Search Publications

Probing the Inner Regions of Protoplanetary Disks with CO Absorption Line Spectroscopy

Herczeg, Gregory J.; Brown, Alexander; France, Kevin +4 more

Carbon monoxide (CO) is the most commonly used tracer of molecular gas in the inner regions of protoplanetary disks. CO can be used to constrain the excitation and structure of the circumstellar environment. Absorption line spectroscopy provides an accurate assessment of a single line of sight through the protoplanetary disk system, giving more st…

Finding η Car Analogs in Nearby Galaxies Using Spitzer. I. Candidate Selection

Kochanek, C. S.; Stanek, K. Z.; Khan, Rubab

The late-stage evolution of the most massive stars such as η Carinae is controlled by the effects of mass loss, which may be dominated by poorly understood eruptive mass ejections. Understanding this population is challenging because no true analogs of η Car have been clearly identified in the Milky Way or other galaxies. We utilize Spitzer IRAC i…

Observations of the Crab Nebula's Asymmetrical Development

Scowen, P. A.; Loll, A. M.; Desch, S. J. +1 more

We present the first Hubble Space Telescope Wide Field Planetary Camera-2 imaging survey of the entire Crab Nebula, in the filters F502N ([O III] emission), F673N ([S II]), F631N ([O I]), and F547M (continuum). We use our mosaics to characterize the pulsar wind nebula (PWN) and its three-dimensional structure, the ionizational structure in the fil…

Erratum: "An Estimate of the Chemical Composition of Titan's Lakes" (2009, ApJL, 707, L128)

Mousis, Olivier; Lunine, Jonathan I.; Lavvas, Panayotis +2 more

The Two-dimensional Projected Spatial Distribution of Globular Clusters. I. Method and Application to NGC 4261

Zezas, A.; Luo, B.; Fabbiano, G. +7 more

We present a new method for the determination of the two-dimensional (2D) projected spatial distribution of globular clusters (GCs) in external galaxies. This method is based on the K-Nearest Neighbor density estimator of Dressler, complemented by Monte-Carlo simulations to establish the statistical significance of the results. We apply this metho…

Observation of Flux-tube Crossings in the Solar Wind

Li, G.; Li, X.; Arnold, L. +1 more

Current sheets are ubiquitous in the solar wind. They are a major source of the solar wind MHD turbulence intermittency. They may result from nonlinear interactions of the solar wind MHD turbulence or are the boundaries of flux tubes that originate from the solar surface. Some current sheets appear in pairs and are the boundaries of transient stru…

Discovery of a Highly Variable Dipping Ultraluminous X-Ray Source in M94

Remillard, Ronald A.; Lin, Dacheng; Webb, Natalie A. +2 more

We report the discovery of a new ultraluminous X-ray source (ULX) 2XMM J125048.6+410743 within the spiral galaxy M94. The source has been observed by ROSAT, Chandra, and XMM-Newton on several occasions, exhibiting as a highly variable persistent source or a recurrent transient with a flux variation factor of gsim100, a high duty cycle (at least ~7…

G048.66-0.29: Physical State of an Isolated Site of Massive Star Formation

Henning, Th.; Krause, O.; Beuther, H. +9 more

We present continuum observations of the infrared dark cloud (IRDC) G48.66-0.22 (G48) obtained with Herschel, Spitzer, and APEX, in addition to several molecular line observations. The Herschel maps are used to derive temperature and column density maps of G48 using a model based on a modified blackbody. We find that G48 has a relatively simple st…

Temporal Variations of X-Ray Solar Flare Loops: Length, Corpulence, Position, Temperature, Plasma Pressure, and Spectra

Kontar, Eduard P.; Jeffrey, Natasha L. S.

The spatial and spectral properties of three solar flare coronal X-ray loops are studied before, during, and after the peak X-ray emission. Using observations from the Ramaty High Energy Solar Spectroscopic Imager (RHESSI), we deduce the temporal changes in emitting X-ray length, corpulence, volume, position, number density, and thermal pressure. …

Swift Observations of 1FGL J1018.6-5856

An, Hongjun; Kaspi, Victoria M.; Harrison, Fiona A. +1 more

We report on X-ray properties of the gamma-ray binary 1FGL J1018.6-5856 using observations obtained with the Swift X-ray telescope. Using 54 observations made between MJD 55575 and 55984, we find that the X-ray flux is modulated at a period of 16.57 ± 0.11 days, which is consistent with previous reports based on gamma-ray data. We find that the X-…