NASA Hubble Space Telescope Daily Report #4086

HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science

DAILY REPORT #4086

PERIOD COVERED: UT April 05, 2006 (DOY 095)

OBSERVATIONS SCHEDULED

ACS/HRC 10602

A Complete Multiplicity Survey of Galactic O2/O3/O3.5 Stars with ACS

Massive stars are preferentially formed in compact multiple systems and clusters and many of them remain spatially unresolved to date, even in our Galaxy. This has hindered the determination of the stellar upper mass limit. The lack of an accurate knowledge of the multiplicity of massive stars can also introduce biases in the calculation of the IMF at its high-mass end. We have recently used ACS/HRC to resolve HD 93129 A, the earliest O-type star known in the Galaxy, into a 55 mas binary. We propose here to extend that work into a complete multi-filter ACS imaging survey of all {20} known O2/O3/O3.5 Galactic stars to characterize the multiplicity of the most massive stars. The data will be combined with existing FGS observations to explore as large a parameter range as possible and to check for consistency. We will also derive the IMF of each system using a crowded-field photometry package and processing the data with CHORIZOS, a code that can derive stellar temperatures, extinctions, and extinction laws from multicolor photometry.

ACS/HRC/WFC 10758

ACS CCDs daily monitor

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. Changes from cycle 13:- The default gain for WFC is 2 e-/DN. As before bias frames will be collected for both gain 1 and gain 2. Dark frames are acquired using the default gain {2}. This program cover the period May, 31 2006- Oct, 1-2006. The first half of the program has a different proposal number: 10729.

ACS/SBC 10535

High Temperature Accretion Flows and Reprocessing in X-ray Binaries: The ADC Source 4U 1822-371

The eclipsing low-mass X-ray binary 4U 1822-371 is the ideal system in which to observe hot accretion and the effects of strong irradiation. Its orbital period is 5.57~hr and its orbital inclination is high enough that flux from the neutron star is blocked by the edge-on accretion disk in the system. Because the neutron star is hidden its Accretion Disk Corona is visible. These ADCs are present in most if not all low-mass X-ray binaries but are generally not visible. 4U 1822-371 provides a unique opportunity to study an ADC and disk irradiation because the eclipse by the secondary star allows their geometry and flux to be mapped. We will perform a multiwavelength light curve synthesis and eclipse analysis of 4U 1822-371. The scientific goal is to map the geometry and flux from its ADC and from its irradiated accretion disk. The crucial and irreplaceable role of HST is to provide the UV data needed to disentangle the ADC from the irradiated accretion disk. We will obtain time-resolved, objective-prism UV spectroscopy of 4U 1822-371 with the ACS/SBC with the PR130L prism, covering most of its orbit and all of the eclipse. This combination will yield excellent orbital light curves in the UV continuum and in the integrated line fluxes.

ACS/SBC 10764

X-Ray Activity and Winds in Young A Stars at the Epoch of Disk Clearing

Herbig Ae stars which are still accreting material from their protoplanetary disks show a gradual evolution in X-ray luminosity and hardness ratio. They resemble T Tauri stars in driving microjets which can be imagaged in Lyman alpha. Older A stars with more centrally cleared debris disks, like beta Pictoris, are not X-ray sources, but still have some stellar activity and can drive coronal winds. We wish to test the hypothesis that the change in the level of stellar activity and hardness of stellar activity signatues are linked to changes in the magnetic field strength and wind geometry. We are requesting 20 ksec of Chandra and 2 orbits of HST time to observe two late-A Herbig Ae stars which appear to be transitional between the accreting objects and the debris disks.

ACS/WFC 10615

Timing Studies of the X-ray Binary Populations in Globular Clusters

Close binaries are fundamental to the dynamical stability and evolution of globular clusters, but large populations have been extremely difficult to identify. Chandra X-ray images provide a revolutionary resource, revealing a few to dozens of low-luminosity X-ray sources in every cluster deeply examined; our own Chandra programs uniformly study these ubiquitous X-ray sources {close binaries and their progeny} in a dozen clusters. We have obtained multicolor, single-epoch, ACS images, from which to obtain initial optical counterparts, especially CVs {the dominant population in most clusters}, BY Dra’s, and qLMXBs. As HST capability for follow-on, confirming, spectra of our multicolor-selected counterparts is now severely curtailed, we propose an ACS time-series imaging program that will yield equivalent follow-on information for 5 of our clusters. The proposed ACS time-series data with 6 min resolution and 8 hr time-span, will: provide variability information to secure our suggested multicolor identifications; allow secure classifications of the various X-ray subpopulations {e.g., CVs vs. BY Dra’s}; yield quality lightcurves, whose shape will help test the notion that magnetic CVs are more common in globular clusters than the field; and, provide interesting contraints on the period distributions of cluster X-ray binaries.

FLIGHT OPERATIONS SUMMARY:

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

HSTARS: (None)

COMPLETED OPS REQUEST:

17689-0 – Battery 6 Capacity Test Script & Battery Pressure Limit COP (thru Step 17) 17695-2 – Monitor VehConLaw.Integral Path Data via TMDIAG Slot 0 (Generic OR) @ 095/1638z 17686-0 – Continuous Engineering Recording for Battery # 6 BCT @ 095/1501z, 095/1614z, 095/1741z, 095/1828z, 095/2338z, 096/0047z, 096/0520z, 096/0638z, 096/0702z, 096/0710z, 096/0837z

COMPLETED OPS NOTES: (None)

                         SCHEDULED      SUCCESSFUL
FGS GSacq               09                     09
FGS REacq               06                     06
OBAD with Maneuver  30                     30

SIGNIFICANT EVENTS:

Flash Report – Battery 6 capacity Test Flash Report #3 (EPS SE Wed, 05 Apr 2006 13:03:50) — Battery 6 discharge switched from High-rate to the Low-rate resistor at 95/0011 GMT.

Battery 6 is expected to reach its target low voltage of 15.07 volts at approximately 96/1600 GMT, at which time the battery will be placed back on line.