Search Publications
Spectral and Rotational Changes in the Isolated Neutron Star RX J0720.4-3125
Mori, Kaya; Pavlov, George G.; Kaplan, David L. +1 more
RX J0720.4-3125 is an isolated neutron star that, uniquely in its class, has shown changes in its thermal X-ray spectrum. We use new spectra taken with Chandra's Low Energy Transmission Grating Spectrometer, as well as archival observations, to try to understand the timescale and nature of these changes. We construct light curves, which show both …
A Photoionization Model for the Soft X-Ray Spectrum of NGC 4151
Turner, T. J.; Kraemer, S. B.; Armentrout, B. K.
We present an analysis of archival data from multiple XMM-Newton observations of the Seyfert 1 galaxy NGC 4151. Spectral data from the RGS instruments reveal several strong soft X-ray emission lines, chiefly from hydrogen-like and helium-like oxygen, nitrogen, neon, and carbon. Radiative recombination continua (RRC) from oxygen and carbon are also…
Stagnant lid convection in the mid-sized icy satellites of Saturn
Spohn, Tilman; Multhaup, Kai
Thermal history models for the mid-sized saturnian satellites Mimas, Tethys, Dione, Iapetus, and Rhea have been calculated assuming stagnant lid convection in undifferentiated satellites and varying parameter values over broad ranges. Of all five satellites under consideration, only Dione, Rhea and Iapetus do show significant internal activities r…
Geologic and spectral mapping of etched terrain deposits in northern Meridiani Planum
Arvidson, R. E.; Gendrin, A.; Poulet, F. +1 more
A ~1 km vertical section of etched terrain and hematite-bearing plains materials and nearby cratered terrain surfaces was mapped in the northern portion of Meridiani Planum using MOC, THEMIS, MOLA, and OMEGA data. The oldest materials are the cratered plains, which have 0.4 to 2.5 µm spectral reflectance dominated by a mix of low and high ca…
The galaxy luminosity-size relation and selection biases in the Hubble Ultra Deep Field
Cameron, E.; Driver, S. P.
We use the Hubble Ultra Deep Field to study the galaxy luminosity-size (M-Re) distribution. With a careful analysis of selection effects due to both detection completeness and measurement reliability, we identify bias-free regions in the M-Re plane for a series of volume-limited samples. By comparison to a nearby survey also …
Near infra-red spectroscopy of the asteroid 21 Lutetia. II. Rotationally resolved spectroscopy of the surface
Colas, F.; Vernazza, P.; Binzel, R. P. +5 more
Aims:In the framework of the ground-based science campaign dedicated to the encounter with the Rosetta spacecraft, the mineralogy of the asteroid (21) Lutetia was investigated.
Methods: Near-infrared (NIR) spectra of the asteroid in the 0.8-2.5 µm spectral range were obtained with SpeX/IRTF in remote observing mode from Meudon, France in…
Dynamical masses of two young globular clusters in the blue compact galaxy ESO 338-IG04
Östlin, G.; Bergvall, N.; Cumming, R. J.
We present high-resolution échelle spectroscopy, obtained with the UVES spectrograph on ESO/VLT, of two luminous star clusters in the metal-poor blue compact galaxy ESO 338-IG04 at a distance of 37.5 Mpc. Cross-correlating with template stars, we obtain line-of-sight velocity dispersions of 33 and 17 km s-1. By combining with size estim…
X-rays from protostellar jets: emission from continuous flows
Orlando, S.; Bonito, R.; Peres, G. +2 more
Context: Recently X-ray emission from protostellar jets has been detected with both XMM-Newton and Chandra satellites, but the physical mechanism which can give rise to this emission is still unclear.
Aims: We performed an extensive exploration of the parameter space for the main parameters influencing the jet/ambient medium interaction. Aims …
Dominant Nuclear Outflow Driving Mechanisms in Powerful Radio Galaxies
O'Dea, Christopher P.; Axon, David J.; Koekemoer, Anton +4 more
In order to identify the dominant nuclear outflow mechanisms in active galactic nuclei, we have undertaken deep, high-resolution observations of two compact radio sources (PKS 1549-79 and PKS 1345+12) with the Advanced Camera for Surveys (ACS) aboard the Hubble Space Telescope. Not only are these targets known to have powerful emission-line outflo…
A Deep Chandra, Very Large Array, and Spitzer Infrared Array Camera Study of the Very Low Luminosity Nucleus of the Elliptical NGC 821
Elvis, M.; Pellegrini, S.; Baldi, A. +5 more
The relatively nearby (distance = 24.1 Mpc) elliptical galaxy NGC 821 hosts an extreme example of a quiescent central massive black hole, for which deep Chandra observations revealed a nuclear source for the first time, with L2-10keV/LEdd~10-8. We present here a multiwavelength study of this nucleus, including Very…