Search Publications
Rotational Broadening of Atomic Spectral Features from Neutron Stars
Chang, Philip; Bildsten, Lars; Morsink, Sharon +1 more
The discovery of the first gravitationally redshifted spectral line from a neutron star (NS) by Cottam et al. has triggered theoretical studies of the physics of atomic line formation in NS atmospheres. Chang et al. showed that the hydrogenic Fe Hα line formed above the photosphere of a bursting NS is intrinsically broad. We now include rotational…
The O VI Absorbers toward PG 0953+415: High-Metallicity, Cosmic-Web Gas Far from Luminous Galaxies
Bowen, David V.; Tripp, Todd M.; Jenkins, Edward B. +1 more
The spectrum of the low-redshift QSO PG 0953+415 (zQSO=0.234) shows two strong, intervening O VI absorption systems. To study the nature of these absorbers, we have used the Gemini Multi-Object Spectrograph to conduct a deep spectroscopic galaxy redshift survey in the 5'×5' field centered on the QSO. This survey is fully complete for r'…
The Light Echo around Supernova 2003gd in Messier 74
Van Dyk, Schuyler D.; Filippenko, Alexei V.; Li, Weidong
We confirm the discovery of a light echo around the Type II-plateau supernova 2003gd in Messier 74 (NGC 628), seen in images obtained with the High Resolution Channel of the Advanced Camera for Surveys on board the Hubble Space Telescope (HST) as part of a larger Snapshot program on the late-time emission from supernovae. The analysis of the echo …
Anti-planetward auroral electron beams at Saturn
Livi, S.; Krupp, N.; Dougherty, M. K. +10 more
Strong discrete aurorae on Earth are excited by electrons, which are accelerated along magnetic field lines towards the planet. Surprisingly, electrons accelerated in the opposite direction have been recently observed. The mechanisms and significance of this anti-earthward acceleration are highly uncertain because only earthward acceleration was t…
Lyman Break Galaxies under a Microscope: The Small-Scale Dynamics and Mass of an Arc in the Cluster 1E 0657-56
Lutz, D.; Genzel, R.; Saglia, R. P. +8 more
Using the near-infrared integral field spectrograph SPIFFI on the VLT, we have studied the spatially resolved dynamics in the z=3.2 strongly lensed galaxy 1E 0657-56 arc+core by observing the rest-frame optical emission lines [O III] λ5007 and Hβ. The lensing configuration suggests that the high surface brightness core is the M~20 magnified centra…
Measurements of the f-Values of the Resonance Transitions of Ni II at 1317.217 and 1370.132 Å
Tripp, Todd M.; Jenkins, Edward B.
We have retrieved high-resolution UV spectra of 69 hot stars from the HST archive and determined the strengths of the interstellar Ni II absorption features at 1317.217 Å arising from the ground 3d92D5/2 electronic state to the 3d8(1G)4p2Fo5/2 excited level. We…
Cluster PEACE observations of electron pressure tensor divergence in the magnetotail
Lucek, E.; Fazakerley, A. N.; Owen, C. J. +4 more
Cluster crossed the magnetotail neutral sheet on four occasions between 16:38 and 16:43 UT on 08/17/2003. The four-spacecraft capabilities of Cluster are used to determine spatial gradients from the magnetic field vectors and, for the first time, full electron pressure tensors. We find that the contribution to the electric field from the Hall term…
Black hole masses from reverberation mapping
Peterson, Bradley M.; Bentz, Misty C.
We review briefly how black hole masses are measured directly using reverberation mapping and indirectly through scaling relationships based on reverberation results, in particular through broad-line region radius-luminosity relationships. We discuss the nature and origin of uncertainties in these measurements, and outline current and future effor…
Chandra monitoring observations of the ultraluminous X-ray source NGC 5204 X-1
Warwick, R. S.; Roberts, T. P.; Ward, M. J. +2 more
We report the results of a two-month campaign conducted with the Chandra X-ray observatory to monitor the ultraluminous X-ray source (ULX) NGC 5204 X-1. This was composed of a 50-ks observation, followed by ten 5-ks follow-ups spaced initially at ~3, then at ~10-d intervals. The ULX flux is seen to vary by factors ~5 on time-scales of a few days, …
X-Ray Properties of Intermediate-Redshift Groups of Galaxies
Mulchaey, John S.; Rosati, Piero; Lubin, Lori M. +2 more
We have undertaken a multiwavelength project to study the relatively unknown properties of groups and poor clusters of galaxies at intermediate redshifts. In this paper, we describe the XMM-Newton observations of six X-ray-selected groups with 0.2<z<0.6. The X-ray properties of these systems are generally in good agreement with the propertie…