Search Publications
Identification and Analysis of Young Star Cluster Candidates in M31
Williams, Benjamin F.; Hodge, Paul W.
We present a method for finding clusters of young stars in M31 using broadband WFPC2 data from the HST data archive. Applying our identification method to 13 WFPC2 fields, covering an area of ~60 arcmin2, has revealed 79 new candidate young star clusters in these portions of the M31 disk. Most of these clusters are small (<~5 pc), yo…
Circumnuclear Spiral Arms and Starburst Rings in Magnetized Barred Spiral Galaxies
Fan, Zuhui; Lou, Yu-Qing; Yuan, Chi +1 more
The Seyfert galaxy NGC 1097 has a prominent bar and a luminous circumnuclear starburst ``ring.'' Magnetic fields as revealed by nonthermal radio continuum emissions correlate well with the optical barred spiral structure on large scales, have a gross enhancement overlapping with the optical/infrared ``ring,'' and show a trailing swirl around and w…
Gas-Phase Polycyclic Aromatic Hydrocarbons in Absorption toward Protostellar Sources?
Bregman, Jesse D.; Temi, Pasquale
One of the major criticisms of identifying the infrared emission bands with polycyclic aromatic hydrocarbon (PAH) molecules has been the lack of a match between laboratory spectra of individual PAHs and the emission features. Part of the difficulty arises from the complexity of modeling the emission mechanism with an a priori unknown mixture of io…
Evidence for Expanding Superbubbles in a Galaxy at z=0.7443
Vogt, Steven S.; Charlton, Jane C.; Churchill, Christopher W. +1 more
The intervening z=0.7443 Mg II absorption system in the spectrum of MC 1331+170 shows an unusual series of line pairs, each with Δv~30 km s-1. These lines could be explained as the shells of expanding superbubbles residing in the outer regions of an edge-on spiral galaxy visible in the optical image of the MC 1331+170 field. The color a…
The Bismuth Abundance in the HGMN Stars χ Lupi and HR 7775 and Improved Atomic Data for Selected Transitions of BI I, BI II, and BI III
Leckrone, D. S.; Wahlgren, G. M.; Johansson, S. +6 more
High-resolution spectra of the chemically peculiar HgMn stars χ Lupi and HR 7775, obtained with the Hubble Space Telescope/Goddard High Resolution Spectrograph, are investigated for their abundance of bismuth by comparison with LTE synthetic spectrum modeling. HR 7775, previously known from International Ultraviolet Explorer spectra to display str…
Hubble Space Telescope Ultraviolet and Ground-based Optical Spectropolarimetry of IRAS Quasi-stellar Objects: Dusty Scattering in Luminous Active Galactic Nuclei
Gordon, Karl D.; Hines, Dean C.; Sitko, Michael L. +4 more
We present UV and optical spectropolarimetry of two highly polarized IRAS-selected quasi-stellar objects (QSOs), IRAS 13349+2438 and the broad absorption line QSO (BALQSO) IRAS 14026+4341. The polarization in both objects rises rapidly toward the blue, peaks near 3000 Å in the rest frame and remains nearly constant for shorter wavelengths. The res…
Model Atmospheres with Individualized Abundances
Piskunov, N.; Kupka, F.
We describe a new method for computing opacity distribution functions (ODFs) for model atmosphere calculations. The method is tailored to model the atmospheres of individual stars on a modern workstation. Our goal is the computation of model atmospheres for stars with abundances significantly different from the solar or scaled solar composition ty…
4U 2206+54: An Unusual High-Mass X-Ray Binary with a 9.6 Day Orbital Period But No Strong Pulsations
Corbet, Robin H. D.; Peele, Andrew G.
Rossi X-Ray Timing Explorer (RXTE) All-Sky Monitor observations of the X-ray source 4U 2206+54, previously proposed to be a Be star system, show the X-ray flux to be modulated with a period of approximately 9.6 days. If the modulation is due to orbital variability, then this would be one of the shortest orbital periods known for a Be star X-ray so…
Results from UVCS and LASCO Observation of the Sungrazing Comet C/2000 C6
Raymond, J. C.; Wu, R.; Uzzo, M. +4 more
During 2000 February 9-10, the Large Angle Spectrometric Coronagraph and Ultraviolet Coronal Spectrometer (UVCS) instruments aboard the Solar and Heliospheric Observatory observed comet C/2000 C6, a member of the Kreutz family of sungrazing comets. A tail nearly 0.5 Rsolar in length was detected in Lyα emission. UVCS was able to observe…
On the Unresolved Fine Structures of the Solar Upper Atmosphere. IV. The Interface with the Chromosphere
Wilhelm, K.; Dammasch, I. E.; Feldman, U.
An important objective of the solar physics community is the unambiguous determination of the morphology of the fine structures of the solar upper atmosphere in quiet-Sun and coronal hole regions and the relationship of the cold chromosphere to the hot corona. Recently the Solar Ultraviolet Measurements of Emitted Radiation spectrometer on board t…