Search Publications
Quantitative Spectroscopy of 24 A Supergiants in the Sculptor Galaxy NGC 300: Flux-weighted Gravity-Luminosity Relationship, Metallicity, and Metallicity Gradient
Bresolin, Fabio; Kudritzki, Rolf-Peter; Urbaneja, Miguel A. +3 more
A quantitative spectral analysis of 24 A supergiants in the Sculptor Group spiral galaxy NGC 300 at a distance of 1.9 Mpc is presented. A new method is introduced to analyze low-resolution (~5 Å) spectra, which yields metallicities accurate to 0.2 dex including the uncertainties arising from the errors in Teff (5%) and log g (0.2 dex). …
Black Holes in Pseudobulges and Spheroidals: A Change in the Black Hole-Bulge Scaling Relations at Low Mass
Ho, Luis C.; Barth, Aaron J.; Greene, Jenny E.
We investigate the relationship between black hole mass and host galaxy properties for active galaxies with the lowest black hole masses currently known in galaxy nuclei. HST imaging confirms that the host galaxies have correspondingly low luminosity; they are ~1 mag below L*. In terms of morphology, ~60% of the members of the sample are disk domi…
Hubble Space Telescope STIS Optical Transit Transmission Spectra of the Hot Jupiter HD 209458b
Sing, David K.; Lecavelier des Etangs, A.; Vidal-Madjar, A. +2 more
We present the transmission spectra of the hot Jupiter HD 209458b taken with the Space Telescope Imaging Spectrograph aboard the Hubble Space Telescope. Our analysis combines data at two resolutions and applies a complete pixel-by-pixel limb-darkening correction to fully reveal the spectral line shapes of atmospheric absorption features. Terrestri…
High-Cadence Observations of a Global Coronal Wave by STEREO EUVI
Veronig, Astrid M.; Temmer, Manuela; Vršnak, Bojan
We report a large-scale coronal wave (so-called EIT wave) observed with high cadence by EUVI on board STEREO in association with the GOES B9.5 flare and double CME event on 2007 May 19. The EUVI instruments provide us with the unprecedented opportunity to study the dynamics of flare/CME associated coronal waves. The coronal wave under study reveal…
Eclipsing Binary Solutions in Physical Units and Direct Distance Estimation
Wilson, R. E.
Opportunities for extraction of distances and temperatures from eclipsing binary light curves that are in standard flux units, as opposed to traditional arbitrary units, are examined. Benefits include (1) distance becomes an ordinary solution parameter with a standard error, (2) temperatures of both stars may be derivable in favorable circumstance…
Polarization of the Crab Pulsar and Nebula as Observed by the INTEGRAL/IBIS Telescope
Grenier, I. A.; Laurent, P.; Lebrun, F. +2 more
Neutron stars generate powerful winds of relativistic particles that form bright synchrotron nebulae around them. Polarimetry provides a unique insight into the geometry and magnetic configuration of the wind, but high-energy measurements have failed until recently. The INTEGRAL/IBIS telescope has been used in its Compton mode to search for linear…
The Spatial Structure of an Accretion Disk
Kochanek, Christopher S.; Poindexter, Shawn; Morgan, Nicholas
Based on the microlensing variability of the two-image gravitational lens HE 1104-1805 observed between 0.4 and 8 µm, we have measured the size and wavelength-dependent structure of the quasar accretion disk. Modeled as a power law in temperature, T propto R-β, we measure a B-band (0.13 µm in the rest frame) half-light radiu…
Magnetic Field Overlying Solar Eruption Regions and Kink and Torus Instabilities
Liu, Y.
Using a potential field source surface (PFSS) model, we study a magnetic field overlying erupted filaments in solar active regions. The filaments studied here were reported to experience a kink instability or a torus instability. The torus instability leads to a full eruption, while the kink instability leads to a full eruption or a failed eruptio…
An Integrated Picture of Star Formation, Metallicity Evolution, and Galactic Stellar Mass Assembly
Barger, A. J.; Cowie, L. L.
We present an integrated study of star formation and galactic stellar mass assembly from z = 0.05 to 1.5 and galactic metallicity evolution from z = 0.05 to 0.9 using a very large and highly spectroscopically complete sample selected by rest-frame NIR bolometric flux in the GOODS-N. We assume a Salpeter IMF and fit Bruzual & Charlot models to …
Study of Nonthermal Emission from SNR RX J1713.7-3946 with Suzaku
Petre, Robert; Kokubun, Motohide; Nakazawa, Kazuhiro +11 more
We present results obtained from a series of observations of the supernova remnant RX J1713.7-3946 by Suzaku. Hard X-rays have been detected up to ~40 keV. The hard X-ray spectra are described by a power law with photon indices of ~3.0, which is larger than those below 10 keV. The combination of the spatially integrated XIS and HXD spectra clearly…