Search Publications
The Signature of 44Ti in Cassiopeia A Revealed by IBIS/ISGRI on INTEGRAL
Knödlseder, J.; Decourchelle, A.; Vink, J. +9 more
We report the detection of both the 67.9 and 78.4 keV 44Sc γ-ray lines in Cassiopeia A with the INTEGRAL IBIS/ISGRI instrument. Besides the robustness provided by spectroimaging observations, the main improvements compared to previous measurements are a clear separation of the two 44Sc lines together with an improved signific…
Penetrating the Deep Cover of Compton-thick Active Galactic Nuclei
Krolik, J. H.; Heckman, T. M.; Levenson, N. A. +2 more
We analyze observations obtained with the Chandra X-Ray Observatory of bright Compton-thick active galactic nuclei (AGNs), those with column densities in excess of 1.5×1024 cm-2 along the lines of sight. We therefore view the powerful central engines only indirectly, even at X-ray energies. Using high spatial resolution and c…
Swift Panchromatic Observations of the Bright Gamma-Ray Burst GRB 050525a
Sakamoto, T.; Campana, S.; Tagliaferri, G. +62 more
The bright gamma-ray burst GRB 050525a has been detected with the Swift observatory, providing unique multiwavelength coverage from the very earliest phases of the burst. The X-ray and optical/UV afterglow decay light curves both exhibit a steeper slope ~0.15 days after the burst, indicative of a jet break. This jet break time combined with the to…
Discovery of an 86 AU Radius Debris Ring around HD 181327
Henning, Thomas; Schneider, Glenn; Hines, Dean C. +11 more
HST NICMOS PSF-subtracted coronagraphic observations of HD 181327 have revealed the presence of a ringlike disk of circumstellar debris seen in 1.1 µm light scattered by the disk grains, surrounded by a diffuse outer region of lower surface brightness. The annular disk appears to be inclined by 31.7d+/-1.6d from face-on, with the disk major-…
The Arches Cluster Mass Function
Najarro, F.; Figer, Donald F.; Kim, Sungsoo S. +1 more
We have analyzed H- and Ks-band images of the Arches cluster obtained using the NIRC2 instrument on Keck with the laser guide star adaptive optics (LGS AO) system. With the help of the LGS AO system, we were able to obtain the deepest ever photometry for this cluster and its neighborhood and derive the background-subtracted present-day …
A Survey of Galaxy Kinematics to z~1 in the TKRS/GOODS-N Field. II. Evolution in the Tully-Fisher Relation
Weiner, Benjamin J.; Faber, S. M.; Willmer, Christopher N. A. +7 more
We use kinematic measurements of a large sample of galaxies from the Team Keck Redshift Survey in the GOODS-N field to measure evolution in the optical and near-IR Tully-Fisher (TF) relations to z=1.2. We construct TF relations with integrated line-of-sight velocity widths of ~1000 galaxies in B and ~670 in J; these relations have large scatter, a…
Solar Sources of Impulsive Solar Energetic Particle Events and Their Magnetic Field Connection to the Earth
Liu, Yang; Yashiro, Seiji; Nitta, Nariaki V. +3 more
This paper investigates the solar origin of impulsive solar energetic particle (SEP) events, often referred to as 3He-rich flares, by attempting to locate the source regions of 117 events as observed at ~2-3 MeV amu-1. Given large uncertainties as to when ions at these energies were injected, we use type III radio bursts that…
Identification of the OGLE-2003-BLG-235/MOA-2003-BLG-53 Planetary Host Star
Anderson, Jay; Udalski, Andrzej; Gould, Andrew +2 more
We present the results of HST observations of the host star for the first definitive extrasolar planet detected by microlensing. The light-curve model for this event predicts that the lens star should be separated from the source star by ~6 mas at the time of the HST images. If the lens star is a late G, K, or early M dwarf, then it will be visibl…
The Enceladus and OH Tori at Saturn
Tokar, R. L.; Johnson, R. E.; Sittler, E. C. +4 more
The remarkable observation that Enceladus, a small icy satellite of Saturn, is actively venting has led to the suggestion that ejected water molecules are the source of the toroidal atmosphere observed at Saturn for over a decade using the Hubble Space Telescope (HST). Here we show that the venting leads directly to a new feature, a narrow Encelad…
New Chandra Observations of the Jet in 3C 273. I. Softer X-Ray than Radio Spectra and the X-Ray Emission Mechanism
Meisenheimer, Klaus; Jester, Sebastian; Harris, D. E. +1 more
The jet in 3C 273 is a high-power quasar jet with radio, optical, and X-ray emission, whose size and brightness allow a detailed study of the emission processes acting in it. We present deep Chandra observations of this jet and analyze the spectral properties of the jet emission from radio through X-rays. We find that the X-ray spectra are signifi…