Search Publications
The Large Magellanic Cloud Eclipsing Binary HV 2274: Fundamental Properties and Comparison with Evolutionary Models
Fitzpatrick, Edward L.; Guinan, Edward F.; Ribas, Ignasi +6 more
We are carrying out an international, multiwavelength program to determine the fundamental properties and independent distance estimates of selected 14th to 15th magnitude eclipsing binaries in the Large and Small Magellanic Clouds (LMC and SMC). Eclipsing binaries with well-defined double-line radial velocity curves and light curves provide valua…
Thomson Thick X-Ray Absorption in a Broad Absorption Line Quasar, PG 0946+301
Arav, N.; Elvis, M.; Peterson, B. M. +14 more
We present a deep ASCA observation of a broad absorption line quasar (BALQSO) PG 0946+301. The source was clearly detected in one of the gas imaging spectrometers, but not in any other detector. If BALQSOs have intrinsic X-ray spectra similar to normal radio-quiet quasars, our observations imply that there is Thomson thick X-ray absorption (N…
Discovery of a Disk-collimated Bipolar Outflow in the Proto-Planetary Nebula IRAS 17106-3046
Kwok, Sun; Hrivnak, Bruce J.; Su, Kate Y. L.
We report the discovery of a collimated bipolar outflow emerging from a visible disk around the proto-planetary nebula IRAS 17106-3046. The radius of the disk, estimated to be 2500 AU at a distance of 4 kpc, is too large for it to be a Keplerian disk created by accretion. The radial intensity profile of the disk suggests that it is consistent with…
Face-on Dust Disks in Galaxies with Optical Jets
Baum, Stefi A.; Sparks, William B.; Macchetto, F. Duccio +2 more
The presence of optical synchrotron jets in radio galaxies is relatively rare. Here we show that of the nearest five FR I 3CR radio galaxies showing optical jets, four show evidence for almost circular, presumably face-on, dust disks. This is strong support for the twofold idea that (1) jets emerge close to perpendicular to inner gas disks and (2)…
Photometry and Photometric Redshifts of Faint Galaxies in the Hubble Deep Field South NICMOS Field
Chen, Hsiao-Wen; Lanzetta, Kenneth M.; Pascarelle, Sebastian M. +4 more
We present a catalog of photometry and photometric redshifts of 335 faint objects in the Hubble Deep Field South near-infrared camera and multiobject spectrograph (NICMOS) field. The analysis is based on (1) infrared images obtained with the Hubble Space Telescope (HST) using the NICMOS with the F110W, F160W, and F222M filters; (2) an optical imag…
Far-Ultraviolet Emission from Elliptical Galaxies at Z = 0.55
Ferguson, Henry C.; Brown, Thomas M.; Kimble, Randy A. +1 more
The rest-frame UV-to-optical flux ratio, which characterizes the ``UV upturn'' phenomenon, is potentially the most sensitive tracer of age in elliptical galaxies; models predict that it may change by orders of magnitude over the course of a few gigayears. In order to trace the evolution of the UV upturn as a function of redshift, we have used the …
Active Region Loops Observed with SUMER on Board the SOHO
Wilhelm, Klaus; Qiu, Jiong; Wang, Haimin +2 more
We study the emission and dynamical characteristics of transition region temperature plasmas in magnetic loops by analyzing a high-resolution, limb observation of the active region NOAA 7962. The observations were performed by the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) instrument on board the Solar and Heliospheric Observatory…
A Chemical Model of the Neutral Envelope of the Planetary Nebula NGC 7027
Hasegawa, Tatsuhiko; Volk, Kevin; Kwok, Sun
In response to the recent molecular observations by ISO and millimeter-wave telescopes, we have developed a spherically symmetric, steady state chemical model for the planetary nebula NGC 7027. In our model, the neutral envelope consists of a geometrically thin, high-density shell of constant density and an outer stellar wind region with an invers…
Morphology and Kinematics of Planetary Nebulae. II. A Diabolo Model for NGC 3132
Morisset, C.; Monteiro, H.; Gruenwald, R. +1 more
We use a three-dimensional photoionization modeling tool to study the morphokinematic properties of the planetary nebula NGC 3132. We show that it is possible to reproduce the low-resolution observations (spectra and images) with an ellipsoidal shell. However, high-resolution observations, as those showing a density variation along the nebula and …
A Search for Rotational Modulation of X-Ray Centers on the Classical BE Star γ Cassiopeiae
Smith, Myron A.; Robinson, Richard D.
In this paper we discuss X-ray observations of γ Cas obtained in 1998 November with the Rossi X-Ray Timing Explorer (RXTE). The data were obtained nearly continuously over 54 hr, which is about twice the expected rotational period. An earlier RXTE light curve obtained in 1996 March over a 27 hr period showed X-ray flux arising from short-duration …