Search Publications
Pulsation Phase-Dependent Dust Shell Models for Oxygen-rich Asymptotic Giant Branch Stars
Suh, Kyung-Won
We investigate the spectral energy distributions (SEDs) of oxygen-rich asymptotic giant branch (AGB) stars at different pulsation phases using infrared observational data, including data from the Infrared Space Observatory. Comparing the results of detailed radiative transfer model calculations with observations, we explore the changes of the rele…
Polycyclic Aromatic Hydrocarbons and Crystalline Silicates in the Bipolar Post-Asymptotic Giant Branch Star IRAS 16279-4757
Waters, L. B. F. M.; Hony, S.; Zijlstra, A. A. +7 more
IRAS 16279-4757 belongs to a group of post-asymptotic giant branch (post-AGB) stars showing both polycyclic aromatic hydrocarbon (PAH) bands and crystalline silicates. We present mid-infrared images that resolve the object for the first time. The morphology is similar to that of the ``Red Rectangle'' (HD 44179), the prototype object with PAHs and …
Are Giant Planets Forming around HR 4796A?
Kamp, I.; Chen, C. H.
We have obtained Far Ultraviolet Spectroscopic Explorer and Hubble Space Telescope STIS spectra of HR 4796A, a nearby 8 Myr old main-sequence star that possesses a dusty circumstellar disk whose inclination has been constrained from high-resolution near-infrared observations to be ~17° from edge-on. We searched for circumstellar absorption in the …
WZ Sagittae: Hubble Space Telescope Spectroscopy of the Cooling of the White Dwarf after the 2001 Outburst
Szkody, Paula; Sion, Edward M.; Gänsicke, Boris T. +1 more
Following an outburst in 2001 July, the UV flux of WZ Sge has declined slowly toward preoutburst levels. Here we describe new 1150-1710 Å Hubble Space Telescope STIS spectra of WZ Sge obtained between 2002 April and 2003 March to follow the decline. A combined analysis of these and spectra obtained in the fall of 2001 show that if logg=8.5, then t…
An Unusual Discontinuity in the X-Ray Surface Brightness Profile of NGC 507: Evidence of an Abundance Gradient?
Churazov, E.; Vikhlinin, A.; Markevitch, M. +5 more
We present results from a 45 ks Chandra ACIS-I observation of the nearby (z=0.01646) NGC 507 group. The X-ray surface brightness profile of the outer region of the group is well described by an isothermal β-profile consistent with earlier ROSAT observations. We find a sharp edge or discontinuity in the radial surface brightness profile 55 kpc east…
XMM-Newton Observations of NGC 507: Supersolar Metal Abundances in the Hot Interstellar Medium
Fabbiano, Giuseppina; Kim, Dong-Woo
We present the results of the X-ray XMM-Newton observations of NGC 507, a dominant elliptical galaxy in a small group of galaxies, and report supersolar metal abundances of both Fe and α-elements in the hot interstellar medium (ISM) of this galaxy. These results are robust in that we considered all possible systematic effects in our analysis. We f…
The Fundamental Plane Evolution of Active Galactic Nucleus Host Galaxies
van der Marel, Roeland P.; Urry, C. Megan; Lira, Paulina +2 more
We measured the stellar velocity dispersions of 15 active galactic nucleus (AGN) host galaxies at redshifts as high as ~0.34. Combining these with published velocity dispersion measurements from the literature, we study the fundamental plane of AGN host galaxies and its evolution. BL Lac object hosts and radio galaxies seem to lie on the same fund…
Tracing the ``Acoustic'' Solar Cycle: A Direct Comparison of BiSON and GOLF Low-l p-Mode Variations
Jiménez-Reyes, S. J.; García, R. A.; Chaplin, W. J. +1 more
We present a detailed, comparative study of low angular degree solar p-mode variations extracted by analyses of two sets of observational data. These were collected by the ground-based Birmingham Solar-Oscillations Network (BiSON) and the Global Oscillations at Low Frequency (GOLF) instrument on board the ESA/NASA SOHO satellite. The ~5.5 yr perio…
Confronting the Superbubble Model with X-Ray Observations of 30 Doradus C
Wang, Q. Daniel; Smith, David A.
We present an analysis of XMM-Newton observations of the superbubble 30 Dor C and compare the results with the predictions from the standard wind-blown bubble model. We find that the observed X-ray spectra cannot be fitted satisfactorily with the model alone and that there is evidence for nonthermal X-ray emission, which is particularly important …
An XMM-Newton Observation of the Seyfert 2 Galaxy NGC 6300. I. The Nucleus
Awaki, Hisamitsu; Maddox, Larry A.; Leighly, Karen M. +4 more
We present results from a half-day observation by XMM-Newton of the nucleus of the nearby Seyfert 2 galaxy NGC 6300. The X-ray spectrum of the nucleus consists of a heavily absorbed hard component dominating the 3-10 keV band and a soft component seen in the 0.2-2 keV band. In the hard band, the spectrum is well fitted by a power-law model with ph…