NASA Hubble Space Telescope Daily Report #4317
Notice: For the foreseeable future, the daily reports may contain apparent discrepancies between some proposal descriptions and the listed instrument usage. This is due to the conversion of previously approved ACS WFC or HRC observations into WFPC2, or NICMOS observations subsequent to the loss of ACS CCD science capability in late January.
HUBBLE SPACE TELESCOPE DAILY REPORT # 4317
– Continuing to collect World Class Science PERIOD COVERED: UT March 12, 2007 (DOY 071)
OBSERVATIONS SCHEDULED
ACS/SBC 10907
Testing the first direct measurement of cataclysmic variable evolution: the search for a circumbinary disk or a low?mass companion around NN Serpentis
We obtained high time-resolution photometry using the high speed CCD camera ULTRACAM between 2002 and 2004, which revealed a gradual reduction in the orbital period of the pre- cataclysmic variable NN Serpentis. There are three possible explanations for this period change: firstly, we may have been successful in obtaining the first and only direct measurement of the braking rate of a close binary system, in which case our measured values are approximately 2 orders of magnitude greater than predicted, and pose serious problems for the theory of close binary evolution. Secondly, the unusually high braking rate may be caused by the presence of a circumbinary disk, which would help to answer two of the outstanding problems with current CV theory – namely the high mass-transfer rates seen in some CVs, and the fact that the minimum observed value in the CV period distribution is approximately 15% longer than expected. Finally, our observations could be explained by a light travel-time effect caused by a third body in orbit around the binary, which would raise major questions about the evolutionary history of the system, in particular how a third body has managed to remain in a stable orbit throughout periods of intense mass-loss in the central binary. We intend to use IRAC observations to search for a mid-infrared excess in the spectral energy distribution of NN Ser, which would confirm the presence of either a disk or a third body. We then propose to use HST imaging to attempt to resolve a third body, allowing us to discriminate between the two possibilities. If both methods fail to reveal any extra system components, we will have ruled out our only remaining alternatives to a genuinely high angular momentum loss rate in this system, with profound implications for CV evolution.
WFPC2 11024
WFPC2 CYCLE 15 INTERNAL MONITOR
This calibration proposal is the Cycle 15 routine internal monitor for WFPC2, to be run weekly to monitor the health of the cameras. A variety of internal exposures are obtained in order to provide a monitor of the integrity of the CCD camera electronics in both bays {both gain 7 and gain 15 — to test stability of gains and bias levels}, a test for quantum efficiency in the CCDs, and a monitor for possible buildup of contaminants on the CCD windows. These also provide raw data for generating annual super-bias reference files for the calibration pipeline.
FGS 10610
Astrometric Masses of Extrasolar Planets and Brown Dwarfs
We propose observations with HST/FGS to estimate the astrometric elements {perturbation orbit semi-major axis and inclination} of extra-solar planets orbiting six stars. These companions were originally detected by radial velocity techniques. We have demonstrated that FGS astrometry of even a short segment of reflex motion, when combined with extensive radial velocity information, can yield useful inclination information {McArthur et al. 2004}, allowing us to determine companion masses. Extrasolar planet masses assist in two ongoing research frontiers. First, they provide useful boundary conditions for models of planetary formation and evolution of planetary systems. Second, knowing that a star in fact has a plantary mass companion, increases the value of that system to future extrasolar planet observation missions such as SIM PlanetQuest, TPF, and GAIA.
NIC1/NIC2/NIC3 8794
NICMOS Post-SAA calibration – CR Persistence Part 5
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 images. Each observation will need its own CRMAP, as different SAA passages leave different imprints on the NICMOS detectors.
NIC2 10802
SHOES-Supernovae, HO, for the Equation of State of Dark energy
The present uncertainty in the value of the Hubble constant {resulting in an uncertainty in Omega_M} and the paucity of Type Ia supernovae at redshifts exceeding 1 are now the leading obstacles to determining the nature of dark energy. We propose a single, integrated set of observations for Cycle 15 that will provide a 40% improvement in constraints on dark energy. This program will observe known Cepheids in six reliable hosts of Type Ia supernovae with NICMOS, reducing the uncertainty in H_0 by a factor of two because of the smaller dispersion along the instability strip, the diminished extinction, and the weaker metallicity dependence in the infrared. In parallel with ACS, at the same time the NICMOS observations are underway, we will discover and follow a sample of Type Ia supernovae at z > 1. Together, these measurements, along with prior constraints from WMAP, will provide a great improvement in HST’s ability to distinguish between a static, cosmological constant and dynamical dark energy. The Hubble Space Telescope is the only instrument in the world that can make these IR measurements of Cepheids beyond the Local Group, and it is the only telescope in the world that can be used to find and follow supernovae at z > 1. Our program exploits both of these unique capabilities of HST to learn more about one of the greatest mysteries in science.
NIC3 11098
Pinning down the redshift of the J-band dropout JD0910+46
The earliest galaxies in the Universe should have formed at very high redshifts, based both on models of hierarchical structure formation, and on observations of the microwave background polarization by WMAP that require significant ionization of the intergalactic medium before z=10. However, direct observation of sources at z>7 remains highly challenging due to their scarcity and faintness. We recently identified a spatially extended J-band dropout, JD0910+46, that is a promising candidate for a z>10 galaxy. Its spectral energy distribution is more extreme than any previously reported: It is undetected in our 2- orbit J-band observation, with a very red J-H color, yet is bluer in H-K than plausible lower redshift {z~3} model SEDs. These colors are, however, natural for a very high redshift star-burst galaxy in which the Lyman-alpha break has moved mostly or entirely through the F110W band. Here we propose deeper F110W and F187W observations to better map the spectral energy distribution of JD910+46, these have the potential to convincingly reject all low redshift solutions for the origin of the observed colours. We believe the importance of such a discovery adds urgency to the followup, and motivates this DD request. Even in the event that JD0910+46 lies at lower redshift understanding the nature of the object will be of great importance since it may lie in a significant overdensity of galaxies at z~4, and will be an important tool for identifying possible interlopers in samples of ultra high-z galaxies.
WFPC2 10999
Testing the first direct measurement of cataclysmic variable evolution: the search for a circumbinary disk or a low?mass companion around NN Serpentis
We obtained high time-resolution photometry using the high speed CCD camera ULTRACAM between 2002 and 2004, which revealed a gradual reduction in the orbital period of the pre- cataclysmic variable NN Serpentis. There are three possible explanations for this period change: firstly, we may have been successful in obtaining the first and only direct measurement of the braking rate of a close binary system, in which case our measured values are approximately 2 orders of magnitude greater than predicted, and pose serious problems for the theory of close binary evolution. Secondly, the unusually high braking rate may be caused by the presence of a circumbinary disk, which would help to answer two of the outstanding problems with current CV theory – namely the high mass-transfer rates seen in some CVs, and the fact that the minimum observed value in the CV period distribution is approximately 15% longer than expected. Finally, our observations could be explained by a light travel-time effect caused by a third body in orbit around the binary, which would raise major questions about the evolutionary history of the system, in particular how a third body has managed to remain in a stable orbit throughout periods of intense mass-loss in the central binary. We intend to use IRAC observations to search for a mid-infrared excess in the spectral energy distribution of NN Ser, which would confirm the presence of either a disk or a third body. We then propose to use HST imaging to attempt to resolve a third body, allowing us to discriminate between the two possibilities. If both methods fail to reveal any extra system components, we will have ruled out our only remaining alternatives to a genuinely high angular momentum loss rate in this system, with profound implications for CV evolution.
WFPC2 11023
WFPC2 CYCLE 15 Standard Darks – part 1
This dark calibration program obtains dark frames every week in order to provide data for the ongoing calibration of the CCD dark current rate, and to monitor and characterize the evolution of hot pixels. Over an extended period these data will also provide a monitor of radiation damage to the CCDs.
FLIGHT OPERATIONS SUMMARY:
Significant Spacecraft Anomalies: (The following are preliminary reports of potential non-nominal performance that will be investigated.)
HSTARS:
10737 – REacq(1,2,2) failed due to a STOP flag on FGS 1
REacq failed after Fine Lock was established on FGS 1. OBAD prior RSS 25.73 a-s
REacq(1,2,2) scheduled at 17:44:21 failed due to SSLEX on FGS 1. QF1SSLEX, QSTEPEXC, QF1STOPF and QSTOP were present. Pre OBAD RSS 18.57 a-s
COMPLETED OPS REQUEST: (None)
COMPLETED OPS NOTES: (None)
SCHEDULED SUCCESSFUL FGS GSacq 09 09 FGS REacq 06 04 OBAD with Maneuver 25 25
SIGNIFICANT EVENTS: (None)
