Search Publications
Delayed Soft X-Ray Emission Lines in the Afterglow of GRB 030227
Watson, D.; Reeves, J. N.; Pedersen, K. +2 more
Strong delayed X-ray line emission is detected in the afterglow of gamma-ray burst GRB 030227, appearing near the end of the XMM-Newton observation, nearly 20 hr after the burst. The observed flux in the lines, not simply the equivalent width, sharply increases from an undetectable level (<1.7×10-14 ergs cm-2 s-1
The Solar Wind and Its Magnetic Sources at Sunspot Maximum
Sheeley, N. R., Jr.; Wang, Y. -M.
We use in situ measurements from the Advanced Composition Explorer and magnetograph data from the National Solar Observatory to relate the properties of the solar wind during 1998-2002 to its source region magnetic fields. The great bulk of the solar maximum wind is characterized by low proton speeds (vp~420 km s-1) and high …
A Comprehensive Study of the L1551 IRS 5 Binary System
Hartmann, Lee; Calvet, Nuria; Muzerolle, James +2 more
We model the Class I source L1551 IRS 5, adopting a flattened infalling envelope surrounding a binary disk system and a circumbinary disk. With our composite model, we calculate self-consistently the spectral energy distribution of each component of the L1551 IRS 5 system, using additional constraints from recent observations by ISO, the water ice…
GRB 011121: A Collimated Outflow into Wind-blown Surroundings
Mitrofanov, I.; Pian, E.; Palazzi, E. +31 more
We report optical and near-infrared follow-up observations of GRB 011121 collected predominantly at ESO telescopes in Chile. We discover a break in the afterglow light curve after 1.3 days, which implies an initial jet opening angle of about 9°. The jet origin of this break is supported by the fact that the spectral energy distribution is achromat…
The X-Ray-faint Emission of the Supermassive Nuclear Black Hole of IC 1459
Zezas, A.; Elvis, M.; Pellegrini, S. +6 more
Chandra observations of the supermassive black hole in the nucleus of IC 1459 show a weak (LX=8×1040 ergs s-1, 0.3-8 keV), unabsorbed nuclear X-ray source, with a slope Γ=1.88+/-0.09, and no strong Fe K line at 6.4 keV (EW<382 eV). This describes a normal active galactic nucleus (AGN) X-ray spectrum but lies at …
The Multiphase Intergalactic Medium toward PKS 2155-304
Shull, J. Michael; Tumlinson, Jason; Giroux, Mark L.
We study the cluster of H I and O VI absorption systems and the claimed detection of O VIII absorption from the intergalactic medium at z~0.0567, associated with a group of galaxies toward the BL Lac object PKS 2155-304. As measured by spectrographs on the Hubble Space Telescope, Far Ultraviolet Spectroscopic Explorer, and Chandra, this system app…
The Kinematics and Physical Conditions of the Ionized Gas in Markarian 509. I. Chandra High Energy Grating Spectroscopy
Yaqoob, Tahir; Crenshaw, D. Michael; George, Ian M. +4 more
We observed the Seyfert 1 galaxy Mrk 509 for ~59 ks with the Chandra high-energy transmission gratings, simultaneously with HST/STIS and RXTE. Here we present a detailed analysis of the soft X-ray spectrum observed with Chandra. We measure strong absorption lines from He-like Ne and Mg and from H-like N, O, and Ne. Weaker absorption lines may also…
Hubble Space Telescope WFPC2 Morphologies of K-selected Extremely Red Galaxies
Yan, Lin; Thompson, David
We selected 115 extremely red objects (EROs) from deep Hubble Space Telescope (HST) WFPC2 archive data combined with ground-based K-band images, with (F814W-Ks) >= 4, K-band signal-to-noise ratio >=5, and a median limiting Ks magnitude of ~18.7, over a corresponding area of 228 arcmin2, for a morphological st…
Chemical Abundances in Broad Emission Line Regions: The ``Nitrogen-loud'' Quasi-Stellar Object Q0353-383
Dietrich, M.; Korista, K. T.; Ferland, G. J. +3 more
The intensity of the strong N V λ1240 line relative to C IV λ1549 or to He II λ1640 has been proposed as an indicator of the metallicity of quasi-stellar object (QSO) broad emission line regions, allowing abundance measurements in a large number of QSOs out to the highest redshifts. Previously, it had been shown that the (normally) much weaker lin…
Physical Parameters of the 2000 February 11 Coronal Mass Ejection: Ultraviolet Spectra versus White-Light Images
Raymond, J. C.; Chen, J.; Ciaravella, A. +5 more
We present spectra of a three-part coronal mass ejection (CME) observed by the Ultraviolet Coronagraph Spectrometer aboard SOHO on 2000 February 11. Images of the CME in different spectral lines show how the morphology depends on the temperature, density, and outflow speed of the ejected plasma. The H I Lyα is the line that best resembles the whit…