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Quantitative Studies of the Far-Ultraviolet, Ultraviolet, and Optical Spectra of Late O- and Early B-Type Supergiants in the Magellanic Clouds
Hillier, D. J.; Crowther, P. A.; Evans, C. J. +1 more
We present quantitative studies of eight late O- and early B-type supergiants in the Magellanic Clouds using far-ultraviolet Far Ultraviolet Spectroscopic Explorer, ultraviolet International Ultraviolet Explorer/Hubble Space Telescope, and optical VLT-UVES spectroscopy. Temperatures, mass-loss rates, and CNO abundances are obtained using the non-L…
The Physical Properties and Effective Temperature Scale of O-Type Stars as a Function of Metallicity. I. A Sample of 20 Stars in the Magellanic Clouds
Massey, Philip; Pauldrach, A. W. A.; Bresolin, Fabio +2 more
We have obtained Hubble Space Telescope (HST) and ground-based observations of a sample of 20 O-type stars in the LMC and SMC, including six of the hottest massive stars known (subtypes O2-O3) in the R136 cluster. In general, these data include (1) the HST UV spectra in order to measure the terminal velocities of the stellar winds, (2) high signal…
The Globular Cluster Systems of Five Nearby Spiral Galaxies: New Insights from Hubble Space Telescope Imaging
Chandar, Rupali; Lee, Myung Gyoon; Whitmore, Bradley
We use available multifilter Hubble Space Telescope (HST) WFPC2 imaging of five (M81, M83, NGC 6946, M101, and M51, in order of distance) low-inclination, nearby spiral galaxies to study ancient star cluster populations. Combining rigorous selection criteria to reject contaminants (individual stars, background galaxies, and blends) with optical ph…
Going Slitless: Images of Forbidden-Line Emission Regions of Classical T Tauri Stars Observed with the Hubble Space Telescope
Edwards, Suzan; Hartigan, Patrick; Pierson, Rachel
We have observed five classical T Tauri stars known to have strong forbidden-line emission with STIS in slitless mode on the Hubble Space Telescope. This technique makes it possible to image jets within a few tens of AU of their exciting sources, a region of great interest for models of accretion disks and jets. Slitless images generate emission-l…
Deuterated Interstellar Polycyclic Aromatic Hydrocarbons
Tielens, A. G. G. M.; Allamandola, L. J.; Peeters, E. +3 more
We report infrared spectral evidence of deuterated interstellar polycyclic aromatic hydrocarbons (PAHs). Two bands are detected in the infrared emission from the ionization bar in Orion at 4.4 and 4.65 µm. The one at 4.65 µm is present at the 4.4 σ level, while the one at 4.4 µm is more tentative, with a σ equal to 1.9. An emissi…
A Very Low Luminosity X-Ray Flash: XMM-Newton Observations of GRB 031203
Watson, D.; O'Brien, P. T.; Reeves, J. N. +9 more
GRB 031203 was observed by XMM-Newton twice, first with an observation beginning 6 hr after the burst and again after 3 days. The afterglow had average 0.2-10.0 keV fluxes for the first and second observations of (4.2+/-0.1)×10-13 and (1.8+/-0.1)×10-13 ergs cm-2 s-1, respectively, decaying very slowly ac…
Chandra Observations of the X-Ray Environs of SN 1998bw/GRB 980425
Pian, E.; Kouveliotou, C.; Wijers, R. A. M. J. +8 more
We report X-ray studies of the environs of SN 1998bw and GRB 980425 using the Chandra X-Ray Observatory 1281 days after the gamma-ray burst (GRB). Eight X-ray point sources were localized, three and five each in the original error boxes, S1 and S2, assigned for variable X-ray counterparts to the GRB by BeppoSAX. The sum of the discrete X-ray sourc…
On the Constancy of the Solar Diameter. II.
Scherrer, P. H.; Kuhn, J. R.; Bush, R. I. +1 more
The Michelson Doppler Imager instrument on board SOHO has operated for most of a solar cycle. Here we present a careful analysis of solar astrometric data obtained with it from above the Earth's turbulent atmosphere. These data yield the most accurate direct constraint on possible solar radius variations on timescales from minutes to years and the…
A Steady, Radiative-Shock Method for Computing X-Ray Emission from Colliding Stellar Winds in Close, Massive-Star Binaries
Owocki, S. P.; Antokhin, I. I.; Brown, J. C.
We present a practical, efficient, semianalytic formalism for computing steady state X-ray emission from radiative shocks between colliding stellar winds in relatively close (orbital period up to order tens of days) massive-star, binary systems. Our simplified approach idealizes the individual wind flows as smooth and steady, ignoring the intrinsi…
X-Ray Sources and Their Optical Counterparts in the Globular Cluster M4
Anderson, Scott F.; Kaspi, Victoria M.; Verbunt, Frank +7 more
We report on the Chandra X-Ray Observatory ACIS-S3 imaging observation of the Galactic globular cluster M4 (NGC 6121). We detect 12 X-ray sources inside the core and 19 more within the cluster half-mass radius. The limiting luminosity of this observation is LX~1029 ergs s-1 for sources associated with the cluster, …