3,154 research outputs found
On the apsidal motion of BP Vulpeculae
BP Vulpeculae is a bright eclipsing binary system showing apsidal motion. It
was found in an earlier study that it shows retrograde apsidal motion which
contradicts theory. In this paper we present the first light curve of the
system and its light curve solution as well as seven new times of the minima
from the years 1959-1963. This way we could expanded the baseline of the
investigation to five decades. Based on this longer baseline we concluded that
the apsidal motion is prograde agreeing with the theoretical expectations and
its period is about 365 years and the determined internal structure constant is
close to the theoretically expected one.Comment: accepted for New Astronomy; two figure
Host Galaxies of Young Dust-Reddened Quasars
We present results on a multiwavelength campaign to identify the nature of dust-reddened Type 1 quasars. These quasars were selected by matching FIRST, 2MASS and very red optical counterparts with r' − K > 5. We find a very high fraction of Low Ionization Broad Absorption Line Quasars (LoBALs) among AGN selected with this method, perhaps a sign of quasar feedback. From X-ray observations and Balmer decrement measurements, the obscuring dust is most likely located in a cold absorber such as the host galaxy, rather than from a torus near the AGN. Hubble ACS imaging of a sub-sample of these sources showed a very high fraction of interacting and merging systems. The quasars appear to be very young in which dust from the merging galaxies is still settling in. Spitzer IRS and MIPS data show star formation signatures and deep Silicate absorption features in these objects, but overall the quasar is the dominant source in the Mid-infrared
Ionized Gas in the Galactic Center: New Observations and Interpretation
We present new observations of the [Ne II] emission from the ionized gas in
Sgr A West with improved resolution and sensitivity. About half of the emission
comes from gas with kinematics indicating it is orbiting in a plane tipped
about 25\degree\ from the Galactic plane. This plane is consistent with that
derived previously for the circumnuclear molecular disk and the northern arm
and western arc ionized features. However, unlike most previous studies, we
conclude that the ionized gas is not moving along the ionized features, but on
more nearly circular paths. The observed speeds are close to, but probably
somewhat less than expected for orbital motions in the potential of the central
black hole and stars and have a small inward component. The spatial
distribution of the emission is well fitted by a spiral pattern. We discuss
possible physical explanations for the spatial distribution and kinematics of
the ionized gas, and conclude that both may be best explained by a one-armed
spiral density wave, which also accounts for both the observed low velocities
and the inward velocity component. We suggest that a density wave may result
from the precession of elliptical orbits in the potential of the black hole and
stellar mass distribution.Comment: 28 pages, 13 figures, ApJ in pres
Hdo And SO2 Thermal Mapping On Venus: Evidence For Strong SO2 Variability
We have been using the TEXES high-resolution imaging spectrometer at the NASA Infrared Telescope Facility to map sulfur dioxide and deuterated water over the disk of Venus. Observations took place on January 10-12, 2012. The diameter of Venus was 13 arcsec, with an illumination factor of 80%. Data were recorded in the 1344-1370 cm(-1) range (around 7.35 mu m) with a spectral resolving power of 80 000 and a spatial resolution of about 1.5 arcsec. In this spectral range, the emission of Venus comes from above the cloud top (z = 60-80 km). Four HDO lines and tens of SO2 lines have been identified in our spectra. Mixing ratios have been estimated from HDO/CO2 and SO2/CO2 line depth ratios, using weak neighboring transitions of comparable depths. The HDO maps, recorded on Jan. 10 and Jan. 12, are globally uniform with no significant variation between the two dates. A slight enhancement of the HDO mixing ratio toward the limb might be interpreted as a possible increase of the D/H ratio with height above the cloud level. The mean H2O mixing ratio is found to be 1.5 +/-0.75 ppm, assuming a D/H ratio of 0.0312 (i.e. 200 times the terrestrial value) over the cloud deck. The SO2 maps, recorded each night from Jan. 10 to Jan. 12, show strong variations over the disk of Venus, by a factor as high as 5 to 10. In addition, the position of the maximum SO2 mixing ratio strongly varies on a timescale of 24 h. The maximum SO2 mixing ratio ranges between 75 +/-25 ppb and 125 +/-50 ppb between Jan. 10 and Jan. 12. The high variability of sulfur dioxide is probably a consequence of its very short photochemical lifetime.NASA NNX-08AE38A, NNX08AW33G S03NSF AST-0607312, AST-0708074Astronom
The eight micron band of silicon monoxide in the expanding cloud around VY Canis Majoris
Observations of vibration-rotation transitions of silicon monoxide in VY CMa show that the lines originate in accelerating, expanding, and cool (600 K) layers of a circumstellar cloud at a distance of roughly 0.15 minutes from the central star. The central stellar velocity, as estimated from observed SiO P Cygni line profiles, is somewhat redshifted from the midpoint of the maser emission features. Most of the silicon is probably in the form of dust grains. The isotopic ratios of silicon are nearly terrestrial
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