Search Publications
Optical Identification of Faint X-Ray Sources in the Core of ω Centauri
Cool, Adrienne M.; Grindlay, Jonathan E.; Carson, Jennifer E.
We present the results of a search for optical counterparts of three faint X-ray sources in the core of NGC 5139 (ω Cen) with the HST Wide Field Planetary Camera 2. Using images taken through the F656N (Hα), F675W, and F336W filters, we have identified two stars with strong Hα and UV excesses, one in each of two of the X-ray error circles, and a p…
An Empirical Test of the Mg II λ1240 Doublet Branching Ratio and Oscillator Strength
Sofia, Ulysses J.; Howk, J. Christopher; Fabian, Dirk
We empirically confirm the theoretical branching ratio and oscillator strength for the weak Mg II 3s-4p doublet at 1240 Å as determined by Theodosiou & Federman. We use the independent methods of apparent optical depth analysis for the sight lines toward µ Col, γ Ara, and ρ Leo and profile component fitting for the sight line toward &mic…
Age, Evolution, and Dispersion of the Loose Groups of Blue Stars in the Northeast Radio Lobe of Centaurus A
Fassett, Caleb I.; Graham, John A.
The association of shocked gas and loose groups of young stars in the northeast radio lobe of Centaurus A (NGC 5128) provides direct evidence for shock-induced star formation. In this paper, we present UBV photometry of the blue stars based on observations made with the 2.5 m du Pont Telescope at Las Campanas Observatory. In a field covering 8.8‧×…
Coronal X-Ray Brightness and Photospheric Magnetic Field: A Study in Correlations
Weber, Mark A.; Sturrock, P. A.; Wolfson, Richard +1 more
We have examined correlations between coronal X-ray emission from the Yohkoh Soft X-Ray Telescope (SXT) and photospheric magnetic field measurements from the Michelson Doppler Imager (MDI) on SOHO. Our data sets span a 521 day period beginning 1996 July 25, and we have averaged the data temporally into one bin per day and spatially into nine latit…
Merging Process and Tidal-induced Star Formation in the Ultraluminous Infrared Galaxy IRAS 08572+3915
Arribas, Santiago; Colina, Luis; Borne, Kirk D.
Integral field optical spectroscopy using the INTEGRAL system, complemented with HST imaging, has been used to characterize the merging process giving rise to the ultraluminous infrared galaxy IRAS 08572+3915, the star formation along the tidal tails of the galaxy, and the nature of the nuclear ionizing sources deep within the galaxy. The overall …
Detection and Mapping of Decoupled Stellar and Ionized Gas Structures in the Ultraluminous Infrared Galaxy IRAS 12112+0305
Arribas, Santiago; Colina, Luis; Borne, Kirk D. +1 more
Integral field optical spectroscopy with the INTEGRAL fiber-fed system and Hubble Space Telescope optical imaging are used to map the complex stellar and warm ionized gas structure in the ultraluminous infrared galaxy IRAS 12112+0305. Images reconstructed from wavelength-delimited extractions of the integral field spectra reveal that the observed …
X1908+075: An X-Ray Binary with a 4.4 Day Period
Remillard, Ronald A.; Wen, Linqing; Bradt, Hale V.
X1908+075 is an optically unidentified and highly absorbed X-ray source that appeared in early surveys such as Uhuru, OSO 7, Ariel 5, HEAO-1, and the EXOSAT Galactic Plane Survey. These surveys measured a source intensity in the range 2-12 mcrab at 2-10 keV, and the position was localized to ~0.5d. We use the Rossi X-Ray Timing Explorer (RXTE) All…
The Hubble Space Telescope Revisits the Proper Motion of Pulsar B0656+14
Caraveo, P. A.; De Luca, A.; Mignani, R. P.
We report the first successful measurement (with the Hubble Space Telescope Wide Field Planetary Camera 2) of a significant proper motion for an mV~25 object, which we had proposed as the optical counterpart of the radio pulsar PSR B0656+14. The yearly displacement of 43+/-2 mas is highly significant and, while in agreement with early r…
Phase Time and Envelope Time in Time-Distance Analysis and Acoustic Imaging
Duvall, Thomas L., Jr.; Chou, Dean-Yi
Time-distance analysis and acoustic imaging are two related techniques for probing the local properties of the solar interior. In this study, we discuss the relation of phase time and envelope time between the two techniques. The location of the envelope peak of the cross-correlation function in time-distance analysis is identified as the travel t…
Langmuir Waves in the Vicinity of interplanetary Shocks and the Consequences for Type II Burst Models
MacDowall, R. J.; Thejappa, G.
The in situ wave data obtained by the Ulysses Unified Radio And Plasma wave experiment in the vicinity of a large number of interplanetary shocks show that Langmuir waves (1) are observed in only ~15% of the interplanetary shocks, (2) occur mostly in the upstream regions, and (3) are produced in the vicinity of both quasi-parallel Q∥ an…