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Dramatic X-Ray Spectral Variability of the Broad Absorption Line Quasar PG 2112+059
Brandt, W. N.; Chartas, G.; Gallagher, S. C. +3 more
With a 1999 ASCA observation, PG 2112+059 became notable as the first broad absorption line (BAL) quasar found to exhibit a typical radio-quiet quasar X-ray continuum underlying a large amount of intrinsic absorption. We present a recent Chandra ACIS-S3 observation of PG 2112+059 that demonstrates remarkable spectral and luminosity variability sin…
The First Detailed X-Ray Observations of High-Redshift, Optically Selected Clusters: XMM-Newton Results for Cl 1324+3011 at z = 0.76 and Cl 1604+4304 at z = 0.90
Mulchaey, John S.; Postman, Marc; Lubin, Lori M.
We present the first detailed X-ray observations of optically selected clusters at high redshift. Two clusters, Cl 1324+3011 at z=0.76 and Cl 1604+4304 at z=0.90, were observed with XMM-Newton. The opticenter of each cluster is coincident with an extended X-ray source whose emission is detected out to a radius of ~0.5 h-170 M…
Hubble Space Telescope STIS Far-Ultraviolet Observations of the Central Nebulae in the Cooling-Core Clusters A1795 and A2597
Koekemoer, Anton M.; Baum, Stefi A.; Mack, Jennifer +2 more
We present Hubble Space Telescope STIS FUV images of the Lyα and FUV continuum emission of the luminous emission-line nebulae in two cooling-core clusters, A1795 and A2597. The Lyα and FUV continuum emission consist of a diffuse component (~60%) and more compact features (knots and filaments), which lie preferentially along the radio source edges.…
The Progenitor of the Type II-P SN 2004dj in NGC 2403
Bond, Howard E.; Maoz, D.; Ofek, E. O. +4 more
The Type II-P supernova SN 2004dj in the nearby galaxy NGC 2403 occurred at a position coincident with object 96 in the list of luminous stars and clusters in this galaxy published by Sandage in 1984. The coincidence is established definitively through astrometric registration of our ground-based archival images of NGC 2403 with our recent images …
Bias in the estimation of global luminosity functions
Maccagni, D.; Ilbert, O.; Adami, C. +13 more
We discuss a bias present in the calculation of the global luminosity function (LF) which occurs when analysing faint galaxy samples. This effect exists as a result of the different spectral energy distributions of galaxies, which are in turn quantified by the k corrections. We demonstrate that this bias occurs because not all galaxy types are vis…
The young pulsar PSR B0540-69.3 and its synchrotron nebula in the optical and X-rays
Sollerman, J.; Lundqvist, P.; Shibanov, Yu. A. +1 more
The young PSR B0540-69.3 in the LMC is the only pulsar (except the Crab pulsar) for which a near-UV spectrum has been obtained. However, the absolute flux and spectral index of the HST/FOS spectrum are significantly higher than suggested by previous broad-band time-resolved groundbased UBVRI photometry. To investigate this difference, observations…
Life cycles of spots on Jupiter from Cassini images
Porco, Carolyn C.; Ingersoll, Andrew P.; Ewald, Shawn P. +3 more
Using the sequence of 70-day continuum-band (751 nm) images from the Cassini Imaging Science System (ISS), we record over 500 compact oval spots and study their relation to the large-scale motions. The ∼100 spots whose vorticity could be measured—the large spots in most cases—were all anticyclonic. We exclude cyclonic features (chaotic regions) be…
A Possible Explanation for the Size Difference of Red and Blue Globular Clusters
Jordán, Andrés
Most observations of the projected half-light radii of metal-rich globular clusters in a variety of galaxies have shown them to be ~20% smaller than those of their metal-poor counterparts. We show using multimass isotropic Michie-King models that the combined effects of mass segregation and the dependence of main-sequence lifetimes on metallicity …
Hubble Space Telescope Observations of NGC 6240: A Case Study of an Ultraluminous Infrared Galaxy with Obscured Activity
Gerssen, Joris; van der Marel, Roeland P.; Hernquist, Lars +3 more
We present results from a Hubble Space Telescope (HST) study of the morphology and kinematics of NGC 6240. This merging galaxy with a double nucleus is one of the nearest and best-studied ultraluminous infrared galaxies. HST resolves both nuclei into separate components. The distance between the northern and southern optical/near-infrared componen…
Multiband modelling of the Sun as a variable star from VIRGO/SoHO data
Pagano, I.; Lanza, A. F.; Rodonò, M.
The time series of total solar irradiance (TSI) and optical spectral irradiance at 402, 500 and 862 nm (SSIs) obtained by the VIRGO experiment on board the satellite SoHO are analysed in order to model their variability in the framework of a purely stellar-like approach. The different time scales of variability are estimated by means of the pooled…