Search Publications
Fragmentation Hierarchy of Bright Sungrazing Comets and the Birth and Orbital Evolution of the Kreutz System. II. The Case for Cascading Fragmentation
Sekanina, Zdenek; Chodas, Paul W.
We examine the process of cascading fragmentation for the Kreutz sungrazer system to continue our exploration of its birth, orbital evolution, and temporal clumping. We modify and broaden the two-superfragment model from Paper I to include clusters of ~30 bright comets spanning four centuries and 1000 SOHO sungrazers from 1996 to 2006. The spectac…
A Correlation between Galaxy Morphology and Mg II Halo Absorption Strength
Kacprzak, Glenn G.; Steidel, Charles C.; Churchill, Christopher W. +2 more
We compared the quantified morphological properties of 37 intermediate redshift Mg II absorption selected galaxies to the properties of the absorbing halo gas [0.03 Å<=Wr(2796)<=2.90 Å], observed in the spectra of background quasars. The galaxy morphologies were measured using GIM2D modeling of Hubble Space Telescope WFPC2 images …
Evidence for a z < 8 Origin of the Source-subtracted Near-Infrared Background
Fan, Xiaohui; Kennicutt, Robert C.; Rieke, Marcia +2 more
This paper extends our previous fluctuation analysis of the near-infrared background at 1.6 µm to the 1.1 µm (F110W) image of the Hubble Ultra Deep Field. When all detectable sources are removed, the ratio of fluctuation power in the two images is consistent with the ratio expected for faint, z<8, sources, and is inconsistent with t…
Origin of the X-Ray Quasi-periodic Oscillations and Identification of a Transient Ultraluminous X-Ray Source in M82
Feng, Hua; Kaaret, Philip
The starburst galaxy M82 contains two ultraluminous X-ray sources (ULXs), CXOM82 J095550.2+694047 (=X41.4+60) and CXOM82 J095551.1+694045 (=X42.3+59), which are unresolved by XMM-Newton. We revisited the two XMM-Newton observations of M82 and analyzed the surface brightness profiles using the known Chandra source positions. We show that the quasi-…
X-Ray Emission from PSR J1809-1917 and Its Pulsar Wind Nebula, Possibly Associated with the TeV Gamma-Ray Source HESS J1809-193
Pavlov, G. G.; Kargaltsev, O.
We detected the 50 kyr old pulsar J1809-1917, and resolved its pulsar wind nebula (PWN) with the Chandra X-Ray Observatory. The pulsar spectrum fits a power-law+blackbody (PL+BB) model, with a photon index Γpsr=1.2+/-0.6 and T~2 MK for nH=0.7×1022 cm-2. At a distance of 3.5 kpc, the luminosities of the P…
Three-dimensional Numerical Simulations of the Acoustic Wave Field in the Upper Convection Zone of the Sun
Kosovichev, A. G.; Parchevsky, K. V.
Results of numerical three-dimensional (3D) simulations of propagation of acoustic waves inside the Sun are presented. A linear 3D code which utilizes the realistic OPAL equation of state was developed. A modified convectively stable standard solar model with a smoothly joined chromosphere was used as a background model. A high-order dispersion re…
On the Remote Galactic Globular Cluster NGC 2419
Marconi, Marcella; Dall'Ora, Massimo; Ripepi, Vincenzo +8 more
We present a new, deep (V~26) study of the Galactic globular cluster NGC 2419 based on B, V, I time-series CCD photometry over about 10 years and extending beyond the cluster published tidal radius. We have identified 101 variable stars, of which 60 are new discoveries, doubling the known RR Lyrae stars and including 12 SX Phoenicis stars. The ave…
A Spectroscopic Study of Mass Outflows in the Interacting Binary RY Scuti
Gies, Douglas R.; Smith, Nathan; Gehrz, Robert D. +5 more
The massive interacting binary RY Scuti is an important representative of an active mass-transferring system that is changing before our eyes and which may be an example of the formation of a Wolf-Rayet star through tidal stripping. Utilizing new and previously published spectra, we present examples of how a number of illustrative absorption and e…
Early Ultraviolet, Optical, and X-Ray Observations of the Type IIP SN 2005cs in M51 with Swift
Modjaz, Maryam; Kirshner, Robert P.; Dewangan, Gulab C. +14 more
We report early photospheric-phase observations of the Type IIP supernova (SN) 2005cs obtained by the Swift ultraviolet-optical and X-ray telescopes. Observations started within 2 days of discovery and continued on a regular basis for 3 weeks. During this time the V-band magnitude remained essentially constant, while the UV was initially bright, b…
The Microjansky Radio Galaxy Population
Wang, W. -H.; Barger, A. J.; Cowie, L. L.
We use highly spectroscopically complete observations of the radio sources from the VLA 1.4 GHz survey of the Hubble Deep Field-North region to study the faint radio galaxy population and its evolution. The fraction that can be optically spectroscopically identified is fairly independent of radio flux, with about 60%-80% identified at all fluxes. …