Search Publications
3D Magnetic Field Configuration of the 2006 December 13 Flare Extrapolated with the Optimization Method
Ding, M. D.; Li, H.; Guo, Y. +1 more
The photospheric vector magnetic field of the active region NOAA 10930 was obtained with the Solar Optical Telescope (SOT) on board the Hinode satellite with a very high spatial resolution (about 0.3''). Observations of the two-ribbon flare on 2006 December 13 in this active region provide us a good sample to study the magnetic field configuration…
The Dearth of UV-Bright Stars in M32: Implications for Stellar Evolution Theory
Ferguson, Henry C.; Brown, Thomas M.; Kimble, Randy A. +3 more
Using the Space Telescope Imaging Spectrograph on the Hubble Space Telescope, we have obtained deep, far-ultraviolet images of the compact elliptical galaxy M32. When combined with earlier near-ultraviolet images of the same field, these data enable the construction of an ultraviolet color-magnitude diagram of the hot horizontal branch (HB) popula…
The Search for Muon Neutrinos from Northern Hemisphere Gamma-Ray Bursts with AMANDA
Kuehn, K.; Kowalski, M.; Ackermann, M. +223 more
We present the results of the analysis of neutrino observations by the Antarctic Muon and Neutrino Detector Array (AMANDA) correlated with photon observations of more than 400 gamma-ray bursts (GRBs) in the northern hemisphere from 1997 to 2003. During this time period, AMANDA's effective collection area for muon neutrinos was larger than that of …
Binarity in Cool Asymptotic Giant Branch Stars: A GALEX Search for Ultraviolet Excesses
Sahai, R.; Sánchez Contreras, C.; Gil de Paz, A. +1 more
The search for binarity in AGB stars is of critical importance for our understanding of how planetary nebulae acquire the dazzling variety of aspherical shapes which characterizes this class. However, detecting binary companions in such stars has been severely hampered due to their extreme luminosities and pulsations. We have carried out a small i…
Stellar Wind Variations during the X-Ray High and Low States of Cygnus X-1
Crenshaw, D. M.; Kaper, L.; Herrero, A. +10 more
We present results from Hubble Space Telescope ultraviolet spectroscopy of the massive X-ray and black hole binary system, HD 226868 = Cyg X-1. The spectra were obtained at both orbital conjunction phases in 2002 and 2003, when the system was in the X-ray high/soft state. The UV stellar wind lines suffer large reductions in absorption strength whe…
Complex Organic Materials in the Circumstellar Disk of HR 4796A
Weinberger, Alycia J.; Debes, John H.; Schneider, Glenn
We combine HST NICMOS imaging photometry of the HR 4796A disk at previously unobserved wavelengths between 1.71-2.22 µm with reprocessed archival observations to produce a measure of the dust's scattering efficiency as a function of wavelength. The spectrum of the dust, synthesized from the seven photometric measures, is characterized by a s…
The High-Velocity Gas toward Messier 5: Tracing Feedback Flows in the Inner Galaxy
Brown, Thomas M.; Lehner, Nicolas; Howk, J. Christopher +2 more
We present FUSE and STIS E140M observations of the post-AGB star ZNG 1 in the globular cluster Messier 5 (l = 3.9°, b = + 47.7° d = 7.5 kpc , z = + 5.3 kpc ). High-velocity absorption is seen in C IV, Si IV, O VI, and lower ionization species at LSR velocities of roughly -140 and -110 km s-1. We conclude that this gas is not circumstell…
NGC 346 in the Small Magellanic Cloud. III. Recent Star Formation and Stellar Clustering Properties in the Bright H II Region N66
Henning, Thomas; Gouliermis, Dimitrios A.; Dolphin, Andrew E. +2 more
In the third part of our photometric study of the star-forming region NGC 346/N66 and its surrounding field in the Small Magellanic Cloud (SMC), we focus on the large number of low-mass pre-main-sequence (PMS) stars revealed by the Hubble Space Telescope observations with the Advanced Camera for Surveys. We investigate the origin of the observed b…
The Once and Future Andromeda Stream
Rich, R. Michael; Mori, Masao
We study the interaction between an accreting satellite and the Andromeda galaxy (M31) analytically and numerically, using a high-resolution N-body simulation with 4 × 107 particles. For the first time, we show the self-gravitating response of the disk, the bulge, and the dark matter halo of M31 to an accreting satellite. We reproduce t…
The Dependence of Ephemeral Region Emergence on Local Flux Imbalance
DeRosa, Marc L.; Schrijver, Carolus J.; Hagenaar, Hermance J.
We investigate the distribution and evolution of existing and emerging magnetic network elements in the quiet-Sun photosphere. The ephemeral region emergence rate is found to depend primarily on the imbalance of magnetic flux in the area surrounding its emergence location, such that the rate of flux emergence is lower within strongly unipolar regi…