Status Report

NASA Hubble Space Telescope Daily Report #4796

By SpaceRef Editor
February 25, 2009
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HUBBLE SPACE TELESCOPE DAILY REPORT #4796

Continuing to collect World Class Science

PERIOD COVERED: 5am February 20 – 5am February 23, 2009 (DOY 051/1000z-054/1000z)

OBSERVATIONS SCHEDULED

WFPC2 11991

Constraining the Late Time Lightcurve and Energy of GRB 090102

We propose to conduct a series of late time observations of the lightcurve of the bright gamma-ray burst GRB 090102. Declared a burst of interest by the Swift team, and with excellent broadband data covering the prompt emission (Swift and Fermi) and afterglow (Swift, TAROT, NOT, WHT, and several more), GRB 090102 offers a rare opportunity to probe the physics and energetics of GRBs. Its high energy budget (>2e53 ergs for isotropic emission) stretches plausible progenitor models, and as yet the signatures of jet-like emission have not been observed. Our late time observations will search for steepening of the afterglow due to lateral expansion of the jet. This will enable us, in tandem with the data already secured, to determine its total energy budget, and compare this to expectations for different progenitors models. HST is vital to this endeavour since it can reach depths essentially unattainable to ground based technology, while its invariant PSF will allow us to accurately remove underlying host contamination. Ultimately, the range and quality of data secured for this burst will enable us to accurately reconstruct the parameters of the explosion, and shed greater light on the physical processes which under lie the production of GRBs.

WFPC2 11986

Completing HST’s Local Volume Legacy

Nearby galaxies offer one of the few laboratories within which stellar populations can be tied to multi-wavelength observations. They are thus essential for calibrating and interpreting key astrophysical observables, such as broad-band luminosities, durations and energy input from starbursts, and timescales of UV, H-alpha, and FIR emission. The study of stellar populations in nearby galaxies requires high-resolution observations with HST, but HST’s legacy for this limited set of galaxies remains incomplete.

As a first attempt to establish this legacy, The ACS Nearby Galaxy Survey Treasury (ANGST) began observations in late 2006. ANGST was designed to carry out a uniform multi-color survey of a volume-limited sample of ~70 nearby galaxies that could be used for systematic studies of resolved stellar populations. The resulting data provide nuanced constraints on the processes which govern star formation and galaxy evolution, for a well-defined population of galaxies. All photometry for the survey has been publicly released.

However, the failure of ACS 4.5 months after ANGST began taking data led to a drastic reduction in the planned survey. The loss is two-fold. First, the goals of completeness and uniformity were greatly compromised, impacting global comparison studies. Second, the variety of observed star formation histories was reduced. Given that we have never found two galaxies with identical star formation histories, and fully sampling the population allows us to catch those few systems whose star formation rates and metallicities place the strongest constraints on key astrophysical processes.

Here we propose WFPC2 observations of all remaining galaxies within the Local Volume (D<3.5Mpc) for which current HST observations are insufficient for meaningful stellar population studies. We will use these observations for research on the star formation histories of individual galaxies and the Local Volume, detailed calibrations of star formation rate indicators, and the durations of starbursts. We will also make them publicly available through the ANGST archive to support future research. The proposed observations will finally complete a lasting legacy of HST

WFPC2 11978

Luminous and Dark Matter in Disk Galaxies from Strong Lensing and Stellar Kinematics

The formation of realistic disk galaxies within the LCDM paradigm is still an unsolved problem. Theory is only now beginning to make predictions for how dark matter halos respond to galaxy formation and for the properties of disk galaxies. Measuring the density profiles of dark matter halos on galaxy scales is therefore a strong test for the standard paradigm of galaxy formation, offering great potential for discovery. However, from an observational point of view, the degeneracy between the stellar and dark matter contributions to galaxy rotation curves remains a major road block. Strong gravitational lensing, when coupled to spatially-resolved kinematics and stellar population models, can solve this long-standing problem. Unfortunately, this joint methodology could not be exploited so far due to the paucity of known edge-on spiral lenses. Exploiting the full SDSS-DR7 archive we have identified a new sample of exactly these systems. We propose multi-color HST imaging to confirm and measure a sample of twenty spiral lenses, covering a range of bulge to disk ratios. By combining dynamical lensing and stellar population information for this unique sample we will deliver the first statistical constraints on halos and disk properties, and a new stringent test of disk galaxy formation theories.

FGS 11945

Asteroseismology of Extrasolar Planet Host Stars

Detections of stellar oscillations, although a very demanding task in terms of observing time, offers a return of more accurate knowledge about the structure of stars than can be obtained in any other way. In particular, detecting the 10-15 highest amplitude modes in solar-like stars to signal-to-noise of just a few sigma each allows robust constraints on the stellar density to <1%, and the stellar age to within 5-10% of its main sequence lifetime. Ten day observing runs using the FGS as a photometer on any of the 5 best transiting planet systems would enable these asteroseismology returns. From more precisely observed transit shapes than can be obtained from the ground a completely independent constraint on stellar density to ~1% can be obtained. The long observation sets required for asteroseismology also provide an excellent opportunity of detecting transits from other planets, e.g. hypothesized inner -orbit Hot Earths, should any exist.

FGS 11943/11944

Binaries at the Extremes of the H-R Diagram

We propose to use HST/Fine Guidance Sensor 1r to survey for binaries among some of the most massive, least massive, and oldest stars in our part of the Galaxy. FGS allows us to spatially resolve binary systems that are too faint for ground-based, speckle or optical long baseline interferometry, and too close to resolve with AO. We propose a SNAP-style program of single orbit FGS TRANS mode observations of very massive stars in the cluster NGC 3603, luminous blue variables, nearby low mass main sequence stars, cool subdwarf stars, and white dwarfs. These observations will help us to (1) identify systems suitable for follow up studies for mass determination, (2) study the role of binaries in stellar birth and in advanced evolutionary states, (3) explore the fundamental properties of stars near the main sequence-brown dwarf boundary, (4) understand the role of binaries for X-ray bright systems, (5) find binaries among ancient and nearby subdwarf stars, and (6) help calibrate the white dwarf mass – radius relation.

WFPC2 11797

Supplemental WFPC2 CYCLE 16 Intflat Linearity Check and Filter Rotation Anomaly Monitor

Supplemental observations to 11029, to cover period from Aug 08 to SM4. Intflat observations will be taken to provide a linearity check: the linearity test consists of a series of intflats in F555W, in each gain and each shutter. A combination of intflats, visflats, and earthflats will be used to check the repeatability of filter wheel motions. (Intflat sequences tied to decons, visits 1-18 in prop 10363, have been moved to the cycle 15 decon proposal 11022 for easier scheduling.)

Note: long-exposure WFPC2 intflats must be scheduled during ACS anneals to prevent stray light from the WFPC2 lamps from contaminating long ACS external exposures.

Note: These are supplemental observations to cover June to SM4 (Oct 8 ’08) + 6 months.

WFPC2 11796

WFPC2 Cycle 16 Decontaminations and Associated Observations

This proposal is for the WFPC2 decons. Also included are instrument monitors tied to decons: photometric stability check, focus monitor, pre- and post-decon internals (bias, intflats, kspots, & darks), UV throughput check, VISFLAT sweep, and internal UV flat check.

FGS 11788

The Architecture of Exoplanetary Systems

Are all planetary systems coplanar? Concordance cosmogony makes that prediction. It is, however, a prediction of extrasolar planetary system architecture as yet untested by direct observation for main sequence stars other than the Sun. To provide such a test, we propose to carry out FGS astrometric studies on four stars hosting seven companions. Our understanding of the planet formation process will grow as we match not only system architecture, but formed planet mass and true distance from the primary with host star characteristics for a wide variety of host stars and exoplanet masses.

We propose that a series of FGS astrometric observations with demonstrated 1 millisecond of arc per-observation precision can establish the degree of coplanarity and component true masses for four extrasolar systems: HD 202206 (brown dwarf+planet); HD 128311 (planet+planet), HD 160691 = mu Arae (planet+planet), and HD 222404AB = gamma Cephei (planet+star). In each case the companion is identified as such by assuming that the minimum mass is the actual mass. For the last target, a known stellar binary system, the companion orbit is stable only if coplanar with the AB binary orbit.

WFPC2 11590

Observing the IR Catastrophe in a Deflagration Type Ia Supernova

Our lack of understanding of Type Ia supernova (SN Ia) explosions limits our confidence in their use for cosmology. While there is broad agreement that these objects represent the explosions of white dwarfs, the details of the explosion mechanism are not well-understood. Recently, we have identified an internally homogeneous subclass of SNe Ia whose photometric and spectroscopic peculiarities make them quite distinct from normal SNe Ia. Models suggest we may be seeing the result of an explosion with a subsonic burning front, called a deflagration. We propose to test SN Ia models by obtaining late-time photometry for SN 2008A, a recent, nearby example of this subclass, using ACS and WFC3 on HST. We will accurately measure the late-time photometric decline rate and spectral energy distribution (SED). These observations will allow us to test whether the ejecta contain the large amount of oxygen predicted by certain models. We also aim to detect major evolution of the SED expected due to the “IR catastrophe, ” a change in the dominant cooling mechanism in the ejecta, as generically predicted by models but only hinted at by current observations.

WFPC2 11196

An Ultraviolet Survey of Luminous Infrared Galaxies in the Local Universe

At luminosities above 10^11.4 L_sun, the space density of far-infrared selected galaxies exceeds that of optically selected galaxies. These Luminous Infrared Galaxies {LIRGs} are primarily interacting or merging disk galaxies undergoing starbursts and creating/fueling central AGN. We propose far {ACS/SBC/F140LP} and near {WFPC2/PC/F218W} UV imaging of a sample of 27 galaxies drawn from the complete IRAS Revised Bright Galaxy Sample {RBGS} LIRGs sample and known, from our Cycle 14 B and I-band ACS imaging observations, to have significant numbers of bright {23 < B < 21 mag} star clusters in the central 30 arcsec. The HST UV data will be combined with previously obtained HST, Spitzer, and GALEX images to {i} calculate the ages of the clusters as function of merger stage, {ii} measure the amount of UV light in massive star clusters relative to diffuse regions of star formation, {iii} assess the feasibility of using the UV slope to predict the far-IR luminosity {and thus the star formation rate} both among and within IR-luminous galaxies, and {iv} provide a much needed catalog of rest- frame UV morphologies for comparison with rest-frame UV images of high-z LIRGs and Lyman Break Galaxies. These observations will achieve the resolution required to perform both detailed photometry of compact structures and spatial correlations between UV and redder wavelengths for a physical interpretation our IRX-Beta results. The HST UV data, combined with the HST ACS, Spitzer, Chandra, and GALEX observations of this sample, will result in the most comprehensive study of luminous starburst galaxies to date.

WFPC2 11013

Continued M31 Monitoring for Black Hole X-ray Nova

We have been carring out a Chandra (GO+GTO) and HST (GO) program to find Black Hole X-ray Nova (BHXN) and their optical counterparts in M31 for several years. To date we have found >2 dozen BHXN and 3 HST optical counterparts for these BHXN. Our results suggest a rather high ratio of BH to neutron star (NS) binaries, or a high duty cycle for the BHXN. We propose to continue this program, with the goal of determining the orbital period distribution and duty cycles of these BHXN. Current results yield 3 orbital periods and 3 upper limits. Our proposed observations will ~double the total number of periods and therefore yield sufficient numbers to make a first approximation of the orbital period distribution. The orbital period distribution is the fundamental observable parameter any binary stellar evolution models must match, and the duty cycle is very poorly known but directly influences the binary lifetime. M31 is the only galaxy in which this extra-galactic study of BHXN is feasible. Furthermore, the 2 HST observations will allow us to estimate the orbital period of a single super-Eddington source.

FLIGHT OPERATIONS SUMMARY:

Significant Spacecraft Anomalies: (The following are preliminary reports of potential non-nominal performance that will be investigated.)

HSTARS:

11694 – At 052/01:12:56, GSAcq (2,3,2) scheduled from 052/01:09:14 – 01:16:41 resulted in Fine Lock Back-up (2,0,2).

0bservations possibly affected: Astrometry Proposal ID# 11943

11695 – REAcq (1,2,2) at 053/18:31:22 failed to RGA control with QF1STOPF and QSTOP flags set.

Observations affected: WFPC 202 to 203, Proposal ID# 11986.

COMPLETED OPS REQUEST:

18404-0 – Uplink new FGS Alignment tables for 054 SMS @ 054/0019z

COMPLETED OPS NOTES: (None)

                        SCHEDULED      SUCCESSFUL

FGS GSacq               18                 18
FGS REacq               22                 21
OBAD with Maneuver      50                 50

SIGNIFICANT EVENTS:

The new FGS alignments were successfully uplinked tonight at the start of the 054 SMS at 2009.054/00:20. The first Guide star acquisition on the SMS was successful

SpaceRef staff editor.