Search Publications
High-Resolution Helioseismic Imaging of Subsurface Structures and Flows of a Solar Active Region Observed by Hinode
Zhao, Junwei; Kosovichev, Alexander G.; Sekii, Takashi
We analyze a solar active region observed by the Hinode Ca II H line using the time-distance helioseismology technique, and infer wave-speed perturbation structures and flow fields beneath the active region with a high spatial resolution. The general subsurface wave-speed structure is similar to the previous results obtained from Solar and Heliosp…
A High Spatial Resolution Mid-Infrared Spectroscopic Study of the Nuclei and Star-Forming Regions in Luminous Infrared Galaxies
Colina, Luis; Alonso-Herrero, Almudena; Díaz-Santos, Tanio +5 more
We present a high spatial (diffraction-limited) resolution (∼0.3") mid-infrared (MIR) spectroscopic study of the nuclei and star-forming regions of four local luminous infrared galaxies (LIRGs) using T-ReCS on the Gemini South telescope. We investigate the spatial variations of the features seen in the N-band spectra of LIRGs on scales of ∼100 pc,…
Evolution of Solar Magnetic Field and Associated Multiwavelength Phenomena: Flare Events on 2003 November 20
Kumar, Pankaj; Uddin, Wahab; Manoharan, P. K.
We analyze Hα images, soft X-ray profiles, magnetograms, extreme ultra-violet images and, radio observations of two homologous flare events (M1.4/1N and M9.6/2B) on 2003 November 20 in the active region NOAA 10501 and study properties of reconnection between twisted filament systems, energy release, and associated launch of coronal mass ejections.…
Variability in Proto-planetary Nebulae. I. Light Curve Studies of 12 Carbon-rich Objects
Lu, Wenxian; Hrivnak, Bruce J.; Maupin, Richard E. +1 more
We have carried out long-term (14 years) V and R photometric monitoring of 12 carbon-rich proto-planetary nebulae. The light and color curves display variability in all of them. The light curves are complex and suggest multiple periods, changing periods, and/or changing amplitudes, which are attributed to pulsation. A dominant period has been dete…
New Abundance Determinations of Cadmium, Lutetium, and Osmium in the r-process Enriched Star BD +17 3248
Roederer, Ian U.; Sneden, Christopher; Cowan, John J. +1 more
We report the detection of Cd I (Z = 48), Lu II (Z = 71), and Os II (Z = 76) in the metal-poor star BD +17 3248. These abundances are derived from an ultraviolet spectrum obtained with the Space Telescope Imaging Spectrograph on the Hubble Space Telescope. This is the first detection of these neutron-capture species in a metal-poor star enriched b…
Discovery of Millihertz X-Ray Oscillations in a Transient Ultraluminous X-Ray Source in M82
Feng, Hua; Kaaret, Philip; Rao, Fengyun
We report on the discovery of X-ray quasi-periodic oscillations (QPOs) at frequencies of 3-4 mHz from a transient ultraluminous X-ray source X42.3+59 in M82. The QPOs are strong and broad and appear with weak or absent red noise, and are detected only in Chandra observations when the source is brighter than 1040 erg s-1. The …
Locating the Accretion Footprint on a Herbig Ae Star: MWC 480
Bouret, J. -C.; Ménard, F.; Kim, S. +27 more
Accretion is a fundamental process which establishes the dynamics of the protoplanetary disk and the final properties of the forming star. In solar-type stars, the star-disk coupling is determined by the magnetic field structure, which is responsible for funneling material from the disk midplane to higher latitudes on the star. Here, we use pan-ch…
Angular Diameters and Effective Temperatures of 25 K Giant Stars from the CHARA Array
Guenther, Eike W.; Hatzes, Artie P.; Goldfinger, P. J. +10 more
Using Georgia State University's Center for High Angular Resolution Astronomy Array interferometer, we measured angular diameters for 25 giant stars, six of which host exoplanets. The combination of these measurements and Hipparcos parallaxes produces physical linear radii for the sample. Except for two outliers, our values match angular diameters…
Optical-Ultraviolet Spectrum and Proper Motion of the Middle-aged Pulsar B1055-52
Mignani, R. P.; Pavlov, G. G.; Kargaltsev, O.
PSR B1055-52 is a middle-aged (τ = 535 kyr) radio, X-ray, and γ-ray pulsar showing X-ray thermal emission from the neutron star (NS) surface. A candidate optical counterpart to PSR B1055-52 was proposed by Mignani and coworkers based on Hubble Space Telescope (HST) observations performed in 1996, in one spectral band only. We report on HST observa…
A New Extensive Catalog of Optically Variable Active Galactic Nuclei in the GOODS Fields and a New Statistical Approach to Variability Selection
Grogin, Norman A.; Koekemoer, Anton M.; Villforth, Carolin
Variability is a property shared by practically all active galactic nuclei (AGNs). This makes variability selection a possible technique for identifying AGNs. Given that variability selection makes no prior assumption about spectral properties, it is a powerful technique for detecting both low-luminosity AGNs in which the host galaxy emission is d…