Search Publications
The Redshift Distribution of Near-Infrared-Selected Galaxies in the Great Observatories Origins Deep Survey as a Test of Galaxy Formation Scenarios
Papovich, Casey; Dickinson, Mark; Somerville, Rachel S. +11 more
The redshift distribution of near-IR-selected galaxies is often used to attempt to discriminate between the classical view of galaxy formation, in which present-day luminous galaxies were assembled at early times and evolve through the passive aging of their stellar populations, and that of hierarchical structure formation, in which galaxies were …
A Strong, Broad Absorption Feature in the X-Ray Spectrum of the Nearby Neutron Star RX J1605.3+3249
Kulkarni, S. R.; van Kerkwijk, M. H.; Kaplan, D. L. +2 more
We present X-ray spectra taken with XMM-Newton of RX J1605.3+3249, the third brightest in the class of nearby thermally emitting neutron stars. In contrast to what is the case for the brightest object, RX J1856.5-3754, we find that the spectrum of RX J1605.3+3249 cannot be described well by a pure blackbody, but shows a broad absorption feature at…
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…