Search Publications
Permitted Oxygen Abundances and the Temperature Scale of Metal-poor Turnoff Stars
Meléndez, Jorge; Shchukina, Nataliya G.; Vasiljeva, Irina E. +1 more
We use high-quality VLT/UVES published data of the permitted O I triplet and Fe II lines to determine oxygen and iron abundances in unevolved (dwarfs, turnoff, subgiants) metal-poor halo stars. The calculations have been performed both in LTE and non-LTE (NLTE), employing effective temperatures obtained with the new infrared flux method (IRFM) tem…
Masses of Astrometrically Discovered and Imaged Binaries: G78-28AB and GJ 231.1BC
Ireland, Michael J.; Martinache, Frantz; Lloyd, James P. +5 more
The Stellar Planet Survey (STEPS) is an ongoing astrometric search for giant planets and brown dwarfs around a sample of ~30 M dwarfs. We have discovered several low-mass companions by measuring the motion of our target stars relative to their reference frames. The highest mass discovery thus far is G78-28B, a companion to the M dwarf G78-28A. The…
Deep Chandra and Multicolor HST Follow-up of the Jets in Two Powerful Radio Quasars
Maraschi, L.; Cheung, C. C.; Tavecchio, F. +5 more
We present deep (70-80 ks) Chandra and multicolor HST ACS images of two jets hosted by the powerful quasars 1136-135 and 1150+497, together with new radio observations. The sources have an FR II morphology and were selected from our previous X-ray and optical jet survey for detailed follow-up aimed at obtaining better constraints on the jet multiw…
FUSE Observation of the Narrow-Line Seyfert 1 Galaxy RE 1034+39: Dependence of Broad Emission Line Strengths on the Shape of the Photoionizing Spectrum
Baron, E.; Leighly, Karen M.; Casebeer, Darrin A.
We present an analysis from simultaneous FUSE, ASCA, and EUVE observations, as well as a reanalysis of archival HST spectra, from the extreme narrow-line Seyfert 1 Galaxy RE 1034+39 (KUG 1031+398). RE 1034+39 has an unusually hard spectral energy distribution (SED) that peaks in the soft X-rays. Its emission lines are unusual in that they can all …
A Strong X-Ray Flux Ratio Anomaly in the Quadruply Lensed Quasar PG 1115+080
Schechter, Paul L.; Fong, Wen-fai; Pooley, David +2 more
PG 1115+080 is a quadruply lensed quasar at z=1.72 whose image positions are well fit by simple models of the lens galaxy (at z=0.31). At optical wavelengths, the bright close pair of images exhibits a modest flux ratio anomaly (factors of ~1.2-1.4 over the past 22 yr) with respect to these same models. We show here that as observed in X-rays with…
Probing the Dust Responsible for Small Magellanic Cloud Extinction
Gordon, Karl D.; Sofia, Ulysses J.; Clayton, Geoffrey C. +4 more
We explore the abundances and depletion levels of elements important to dust composition in four Small Magellanic Cloud (SMC) sight lines observed with the Hubble Space Telescope. The apparent optical depth method is used to interpret the high-resolution ultraviolet absorption data toward AzV 18, AzV 456, Sk 108, and Sk 155; the latter two sight l…
An Asymmetric Outflow from the Herbig Ae Star HD 163296
Bruhweiler, F. C.; Grady, C. A.; Kimble, R. A. +2 more
We present an observational picture of the HH 409 bipolar outflow including the detection of six previously unreported Herbig-Haro knots from the Herbig Ae star HD 163296. This study combines seven years of data from ground-based Fabry-Pérot and HST coronagraphic imagery, as well as HST long-slit spectral imagery. The redshifted counterjet include…
The Current-Free Electric Double Layer in a Coronal Magnetic Funnel
Marsch, Eckart; Boswell, Roderick W.; Charles, Christine
Current-free double layers (CFDLs) have been recently discovered in a number of laboratory devices, when a low collisional plasma is forced to expand from a high magnetic field source region to a low magnetic field diffusion region. This experimental setup bears a striking resemblance to the natural conditions prevailing in the magnetic funnels of…
Electron Density Modeling of a Streamer Using LASCO Data of 2004 January and February
Thernisien, A. F.; Howard, R. A.
We present a three-dimensional reconstruction of the electron density of a streamer using a newly developed forward modeling technique. The streamer was observed by SOHO LASCO continuously at the end of 2004 January, but for this study we consider two dates, about 7 days apart. On the first day the streamer was seen ``edge-on,'' in which the coron…
Detailed Atmosphere Modeling for the Neutron Star 1E1207.4-5209: Evidence of Oxygen/Neon Atmosphere
Hailey, Charles J.; Mori, Kaya
We present a comprehensive investigation of the two broad absorption features observed in the X-ray spectrum of the neutron star 1E1207.4-5209 based on a recent analysis of the 260 ks XMM-Newton data by Mori et al. Expanding on earlier work by Hailey & Mori, we have examined all previously proposed atmospheric models for 1E1207.4-5209. Using o…