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H2 and CO Emission from Disks around T Tauri and Herbig Ae Pre-Main-Sequence Stars and from Debris Disks around Young Stars: Warm and Cold Circumstellar Gas
Thi, W. F.; Natta, A.; van Dishoeck, E. F. +8 more
We present ISO Short-Wavelength Spectrometer observations of H2 pure-rotational line emission from the disks around low- and intermediate-mass pre-main-sequence stars as well as from young stars thought to be surrounded by debris disks. The pre-main-sequence sources have been selected to be isolated from molecular clouds and to have cir…
The Nuclear and Circumnuclear Stellar Population in Seyfert 2 Galaxies: Implications for the Starburst-Active Galactic Nucleus Connection
Heckman, Timothy; Leitherer, Claus; González Delgado, Rosa M.
We report the results of a spectroscopic investigation of a sample of 20 of the brightest type 2 Seyfert nuclei. Our goal is to search for the direct spectroscopic signature of massive stars and thereby probe the role of circumnuclear starbursts in the Seyfert phenomenon. The method used is based on the detection of the higher order Balmer lines a…
Flash Mixing on the White Dwarf Cooling Curve: Understanding Hot Horizontal Branch Anomalies in NGC 2808
Brown, Thomas M.; Hubeny, Ivan; Sweigart, Allen V. +2 more
We present an ultraviolet color-magnitude diagram (CMD) spanning the hot horizontal branch (HB), blue straggler, and white dwarf populations of the globular cluster NGC 2808. These data were obtained with the far-UV and near-UV cameras on the Space Telescope Imaging Spectrograph (STIS). Although previous optical CMDs of NGC 2808 show a high-temper…
Theory of Extrasolar Giant Planet Transits
Hubbard, W. B.; Fortney, J. J.; Lunine, J. I. +3 more
We present a synthesis of physical effects influencing the observed light curve of an extrasolar giant planet (EGP) transiting its host star. The synthesis includes a treatment of Rayleigh scattering, cloud scattering, refraction, and molecular absorption of starlight in the EGP atmosphere. Of these effects, molecular absorption dominates in deter…
High-Resolution X-Ray Spectroscopy and Modeling of the Absorbing and Emitting Outflow in NGC 3783
Brandt, W. N.; Kaspi, Shai; Garmire, Gordon P. +6 more
The high-resolution X-ray spectrum of NGC 3783 shows several dozen absorption lines and a few emission lines from the H-like and He-like ions of O, Ne, Mg, Si, and S, as well as from Fe XVII-Fe XXIII L-shell transitions. We have reanalyzed the Chandra HETGS spectrum using better flux and wavelength calibrations, along with more robust methods. Com…
The X-Ray Globular Cluster Population in NGC 1399
Angelini, Lorella; Loewenstein, Michael; Mushotzky, Richard F.
We report on the Chandra observations of the elliptical galaxy NGC 1399, concentrating on the X-ray sources identified with globular clusters (GCs). A large fraction of the 2-10 keV X-ray emission in the 8'×8' Chandra image is resolved into point sources with luminosities >=5×1037 ergs s-1. These sour…
The Formation of a Prominence in Active Region NOAA 8668. I. SOHO/MDI Observations of Magnetic Field Evolution
Qiu, Jiong; Wang, Haimin; Chae, Jongchul +3 more
We have studied the evolution of the photospheric magnetic field in active region NOAA 8668 for 3 days while the formation of a reverse S-shaped filament proceeded. From a set of full-disk line-of-sight magnetograms taken by the Michelson Doppler Imager (MDI) on board the Solar and Heliospheric Observatory (SOHO), we have found a large canceling m…
A Multiwavelength Study of the Young Star Clusters and Interstellar Medium in the Antennae Galaxies
Whitmore, Bradley C.; Fall, S. Michael; Zhang, Qing
We report on a multiwavelength study of the relationship between young star clusters in the Antennae galaxies (NGC 4038/9) and their interstellar environment, with the goal of understanding the formation and feedback effects of star clusters in merging galaxies. This is possible for the first time because various new observations (from X-rays to r…
Searching for the Physical Drivers of the Eigenvector 1 Correlation Space
Marziani, P.; Zwitter, T.; Sulentic, J. W. +2 more
We recently discussed an Eigenvector 1 (E1) parameter space that provides optimal discrimination between the principal classes of broad-line active galactic nuclei (AGNs). In this paper we begin a search for the most important physical parameters that are likely to govern correlations and data point distribution in E1 space. We focus on the princi…
Are Magnetic Dips Necessary for Prominence Formation?
Klimchuk, J. A.; MacNeice, P. J.; Antiochos, S. K. +2 more
The short answer: No.