Status Report

NASA Hubble Space Telescope Daily Report # 4457

By SpaceRef Editor
September 28, 2007
Filed under , ,
NASA Hubble Space Telescope Daily Report # 4457

Notice: Due to the conversion of some ACS WFC or HRC observations into WFPC2, or NICMOS observations after the loss of ACS CCD science capability in January, there may be an occasional discrepancy between a proposal’s listed (and correct) instrument usage and the abstract that follows it.


– Continuing to collect World Class Science

PERIOD COVERED: UT September 27, 2007 (DOY 270)


WFPC2 10909

Exploring the diversity of cosmic explosions: The supernovae of gamma-ray bursts

While the connection between gamma-ray bursts {GRBs} and supernovae {SNe} is now clearly established, there is a large variety of observational properties among these SNe and the physical parameters of these explosions are poorly known. As part of a comprehensive program, we propose to use HST in order to obtain basic information about the supernovae associated with gamma-ray bursts. HST offers the means to cleanly separate the light curves of the GRB afterglow from the supernova, and to remove the contamination from the host galaxy, opening a clear route to the fundamental parameters of the SN. From these observations, we will determine the absolute magnitude at maximum, the shape of the spectral energy distribution, and any change over time of the energy distribution. We will also measure the rate of decay of the exponential tail. Merged with the ground-based data that we will obtain for each event, we will be able to compare our data set to models and constrain the energy of the explosion, the mass of the ejecta and the mass of Nickel synthesized during the explosion. These results will shed light on the apparent variety of supernovae associated with gamma-ray bursts and X-ray flashes, and on the relation between these SNe and other, more common varieties of core-collapse explosions.

FGS 10930

Mass and Radius of a Near-Chandrasekhar-limit magnetic white dwarf

REJ0317-853 is a unique object. According to our analyses it is the most massive white dwarf ever found, with a mass of 1.35 solar masses, approaching the Chandrasekhar limit. With a period of just 725 seconds it is the most rapidly rotating isolated white dwarf ever found. Moreover, RE J0317-853 is the hottest magnetic white dwarf discovered so far and has a strong magnetic field varying from about 180 to more than 700 MG over the stellar surface. Due to its strong polarization and high mass it has been used to test gravitational theories predicting gravitational birefringence. However, the existing mass and radius determination is indirect and still uncertain and would greatly profit from a high-precision parallax determination with the HST FGS.

NIC1/NIC2/NIC3 8795

NICMOS Post-SAA calibration – CR Persistence Part 6

A new procedure proposed to alleviate the CR-persistence problem of NICMOS. Dark frames will be obtained immediately upon exiting the SAA contour 23, and every time a NICMOS exposure is scheduled within 50 minutes of coming out of the SAA. The darks will be obtained in parallel in all three NICMOS Cameras. The POST-SAA darks will be non- standard reference files available to users with a USEAFTER date/time mark. The keyword ‘USEAFTER=date/time’ will also be added to the header of each POST-SAA DARK frame. The keyword must be populated with the time, in addition to the date, because HST crosses the SAA ~8 times per day so each POST-SAA DARK will need to have the appropriate time specified, for users to identify the ones they need. Both the raw and processed images will be archived as POST-SAA DARKSs. Generally we expect that all NICMOS science/calibration observations started within 50 minutes of leaving an SAA will need such maps to remove the CR persistence from the science i mages. Each observation will need its own CRMAP, as different SAA passages leave different imprints on the NICMOS detectors.

WFPC2 11033

Full Moon Earth Flats Closeout

Flat field exposures will be obtained by observing the moonlit Earth with the broadband WFPC2 filters F606W and F814W, which saturate in the minimum exposure time on the sunlit Earth. These observations will be used to improve the flats currently in the pipeline and are part of the WFPC2 closeout operations. Because CTE effects are large for star flats and small for full field illumination, Earth flats are the superior technique.

WFPC2 11202

The Structure of Early-type Galaxies: 0.1-100 Effective Radii

The structure, formation and evolution of early-type galaxies is still largely an open problem in cosmology: how does the Universe evolve from large linear scales dominated by dark matter to the highly non-linear scales of galaxies, where baryons and dark matter both play important, interacting, roles? To understand the complex physical processes involved in their formation scenario, and why they have the tight scaling relations that we observe today {e.g. the Fundamental Plane}, it is critically important not only to understand their stellar structure, but also their dark-matter distribution from the smallest to the largest scales. Over the last three years the SLACS collaboration has developed a toolbox to tackle these issues in a unique and encompassing way by combining new non-parametric strong lensing techniques, stellar dynamics, and most recently weak gravitational lensing, with high-quality Hubble Space Telescope imaging and VLT/Keck spectroscopic data of early-type lens systems. This allows us to break degeneracies that are inherent to each of these techniques separately and probe the mass structure of early-type galaxies from 0.1 to 100 effective radii. The large dynamic range to which lensing is sensitive allows us both to probe the clumpy substructure of these galaxies, as well as their low-density outer haloes. These methods have convincingly been demonstrated, by our team, using smaller pilot-samples of SLACS lens systems with HST data. In this proposal, we request observing time with WFPC2 and NICMOS to observe 53 strong lens systems from SLACS, to obtain complete multi-color imaging for each system. This would bring the total number of SLACS lens systems to 87 with completed HST imaging and effectively doubles the known number of galaxy-scale strong lenses. The deep HST images enable us to fully exploit our new techniques, beat down low-number statistics, and probe the structure and evolution of early-type galaxies, not only with a uniform data-set an order of magnitude larger than what is available now, but also with a fully coherent and self-consistent methodological approach!


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

HSTARS: (None)



                         SCHEDULED      SUCCESSFUL 
FGS GSacq                 03                 03 
FGS REacq                 11                  11 
OBAD with Maneuver        28                  28 


SpaceRef staff editor.