Search Publications
Optical Spectroscopic Observations of Gamma-Ray Blazar Candidates. VI. Further Observations from TNG, WHT, OAN, SOAR, and Magellan Telescopes
Smith, Howard A.; Masetti, N.; Jiménez-Bailón, E. +16 more
Blazars, one of the most extreme classes of active galaxies, constitute so far the largest known population of γ-ray sources, and their number is continuously growing in the Fermi catalogs. However, in the latest release of the Fermi catalog there is still a large fraction of sources that are classified as blazar candidates of uncertain type (BCUs…
Optical Spectroscopic Observations of Gamma-ray Blazar Candidates. V. TNG, KPNO, and OAN Observations of Blazar Candidates of Uncertain Type in the Northern Hemisphere
Smith, Howard A.; Masetti, N.; Jiménez-Bailón, E. +12 more
The extragalactic γ-ray sky is dominated by emission from blazars, a peculiar class of active galactic nuclei. Many of the γ-ray sources included in the Fermi-Large Area Telescope Third Source catalog (3FGL) are classified as blazar candidates of uncertain type (BCUs) because there are no optical spectra available in the literature to confirm thei…
Hubble Space Telescope Snapshot Survey for Resolved Companions of Galactic Cepheids
Schaefer, Gail H.; Bond, Howard E.; Evans, Nancy Remage +4 more
We have conducted an imaging survey with the Hubble Space Telescope Wide Field Camera 3 (WFC3) of 70 Galactic Cepheids, typically within 1 kpc, with the aim of finding resolved physical companions. The WFC3 field typically covers the 0.1 pc area where companions are expected. In this paper, we identify 39 Cepheids having candidate companions, base…
Resolved Companions of Cepheids: Testing the Candidates with X-Ray Observations
Schaefer, Gail H.; Bond, Howard E.; Evans, Nancy Remage +7 more
We have made XMM-Newton observations of 14 Galactic Cepheids that have candidate resolved (≥5″) companion stars based on our earlier HST Wide Field Camera 3 (WFC3) imaging survey. Main-sequence stars that are young enough to be physical companions of Cepheids are expected to be strong X-ray producers in contrast to field stars. XMM-Newton exposure…
A Direct Linkage between AGN Outflows in the Narrow-line Regions and the X-Ray Emission from the Accretion Disks
Wang, J.; Wei, J. Y.; Xu, D. W.
The origin of outflow in the narrow-line region (NLR) of the active galactic nucleus (AGN) is studied in this paper by focusing on the relationship between the [O III]λ5007 line profile and the hard-X-ray (in a bandpass of 2-10 keV) emission from the central super-massive black hole (SMBH) in type-I AGNs. A sample of 47 local X-ray selected type-I…
Discovery of an X-Ray-emitting Contact Binary System 2MASS J11201034-2201340
Chen, W. P.; Kong, Albert K. H.; Ip, Wing-Huen +10 more
We report the detection of orbital modulation, a model solution, and the X-ray properties of a newly discovered contact binary, Two Micron All Sky Survey (2MASS) J11201034-2201340. We serendipitously found this X-ray point source outside the error ellipse when searching for possible X-ray counterparts of γ-ray millisecond pulsars among the unident…
A Search for Coronal Activity Among Two Metal-poor Subdwarfs and One Subgiant
Dupree, Andrea K.; Smith, Graeme H.; Günther, Hans Moritz
A search has been made using the XMM-Newton satellite for coronal soft X-ray emission from HD 19445, HD 25329, and HD 140283, three Population II stars in the Galactic halo having metallicities of {{[Fe/H]}}∼ -2. The program stars, consisting of two subdwarfs and one metal-poor subgiant, were pre-selected from ground-based observations to have He …