Search Publications
The Double-Peak Spectral Energy Density of Gamma-Ray Bursts and the True Identity of GRB 031203
Dar, Arnon; Dado, Shlomo
A double-peak spectral energy density of prompt γ-rays, similar to that observed in blazars, is expected in the cannonball (CB) model of gamma-ray bursts (GRBs) produced in supernova (SN) explosions. The first sub-MeV ordinary peak is formed by inverse Compton scattering (ICS) of the ambient SN light by the CBs' electrons, while the second peak at…
Clusters in the Luminous Giant H II Regions in M101
Johnson, Kelsey E.; Chu, You-Hua; Chen, C. -H. Rosie
We have obtained HST WFPC2 observations of three very luminous but morphologically different giant H II regions (GHRs) in M101, NGC 5461, NGC 5462, and NGC 5471, in order to study cluster formation in GHRs. Images obtained in the F547M and F675W bands are used to identify cluster candidates and for photometric measurements, and images in the F656N…
Cataclysmic and Close Binaries in Star Clusters. V. Erupting Dwarf Novae, Faint Blue Stars, X-Ray Sources, and the Classical Nova in the Core of M80
Zurek, David R.; Hinkley, Sasha; Shara, Michael M.
Large populations of cataclysmic variables (CVs) in globular clusters have long been predicted, but the number of absolutely certain cluster CVs known in globular clusters is still less than 10. HST and Chandra observers have recently found dozens of CV candidates in several populous globular clusters. Confirmation and characterization of these ca…
Density Structure of a Preeruption Coronal Flux Rope
Chen, J.; Krall, J.
A density model is developed for a coronal flux rope with a specified magnetic field configuration in the noninteracting limit, for which transverse pressure forces can be neglected and flows are rapid enough (>1 km s-1) to invalidate a hydrostatic solution. In the coronal portion of the flux rope, we find that the plasma density is …
X-Ray Observations of Solar Long-Duration Flares
Phillips, K. J. H.; Harra, L. K.; Feldman, U.
Yohkoh X-ray observations during the several-hour decay of six large solar flares show that the main emitting region is in the form of a bright loop-top source whose spatial extent well after the impulsive stage explains most of the broadening of S XV and Ca XIX X-ray lines, which would otherwise imply nonthermal velocities of 100 km s-1
Irregular Mass Transfer in the Polars VV Puppis and V393 Pavonis during the Low State
Pandel, Dirk; Córdova, France A.
The polars VV Pup and V393 Pav were observed with XMM-Newton during states of low accretion with peak X-ray luminosities of ~1×1030 and ~1×1031 ergs s-1, respectively. In both polars, accretion onto the white dwarf was extremely irregular, and the accretion rate varied by more than 1 order of magnitude on timescale…
Rotation Rates of Particles in Saturn's Rings
Ohtsuki, Keiji
Rotational states of particles in Saturn's rings are not directly observable but have been inferred from spacecraft and ground-based observations of their thermal emission. A temperature contrast between night- and daysides of particles in Saturn's C ring during crossing of the planetary shadow has been detected and interpreted as indicating the p…
Is the INTEGRAL IBIS Source IGR J17204-3554 a Gamma-Ray-emitting Galaxy Hidden behind the Molecular Cloud NGC 6334?
Gehrels, N.; Walter, R.; Bird, A. J. +9 more
We report on the identification of a soft gamma-ray source, IGR J17204-3554, detected with IBIS, the Imager on Board the INTEGRAL Satellite. The source has a 20-100 keV flux of ~3×10-11 ergs cm-2 s-1 and is spatially coincident with NGC 6334, a molecular cloud located in the Sagittarius arm of the Milky Way. Diffus…
Dust in the Host Galaxies of Supernovae
Chary, R.; Pope, A.; Ravindranath, S. +2 more
We present Spitzer MIPS 24 µm observations of 50 supernova host galaxies at 0.1<z<1.7 in the Great Observatories Origins Deep Survey (GOODS) fields. We also discuss the detection of SN host galaxies in SCUBA/850 µm observations of GOODS-N and Spitzer Infrared Spectrograph (IRS) 16 µm observations of GOODS-S. About 60% of th…
A Variability Study of the Seyfert 2 Galaxy NGC 6300 with XMM-Newton
Awaki, Hisamitsu; Hayashida, Kiyoshi; Leighly, Karen M. +3 more
We present the results of timing analysis of the XMM-Newton observation of the Seyfert 2 galaxy NGC 6300. The hard X-ray spectrum above 2 keV consists of a Compton-thin absorbed power law, as is often seen in Seyfert 2 galaxies. We clearly detected rapid time variability on a timescale of about 1000 s from the light curve above 2 keV. The excess v…