HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT      # 4624

PERIOD COVERED: 5am June 03 - 5am June 04, 2008 (DOY 155/0900z-156/0900z)

OBSERVATIONS SCHEDULED

WFPC2 10583

Resolving the LMC Microlensing Puzzle: Where Are the Lensing Objects ?

We are requesting 32 HST orbits to help ascertain the nature of the

population that gives rise to the observed set of microlensing events

towards the LMC. The SuperMACHO project is an ongoing ground-based

survey on the CTIO 4m that has demonstrated the ability to detect LMC

microlensing events in real-time via frame subtraction. The improvement

in angular resolution and photometric accuracy available from HST will

allow us to 1} confirm that the detected flux excursions arise from LMC

source stars rather than extended objects {such as for background

supernovae or AGN}, and 2} obtain reliable baseline flux measurements

for the objects in their unlensed state. The latter measurement is

important to resolve degeneracies between the event timescale and

baseline flux, which will yield a tighter constraint on the microlensing

optical depth.

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 11212

Filling the Period Gap for Massive Binaries

The current census of binaries among the massive O-type stars is

seriously incomplete for systems in the period range from years to

millennia because the radial velocity variations are too small and the

angular separations too close for easy detection. Here we propose to

discover binaries in this observational gap through a Faint Guidance

Sensor SNAP survey of relatively bright targets listed in the Galactic O

Star Catalog. Our primary goal is to determine the binary frequency

among those in the cluster/association, field, and runaway groups. The

results will help us assess the role of binaries in massive star

formation and in the processes that lead to the ejection of massive

stars from their natal clusters. The program will also lead to the

identification of new, close binaries that will be targets of long term

spectroscopic and high angular resolution observations to determine

their masses and distances. The results will also be important for the

interpretation of the spectra of suspected and newly identified binary

and multiple systems.

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 DARKs. 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 11123

A NICMOS Survey for Proplyds in the RCW 38 Massive Embedded Cluster

We propose a search for line emission from photoevaporating

protoplanetary disks in the Massive Embedded Cluster RCW 38. These disks

would be analogous to the "proplyds" discovered in the Orion Nebula:

disks around young low mass stars which are being photoionized by a

nearby O star. We will search for these disks in RCW 38 using narrowband

imaging in the lines of Paschen alpha and molecular hydrogen (1-0) S(1)

with NICMOS. The RCW 38 region is an excellent target for determining

whether proplyds are observable in large numbers outside of Orion. It is

a young embedded cluster hosting a few hundred low mass young stars with

a large percentage showing infrared excess indicating the presence of

disks. About 100 of these stars are found within 0.1 pc of the central

O5 star, and the cluster is located within a cleared cavity 0.2 pc in

size, embedded within a molecular cloud, exposing the cluster members

directly to the UV radiation from the O star. Unlike Orion, but like

many other young clusters, RCW 38 is not seen in visible light, and

infrared imaging is needed. The best line in the infrared for revealing

proplyds is the Paschen alpha line, which is not detectable from the

ground. Only HST is able to perform these observations. From these

observations we will estimate the lifetime of the evaporating disks, and

ascertain whether these disks will survive long enough to form planets.

NIC3 11120

A Paschen-Alpha Study of Massive Stars and the ISM in the Galactic

Center

The Galactic center (GC) is a unique site for a detailed study of a

multitude of complex astrophysical phenomena, which may be common to

nuclear regions of many galaxies. Observable at resolutions

unapproachable in other galaxies, the GC provides an unparalleled

opportunity to improve our understanding of the interrelationships of

massive stars, young stellar clusters, warm and hot ionized gases,

molecular clouds, large scale magnetic fields, and black holes. We

propose the first large-scale hydrogen Paschen alpha line survey of the

GC using NICMOS on the Hubble Space Telescope. This survey will lead to

a high resolution and high sensitivity map of the Paschen alpha line

emission in addition to a map of foreground extinction, made by

comparing Paschen alpha to radio emission. This survey of the inner 75

pc of the Galaxy will provide an unprecedented and complete search for

sites of massive star formation. In particular, we will be able to (1)

uncover the distribution of young massive stars in this region, (2)

locate the surfaces of adjacent molecular clouds, (3) determine

important physical parameters of the ionized gas, (4) identify compact

and ultra-compact HII regions throughout the GC. When combined with

existing Chandra and Spitzer surveys as well as a wealth of other

multi-wavelength observations, the results will allow us to address such

questions as where and how massive stars form, how stellar clusters are

disrupted, how massive stars shape and heat the surrounding medium, and

how various phases of this medium are interspersed.

WFPC2 11070

WFPC2 CYCLE 15 Standard Darks - part II

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.

WFPC2 11222

Direct Detection and Mapping of Star Forming Regions in Nearby, Luminous

Quasars

We propose to carry out narrow-band emission line imaging observations

of 8 quasars at z=0.05-0.15 with the WFPC2 ramp filters and with the

NICMOS narrow-band filters. We will obtain images in the [O II], [O

III], H-beta, and Pa-alpha emission line bands to carry out a series of

diagnostic tests aimed at detecting and mapping out star-forming regions

in the quasar host galaxies. This direct detection of star-forming

regions will confirm indirect indications for star formation in quasar

host galaxies. It will provide a crucial test for models of quasar and

galaxy evolution, that predict the co-existence of starbursts and

"monsters" and will solve the puzzle of why different indicators of star

formation give contradictory results. A secondary science goal is to

assess suggested correlations between quasar luminosity and the size of

the narrow-line region.

WFPC2 11227

The Orbital Period for an Ultraluminous X-ray Source in NGC1313

The ultraluminous X-ray sources {ULXs} are extragalactic point sources

with luminosities that exceed the Eddington luminosity for conventional

stellar-mass black holes by factors of 10 - 100. It has been hotly

debated whether the ULXs are just common stellar-mass black hole sources

with beamed emission or whether they are sub-Eddington sources that are

powered by the long-sought intermediate mass black holes {IMBH}. To

firmly decide this question, one must obtain dynamical mass measurements

through photometric and spectroscopic monitoring of the secondaries of

these system. The crucial first step is to establish the orbital period

of a ULX, and arguably the best way to achieve this goal is by

monitoring its ellipsoidal light curve. The extreme ULX NGC1313 X-2

provides an outstanding target for an orbital period determination

because its relatively bright optical counterpart {V = 23.5} showed a

15% variation between two HST observations separated by three months.

This level of variability is consistent with that expected for a tidally

distorted secondary star. Here we propose a set of 20 imaging

observations with HST/WFPC2 to define the orbital period. This would be

the first photometric measurement of the orbital period of a ULX binary.

Subsequently, we will propose to obtain spectroscopic observations to

obtain its radial velocity amplitude and thereby a dynamical estimate of

its mass.

WFPC2 11337

Investigating the X-ray Variability of Cassiopeia A

We propose a 50 ksec ACIS-S observation of Cas A to follow X-ray flux

changes associated with ejecta recently encountered by the reverse

shock. This will allow us to investigate Cas A's near-term X-ray

evolution and the fine-scale structure of its SN debris. We also request

the Chandra observation be followed by HST NICMOS & WFPC2 images of four

identified X-ray variable features in the high ionization NIR lines of

[Si VI] and [Si X] and low ionization optical lines of [S II] and [O

III]. The proposed X-ray/optical/NIR observations will yield a

multi-wavelength study of the remnant's advancing reverse shock in an

inhomogeneous multi-phase ejecta medium at resolutions down to a

fraction of an arcsecond, providing a hi-resolution broad temperature

study of reverse shock heated SN ejecta.

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:

18239-0 - RMGA Power On/Off (06/08) @ 155/1431z

COMPLETED OPS NOTES: (None)

                       SCHEDULED      SUCCESSFUL 

FGS GSacq               08                  08

FGS REacq               06                  06                      

OBAD with Maneuver 28                 28                                 

SIGNIFICANT EVENTS: (None)