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Reconstructing a Cepheid Light Curve with Fourier Techniques. I. The Fourier Expansion and Interrelations
Tanvir, Nial R.; Ngeow, Chow-Choong; Kanbur, Shashi M. +2 more
Fourier decomposition is a well-established technique used in the study of stellar pulsation. However, the quality of reconstructed light curves using this method is reduced when the observed data have uneven phase coverage. We use simulated annealing techniques together with Fourier decomposition to improve the quality of the Fourier decompositio…
XMM-Newton Observation of the 5.25 Millisecond Transient Pulsar XTE J1807-294 in Outburst
Campana, S.; Belloni, T.; Israel, G. L. +2 more
We report on the results obtained for the millisecond transient X-ray pulsar XTE J1807-294 in a 40 minute orbital period system, based on an XMM-Newton target-of-opportunity observation carried out during 2003 March. The source was found at a luminosity level of about 2×1036 ergs s-1 in the 0.5-10 keV range (assuming a distan…
The Optical Counterpart of the Isolated Neutron Star RX J1605.3+3249
Kulkarni, S. R.; van Kerkwijk, M. H.; Kaplan, D. L.
We have detected the optical counterpart to the nearby isolated neutron star RX J1605.3+3249 using observations from the Space Telescope Imaging Spectrometer aboard the Hubble Space Telescope. The counterpart, with m50CCD=26.84+/-0.07 mag and very blue colors, lies close to the ROSAT HRI error circle and within the Chandra error circle.…
The Spatial Distribution of Fluorescent H2 Emission near T Tauri
Raymond, John; Hartmann, Lee; Calvet, Nuria +1 more
New subarcsecond far-UV observations of T Tau with Hubble Space Telescope STIS show spatially resolved structures in the 2''×2'' area around the star. The structures are apparent in multiline emission of fluorescent H2 pumped by Lyα. One emission structure follows the cavity walls observed around T Tau N in scatter…
XMM-Newton Spectroscopy of the Accretion-driven Millisecond X-Ray Pulsar XTE J1751-305 in Outburst
Tiengo, A.; Wijnands, R.; Miller, J. M. +6 more
We present an analysis of the first high-resolution spectra measured from an accretion-driven millisecond X-ray pulsar in outburst. We observed XTE J1751-305 with XMM-Newton on 2002 April 7 for approximately 35 ks. Using a simple absorbed blackbody plus power-law model, we measure an unabsorbed flux of (6.6+/-0.1)×10-10 ergs cm-2
Nonthermal Chemistry in Diffuse Clouds with Low Molecular Abundances
Federman, S. R.; Zsargó, J.
High-quality archival spectra of interstellar absorption from C I toward nine stars, taken with the Goddard High Resolution Spectrograph on the Hubble Space Telescope, were analyzed. Our sample was supplemented by two sight lines, 23 Ori and β1 Sco, for which the C I measurements of Federman, Welty, & Cardelli were used. Directions …
Spatial Study with the Very Large Telescope of a New Resolved Edge-on Circumstellar Dust Disk Discovered at the Periphery of the ρ Ophiuchi Dark Cloud
Neuhäuser, R.; Grosso, N.; Alves, J. +3 more
We report the discovery in near-infrared (NIR) with SofI at the New Technology Telescope (NTT) of a resolved circumstellar dust disk around a 2MASS source at the periphery of the ρ Ophiuchi dark cloud. We present follow-up observations in J, H, and Ks bands, obtained with ISAAC at the Very Large Telescope (VLT) under 0.4" seeing conditi…
Radio Emission Associated with Ultraluminous X-Ray Sources in the Galaxy Merger NGC 3256
Neff, S. G.; Ulvestad, James S.; Campion, S. D.
We present new 6, 3.6, and 2 cm VLA radio observations of the nearby merger system NGC 3256, with resolutions of ~100 pc, which reveal compact radio sources embedded in more diffuse emission at all three wavelengths. The two radio nuclei are partially resolved, but the two dominant compact sources that remain coincide with the two most powerful co…
Hubble Space Telescope and Ground-based Optical and Ultraviolet Observations of GRB 010222
Price, P. A.; Harrison, F. A.; Galama, T. J. +12 more
We report on Hubble Space Telescope (HST) Wide Field Planetary Camera 2 optical and Space Telescope Imaging Spectrograph (STIS) near-ultraviolet MAMA observations and ground-based optical observations of GRB 010222, spanning 15 hr to 71 days. The observations are well described by a relativistic blast wave model with a hard electron energy distrib…
Contrasting the Ultraviolet and X-Ray O VI Column Density Inferred for the Outflow in NGC 5548
Kaastra, Jelle; Korista, Kirk T.; Arav, Nahum +4 more
We compare X-ray and UV spectroscopic observations of NGC 5548. Both data sets show O VI absorption troughs associated with the active galactic nuclei outflow from this galaxy. We find that the robust lower limit on the column density of the O VI X-ray trough is 7 times larger than the column density found in a study of the O VI UV troughs. This d…