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The Age and Progenitor Mass of Sirius B
Holberg, J. B.; Liebert, James; Williams, Kurtis A. +2 more
The Sirius AB binary system has masses that are well determined from many decades of astrometric measurements. Because of the well-measured radius and luminosity of Sirius A, we employed the TYCHO stellar evolution code to determine the age of the Sirius AB binary system accurately, at 225-250 Myr. Note that this fit requires the assumption of sol…
XMM-Newton Detection of Pulsations and a Spectral Feature in the X-Ray Emission of the Isolated Neutron Star 1RXS J214303.7+065419/RBS 1774
Treves, A.; Cropper, M.; Zane, S. +4 more
We report on the results of a deep XMM-Newton observation of RBS 1774, the most recent dim isolated neutron star candidate found in the ROSAT archive data. Spectral and timing analysis of the high-quality pn and MOS data confirm the association of this source with an isolated neutron star. The spectrum is thermal and blackbody-like, and there is e…
A Change in the Physical State of η Carinae?
Weis, K.; Stahl, O.; Davidson, K. +8 more
During η Car's spectroscopic event in mid-2003, the stellar wind's bright Hα and Hβ emission lines temporarily had a distinctive shape unlike that reported on any previous occasion and particularly unlike the 1997-1998 event. Evidently the structure of the wind changed between 1997 and 2003. Combining this with other evidence, we suspect that the …
Molecular gas in a z ∼ 2.5 triply-imaged, sub-mJy submillimetre galaxy typical of the cosmic far-infrared background
Smail, I.; Kneib, J. -P.; van der Werf, P. +4 more
We present the results of observations from the Plateau de Bure IRAM interferometric array of the submillimetre (submm) galaxy SMMJ16359+6612 lying at z=2.516 behind the core of the massive cluster A 2218. The foreground gravitational lens produces three images with a total magnification of 45 of this faint submm galaxy, which has an intrinsic sub…
Electron anisotropy constraint in the magnetosheath: Cluster observations
Lavraud, Benoit; Gary, S. Peter; Thomsen, Michelle F. +2 more
The whistler anisotropy instability is driven by the condition T$\perp$e/T$\parallel$e > 1, where the subscript e denotes electrons and the other subscripts denote directions relative to the background magnetic field Bo. Instability growth leads to enhanced field fluctuations which scatter the electrons; theory …
Mass Segregation and the Initial Mass Function of Super Star Cluster M82-F
Graham, James R.; McCrady, Nate; Vacca, William D.
We investigate the initial mass function and mass segregation in super star cluster M82-F with high-resolution Keck NIRSPEC echelle spectroscopy. Cross-correlation with template supergiant spectra provides the velocity dispersion of the cluster, enabling measurement of the kinematic (virial) mass of the cluster when combined with sizes from NICMOS…
X-ray spectra of XMM-Newton serendipitous medium flux sources
Page, M. J.; Barcons, X.; Carrera, F. J. +7 more
We report on the results of a detailed analysis of the X-ray spectral properties of a large sample of sources detected serendipitously with the XMM-Newton observatory in 25 selected fields, for which optical identification is in progress. The survey covers a total solid angle of ~3.5 deg2 and contains 1137 sources with ~10-15…
Biologically Enhanced Energy and Carbon Cycling on Titan?
Grinspoon, David H.; Schulze-Makuch, Dirk
With the Cassini-Huygens Mission in orbit around Saturn, the large moon Titan, with its reducing atmosphere, rich organic chemistry, and heterogeneous surface, moves into the astrobiological spotlight. Environmental conditions on Titan and Earth were similar in many respects 4 billion years ago, the approximate time when life originated on Earth. …
INTEGRAL IGR J18135-1751 = HESS J1813-178: A New Cosmic High-Energy Accelerator from keV to TeV Energies
Walter, R.; Bird, A. J.; Ubertini, P. +10 more
We report the discovery of a soft gamma-ray source, namely, IGR J18135-1751, detected with IBIS, the Imager on Board the INTEGRAL Satellite. The source is persistent and has a 20-100 keV luminosity of ~5.7× 1034 ergs s-1 (assuming a distance of 4 kpc). This source is coincident with one of the eight unidentified objects recen…
Chandra and XMM-Newton observations of NGC 6251
Hardcastle, M. J.; Croston, J. H.; Birkinshaw, M. +2 more
We present new X-ray observations of the nucleus, jet and extended emission of the nearby radio galaxy NGC 6251 using the Chandra/ACIS-S camera, together with a reanalysis of archival Chandra/ACIS-I and XMM-Newton/EPIC data. We find that the nuclear X-ray spectrum is well fitted with an absorbed power law, and that there is tentative, but not high…