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NICMOS Images of the GG Tauri Circumbinary Disk
Duchêne, G.; Ghez, A. M.; McCabe, C.
We present deep, near-infrared images of the circumbinary disk surrounding the pre-main-sequence binary star GG Tau A, obtained with NICMOS aboard the Hubble Space Telescope. The spatially resolved protoplanetary disk scatters ~1.5% of the stellar flux, with a near-side-to-far-side flux ratio of ~1.4, independent of wavelength, and colors that are…
Cepheids and Long-Period Variables in IC 342
Saha, A.; Hoessel, J. G.; Claver, J.
Using repeated imaging with the WIYN 3.5 m telescope at Kitt Peak, we have identified 24 Cepheids in IC 342. For 20 of them, we have obtained reliable r and i photometry. In addition, we have identified 52 other variables (with varying degrees of data quality) for which we are unable to derive definite periods from the data at hand. Most of these …
The Effective Temperatures of Mid-O Stars
Bianchi, Luciana; Garcia, Miriam
We derived photospheric parameters, mass-loss rates, and wind velocities of Galactic O6-O7 stars by analyzing high-resolution spectra in the far-UV and UV ranges with line-blanketed, hydrodynamic, non-LTE spherical models. We combined spectra from the Far Ultraviolet Spectroscopic Explorer (FUSE) in the range 905-1187 Å and International Ultraviol…
The Progenitor of Supernova 1993J Revisited
Van Dyk, Schuyler D.; Filippenko, Alexei V.; Kirshner, Robert P. +4 more
From Hubble Space Telescope images with 0.05" resolution, we identify four stars brighter than V=25 mag within 2.5" of SN 1993J in M81, which contaminated previous ground-based brightness estimates for the supernova progenitor. Correcting for the contamination, we find that the energy distribution of the progenitor is consistent with that of an ea…
A Far-Ultraviolet Survey of 47 Tucanae. I. Imaging
Zurek, David R.; Shara, Michael M.; Long, Knox S. +1 more
We present results from the imaging portion of a far-ultraviolet (FUV) survey of the core of 47 Tucanae. We have detected 767 FUV sources, 527 of which have optical counterparts in archival HST/WFPC2 images of the same field. Most of our FUV sources are main-sequence (MS) turnoff stars near the detection limit of our survey. However, the FUV/optic…
Mass segregation in young compact clusters in the Large Magellanic Cloud - III. Implications for the initial mass function
Santiago, B. X.; Mackey, A. D.; de Grijs, R. +4 more
The distribution of core radii of rich clusters in the Large Magellanic Cloud (LMC) systematically increases in both upper limit and spread with increasing cluster age. Cluster-to-cluster variations in the stellar initial mass function (IMF) have been suggested as an explanation. We discuss the implications of the observed degree of mass segregati…
Rotation and Activity in the Solar-Metallicity Open Cluster NGC 2516
Pinsonneault, Marc; Sills, Alison; Jeffries, Robin D. +3 more
We report new measures of radial velocities and rotation rates (vsini) for 51 F and early G stars in the open cluster NGC 2516 and combine these with previously published data. From high signal-to-noise ratio spectra of two stars, we show that NGC 2516 has a relative iron abundance with respect to the Pleiades of Δ[Fe/H]=+0.04+/-0.07 at the canoni…
The Nuclei of Radio Galaxies in the Ultraviolet: The Signature of Different Emission Processes
Sparks, William B.; Chiaberge, Marco; Capetti, Alessandro +3 more
We have studied the nuclei of 28 radio galaxies from the 3CR sample in the UV band. Unresolved nuclei (central compact cores: CCCs) are observed in 10 of the 13 FR I galaxies, and in five of the 15 FR II galaxies. All sources that do not have a CCC in the optical do not have a CCC in the UV. Two FR I galaxies (3C 270 and 3C 296) have a CCC in the …
The SCUBA 8-mJy survey - II. Multiwavelength analysis of bright submillimetre sources
Ivison, R. J.; Dunlop, J. S.; Serjeant, S. +13 more
We present the results of a multiwavelength study of the 19 most significant submillimetre (submm) sources detected in the SCUBA 8-mJy survey. As described in Scott et al. , this survey covers ~=260arcmin2 using the submillimetre camera SCUBA, to a limiting source detection limit S 850µm ~=8mJy. One advantage of this re…
Seismic tests for solar models with tachocline mixing
Antia, H. M.; Brun, A. S.; Chitre, S. M. +1 more
We have computed accurate 1-D solar models including both a macroscopic mixing process in the solar tachocline as well as up-to-date microscopic physical ingredients. Using sound speed and density profiles inferred through primary inversion of the solar oscillation frequencies coupled with the equation of thermal equilibrium, we have extracted the…