Search Publications
Formation and Evolution of Planetary Systems: Upper Limits to the Gas Mass in Disks around Sun-like Stars
Wolf, S.; Pascucci, I.; Carpenter, J. M. +17 more
We have carried out a sensitive search for gas emission lines at IR and millimeter wavelengths for a sample of 15 young Sun-like stars selected from our dust disk survey with Spitzer. We have used mid-IR lines to trace the warm (300-100 K) gas in the inner disk and millimeter transitions of 12CO to probe the cold (~20 K) outer disk. We …
Magnetars as persistent hard X-ray sources: INTEGRAL discovery of a hard tail in SGR 1900+14
Tiengo, A.; Götz, D.; Mereghetti, S. +1 more
Using 2.5 Ms of data obtained by the INTEGRAL satellite in 2003-2004, we discovered persistent hard X-ray emission from the soft gamma-ray repeater SGR 1900+14. Its 20-100 keV spectrum is well described by a steep power law with photon index Γ=3.1±0.5 and flux 1.5×10-11 erg cm-2 s-1. Contrary to SGR 1806-20, the on…
A ``Combination Nova'' Outburst in Z Andromedae: Nuclear Shell Burning Triggered by a Disk Instability
Sokoloski, J. L.; Filippenko, A. V.; Charles, P. A. +11 more
We describe observational evidence for a new kind of interacting binary star outburst that involves both an accretion instability and an increase in thermonuclear shell burning on the surface of an accreting white dwarf. We refer to this new type of eruption as a combination nova. In late 2000, the prototypical symbiotic star Z Andromedae brighten…
Nonthermal Spectral Line Broadening and the Nanoflare Model
Klimchuk, J. A.; Patsourakos, S.
A number of theoretical and observational considerations suggest that coronal loops are bundles of unresolved, impulsively heated strands. This ``nanoflare'' model, as it is sometimes called, predicts high-speed evaporative upflows, which might be revealed as nonthermal broadening of spectral line profiles. We have therefore generated synthetic li…
Parametric strong gravitational lensing analysis of Abell 1689
Pannella, M.; Seitz, S.; Halkola, A.
We have derived the mass distribution of galaxy cluster Abell 1689 within 0.3h-170Mpc of the cluster centre using its strong lensing (SL) effect on 32 background galaxies, which are mapped in altogether 107 multiple images. The multiple images are based on some from the literature with modifications to both include new and ex…
Investigating the nature of narrow-line Seyfert 1 galaxies with high-energy spectral complexity
Gallo, L. C.
With the commissioning of XMM-Newton came the discovery of 2.5-10keV spectral complexity in some narrow-line Seyfert 1 galaxies (NLS1). This high-energy complexity can be manifested as sharp, spectral drops or gradual curvature in the spectrum. Models which are normally considered are ionized reflection and partial covering. In this work, we defin…
Elemental abundances in the atmosphere of clump giants
Soubiran, C.; Korotin, S. A.; Bienaymé, O. +4 more
Aims.The aim of this paper is to provide the fundamental parameters and abundances for a large sample of local clump giants with a high accuracy. This study is a part of a big project, in which the vertical distribution of the stars in the Galactic disc and the chemical and dynamical evolution of the Galaxy are being investigated.
Methods: .Th…
A Search for Binary Systems among the Nearest L Dwarfs
Burgasser, Adam J.; Reid, I. Neill; Cruz, Kelle L. +2 more
We have used the Near-Infrared Camera and Multi-Object Spectrometer NIC1 camera on the Hubble Space Telescope to obtain high angular resolution images of 52 ultracool dwarfs in the immediate solar neighborhood. Nine systems are resolved as binary, with component separations from 1.5 to 15 AU. Based on current theoretical models and empirical bolom…
Gamma-Ray Imaging of the 2003 October/November Solar Flares
Krucker, S.; Lin, R. P.; Smith, D. M. +3 more
We present RHESSI imaging of three flares (2003 October 28 and 29 and November 2) in the 2.223 MeV neutron-capture gamma-ray line with angular resolution as high as 35". Comparisons of imaged and spatially integrated fluences show that in all cases most, if not all, of the emission was confined to compact sources with size scales of tens of arcsec…
A Chandra Survey of Early-Type Galaxies. I. Metal Enrichment in the Interstellar Medium
Humphrey, Philip J.; Buote, David A.
We present a Chandra study of the emission-weighted metal abundances in 28 early-type galaxies, spanning ~3 orders of magnitude in X-ray luminosity (LX). We report constraints for Fe, O, Ne, Mg, Si, S, and Ni. We find no evidence of the very subsolar Fe abundance (ZFe) historically reported, confirming a trend in recent obser…