Search Publications
The COSMOS Active Galactic Nucleus Spectroscopic Survey. I. XMM-Newton Counterparts
Trump, Jonathan R.; McCarthy, Patrick J.; Comastri, Andrea +17 more
We present optical spectroscopy for an X-ray and optical flux-limited sample of 677 XMM-Newton selected targets covering the 2 deg2 Cosmic Evolution Survey field, with a yield of 485 high-confidence redshifts. The majority of the spectra were obtained over three seasons (2005-2007) with the Inamori Magellan Areal Camera and Spectrograph…
On the Nature of the Prototype Luminous Blue Variable Ag Carinae. I. Fundamental Parameters During Visual Minimum Phases and Changes in the Bolometric Luminosity During the S-Dor Cycle
Hillier, D. J.; Rossi, C.; Whitelock, P. A. +3 more
We present a detailed spectroscopic analysis of the luminous blue variable (LBV) AG Carinae (AG Car) during the last two visual minimum phases of its S-Dor cycle (1985-1990 and 2000-2003). The analysis reveals an overabundance of He, N, and Na, and a depletion of H, C, and O, on the surface of the AG Car, indicating the presence of a CNO-processed…
An Intermediate Luminosity Transient in NGC 300: The Eruption of a Dust-Enshrouded Massive Star
Berger, E.; Fransson, C.; Chevalier, R. A. +10 more
We present multi-epoch high-resolution optical spectroscopy, UV/radio/X-ray imaging, and archival Hubble and Spitzer observations of an intermediate luminosity optical transient recently discovered in the nearby galaxy NGC 300. We find that the transient (NGC 300 OT2008-1) has a peak absolute magnitude of M bol ≈ -11.8 mag, intermediate…
An Estimate of the Chemical Composition of Titan's Lakes
Mousis, Olivier; Lunine, Jonathan I.; Lavvas, Panayotis +2 more
Hundreds of radar-dark patches interpreted as lakes have been discovered in the north and south polar regions of Titan. We have estimated the composition of these lakes by using the direct abundance measurements from the Gas Chromatograph Mass Spectrometer aboard the Huygens probe and recent photochemical models based on the vertical temperature p…
Fresh Insights on the Structure of the Solar Core
Chaplin, William J.; Basu, Sarbani; Serenelli, Aldo M. +2 more
We present new results on the structure of the solar core, obtained with new sets of frequencies of solar low-degree p modes obtained from the BiSON network. We find that different methods used in extracting the different sets of frequencies cause shifts in frequencies, but the shifts are not large enough to affect solar structure results. We find…
The Sloan Digital Sky Survey/XMM-Newton Quasar Survey: Correlation Between X-Ray Spectral Slope and Eddington Ratio
Elvis, M.; Risaliti, G.; Young, M.
We present a correlation between the 2-10 keV spectral slope Γ X and the Eddington ratio L/L EDD in a sample of ~400 Sloan Digital Sky Survey (SDSS) quasars with available hard X-ray spectra from XMM-Newton serendipitous observations. We find that the Γ X -L/L EDD correlation is strongest in objects wit…
Mixed Populations in Globular Clusters: Et Tu, 47 Tuc?
Anderson, J.; Bedin, L. R.; King, I. R. +2 more
We exploit the large number of archival Hubble Space Telescope images of 47 Tuc to examine its subgiant branch (SGB) and main sequence (MS) for signs of multiple populations. In the cluster core, we find that the cluster's SGB exhibits a clear spread in luminosity, with at least two distinct components: a brighter one with a spread that is real bu…
The Black Hole Mass-Bulge Luminosity Relationship for Active Galactic Nuclei From Reverberation Mapping and Hubble Space Telescope Imaging
Peterson, Bradley M.; Pogge, Richard W.; Vestergaard, Marianne +1 more
We investigate the relationship between black hole mass and bulge luminosity for active galactic nuclei (AGNs) with reverberation-based black hole mass measurements and bulge luminosities from two-dimensional decompositions of Hubble Space Telescope host galaxy images. We find that the slope of the relationship for AGNs is 0.76-0.85 with an uncert…
Active Region Loops: Hinode/Extreme-Ultraviolet Imaging Spectrometer Observations
Young, Peter R.; Dwivedi, Bhola N.; Tripathi, Durgesh +2 more
We have carried out a study of active region loops using observations from the Extreme-ultraviolet Imaging Spectrometer (EIS) on board Hinode using 1'' raster data for an active region observed on 2007 May 19. We find that active region structures which are clearly discernible in cooler lines (≈1 MK) become "fuzzy" at higher temperatures (≈2 MK). …
HESS J0632+057: A New Gamma-Ray Binary?
Funk, S.; Reimer, O.; Dubus, G. +8 more
The High Energy Stereoscopic System (HESS) survey of the Galactic plane has established the existence of a substantial number (~ 40) of Galactic TeV γ-ray sources, a large fraction of which remain unidentified. HESS J0632+057 is one of a small fraction of these objects, which is point-like in nature (<2' rms), and is one of only two point-like …