This week on HST


HST Programs: June 23 - June 29, 2014

Program Number Principal Investigator Program Title
12965 David Ehrenreich, Observatoire de Geneve Properties and dynamics of the upper atmosphere of the hot-Neptune GJ 436b
13111 Robin Barnard, Smithsonian Institution Astrophysical Observatory Monitoring M31 for BHXNe
13282 You-Hua Chu, University of Illinois at Urbana - Champaign A Search for Surviving Companions of Type Ia Supernovae in the Large Magellanic Cloud
13297 Giampaolo Piotto, Universita degli Studi di Padova The HST Legacy Survey of Galactic Globular Clusters: Shedding UV Light on Their Populations and Formation
13302 J. Michael Shull, University of Colorado at Boulder COS Spectra of High-Redshift AGN: Probing Deep into the Rest-Frame Ionizing Continuum and Broad Emission Lines
13309 Yicheng Guo, University of California - Santa Cruz UV Snapshot of Low-redshift Massive Star-forming Galaxies: Searching for the Analogs of High-redshift Clumpy Galaxies
13314 Sanchayeeta Borthakur, The Johns Hopkins University Characterizing the Elusive Intragroup Medium and Its Role in Galaxy Evolution
13315 Marc W. Buie, Southwest Research Institute Pluto Satellite Orbits in Support of New Horizons
13324 Davor Krajnovic, Astrophysikalisches Institut Potsdam Where cores are no more: assessing the role of dissipation in the assembly of early-type galaxies
13330 Bradley M Peterson, The Ohio State University Mapping the AGN Broad Line Region by Reverberation
13331 Laurent Pueyo, Space Telescope Science Institute Confirmation and characterization of young planetary companions hidden in the HST NICMOS archive
13352 Matthew A. Malkan, University of California - Los Angeles WFC3 Infrared Spectroscopic Parallel Survey WISP: A Survey of Star Formation Across Cosmic Time
13356 Ian McGreer, University of Arizona A Candidate Gravitationally Lensed Quasar at z=6.09
13367 Megan Donahue, Michigan State University UV Line Emission from Million Degree Gas in a Galaxy Cluster Core
13369 Nancy R. Evans, Smithsonian Institution Astrophysical Observatory The Dynamical Mass of Polaris, the Nearest Cepheid
13386 Steven A. Rodney, The Johns Hopkins University Frontier Field Supernova Search
13394 David R. Zurek, American Museum of Natural History Spectroscopic confirmation of the first symbiotic star in a globular cluster
13409 Richard Mushotzky, University of Maryland Hubble Observations of Kepler-Monitored Seyfert Is
13412 Tim Schrabback, Universitat Bonn, Argelander Institute for Astronomy An ACS Snapshot Survey of the Most Massive Distant Galaxy Clusters in the South Pole Telescope Sunyaev-Zel'dovich Survey
13415 David Syphers, University of Colorado at Boulder The First Study of the Quasar Broad Line Region in the <550A Extreme UV
13429 Margherita Giustini, European Space Agency - ESTEC Unveiling the X-ray/UV Connection in AGN Winds: the PG 1126-041 Case Study
13467 Jacob L. Bean, University of Chicago Follow The Water: The Ultimate WFC3 Exoplanet Atmosphere Survey
13495 Jennifer Lotz, Space Telescope Science Institute HST Frontier Fields - Observations of Abell 2744
13513 Julia Comerford, University of Colorado at Boulder A Pilot Search for Spatially Offset AGN in Galaxy Merger Remnants
13515 Breanna Binder, University of Washington The Effect of Intermediate-Luminosity Transients on the X-ray Luminosity Functions of Spiral Disks
13517 Matthew A. Malkan, University of California - Los Angeles WFC3 Infrared Spectroscopic Parallel Survey WISP: A Survey of Star Formation Across Cosmic Time
13613 C. S. Kochanek, The Ohio State University Dust to Dust: Monitoring the Evolution of the New Class of Self-Obscured Transients
13633 John R. Spencer, Southwest Research Institute A Kuiper Belt Object for the New Horizons Mission

Selected highlights

GO 12965:Properties and dynamics of the upper atmosphere of the hot-Neptune GJ 436b


Artist's impression of the exo-Neptune in orbit around Gliese 436
Gliese 436 is an early-type M dwarf (spectral type M2.5) with a mass approximately 40% that of the Sun lying at a distance of ~10 parsecs. In August 2004, the Lick/Carnegie planet search team (led by Geoff Marcy and Paul Butler) announced the discovery of a ~22 Earth-mass planet in a 2.64 day orbit around this star. Unlike most "hot jupiters", this "hot Neptune", one of the first such objects discovered, is on an elliptical orbit, e=0.16, which, with a semi-major axis of 0.0278 AU, brings it within 3.5 million kilometres of the central star. Gl 436 is significantly cooler than the Sun, with a surface temperature close to ~3400 degrees Kelvin; even so, the "surface" temperatures on Gl 436b are expected to reach ~740 K (~370 C). In May of 2007, a team led by F. Pont demonstrated that Gl 436b transits the parent star. The initial ground-based observations allowed them to derive a diameter approximately 4 times that of Earth, directly comparable with Uranus and Neptune. Follow-up observations with NICMOS and FGS on HST and with IRAC on Spitzer refined the radius measurement to 4.9 Earth radii. This provides key insight into the likely origins of Gl 436b, since combining the diameter with the measured mass gives the mean density, and, by inference, the likely composition. For Gl 436b, the indications are that the planet is a displaced "ice giant". The present program aims to probe the atmospheric structure by using STIS to searching for Lyman alpha absorption that might be the signature of evaporation driven by stellar irradiation.

GO 13315: Pluto Satellite Orbits in Support of New Horizons


Hubble Space Telescope images of the Pluto system, including the recently discovered moons, P4 and P5
Pluto, one of the largest members of the Kuiper Belt and, until recently, the outermost planet in the solar system, has been in the news over the last year or two. Besides the extended "planet"/"dwarf planet" debate, Pluto is the primary target of the New Horizons Mission. In 1978, James Christy discovered from analyses of photographic plates that Pluto has a relatively large companion moon, Charon, with a diameter of ~1200 km, or almost half that of Pluto itself. In 2005, Hubble observations led to the discovery of two small moons, christened Nix and Hydra. These two new moons are 5,000 fainter than Pluto itself, implying diameters as small as ~30-50 km if the surface composition is similar to Pluto itself. Over the past two years, a series of observations were taken in support of the New Horizons mission, using WFC3 to search for faint rings due to dust particles that might jeopardise the space craft and require a course correction. While no rings were detected unequivocally, two small satellite, christened "P4" and "P5", have been discovered. Both are significantly fainter than Nix and Hydra, and may well be as small as 10-13 km in size. There is also some evidence that might point to the presence of a debris ring within Charon's orbit. The present observations, again in support of New Horizons, will use WFC3 to push to fainter magnitudes to both better characterise the P4 and P5 orbits and search for even fainter moons.

GO 13467: Follow The Water: The Ultimate WFC3 Exoplanet Atmosphere Survey


Probing the atmosphere of a transiting exoplanet
The first exoplanet, 51 Peg b, was discovered in 1995 through high-precision radial velocity measurements. 51 Pegb was followed by a trickle, and then a flood of other discoveries, as astronomers realised that there were other solar systems radically different from our own, where "hot jupiters" led to short-period, high-amplitude velocity variations. Then, in 1999, came the inevitable discovery that one of those hot jupiters. HD 209458b, was in an orbit aligned with our line of sight to the star, resulting in transits. Since that date, the number of known transiting exoplanet systems has grown to more than 400 in over 300 planetary systems, with the overwhelming majority identified by the Kepler satellite, which has also contributed close to 3,000 additional (very strong) candidates. As these observations have accumulated,the broad diversity of exoplanet systems has become increasingly apparent. Transiting systems are invaluable, since they provide not only unambiguous measurements of mass and diameter, but also an opportunity to probe the atmospheric structure by differencing spectra taken during and between primary secondary transit. Such observations are best done from space: indeed, while high-precision ground-based observations have succeeded in constraining atmospheric properties in a few systems, the only successful detections of atmospheric features to date have been with HST and Spitzer. HST capabilities have been enhanced in the last few years with addition of spatial scanning, moving the target star over the chip in a controlled fashion during an observation. This allows observers to accumulate images or spectra of substantially higher signal-to-noise, a crucial advantage if one is looking for flux differences of elss than 1 part in 104. Past programs have accumulated observations of over a dozen exoplanets, using STIS at optical wavelengths and WFC3 in the near-infrared. The present program targets eight exoplanet systems with a diverse range of properties: HD 209458b,GL 3470b, HAT-P-26b, WASP-12b, WASP-18b, WASP-43b, WASP-80b and WASP-19b. The WFC3-IR G141 grism will be used to search for the characteristic near-infrared spectral features due to water in the amospheres of these exoplanets.

GO 13517: WISP - A Survey of Star Formation Across Cosmic Time


A region of massive star formation
Star formation is the key astrophysical process in determining the overall evolution of galactic systems, the generation of heavy elements, and the overall enrichment of interstellar and intergalactic material. Tracing the overall evolution through a wide redshift range is crucial to understanding how gas and stars evolved to form the galaxies that we see around us now. The present program builds on the ability of HST to carry out parallel observations, using more than one instrument. While the Cosmic Origins Spectrograph is focused on obtaining ultraviolet spectra of unparalleled signal-to-noise, this program uses the near-infrared grisms mounted on the Wide-Field Camera 3 infrared channel to obtain low resolution spectra between 1 and 1.6 microns of randomly-selected nearby fields. The goal is to search for emission lines characteristic of star-forming regions. In particular, these observations are capable of detecting Lyman-alpha emission generated by star formation at redshifts z > 5.6. A total of up to 40 "deep" (4-5 orbit) and 20 "shallow" (2-3 orbit) fields will be targeted in the course of this observing campaign.

Past weeks:
page by Neill Reid, updated 18/5/2014
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