Search Publications
Further Evidence for Chemical Fractionation from Ultraviolet Observations of Carbon Monoxide
Andersson, B. -G.; van Dishoeck, Ewine F.; Federman, S. R. +4 more
Ultraviolet absorption from interstellar 12CO and 13CO was detected toward ρ Oph A and χ Oph. The measurements were obtained at medium resolution with the Goddard High Resolution Spectrograph on the Hubble Space Telescope. Column density ratios, N(12CO)/N(13CO), of 125+/-23 and 117+/-35 were derived for …
Follow-Up Hubble Space Telescope/Space Telescope Imaging Spectroscopy of Three Candidate Tidal Disruption Events
Komossa, S.; Grupe, D.; Halpern, J. P. +2 more
Large-amplitude, high-luminosity, soft X-ray flares were detected by the ROSAT All-Sky Survey in several galaxies with no evidence for Seyfert activity in their ground-based optical spectra. These flares had the properties predicted for a tidal disruption event by a central supermassive black hole: soft X-ray spectrum, timescale of months, and lar…
The Nearby Neutron Star RX J0720.4-3125 from Radio to X-Rays
Frail, D. A.; Kulkarni, S. R.; van Kerkwijk, M. H. +3 more
We present radio, optical, ultraviolet, and X-ray observations of the isolated, thermally emitting neutron star RX J0720.4-3125 using the Parkes radio telescope, the Very Large Array, the Hubble Space Telescope, and the Chandra X-Ray Observatory. From these data we show that the optical/UV spectrum of RX J0720.4-3125 is not well fitted by a Raylei…
Buried Alive in the Coronal Graveyard
Ayres, Thomas R.; Harper, Graham M.; Brown, Alexander
We have used the High Resolution Camera (HRC-I) of the Chandra X-Ray Observatory to search for coronal (T~106 K) emission from the archetype ``noncoronal'' red giants Arcturus (α Bootis=HD 124897, K1 III) and Aldebaran (α Tauri=HD 29139, K5 III). Our program follows up previous detections of ultraviolet coronal proxies such as C IV λ154…
Cloning Dropouts: Implications for Galaxy Evolution at High Redshift
Broadhurst, Tom; Bouwens, Rychard; Illingworth, Garth
The evolution of high-redshift galaxies in the two Hubble Deep Fields, HDF-N and HDF-S, is investigated using a cloning technique that replicates z~2-3 U dropouts to higher redshifts, allowing a comparison with the observed B and V dropouts at higher redshifts (z~4-5). We treat each galaxy selected for replication as a set of pixels that are k-cor…
The Evolution of the Galaxy Luminosity Function in the Rest-Frame Blue Band up to z=3.5
Cimatti, A.; Daddi, E.; Fontana, A. +14 more
We present an estimate of the cosmological evolution of the field galaxy luminosity function (LF) in the rest-frame 4400 Å B band up to redshift z=3.5. To this purpose, we use a composite sample of 1541 I-selected galaxies selected down to IAB=27.2 and 138 galaxies selected down to KAB=25 from ground-based and HST multicolor …
Solar Energetic Particle Production by Coronal Mass Ejection-driven Shocks in Solar Fast-Wind Regions
Kahler, S. W.; Reames, D. V.
Gradual solar energetic particle (SEP) events at 1 AU are produced by coronal/interplanetary shocks driven by coronal mass ejections (CMEs). Fast (vCME>~900 km s-1) CMEs might produce stronger shocks in solar slow-wind regions, where the flow and fast-mode MHD wave speeds are low, than in fast-wind regions, where those spe…
Does M15 Possess an Intermediate-Mass Black Hole in Its Core?
Anderson, J.; Harrison, T. E.; McNamara, B. J.
We present the results of an internal proper motion analysis of the inner region of M15 using Hubble Space Telescope Wide Field Planetary Camera 2 images. The motions of 704 stars with brightnesses above that of the cluster turnoff (V<18.3) are analyzed to determine the velocity dispersion profile within about 15" of the cluster center. The ave…
A Transient Heating Model for Coronal Structure and Dynamics
Klimchuk, J. A.; Lanzafame, A. C.; Lanza, A. F. +4 more
A wealth of observational evidence for flows and intensity variations in nonflaring coronal loops leads to the conclusion that coronal heating is intrinsically unsteady and concentrated near the chromosphere. We have investigated the hydrodynamic behavior of coronal loops undergoing transient heating with one-dimensional numerical simulations in w…
Is There Really a Black Hole at the Center of NGC 4041? Constraints from Gas Kinematics
Marconi, A.; Capetti, A.; Carollo, C. M. +16 more
We present Space Telescope Imaging Spectrograph spectra of the Sbc spiral galaxy NGC 4041, which were used to map the velocity field of the gas in its nuclear region. We detect the presence of a compact (r~=0.4"~=40 pc), high surface brightness, rotating nuclear disk cospatial with a nuclear star cluster. The disk is characterized by a rotation cu…