Search Publications
The Spectral Evolution of Transient Anomalous X-Ray Pulsar XTE J1810-197
Gotthelf, E. V.; Halpern, J. P.
We present a multiepoch spectral study of the transient anomalous X-ray pulsar XTE J1810-197 obtained with the X-Ray Multi-Mirror Mission (XMM-Newton). Four observations taken over the course of a year reveal strong spectral evolution as the source fades from outburst. The origin of this is traced to the individual decay rates of the pulsar's spec…
The ACS Virgo Cluster Survey. IV. Data Reduction Procedures for Surface Brightness Fluctuation Measurements with the Advanced Camera for Surveys
Jordán, Andrés; Tonry, John L.; Côté, Patrick +7 more
The Advanced Camera for Surveys (ACS) Virgo Cluster Survey is a large program to image 100 early-type Virgo galaxies using the F475W and F850LP bandpasses of the Wide Field Channel of the ACS instrument on the Hubble Space Telescope (HST). The scientific goals of this survey include an exploration of the three-dimensional structure of the Virgo Cl…
The Core of NGC 6240 from Keck Adaptive Optics and Hubble Space Telescope NICMOS Observations
Antonucci, R.; Schneider, G.; Canalizo, G. +4 more
We present results of near-infrared imaging of the disk-galaxy merger NGC 6240 using adaptive optics on the Keck II telescope and reprocessed archival data from NICMOS on the Hubble Space Telescope. Both the northern and southern nuclei of NGC 6240 are clearly elongated, with considerable substructure within each nucleus. In K' band there are at l…
A Near-Solar Metallicity, Nitrogen-deficient Lyman Limit Absorber Associated with Two S0 Galaxies
Bowen, David V.; Tripp, Todd M.; Jenkins, Edward B. +1 more
The UV spectrum of the bright quasar PHL 1811 at zem=0.192 reveals a foreground gas system at z=0.080923 with logN(HI)=17.98+/-0.05. We have determined the abundances of various atomic species in this system from a spectrum covering the wavelength range 1160-1730 Å recorded at 7 km s-1 resolution by the E140M grating of the S…
Massive Young Clusters in the Disk of M31
Bellazzini, M.; Galleti, S.; Federici, L. +3 more
We have studied the properties of a sample of 67 very blue and likely young massive clusters in M31 extracted from the Bologna Revised Catalog of globular clusters, selected according to their color [(B-V)0<=0.45] and/or the strength of their Hβ spectral index (Hβ>=3.5 Å). Their existence in M31 has been noted by several authors i…
Can surface magnetic fields reproduce solar irradiance variations in cycles 22 and 23?
Solanki, S. K.; Krivova, N. A.; Wenzler, T.
Total solar irradiance is reconstructed using data from the spectromagnetograph on Kitt Peak for 1992 2003 (covering parts of cycles 22 and 23) and compared with observational data. The model assumes that solar irradiance variations are caused by surface magnetism and its single free parameter is kept at the same value for both cycles. A good corr…
INTEGRAL observation of V 0332+53 in outburst
Santangelo, A.; Walter, R.; Mowlavi, N. +9 more
We present the analysis of a 100 ks INTEGRAL (3-100 keV) observation of the transient X-ray pulsar V 0332+53in outburst. The source is pulsating at PPulse=4.3751±0.0002 s with a clear double pulse from 6 keVto 60 keV. The average flux was ~550 mCrab between 20 keVand 60 keV. We modeled the broad band continuum from 5 keVto 100 keVwith a…
Hubble Space Telescope STIS Observations of the Accreting White Dwarfs in BW Sculptoris, BC Ursae Majoris, and SW Ursae Majoris
Szkody, Paula; Howell, Steve B.; Sion, Edward M. +1 more
We have observed the short-period dwarf novae BW Scl, BC UMa, and SW UMa using the Hubble Space Telescope Space Telescope Imaging Spectrograph (STIS). In all three systems, the white dwarf is the dominant source of far-ultraviolet flux, even though in BC UMa and SW UMa an additional continuum component contributes ~10% and ~20% of the 1400 Å flux,…
High mass X-ray binaries in the LMC: Dependence on the stellar population age and the ``propeller'' effect
Gilfanov, M.; Shtykovskiy, P.
We study the population of compact X-ray sources in the Large Magellanic Cloud using the archival data of the XMM-Newton observatory. The total area of the survey is ≈ 3.8 square degrees with a limiting sensitivity of ≈10-14 erg/s/cm2, corresponding to a luminosity of ≈3× 1033 erg/s at the LMC distance. Out of ∼460…
Changes in the Subsurface Stratification of the Sun with the 11-Year Activity Cycle
Kosovichev, A. G.; Lefebvre, S.
We report on changes in the Sun's subsurface stratification inferred from helioseismology data. Using data from the Solar and Heliospheric Observatory (SOHO) Michelson Doppler Imager (MDI) for the last 9 years and, more precisely, the temporal variation of f-mode frequencies, we have computed the variation in the radius of subsurface layers of the…