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Galactic Center Extinction: Evidence of Metallic Needles in the General Interstellar Medium
Dwek, Eli
The extinction curve derived from Infrared Space Observatory mid-infrared observations of the Galactic center (GC) exhibits a surprisingly flat behavior in the ~3-8 µm region, contrary to the deep minimum expected from standard interstellar dust models consisting of bare silicate and graphite dust particles. We show that this extinction is l…
A variable ultra-luminous X-ray source in the colliding galaxy NGC 7714
Motch, C.; Soria, R.
We studied the colliding galaxy NGC 7714 with two XMM-Newton observations, six months apart. The galaxy contains two bright X-ray sources: we show that they have different physical nature. The off-nuclear source is an accreting compact object, one of the brightest ultraluminous X-ray sources (ULXs) found to date. It showed spectral and luminosity …
GRB 021211 as a Faint Analog of GRB 990123: Exploring the Similarities and Differences in the Optical Afterglows
Bloom, J. S.; Caldwell, Nelson; Garnavich, Peter M. +7 more
We present BVRCJHKs photometry of the optical afterglow of the gamma-ray burst GRB 021211 taken at the Magellan, MMT, and WIYN observatories between 0.7 and 50 days after the burst. We find an intrinsic spectral slope at optical and near-infrared wavelengths of 0.69+/-0.14 at 0.87 days. The optical decay during the first day …
The heliospheric hydrogen wall and astrospheres
Linsky, J. L.; Zank, G. P.; Wood, B. E. +2 more
Charge exchange processes in the outer heliosphere produce a population of hot hydrogen gas within the heliosphere, creating a "hydrogen wall" between the heliopause and bow shock. The heliospheric hydrogen wall scatters Lyα photons passing through it, producing a detectable absorption signature in observations of H I Lyα emission from nearby star…
HST observations of nuclear stellar disks
Jaffe, W.; Krajnović, D.
We present observations of four nearby early-type galaxies with previously known nuclear stellar disks using two instruments on-board the Hubble Space Telescope. We observed NGC 4128, NGC 4612, and NGC 5308 with the Wide Field Planetary Camera 2, and the same three galaxies, plus NGC 4570, with the Space Telescope Imaging Spectrograph. We have det…
Photometric estimates of stellar masses in high-redshift galaxies
Berta, S.; Fritz, J.; Franceschini, A. +2 more
We present a new tool for the photometric estimate of stellar masses in distant galaxies. The observed source spectral energy distributions are fitted by combining sets of various simple stellar populations, with different normalizations and different amounts of dust extinction, for a given (Salpeter) IMF. This treatment gives us the best flexibil…
XMM-Newton Observations of the Extremely Low Accretion Rate Polars SDSS J155331.12+551614.5 and SDSS J132411.57+032050.5
Anderson, Scott F.; Brinkmann, J.; Szkody, Paula +6 more
XMM-Newton observations of the polar SDSS J155331.12+551614.5 reveal that all the X-ray flux emerges at energies less than 2 keV. The best fit to the spectrum is with a thermal plasma with kT=0.8 keV plus a 20-90 eV black body, yielding a thermal X-ray luminosity of (8.0-9.5)×1028 ergs s-1. The low temperature and X-ray lumin…
Twisted accretion curtains in the intermediate polar FO Aquarii
Cropper, Mark; Hellier, Coel; Ramsay, Gavin +1 more
We report on a ~37-ks XMM-Newton observation of the intermediate polar FO Aquarii, presenting X-ray and ultraviolet data from the EPIC and OM cameras. We find that the system has changed from its previously reported state of disc-overflow accretion to one of purely disc-fed accretion. We detect the previously reported `notch' feature in the X-ray …
New properties of energy-dispersed ions in the plasma sheet boundary layer observed by Cluster
Lundin, R.; Sauvaud, J. -A.; Escoubet, C. P. +18 more
Using multipoint measurements from the Cluster ion spectrometry instruments and the research with adaptive particle imaging detectors, we identified new properties of multiple energy-dispersed ion structures in the plasma sheet boundary layer (PSBL). On 14 February 2001 at about 4.5 RE midnight local time, the PSBL was highly structured…
Observations of the Pulsating White Dwarf G 185-32
Mazeh, T.; Hansen, C. J.; Kepler, S. O. +32 more
We observed the pulsating hydrogen atmosphere white dwarf G 185-32 with the Whole Earth Telescope in 1992. We report on a weighted Fourier transform of the data detecting 18 periodicities in its light curve. Using the Hubble Space Telescope Faint Object Spectrograph time resolved spectroscopy, and the wavelength dependence of the relative amplitud…