Search Publications
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…
Optical observations and dust modelling of comet 156P/Russell-LINEAR
Aravind, K.; Halder, Prithish; Ganesh, Shashikiran +5 more
Comet 156P/Russell-LINEAR is a short period Jupiter family comet with an orbital period of 6.44 years. The results from spectroscopic, photometric, polarimetric observations and dust modelling studies are presented here. From the spectroscopic study, strong emissions from CN(Δν = 0) , C3 (λ 4050 Å), C2(Δν = + 1) and C2
Spectroscopy of an extreme [O III] emitting active galactic nucleus at z = 3.212: implications for the reionization era
Feltre, Anna; Charlot, Stéphane; Shapley, Alice E. +4 more
Reionization-era galaxies often display intense nebular emission lines, both in rest-frame optical ([O III] + H β) and ultraviolet (UV; C III], C IV). How such strong nebular emission is powered remains unclear, with both active galactic nuclei (AGNs) and hot stars considered equally viable. The UV continuum slopes of these early systems tend to b…
Searching the SETI Ellipsoid with Gaia
Davenport, James R. A.; Siemion, Andrew P. V.; Cody, Ann Marie +4 more
The search for extraterrestrial intelligence (SETI) Ellipsoid is a geometric method for prioritizing technosignature observations based on the strategy of receiving signals synchronized to conspicuous astronomical events. Precise distances to nearby stars from Gaia makes constraining Ellipsoid crossing times possible. Here we explore the utility o…