#1
|
|||
|
|||
Daily 3831
HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science
DAILY REPORT # 3831 PERIOD COVERED: DOY 94 OBSERVATIONS SCHEDULED ACS/HRC 10255 A Never Before Explored Phase Space: Resolving Close White Dwarf / Red Dwarf Binaries We propose an ACS Snapshot imaging survey to resolve a well-defined sample of highly probable white dwarf plus red dwarf close binaries. These candidates were selected from a search for white dwarfs with infrared excess from the 2MASS database. They represent unresolved systems {separations less than approximately 2" in the 2MASS images} and are distributed over the whole sky. Our HST+ACS observations will be sensitive to a separation range {1-20 AU} never before probed by any means. The proposed study will be the first empirical test of binary star parameters in the post-AGB phase, and cannot be accomplished from the ground. By resolving as few as 20 of our ~100 targets with HST, we will be able to characterize the distribution of orbital semi- major axes and secondary star masses. ACS/HRC/WFC 10389 ACS CCDs daily monitor - Cycle 13 - Part 2 This program consists of a set of basic tests to monitor, the read noise, the development of hot pixels and test for any source of noise in ACS CCD detectors. The files, biases and dark will be used to create reference files for science calibration. This programme will be for the entire lifetime of ACS. ACS/HRC/WFPC2 9827 UV extinction by dust in unexplored LMC environments The ensemble of results from studies of the UV extinction in the Milky Way, Magellanic Clouds {MC}, M31 and M33, indicates a complex dependence of the dust properties with environment, where starburst activity and metallicity are relevant factors. Work in the LMC to date, based on IUE data, has several drawbacks: a} only supergiants could be used, b} they all have moderate extinction, c} the IUE S/N is limited, d} the large IUE slit may include light from other sources, such as scattered light from dust or faint companion stars, e} studies are confined to few {extreme} environments. We propose to obtain UV extinction curves more accurate than previous ones, sampling four environments in the LMC with different levels of star formation activity, including the general field, hitherto unexplored. The results will characterize the properties of dust in different conditions, at the LMC metallicity, which is useful to interpret integrated properties of distant galaxies, as well as GALEX upcoming UV surveys. A complementary study is under way with FUSE in the far-UV range. The combined results will provide insight on the properties of small grains. ACS/WFC/NIC/NIC3/WFPC 10246 2 The HST survey of the Orion Nebula Cluster We propose a Treasury Program of 104 HST orbits to perform the definitive study of the Orion Nebula Cluster, the Rosetta stone of star formation. We will cover with unprecedented sensitivity {23-25 mag}, dynamic range {~12 mag}, spatial resolution {50mas}, and simultaneous spectral coverage {5 bands} a ~450 square arcmin field centered on the Trapezium stars. This represents a tremendous gain over the shallow WFC1 study made in 1991 with the aberrated HST on an area ~15 times smaller. We maximize the HST observing efficiency using ACS/WFC and WFPC2 in parallel with two opposite roll angles, to cover the same total field. We will assemble the richest, most accurate and unbiased HR diagram for pre-main-sequence objects ever made. Combined with the optical spectroscopy already available for ~1000 sources and new deep near-IR imaging and spectroscopy {that we propose as Joint HST-NOAO observations}, we will be able to attack and possibly solve the most compelling questions on stellar evolution: the calibration of pre-main-sequence evolutionary tracks, mass segration and the variation of the initial mass function in different environments, the evolution of mass accretion rates vs. age and environment, disk dissipation in environments dominated by hard vs. soft-UV radiation, stellar multiplicity vs. disk fraction. In addition, we expect to discover and classify an unknown, but substantial, population of pre-Main Sequence binaries, low mass stars and brown dwarfs down to ~10 MJup. This is also the best possible way to discover dark silhouette disks in the outskirts of the Orion Nebula and study their evolutionary status through multicolor imaging. This program is timely and extremely well leveraged to other programs targeting Orion: the ACS H-alpha survey of the Orion Nebula, the recently completed 850ks ultradeep Chandra survey, the large GTO programs to be performed with SIRTF, plus the availability of 2MASS and various deep JHK surveys of the core recently done with 8m class telescopes. ACS/WFC/WFPC2 10424 The White Dwarf Cooling Age and Dynamical History of the Metal-Poor Globular Cluster NGC 6397 We propose to determine the white dwarf cooling age in the nearest metal-poor {[Fe/H]=- 2} globular cluster, NGC 6397. This globular cluster provides the best opportunity to test the white dwarf cooling age in such a metal-poor system and at the same time provide a comparison with the more metal-rich cluster {M4} which we recently successfully observed with HST. Any {or even no} age difference between these clusters will be important in understanding the age-metallicity relation for these systems which reflects the star formation history in the early Galaxy. The absolute age is an important cosmological constraint. We expect to be able to detect age DIFFERENCES between these clusters at the 0.5 Gyr level and absolute ages should be accurate to 1.0 Gyr. In addition, and in contrast with M4, NGC 6397 is highly dynamically evolved, has a collapsed core, and the distribution of its white dwarfs throughout the cluster have almost certainly been modified by dynamical processes. We are using N-body simulations specifically developed for this cluster to understand these modifications and to include their effects in our measurement of the white dwarf luminosity function and cooling age. Among the dynamical questions we expect to answer with this proposal a 1} what was the primordial binary frequency in NGC 6397? 2} can we explain the high central concentration with a population of massive white dwarfs and/or neutron stars? 3} do we see sufficient central binaries to reverse the core collapse of the cluster? FGS 10106 An Astrometric Calibration of the Cepheid Period-Luminosity Relation We propose to measure the parallaxes of 10 Galactic Cepheid variables. When these parallaxes {with 1-sigma precisions of 10% or better} are added to our recent HST FGS parallax determination of delta Cep {Benedict et al 2002}, we anticipate determining the Period-Luminosity relation zero point with a 0.03 mag precision. In addition to permitting the test of assumptions that enter into other Cepheid distance determination techniques, this calibration will reintroduce Galactic Cepheids as a fundamental step in the extragalactic distance scale ladder. A Period-Luminosity relation derived from solar metallicity Cepheids can be applied directly to extragalactic solar metallicity Cepheids, removing the need to bridge with the Large Magellanic Cloud and its associated metallicity complications. FGS 10107 The Masses of the O-type Binary 15 Monocerotis The O-type star 15 Mon {HD 47839} was recently discovered to be an astrometric and spectroscopic binary with a period of 25 years; it is the first known O-star system to bridge the observational gap between the period regimes normally probed by these techniques. An analysis of both the radial velocity curve and astrometric orbit yields the masses of the components and distance to the system. Continuing radial velocity and HST/FGS astrometric measurements will lead to a definitive orbit and yield key information about the masses of O-type stars. FGS TRANS mode measurements of separation, position angle, and magnitude difference {begun in Cycle 5} are needed to link existing speckle observations and anticipated observations with the CHARA Array optical interferometer. In addition, field astrometry measurements {FGS POS mode} will provide the proper motion, parallax, and the binary motion around the center of mass. The POS data will provide an accurate estimate of the mass ratio and an improved estimate of distance, and taken together with the spectroscopic and astrometric orbital data, we will obtain masses for both components accurate to a few percent. FGS 10202 Resolving OB Binaries in the Carina Nebula, Resuming the Survey In March 2002 we carried out a small, high-angular resolution survey of some of the brightest OB stars in the Carina Nebula with FGS1r in an attempt to resolve binary systems which had thus far evaded detection by other techniques. Of 23 stars observed, 5 new OB binaries were discovered with component separations ranging from 0.015" to0.325". This yield over the spatial domain of FGS1r's angular resolution, coupled with published statistics of the incidence of OB stars in short-period spectroscopic, and long-period visual binaries suggests that the fraction of binarity or multiplicity among OB stars is near unity. Our unexpected resolution of the prototype O2 If* star HD 93129A as a 55 milli-arcsecond double is a case in point that great care must be exercised when one attempts to establish the IMF and upper-mass cuttoff at the high-mass end of the HR diagram. We propose to resume the survey to observe a larger, statistically meaningful sample of OB stars to establish a firm assessment of multiplicity at the high-mass end of the IMF in these clusters. We will also investigate the single- star/binary-star status of several astrophysically important, individual stars in order to enable a better understanding of the evolution of high-mass stars. NIC1/NIC2/NIC3 8792 NICMOS Post-SAA calibration - CR Persistence Part 3 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. WFPC2 10359 WFPC2 CYCLE 13 Standard Darks 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.) None COMPLETED OPS REQs: 17413-0 ESTR Reconditioning @ 094/1738z 17414-0 Genslew for proposal 10431 - slot 11 @ 094/1545z 17415-0 Genslew for proposal 10431 - slot 10 @ 094/1547z OPS NOTES EXECUTED: None SCHEDULED SUCCESSFUL FAILURE TIMES FGS Gsacq 10 10 FGS Reacq 06 06 FHST Update 13 13 LOSS of LOCK SIGNIFICANT EVENTS: None |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
EVOLUTION DEAD AT AGE 126 -- R.I.P. | Ed Conrad | Astronomy Misc | 4 | August 21st 04 12:01 AM |
Monitoring NASA Daily ISS Report | JimO | Space Station | 2 | June 1st 04 10:33 PM |
Monitoring NASA Daily ISS Report | JimO | History | 2 | June 1st 04 10:33 PM |
Spirit's daily activities schedule? | Matti Anttila | Policy | 0 | January 15th 04 08:39 AM |
best site for daily schedule of rover activity? | bob | History | 2 | January 5th 04 12:16 PM |