Search Publications
Statistical Properties of Galactic δ Scuti Stars: Revisited
Byun, Y. -I.; Kim, D. -W.; Protopapas, P. +1 more
We present statistical characteristics of 1578 δ Scuti stars including nearby field stars and cluster member stars within the Milky Way. We obtained 46% of these stars (718 stars) from work by Rodríguez and collected the remaining 54% of stars (860 stars) from other literature. We updated the entries with the latest information of sky coordinates,…
Binary Cepheids: Separations and Mass Ratios in 5 M ⊙ Binaries
Schaefer, Gail H.; Bond, Howard E.; Karovska, Margarita +3 more
Deriving the distribution of binary parameters for a particular class of stars over the full range of orbital separations usually requires the combination of results from many different observing techniques (radial velocities, interferometry, astrometry, photometry, direct imaging), each with selection biases. However, Cepheids—cool, evolved stars…
The Distance to the Massive Galactic Cluster Westerlund 2 from a Spectroscopic and HST Photometric Study
Kobulnicky, Henry A.; Vargas Álvarez, Carlos A.; Bradley, David R. +4 more
We present a spectroscopic and photometric determination of the distance to the young Galactic open cluster Westerlund 2 using WFPC2 imaging from the Hubble Space Telescope (HST) and ground-based optical spectroscopy. HST imaging in the F336W, F439W, F555W, and F814W filters resolved many sources previously undetected in ground-based observations …
Variable Stars in the Globular Cluster NGC 2808
Kunder, Andrea; Walker, Alistair R.; Stetson, Peter B. +2 more
The first calibrated broadband BVI time-series photometry is presented for the variable stars in NGC 2808, with observations spanning a range of 28 years. We have also redetermined the variability types and periods for the variable stars identified previously by Corwin et al., revising the number of probable fundamental-mode RR Lyrae variables (RR…
Studies of NGC 6720 with Calibrated HST/WFC3 Emission-line Filter Images. I. Structure and Evolution
O'Dell, C. R.; Henney, W. J.; Ferland, G. J. +1 more
We have performed a detailed analysis of the Ring Nebula (NGC 6720) using Hubble Space Telescope WFC3 images and derived a new three-dimensional model. Existing high spectral resolution spectra played an important supplementary role in our modeling. It is shown that the Main Ring of the nebula is an ionization-bounded irregular non-symmetric disk …
Anomalously Steep Reddening Law in Quasars: An Exceptional Example Observed in IRAS 14026+4341
Wang, Jianguo; Bai, Jinming; Shu, Xinwen +7 more
A fraction of the heavily reddened quasars require a reddening curve that is even steeper than that of the Small Magellanic Cloud. In this paper, we thoroughly characterize the anomalously steep reddening law in quasars via an exceptional example observed in IRAS 14026+4341. By comparing the observed spectrum to the quasar composite spectrum, we d…
The Top 10 Spitzer Young Stellar Objects in 30 Doradus
Walborn, Nolan R.; Barbá, Rodolfo H.; Sewiło, Marta M.
The most luminous Spitzer point sources in the 30 Doradus triggered second generation are investigated coherently in the 3-8 µm region. Remarkable diversity and complexity in their natures are revealed. Some are also among the brightest JHK sources, while others are not. Several of them are multiple when examined at higher angular resolution…
Optical and X-Ray Studies of 10 X-Ray-selected Cataclysmic Binaries
Thorstensen, John R.; Halpern, Jules
We report on ground-based optical observations of 10 cataclysmic binaries that were discovered through their X-ray emission. Time-resolved radial velocity spectroscopy yields unambiguous orbital periods for eight objects and ambiguous results for the remaining two. The orbital periods range from 87 minutes to 9.38 hr. We also obtained time-series …
An Echo of Supernova 2008bk
Van Dyk, Schuyler D.
I have discovered a prominent light echo around the low-luminosity Type II-plateau supernova (SN) 2008bk in NGC 7793, seen in archival images obtained with the Wide Field Channel of the Advanced Camera for Surveys on board the Hubble Space Telescope (HST). The echo is a partial ring, brighter to the north and east than to the south and west. The a…
The Snapshot Hubble U-band Cluster Survey (SHUCS). I. Survey Description and First Application to the Mixed Star Cluster Population of NGC 4041
Bastian, N.; Larsen, S. S.; Gallagher, J. S. +9 more
We present the Snapshot Hubble U-band Cluster Survey (SHUCS), a project aimed at characterizing the star cluster populations of 10 nearby galaxies (d < 23 Mpc, half within ≈12 Mpc) through new F336W (U-band equivalent) imaging from Wide Field Camera 3, and archival BVI-equivalent data with the Hubble Space Telescope. Completing the UBVI baselin…