Search Publications
Hubble Space Telescope Imaging of the Ultracompact Blue Dwarf Galaxy HS 0822+3542: An Assembling Galaxy in a Local Void?
Somerville, Rachel S.; Windhorst, Rogier A.; Vacca, William D. +2 more
We present deep U-band, narrow V-band, and I-band images and photometry of the ultracompact blue dwarf galaxy HS 0822+3542 obtained with the Advanced Camera for Surveys/High Resolution Channel of the Hubble Space Telescope. This object is also extremely metal-poor [12+log(O/H)=7.45] and resides in a nearby void. The images resolve it into two phys…
Chandra and HST Study of a New Transient X-Ray Source in M31
Williams, Benjamin F.; McClintock, Jeffrey E.; Murray, Stephen S. +2 more
We present X-ray and optical observations of a new transient X-ray source in M31 first detected 2004 May 23 at R.A.=00h43m09.940s+/-0.65", decl.=41deg23'32.49"+/-0.66". The X-ray light curve shows two peaks separated by several months, reminiscent of many Galactic X-ray novae. The location and X-ray spec…
The GRB 011211 X-Ray Lines: Toward Resolving the Significance Debate
Ricker, G.; Vanderspek, R.; Ford, P. +4 more
We demonstrate for the GRB 011211 X-ray afterglow lines that the significance estimation methods used by Reeves et al. and Rutledge & Sako are consistent and that the conflicting estimates found by those authors arise from different assumptions in the continuum modeling. If the column density is fixed at the Galactic value as in the Reeves et …
Galaxy Evolution Explorer Observations of the Ultraviolet Surface Brightness and Color Profiles of the Local Group Elliptical Galaxy M32 (NGC 221)
Heckman, Timothy M.; Madore, Barry F.; Rich, R. Michael +22 more
M32, the compact elliptical galaxy companion to the Andromeda spiral galaxy, has been imaged by the Galaxy Evolution Explorer (GALEX) in two UV bands, centered at ~1500 (far-ultraviolet [FUV]) and 2300 Å (near-ultraviolet). The imaging data have been carefully decomposed so as to properly account for the complicated background contamination from t…
Precision Limits to Emission-Line Profile Measuring Experiments
Ireland, J.
Spectra, such as astrophysical spectra, can provide detailed diagnostics on the state of their emitting volume. Emission-line diagnostics are found by assuming a model for the spectral emission line and then fitting the model to the data. It is shown for Poisson noisy emission-line data, via the application of Cramér-Rao lower bounds, that there a…
The Infrared-dominated Jet of 3C 401
Axon, David J.; Chiaberge, Marco; Capetti, Alessandro +6 more
We present a Hubble Space Telescope image of the FR II radio galaxy 3C 401, obtained at 1.6 µm with NICMOS, in which we identify the infrared counterpart of the brightest region of the radio jet. The jet has a complex radio structure and brightens where bending occurs, most likely as a result of relativistic beaming. We analyze archival data…
Possible Optical Detection of the Anomalous X-Ray Pulsar CXOU J010043.1-721134
Durant, Martin; van Kerkwijk, Marten H.
Archival Hubble Space Telescope Wide Field Planetary Camera 2 observations of the Small Magellanic Cloud have serendipitously revealed a possible counterpart to the anomalous X-ray pulsar CXOU J010043.1-721134. The candidate is faint, but its location and strange colors make it an interesting object. We estimate that the probability of such a dete…
Coronal Element Comparison Observed by SOHO SUMER in the Quiet Southeast and Northwest Limb Regions at 1.04 Rsolar above the Solar Disk
Landi, E.; Feldman, U.; Widing, K. G.
The composition in an isothermal region at 1.04 Rsolar above a diffuse, quiet coronal region on the northwest limb is studied and compared with a similar region above the southeast limb analyzed by Warren in 1999. Elemental abundances relative to H in the corona are measured and normalized to the abundance ratios in the photosphere. The…
Detectability of Gamma-Ray Burst Iron Lines by Swift, Chandra, and XMM-Newton
Kallman, T. R.; Mészáros, P.; Gou, L. J.
The rapid acquisition of positions by the upcoming Swift satellite will allow monitoring for X-ray lines in gamma-ray burst (GRB) afterglows at much earlier epochs than was previously feasible. We calculate the possible significance levels of iron-line detections as a function of source redshift and observing time after the trigger for the Swift X…
An X-Ray Transient and Optical Counterpart in the M31 Bulge
Williams, Benjamin F.; McClintock, Jeffrey E.; Kong, Albert K. H. +3 more
We have obtained snapshot images of a transient X-ray source in M31 from Chandra ACIS-I and the Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS). The Chandra position of the X-ray nova was R.A.=00h42m56.038s+/-0.08", decl.=+41deg12'18.50"+/-0.07". The transient was active for at least 6 mon…