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Daily Report #4839
HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science
DAILY REPORT***** #4839 PERIOD COVERED: 5am April 22 - 5am April 23, 2009 (DOY ************************** 112/0900z-113/0900z) OBSERVATIONS SCHEDULED WFPC2 11975 UV Light from Old Stellar Populations: a Census of UV Sources in Galactic Globular Clusters In spite of the fact that HST has been the only operative high-resolution eye in the UV-window over the last 18 years, no homogeneous UV survey of Galactic globular clusters (GGCs) has been performed to date. In order to fill this gap in the stellar population studies, we propose a program that exploits the unique capability of the WFPC2 and the SBC in the far-/mid- UV for securing deep UV imaging of 46 GGCs. The proposed observations will allow to study with unprecedented accuracy the hottest GGC stars, comprising the extreme horizontal branch (HB) stars and their progeny (the so-called AGB-manque', and Post-early AGB stars), and "exotic stellar populations" like the blue straggler stars and the interacting binaries. The targets have been selected to properly sample the GGC metallicity/structural parameter space, thus to unveil any possible correlation between the properties of the hot stellar populations and the cluster characteristics. In addition, most of the targets have extended HB "blue tails", that can be properly studied only by means of deep UV observations, especially in the far-UV filters like the F160BW, that is not foreseen on the WFC3. This data base is complemented with GALEX observations in the cluster outermost regions, thus allowing to investigate any possible trend of the UV-bright stellar types over the entire radial extension of the clusters. Although the hottest GGC stars are just a small class of "special" objects, their study has a broad relevance in the context of structure formation and chemical evolution in the early Universe, bringing precious information on the basic star formation processes and the origin of blue light from galaxies. Indeed, the proposed observations will provide the community with an unprecedented data set suitable for addressing a number of still open astrophysical questions, ranging from the main drivers of the HB morphology and the mass loss processes, to the origin of the UV upturn in elliptical galaxies, the dating of distant systems from integrated light, and the complex interplay between stellar evolution and dynamics in dense stellar aggregates. In the spirit of constructing a community resource, we entirely waive the proprietary period for these observations. WFPC2 11979 WFPC2 Imaging of Fomalhaut b: Determining its Orbit and Testing for H-alpha Emission Fomalhaut is a bright nearby star that harbors a belt of dusty material with a morphology that has been used to predict the presence of a shepherding planet. With ACS/HRC coronagraphy, we have achieved the direct detection of a planet candidate (Fomalhaut b) in F606W and F814W. The planet candidate lies 18 AU interior to the dust belt and we detect counterclockwise orbital motion in two epochs of observations (2004 and 2006). Fomalhaut b has mass no greater than three Jupiter masses based on an analysis of its luminosity, including non-detections at infrared wavelengths, and the dynamical argument that a significantly more massive object would disrupt the dust belt. Variability at optical wavelengths and the brightness in the F606W passband suggest additional sources of luminosity such as starlight reflected from a circumplanetary ring system. A second possibility that has been invoked for substellar objects is a significant contribution of H-alpha emission. Here we propose follow-up WFPC2 observations to test the possibility that the F606W flux is contaminated by H-alpha emission. We demonstrate that the detection of Fomalhaut b using WFPC2 is feasible using roll deconvolution. Furthermore, a detection of Fomalhaut b in 2009 will provide a crucial third epoch for astrometry. With the existing two epochs of data, the orbit of Fomalhaut b cannot be determined uniquely. The third epoch will be used to test the prediction of apsidal alignment and more accurately determine the dynamical mass of Fomalhaut b. If apsidal mis-alignment is found between the planet and the belt, this result would point to the existence of still other planets lurking unseen in the Fomalhaut system. WFPC2 11983 An Imaging Survey of Protoplanetary Disks and Brown Dwarfs in the Chamaeleon I Region We propose to carry out a HST/WFPC2 survey of young brown dwarfs, Class I and Class II sources in the Chamaelon I region, one of the best-studied star-forming regions, in order to investigate the link between disk evolution and the formation of substellar-mass objects. We will use deep broad-band imaging in the I and z-equivalent HST bands to unveil the unknown population of substellar binary companions, down to a few Jupiter masses for separations of a few tens of AU. We will also perform narrow-band imaging to directly detect accreting circumstellar disks and jets around brown dwarfs, Class-I and class-II objects. Chamaelon I is nearly coeaval of Orion (~1-2Myr) but at ~1/3 its distance, allowing 3x higher resolution and 10x more flux for comparable objects. Unlike Orion, low-mass objects and protoplanetary disks in Chamaeleon I have been extensively studied with Spitzer, but not yet with the HST. The Chamaeleon I region is an ideal HST target, as it lies in the CVZ of the HST and therefore it is easily accessible any time of the year with long orbits. FLIGHT OPERATIONS SUMMARY: Significant Spacecraft Anomalies: (The following are preliminary reports of potential non-nominal performance that will be investigated.) HSTARS: 11779 - GSAcq(2,0,2) at 112/20:54:49 failed to RGA control with Search Radius Limit exceeded on FGS 2. Observations affected: WFPC 169 - 174, Proposal ID# 11979. COMPLETED OPS REQUEST: (None) COMPLETED OPS NOTES: (None) *********************** SCHEDULED***** SUCCESSFUL FGS GSAcq************** 09***************** 08 FGS REAcq************** 05***************** 05 OBAD with Maneuver **** 28***************** 27 SIGNIFICANT EVENTS: (None) |
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