1,172 research outputs found
A Parallactic Distance of 389 +24/-21 parsecs to the Orion Nebula Cluster from Very Long Baseline Array Observations
We determine the parallax and proper motion of the flaring, non-thermal radio
star GMR A, a member of the Orion Nebula Cluster, using Very Long Baseline
Array observations. Based on the parallax, we measure a distance of 389 +24/-21
parsecs to the source. Our measurement places the Orion Nebula Cluster
considerably closer than the canonical distance of 480 +/- 80 parsecs
determined by Genzel et al. (1981). A change of this magnitude in distance
lowers the luminosities of the stars in the cluster by a factor of ~ 1.5. We
briefly discuss two effects of this change--an increase in the age spread of
the pre-main sequence stars and better agreement between the zero-age
main-sequence and the temperatures and luminosities of massive stars.Comment: 10 pages, 4 figures, emulateapj, accepted to Ap
Mapping Hydrogen in the Galaxy, Galactic Halo, and Local Group with ALFA: The GALFA-HI Survey Starting with TOGS
Radio observations of gas in the Milky Way and Local Group are vital for
understanding how galaxies function as systems. The unique sensitivity of
Arecibo's 305m dish, coupled with the 7-beam Arecibo L-Band Feed Array (ALFA),
provides an unparalleled tool for investigating the full range of interstellar
phenomena traced by the HI 21cm line. The GALFA (Galactic ALFA) HI Survey is
mapping the entire Arecibo sky over a velocity range of -700 to +700 km/s with
0.2 km/s velocity channels and an angular resolution of 3.4 arcminutes. We
present highlights from the TOGS (Turn on GALFA Survey) portion of GALFA-HI,
which is covering thousands of square degrees in commensal drift scan
observations with the ALFALFA and AGES extragalactic ALFA surveys. This work is
supported in part by the National Astronomy and Ionosphere Center, operated by
Cornell University under cooperative agreement with the National Science
Foundation.Comment: 3 pages, including 2 figure pages; figure image quality significantly
reduced; for full resolution version, please see
http://www.naic.edu/~gibson/cv/ao08_writeup.pdf ; to be published in AIP
conference proceedings for ``The Evolution of Galaxies through the Neutral
Hydrogen Window'', eds. R. Minchin & E. Momjia
The GALFA-HI Compact Cloud Catalog
We present a catalog of 1964 isolated, compact neutral hydrogen clouds from
the Galactic Arecibo L-Band Feed Array Survey Data Release One (GALFA-HI DR1).
The clouds were identified by a custom machine-vision algorithm utilizing
Difference of Gaussian kernels to search for clouds smaller than 20'. The
clouds have velocities typically between |VLSR| = 20-400 km/s, linewidths of
2.5-35 km/s, and column densities ranging from 1 - 35 x 10^18 cm^-2. The
distances to the clouds in this catalog may cover several orders of magnitude,
so the masses may range from less than a Solar mass for clouds within the
Galactic disc, to greater than 10^4 Solar Masses for HVCs at the tip of the
Magellanic Stream. To search for trends, we separate the catalog into five
populations based on position, velocity, and linewidth: high velocity clouds
(HVCs); galaxy candidates; cold low velocity clouds (LVCs); warm, low
positive-velocity clouds in the third Galactic Quadrant; and the remaining warm
LVCs. The observed HVCs are found to be associated with previously-identified
HVC complexes. We do not observe a large population of isolated clouds at high
velocities as some models predict. We see evidence for distinct histories at
low velocities in detecting populations of clouds corotating with the Galactic
disc and a set of clouds that is not corotating.Comment: 34 Pages, 9 Figures, published in ApJ (2012, ApJ, 758, 44), this
version has the corrected fluxes and corresponding flux histogram and masse
An Accurate Distance to High-Velocity Cloud Complex C
We report an accurate distance of d = 10+/-2.5kpc to the high-velocity cloud
Complex C. Using high signal-to-noise Keck/HIRES spectra of two
horizontal-branch stars, we have detected CaII K absorption lines from the
cloud. Significant non-detections toward a further 3 stars yield robust lower
distance limits. The resulting HI mass of Complex C is 4.9^{+2.8}_{-2.2} x 10^6
Msun; a total mass of 8.2^{+4.6}_{-2.6} x 10^6 Msun is implied, after
corrections for helium and ionization. At 10kpc, Complex C has physical
dimensions 3x15 kpc, and if it is as thick as it is wide, then the average
density is log ~ -2.5. We estimate the contribution of Complex C to the mass
influx may be as high as ~0.14 Msun/yr.Comment: Resubmitted to ApJ. 8 figure
Retired A Stars and Their Companions II: Jovian planets orbiting kappa Coronae Borealis and HD167042
We report precise Doppler measurements of two evolved stars, kappa CrB
(HD142091) and HD 167042, obtained at Lick Observatory as part of our search
for planets orbiting intermediate-mass subgiants. Periodic variations in the
radial velocities of both stars reveal the presence of substellar orbital
companions. These two stars are notably massive with stellar masses of 1.80
Msun and 1.64 Msun, indicating that they are former A-type dwarfs that have
evolved off of the main sequence and are now K-type subgiants. The planet
orbiting kappa CrB has a minimum mass Msini = 1.8 Mjup, eccentricity e = 0.146
and a 1208 day period, corresponding to a semimajor axis of 2.7 AU. The planet
around HD167042 has a minimum mass Msini = 1.7 Mjup and a 412.6 day orbit,
corresponding to a semimajor axis of 1.3 AU. The eccentricity of HD167042b is
consistent with circular (e = 0.027+/-0.04), adding to the rare class of known
exoplanets in long-period, circular orbits similar to the Solar System gas
giants. Like all of the planets previously discovered around evolved A stars,
kappa CrBb and HD167042b orbit beyond 0.8 AU.Comment: 8 pages, 3 figures, 4 tables, ApJ Accepte
Transmission of a global financial crisis shock to an emerging economy
Using a unique dataset consisting of all corporate loans in Pakistan, we study the impact of the global financial crisis (GFC) on the lending ability of its banking sector. We also take into account various bank and loan types along with extensive margins, firm size effects, and impact of information asymmetry. Our findings show that the Pakistani banking sector was indeed affected by the GFC as high exposure banks, who borrow relatively more internationally, reduce lending to local firms and this impact is larger for small firms. We also find differences in the lending ability of various bank types and loan types. By using direct information asymmetry measure, we find that banks reduced lending after the global financial crisis shock. However, the information gathered from the previous relationship of the borrower with relatively low exposure banks can overcome the negative financial shock and increase lending after the shock. These findings are very relevant in the context of the spillover effects of the GFC and have important policy implications for emerging markets
Kinetic energy of solid neon by Monte Carlo with improved Trotter- and finite-size extrapolation
The kinetic energy of solid neon is calculated by a path-integral Monte Carlo
approach with a refined Trotter- and finite-size extrapolation. These accurate
data present significant quantum effects up to temperature T=20 K. They confirm
previous simulations and are consistent with recent experiments.Comment: Text and figures revised for minor corrections (4 pages, 3 figures
included by psfig
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