This week on HST

HST Programs: February 4 - February 10, 2013

Program Number Principal Investigator Program Title
12473 David Kent Sing, University of Exeter An Optical Transmission Spectral Survey of hot-Jupiter Exoplanetary Atmospheres
12474 Boris T. Gaensicke, The University of Warwick The frequency and chemical composition of rocky planetary debris around young white dwarfs
12506 Adam L. Kraus, University of Hawaii A Precise Mass-Luminosity-Temperature Relation for Young Stars
12562 Geoffrey C. Clayton, Louisiana State University and A & M College The UV Interstellar Extinction Properties in the Super-Solar Metallicity Galaxy M31
12568 Matthew A. Malkan, University of California - Los Angeles WFC3 Infrared Spectroscopic Parallel Survey WISP: A Survey of Star Formation Across Cosmic Time
12572 Michele Trenti, University of Cambridge The Brightest of Reionizing Galaxies Pure Parallel Survey
12590 Casey Papovich, Texas A & M University Galaxy Assembly at High Densities: HST Dissection of a Cluster at z=1.62
12790 Marc Postman, Space Telescope Science Institute Through a Lens, Darkly - New Constraints on the Fundamental Components of the Cosmos
12815 Kevin Luhman, The Pennsylvania State University Photometry of the Coldest Benchmark Brown Dwarf
12861 Xiaohui Fan, University of Arizona Morphologies of the Most UV luminous Lyman Break Galaxies at z~3
12870 Boris T. Gaensicke, The University of Warwick The mass and temperature distribution of accreting white dwarfs
12876 Kevin France, University of Colorado at Boulder Project WHIPS {Warm H2 In Protoplanetary Systems}: Direct Measurement of Molecular Abundances in Circumstellar Disks
12879 Adam Riess, The Johns Hopkins University A 1% Measurement of the Distance Scale with Perpendicular Spatial Scanning
12880 Adam Riess, The Johns Hopkins University The Hubble Constant: Completing HST's Legacy with WFC3
12891 Keith S. Noll, NASA Goddard Space Flight Center Search For Binaries Among Ultra-Slow Rotating Trojans, Hildas, and Outer Main Belt Asteroids
12893 Ronald L Gilliland, The Pennsylvania State University Study of Small and Cool Kepler Planet Candidates with High Resolution Imaging
12896 Kim-Vy Tran, Texas A & M University At the Turn of the Tide: WFC3/IR Imaging and Spectroscopy of Two Galaxy Clusters at z~2
12902 Matthew A. Malkan, University of California - Los Angeles WFC3 Infrared Spectroscopic Parallel Survey WISP: A Survey of Star Formation Across Cosmic Time
12941 Ian William Stephens, University of Illinois at Urbana - Champaign Probing Isolated Massive Star Formation in the LMC
12949 Daniel Perley, California Institute of Technology Unveiling the Dusty Universe with the Host Galaxies of Obscured GRBs
12970 Michael C. Cushing, University of Toledo Completing the Census of Ultracool Brown Dwarfs in the Solar Neighborhood using HST/WFC3
12980 Kohji Tsumura, ISAS, Japan Aerospace Exploration Agency Absolute Measurement of the Cosmic Near-Infrared Background Using Eclipsed Galilean Satellites as Occulters
12982 Nicolas Lehner, University of Notre Dame Are the Milky Way's High Velocity Clouds Fuel for Star Formation or for the Galactic Corona?
12987 Saul A Rappaport, Eureka Scientific Inc. Possible Disintegrating Short-Period Super-Mercury Orbiting KIC 12557548
12995 Christopher Johns-Krull, Rice University Testing Disk Locking in the Orion Nebula Cluster
12998 Deborah Padgett, NASA Goddard Space Flight Center STIS Coronagraphy of Bright New Debris Disks from the WISE All-Sky Survey
13007 Lee Armus, California Institute of Technology UV Imaging of Luminous Infrared Galaxies in the GOALS Sample
13010 Fabio Bresolin, University of Hawaii A precise calibration of the zero point of the cosmic distance scale from late-type eclipsing binaries in the LMC
13019 Edward F. Guinan, Villanova University Probing the Complicated Atmospheres of Cepheids with HST-COS: Plasma Dynamics, Shock Energetics and Heating Mechanisms
13023 Marco Chiaberge, Space Telescope Science Institute - ESA Universe in transition: powerful activity in the Bright Ages
13025 Andrew J. Levan, The University of Warwick Unveiling the progenitors of the most luminous supernovae
13046 Robert P. Kirshner, Harvard University RAISIN: Tracers of cosmic expansion with SN IA in the IR
13050 Remco van den Bosch, Max-Planck-Institut fur Astronomie, Heidelberg The Most Massive Black Holes in Small Galaxies
13057 Kailash C. Sahu, Space Telescope Science Institute Detecting and Measuring the Masses of Isolated Black Holes and Neutron Stars through Astrometric Microlensing
13064 David Ehrenreich, Observatoire de Geneve Investigating the nature of GJ 3470b, the missing link between super-Earths and Neptunes
13178 J. Davy Kirkpatrick, California Institute of Technology Spitzer Trigonometric Parallaxes of the Solar Neighborhood's Coldest Brown Dwarfs
13181 Robert P. Kirshner, Harvard University SN 1987A-- Bridging the Gap for HST's Legacy

Selected highlights

GO 12506:A Precise Mass-Luminosity-Temperature Relation for Young Stars

Artist's impression of the young, low-mass binary system, Coku Tau4
Mass, luminosity and temperature are the three of the five fundamental quantities that we'd like to know for every star (the other two are chemical composition and age, with age being the least accessible to direct measurement). Binary systems offer one of the most effective means of determining the former three parameters, where measurements of the orbital period and velocity variation permit direct determination of the system mass and, by scaling against angular measurements for visual binaries. the distance. Given the luminosity and temperature, the individual stellar radii can also be derived. These quantities are particularly useful in constraining models of young stars. The present program focuses on observations 16 low-mass systems in nearby star-forming regions. All 16 have orbital determinations, derived from AO-assisted K-band ground-based imaging. the WFC3-UVIS camera will be used to obtain multi-colour imaging, providing measurements of the spectral energy distributions of the individual components in each system, and hence estimates of the surface temperatures.

GO12949: Unveiling the Dusty Universe with the Host Galaxies of Obscured GRBs

Artist's impression of a gamma-ray burst
Gamma ray bursts are events that tap extraordinary energies (1045 to 1047 joules) in remarkably short periods of time. Several thousands bursts have been detected over the last 30+ years, and analyses indicate that they can be divided into two classes with durations longer or shorter than 2 seconds. The short bursts appear to release more high energy radiation, so the two subsets are known as long/soft and short/hard bursts.The short/hard bursts appear to arise from coalescing binary systems (probably pairs of neutron stars or black holes), but the long/soft bursts appear to originate in the collapse of very massive stars. The latter sources are therefore almost certainly associated with star formation, so they act as signposts to active star-forming regions in the high redshift universe. Recent observations have revealed the presence of a subset of highly-obscured long-duration GRBs, which are believed to be associated with galaxies that are both significantly more metal-rich and dustier than the canonical long-duration GRB hosts. The present program aims to combine HST and Spitzer measurements of a sample of 18 such objects, obtaining deep images with the WFC3-IR camera in the F160W filter, potentially supplemented by data in F105W, F110W or F125W, to add to the Spitzer mid-IR imaging. The goal is to better understand the environment and stellar populations in these dusty host galaxies.

GO 12970: Completing the Census of Ultracool Brown Dwarfs in the Solar Neighborhood using HST/WFC3

The stellar menagerie: Sun to Jupiter, via brown dwarfs
Brown dwarfs are objects that form in the same manner as stars, by gravitational collapse within molecular clouds, but which do not accrete sufficient mass to raise the central temperature above ~2 million Kelvin and ignite hydrogen fusion. As a result, these objects, which have masses less than 0.075 MSun or ~75 M<\sub>Jup, lack a sustained source of energy, and they fade and cool on relatively short astronomical (albeit, long anthropological) timescales. Following their discovery over a decade ago, considerable observational and theoretical attention has focused on the evolution of their intrinsic properties, particularly the details of the atmospheric changes. At their formation, most brown dwarfs have temperatures of ~3,000 to 3,500K, comparable with early-type M dwarfs, but they rapidly cool, with the rate of cooling increasing with decreasing mass. As temperatures drop below ~2,000K, dust condenses within the atmosphere, molecular bands of titanium oxide and vanadium oxide disappear from the spectrum to be replaced by metal hydrides, and the objects are characterised as spectral type L. Below 1,300K, strong methane bands appear in the near-infrared, characteristics of spectral type T. At present, the coolest T dwarfs known have temperatures of ~650 to 700K. At lower temperatures, other species, notably ammonia, are expected to become prominent, and a number of efforts have been undertaken recently to find examples of these "Y" dwarfs. The search is complicated by the fact that such objects are extremely faint instrinsically, so only the nearest will be detectable. Identifying such ultra-ultracool dwarfs was a goal of the WISE satellite mission, which recently completed its all-sky survey. WISE has succeeded in identifying a number of extremely interesting sources, including at least 4 objects that have been confirmed as dwarfs with temperatures lower than 350K. These are among the first examples of Y dwarfs, and all are too faint to be characterised with any degree of certainty using ground-based observations. The current program will use WFC3 G102 grism spectroscopy to verify the nature of a further 20 candidates.

GO Investigating the nature of GJ 3470b, the missing link between super-Earths and Neptunes

Artist's impression of an Earthlike world around an M dwarf
M dwarfs are the most common stars in the galaxy and, with the continued accumulation of observations showing that the presence of planetary companions, they are also likely to the best candidates for finding nearby habitable planets. GJ 3470 is an early type M dwarf (spectral type M1.5) a mass approximately half that of the Sun lying at a distance of 25 parsecs lying in the constellation of Cancer. Early last year (February-April, 2012), the HARPS planet search team announced the discovery of a ~14 MEarth planetary companion with a 3.3371 day period orbit, corresponding to a semi-major axis of 0.035 Astronomical units, or 10% the size of Mercury's orbit. The radial velocity semi-amplitude is less than 10 m/sec. Crucially, the planet transits the parent star, allowing its diameter to be measured as 4.2 Earth radii. With these parameters, the companion is more comparable with Uranus than with the "hot Neptune" systems like Gl 436b (a ~22 Earth-mass planet in a 2.64 day, 0.0278 AU orbit around the M2 dwarf, ~10 parsecs distant). Those parameters indicate a relatively low density, suggestive of a thick hydrogen/helium atmosphere and/or substantial water-ice content. The present program aims to obtain transit spectroscopy using the G141 grating on the WFC3-IR camera. The observations cover significant water features, whose detection might indicate that the former model is correct, and whose non-detection might argue for a water-rich interior content or high altitude hazes within the atmosphere.

Past weeks:
page by Neill Reid, updated 14/10/2012
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