C IV and Si IV in IUE spectra of normal B8-A0 stars: UV identified Be/Ae stars

Archival IUE high dispersion spectra of 42 B6-A2 stars within 200 pc were surveyed. Five of the program stars show significant C IV and Si IV absorption. All of the stars with detected C IV have v sin i less than or = 190 km/sec. Sharp absorption cores are present in Si II lambda 1533 in 3 of the objects, indicating that these are previously unrecognized shell stars. Three of the stars have variable or asymmetric C IV profiles which are consistent with the C IV and Si IV being produced in stellar winds. One star has C IV in the form of a shortward-shifted discrete absorption component, similar to those observed in Be stars. The data are compared with similar data for Be and B shell stars

The Optical and Infrared Photometric Evolution of the Recent Stellar Merger, V1309 Sco

Nova Sco 2008 was recently shown to have resulted from the merger of the two stars in the contact binary V1309 Sco. This is the first stellar merger ever observed between two convective stars. We present archival data, new infrared photometry, and Hubble Space Telescope WFC3 imaging of V1309 Sco. Spitzer observations show that it had a large infrared excess in the 3.6 μm to 8 μm range more than a year before the merger. Standard color diagnostics of the pre-merger infrared colors place V1309 Sco in the same region where evolved stars with chemically complex mass loss are located. Since the nova outburst subsided in optical bandpasses in 2008, the merger remnant's brightness in optical bandpasses, near-IR bandpasses, and the Spitzer 3.6 μm and 4.5 μm channels has varied by several magnitudes and in complex ways. A temporary, strong increase in the reddening during 2010 suggests the occurrence of a dust formation event. We point out several peculiarities in the relative fluxes and time behavior of the optical and near-IR magnitudes, which could be explained if some of the photometric bandpasses in the 1–5 μm range are strongly affected by emission lines

Physical Conditions in the Narrow-Line Region of Markarian 3. I. Observational Results

We use Hubble Space Telescope/Space Telescope Imaging Spectrograph (HST/STIS) longslit low-resolution spectroscopy from 1150A to 10,300A to study the physical conditions in the narrow-line region (NLR) of the Seyfert 2 galaxy Markarian 3. We find from the HeII 1640/4686 line ratio and the Balmer decrement that the extinction within Markarian 3 along the line-of-sight to the NLR is best characterized by a Large Magellanic Cloud (LMC) type extinction curve. We observe an extinction gradient increasing from west to east along the STIS slit in both line and continuum emission. We infer from this gradient that the host galaxy disk is tilted towards the observer in the east: the line-of-sight to the eastern emission-line cone intersects more dust in the plane of the galaxy than that to the western cone. We model the observed continuum as a combination of reddened host galaxy light from an old stellar population, reddened H+ and He++ recombination continua, and less reddened scattered light from the central engine with spectral index alpha=1 (L(nu) proportional to nu^(-alpha)). The host galaxy to scattered-light ratio is estimated to be 3:1 at 8125 A in 0.1 X 1.8 square-arcsecond aperture. We estimate that the amount of intrinsic non-ionizing UV continuum scattered into our line-of-sight is 0.04%. This is consistent with our estimate of the scattering fraction for broad CIV 1548,1551 emission.Comment: 57 pages, 21 Figures; LaTeX; accepted for publication in Ap

Kepler Planet-Detection Mission: Introduction and First Results

The Kepler mission was designed to determine the frequency of Earth-sized planets in and near the habitable zone of Sun-like stars. The habitable zone is the region where planetary temperatures are suitable for water to exist on a planet’s surface. During the first 6 weeks of observations, Kepler monitored 156,000 stars, and five new exoplanets with sizes between 0.37 and 1.6 Jupiter radii and orbital periods from 3.2 to 4.9 days were discovered. The density of the Neptune-sized Kepler-4b is similar to that of Neptune and GJ 436b, even though the irradiation level is 800,000 times higher. Kepler-7b is one of the lowest-density planets (~0.17 gram per cubic centimeter) yet detected. Kepler-5b, -6b, and -8b confirm the existence of planets with densities lower than those predicted for gas giant planets