzed the X-ray spectra of these 68 objects using data from th…
Application of Random Forest Regressions on Stellar Parameters of A-type Stars and Feature Extraction
He, Ying; Chen, Shu-Xin; Sun, Wei-Min
Measuring the stellar parameters of A-type stars is more difficult than FGK stars because of the sparse features in their spectra and the degeneracy between effective temperature (T eff) and gravity (log g). Modeling the relationship between fundamental stellar parameters and features through machine learning is possible because we can …
VVVX Near-IR Photometry for 99 Low-mass Stars in the Gaia EDR3 Catalog of Nearby Stars
Minniti, D.; Solano, E.; Saito, R. K. +3 more
Context. Red dwarf stars, which represent 75% of stars in the Milky Way, can be studied in great detail in the solar neighborhood, where the sample is more complete.
Aims: We intend to better characterize red-dwarf candidates selected from the Gαìα Catalog of Nearby Stars using optical and near-infrared multi-filter photometry from the Vista …
Temperature Discrepancy with Photoionization Models of the Narrow-Line Region
Binette, L.; Villar Martín, M.; Magris C., G. +4 more
Using published work on the narrow-line region of Active Galactic Nuclei, a comparison is carried out among the [OIII] λ4363Å/5007Å ratios (ROIII) observed in quasars, Seyfert 2's and the spatially resolved ENLR plasma. Using the weak [ArIV] λ4711Å/λ4740Å doublet observed by Koski (1978) among Seyfert 2's, we find …
The XXL Survey - XLVIII. X-ray follow-up of distant XXL clusters: masses, scaling relations, and AGN contamination
Valtchanov, I.; Pierre, M.; Gastaldello, F. +11 more
We use deep follow-up XMM-Newton observations of six clusters discovered in the XXL Survey at z > 1 to gain robust measurements of their X-ray properties and to investigate the extent to which scaling relations at low redshift are valid at z > 1. This sample is unique as it has been investigated for active galactic nucleus (AGN) contaminatio…
The relation between X-ray and ultraviolet variability of quasars
Xie, Zhang-Liang; Cai, Zhen-Yi; Wang, Jun-Xian +2 more
The relation between X-ray and UV/optical variability in AGNs has been explored in many individual sources, however a large sample study is yet absent. Through matching the XMM-Newton serendipitous X-ray and UV source catalogs with SDSS quasars, we build a sample of 802 epoch-pairs of 525 quasars showing clear variability in logFX - log…