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The 3.6-8.0 μm Broadband Emission Spectrum of HD 209458b: Evidence for an Atmospheric Temperature Inversion
We estimate the strength of the bandpass-integrated thermal emissionfrom the extrasolar planet HD 209458b at 3.6, 4.5, 5.8, and 8.0 μmusing the Infrared Array Camera (IRAC) on the Spitzer Space Telescope.We observe a single secondary eclipse simultaneously in all fourbandpasses and find relative eclipse depths of 0.00094+/-0.00009,0.00213+/-0.00015, 0.00301+/-0.00043, and 0.00240+/-0.00026,respectively. These eclipse depths reveal that the shape of the inferredemission spectrum for the planet differs significantly from thepredictions of standard atmosphere models; instead, the most plausibleexplanation would require the presence of an inversion layer high in theatmosphere leading to significant water emission in the 4.5 and 5.8μm bandpasses. This is the first clear indication of such atemperature inversion in the atmosphere of a hot Jupiter, as previousobservations of other planets appeared to be in reasonably goodagreement with the predictions of models without such an inversionlayer.
| XO-2b: Transiting Hot Jupiter in a Metal-rich Common Proper Motion Binary
We report on a V=11.2 early K dwarf, XO-2 (GSC 03413-00005), that hostsa Rp=0.98+/-0.030.01 RJ,Mp=0.57+/-0.06 MJ transiting extrasolar planet,XO-2b, with an orbital period of 2.615857+/-0.000005 days. XO-2 has highmetallicity, [Fe/H]=0.45+/-0.02, high proper motion,μtot=157 mas yr-1, and a common proper motionstellar companion with 31" separation. The two stars are nearlyidentical twins, with very similar spectra and apparent magnitudes. Dueto the high metallicity, these early K dwarf stars have a mass andradius close to solar, M*=0.98+/-0.02 Msolar andR*=0.97+/-0.020.01 Rsolar.The high proper motion of XO-2 results from an eccentric orbit (Galacticpericenter, Rper<4 kpc) well confined to the Galactic disk(Zmax~100 pc). In addition, the phase-space position of XO-2is near the Hercules dynamical stream, which points to an origin of XO-2in the metal-rich, inner thin disk and subsequent dynamical scatteringinto the solar neighborhood. We describe an efficient Markov chain MonteCarlo algorithm for calculating the Bayesian posterior probability ofthe system parameters from a transit light curve.
| A Catalog of Northern Stars with Annual Proper Motions Larger than 0.15" (LSPM-NORTH Catalog)
The LSPM catalog is a comprehensive list of 61,977 stars north of theJ2000 celestial equator that have proper motions larger than 0.15"yr-1 (local-background-stars frame). The catalog has beengenerated primarily as a result of our systematic search for high propermotion stars in the Digitized Sky Surveys using our SUPERBLINK software.At brighter magnitudes, the catalog incorporates stars and data from theTycho-2 Catalogue and also, to a lesser extent, from the All-SkyCompiled Catalogue of 2.5 million stars. The LSPM catalog considerablyexpands over the old Luyten (Luyten Half-Second [LHS] and New LuytenTwo-Tenths [NLTT]) catalogs, superseding them for northern declinations.Positions are given with an accuracy of <~100 mas at the 2000.0epoch, and absolute proper motions are given with an accuracy of ~8 masyr-1. Corrections to the local-background-stars propermotions have been calculated, and absolute proper motions in theextragalactic frame are given. Whenever available, we also give opticalBT and VT magnitudes (from Tycho-2, ASCC-2.5),photographic BJ, RF, and IN magnitudes(from USNO-B1 catalog), and infrared J, H, and Ks magnitudes(from 2MASS). We also provide an estimated V magnitude and V-J color fornearly all catalog entries, useful for initial classification of thestars. The catalog is estimated to be over 99% complete at high Galacticlatitudes (|b|>15deg) and over 90% complete at lowGalactic latitudes (|b|>15deg), down to a magnitudeV=19.0, and has a limiting magnitude V=21.0. All the northern starslisted in the LHS and NLTT catalogs have been reidentified, and theirpositions, proper motions, and magnitudes reevaluated. The catalog alsolists a large number of completely new objects, which promise to expandvery significantly the census of red dwarfs, subdwarfs, and white dwarfsin the vicinity of the Sun.Based on data mining of the Digitized Sky Surveys (DSSs), developed andoperated by the Catalogs and Surveys Branch of the Space TelescopeScience Institute (STScI), Baltimore.Developed with support from the National Science Foundation (NSF), aspart of the NASA/NSF NStars program.
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