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What Produced the Ultraluminous Supernova Remnant in NGC 6946?
Chu, You-Hua; Gruendl, Robert A.; Dunne, Bryan C.
The ultraluminous supernova remnant (SNR) in NGC 6946 is the brightest known SNR in X-rays, about 1000 times brighter than Cas A. To probe the nature of this remnant and its progenitor, we have obtained high-dispersion optical echelle spectra. The echelle spectra detect Hα, [N II], and [O III] lines and resolve these lines into a narrow (FWHM ~20-…
Resolving the Stellar Populations in a z=4 Lensed Galaxy
Bunker, Andrew J.; Davis, Marc; Moustakas, Leonidas A.
We present deep near-infrared Keck Near-Infrared Camera (NIRC) imaging of a recently discovered z=4.04 galaxy. This is lensed by the rich foreground cluster Abell 2390 (z~0.23) into highly magnified arcs 3"-5" in length. Our H and K' band NIRC imaging allows us to map the Balmer+4000 Å break amplitude. In combination with high-quality a…
NOAA AR 8210: Evolution and Flares from Multiband Diagnostics
Warmuth, Alexander; Hanslmeier, Arnold; Messerotti, Mauro +3 more
NOAA 8210 has been a region showing a remarkable level of activity well before solar maximum. Dominated by a large, rapidly rotating δ spot, it produced several intense flares during its disk passage at the end of April-beginning of May 1998. We examine the development of AR 8210 in Hα and white light (WL) and study the evolution of its complex ma…
The Age of the Inner Halo Globular Cluster NGC 6652
Sarajedini, Ata; Chaboyer, Brian; Armandroff, Taft E.
Hubble Space Telescope (V, I) photometry has been obtained for the inner halo globular cluster NGC 6652. The photometry reaches ~4 mag below the turnoff and includes a well-populated horizontal branch. This cluster is located close to the Galactic center, at RGC~=2.0 kpc, with a reddening of E(V-I)=0.15+/-0.02, and has a metallicity of …
Recent Star Formation in Several Galaxies of the Tidally Disturbed System HCG 31
Johnson, Kelsey E.; Conti, Peter S.
High-resolution (0.7" to 0.8") Hα images of the Hickson Compact Group 31 (HCG 31) obtained with the WIYN telescope are used in conjunction with broadband optical images from the Hubble Space Telescope (HST) to examine the star formation history and properties of the component galaxies. The high spatial resolution of the WIYN telescope has allowed …
Magnetic field geometries of two slowly rotating Ap/Bp stars: HD 12288 and HD 14437
Wade, G. A.; Mathys, G.; Romanyuk, I. I. +2 more
In this paper we report magnetic field models and basic physical parameters for the slowly rotating Ap/Bp stars HD 12288 and HD 14437. Using new and previously published mean longitudinal magnetic field, mean magnetic field modulus, and hipparcos photometric measurements, we have inferred the rotational periods of both stars (HD 12288: P_rot=34.9<…
Structure of the Solar Core: Effect of Asymmetry of Peak Profiles
Christensen-Dalsgaard, J.; Provost, J.; Berthomieu, G. +8 more
Recent studies have established that peaks in solar oscillation power spectra are not Lorentzian in shape but have a distinct asymmetry. Fitting a symmetric Lorentzian profile to the peaks, therefore, produces a shift in frequency of the modes. Accurate determination of low-frequency modes is essential to infer the structure of the solar core by i…
Progress on a model for β Lyrae
Linnell, A. P.
It is generally accepted that β Lyrae is a massive mass-transfer system in which the more massive gainer is embedded in a thick accretion disc. No detailed, quantitative accretion disc model of the system, which fits both the available photometric and spectroscopic data, has been published. This paper considers a thick accretion disc model. An emp…
Hubble Space Telescope Photometry of the Dwarf Spheroidal Galaxy ESO 410-G005
Dolphin, Andrew E.; Grebel, Eva K.; Seitzer, Patrick +7 more
We present Hubble Space Telescope WFPC2 imaging of the nearby low surface brightness dwarf spheroidal galaxy ESO 410-G005, which has been resolved into stars for the first time. The resulting color-magnitude diagram for about 2500 stars shows a red giant branch with a tip at I=22.4+/-0.15 mag, which yields a distance of DMW=1.9+/-0.2 Mp…
NOTE: The Thermal Structure of Triton's Middle Atmosphere
Strobel, D. F.; Franz, O. G.; Elliot, J. L. +3 more
The atmospheric structure of Triton in the altitude range 25-150 km shows an unexpectedly steep thermal gradient of 0.26 K km -1 above 50 km altitude, with a nearly isothermal profile below. The upper part of the profile can be explained by downward conduction of heat deposited by magnetospheric electrons and solar UV. However, the atmo…