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The Acoustic Showerglass. I. Seismic Diagnostics of Photospheric Magnetic Fields
Braun, D. C.; Lindsey, Charles
A problem of major interest in the helioseismology of active regions is the acoustics of magnetic photospheres and shallow subphotospheres. Magnetic fields suppress the photospheric signatures of acoustic waves impinging onto them from the underlying solar interior and shift their phases. The phase shifts function as a sort of acoustic showerglass…
Post-glitch variability in the anomalous X-ray pulsar 1RXSJ170849.0-400910
Haberl, F.; Stella, L.; Rea, N. +5 more
Here we report on the first XMM-Newton observation of the anomalous X-ray pulsar 1RXSJ170849.0-400910. The source was observed in 2003 August, and was found at a flux level factor of about 2 lower than previous observations. Moreover, a significant spectral evolution appears to be present, the source exhibiting a much softer spectrum than in the p…
On the possibility of measuring the solar oblateness and some relativistic effects from planetary ranging
Iorio, L.
In this paper we first calculate the post-Newtonian gravitoelectric secular rate of the mean anomaly of a test particle freely orbiting a spherically symmetric central mass. Then, we propose a novel approach to suitably combine the presently available planetary ranging data to Mercury, Venus and Mars in order to determine, simultaneously and indep…
On the Origin of Exponential Disks at High Redshift
Elmegreen, Bruce G.; Elmegreen, Debra Meloy; Vollbach, David R. +2 more
The major-axis and ellipse-fit intensity profiles of spiral galaxies larger than 0.3" in the Hubble Space Telescope Ultra Deep Field (UDF) are generally exponential, whereas the major-axis profiles in irregular disk galaxies, called clump clusters in our previous studies, are clearly not. Here we show that the deprojected positions of star-forming…
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…