Search Publications
The Unusual X-Ray Spectrum of FU Orionis
Skinner, Stephen L.; Güdel, Manuel; Briggs, Kevin R.
FU Orionis objects (FUors) have undergone strong optical outbursts and are thought to be young low-mass stars accreting at high rates of up to M˙acc~10-4 Msolar yr-1. FUors have been extensively studied at optical and infrared wavelengths, but little is known about their X-ray properties. We have thus in…
Proper-Motion Measurements of the Cygnus Egg Nebula
Ueta, Toshiya; Meixner, Margaret; Murakawa, Koji
We present the results of proper-motion measurements of the dust shell structure in the Egg Nebula (AFGL 2688, CRL 2688, V1610 Cyg), based on the archived two-epoch data at 2 µm taken with the Hubble Space Telescope. We measured the amount of motion of local structures in the nebula by determining their relative shifts over an interval of 5.…
Swift XRT Follow-up Observations of TeV Sources of the HESS Inner Galaxy Survey
Masetti, N.; Bird, A. J.; Ubertini, P. +6 more
In order to provide a firm identification of the newly discovered Galactic TeV sources, a search for counterparts in a broad band from soft X-ray to soft gamma rays is crucial as data in these wave bands allow us to distinguish between different types of suggested models (for example, leptonic vs. hadronic) and, in turn, to disentangle their natur…
Clues to Active Galactic Nucleus Growth from Optically Variable Objects in the Hubble Ultra Deep Field
Koekemoer, A. M.; Mobasher, B.; Hathi, N. P. +9 more
We present a photometric search for objects with point-source components that are optically variable on timescales of weeks to months in the Hubble Ultra Deep Field (HUDF) to i'AB=28.0 mag. The data are split into four substacks of approximately equal exposure times. Objects exhibiting the signature of optical variability are…
Supergranule Superrotation Identified as a Projection Effect
Hathaway, D. H.; Cuntz, M.; Williams, P. E.
Previous measurements of the rotation rate of the supergranule Doppler velocity pattern revealed surprising characteristics: (1) the pattern rotates faster than the plasma at the surface, and, at each latitude, it rotates faster than the plasma at any level below the surface (superrotation), (2) larger cells rotate more rapidly than smaller cells,…
Hubble Space Telescope NICMOS Polarization Measurements of OMC-1
Schultz, A. S. B.; Colgan, Sean W. J.; Burton, Michael G. +2 more
We present 2 µm polarization measurements of positions in the IRc2 and BN regions of the Orion Molecular Cloud (OMC-1) made with NICMOS Camera 2 (0.2" resolution) on the Hubble Space Telescope. Our results are as follows: BN is ~29% polarized by dichroic absorption and appears to be the illuminating source for most of the nebulosity to its n…
Spatially Resolved Narrow-Line Region Kinematics in Active Galactic Nuclei
Shields, Joseph C.; Greene, Jenny E.; Pogge, Richard W. +4 more
We have analyzed Hubble Space Telescope spectroscopy of 24 nearby active galactic nuclei (AGNs) to investigate spatially resolved gas kinematics in the narrow-line region (NLR). These observations effectively isolate the nuclear line profiles on less than 100 pc scales and are used to investigate the origin of the substantial scatter between the w…
ACS Photometry of the Remote M31 Globular Cluster B514
Bellazzini, M.; Galleti, S.; Federici, L. +2 more
We present deep F606W, F814W ACS photometry of the recently discovered globular cluster B514, the outermost known globular in the M31 galaxy. The cluster appears quite extended, and member stars are unequivocally identified out to ~200 pc from the center. The color-magnitude diagram reveals a steep red giant branch (RGB), and a horizontal branch e…
The Remarkable Be Star HD 110432 (BZ Crucis)
Smith, Myron A.; Balona, Luis
HD 110432 (B1e) has gained considerable recent attention because it is a hard, variable X-ray source with local absorption and also because its optical spectrum is affected by an extensive Be disk. From time-serial echelle data obtained over 2 weeks during 2005 January and February, we have discovered several remarkable characteristics in the star…
Electron Density and Turbulence Gradients within the Extended Atmosphere of the M Supergiant Betelgeuse (α Orionis)
Harper, Graham M.; Brown, Alexander
The extended atmosphere of the M supergiant Betelgeuse is complex with cool plasma dominating the structure by mass and small amounts of embedded hotter chromospheric plasma. A major challenge is to understand the interrelationship and juxtaposition of these different components, which in turn may provide clues to the nature of the process of nonr…