HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT      # 4623

PERIOD COVERED: 5am June 02 - 5am June 03, 2008 (DOY 154/0900z-155/0900z)

OBSERVATIONS SCHEDULED

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.

NIC2 11164

Molecular Hydrogen Disks Around T Tauri Stars

We propose to measure the properties of planetary system-sized disks

around Sun- like, pre-main sequence stars by imaging the inner parts of

these disks for the first time in gaseous emission from their most

dominant constituent, molecular hydrogen gas. Specifically, we will use

the F212N filter and NICMOS to determine the spatial distribution of

ro-vibrational H2 emission from protoplanetary disks around selected

classical and weak-lined T Tauri stars. The target stars are among those

detected by members of this team through high resolution, ground-based

infrared spectroscopy. The spectra reveal H2 emission at the rest

velocities of the stars and at positions spatially coincident with the

stars at the spatial resolution of the spectroscopic data. This imaging

experiment, which is impossible to do using ground- based facilities, is

possible using the NICMOS camera aboard the HST because the point spread

function of this system is extremely stable and can be measured to a

very high accuracy. This experiment is an important test of the

interpretation that the 2.122 micron H2 line emission seen toward T

Tauri stars is produced at distances of 10 to 30 AU from the stars, the

region in which giant planets are expected to form around these stars.

These observations will contribute toward developing a better

understanding of the process, likelihood, and timescale for the

formation of planets around Sun-like stars.

WFPC2 11029

WFPC2 CYCLE 15 Intflat Linearity Check and Filter Rotation Anomaly

Monitor

Intflat observations will be taken to provide a linearity check: the

linearity test consists of a series of intflats in F555W, in each gain

and each shutter. A combination of intflats, visflats, and earthflats

will be used to check the repeatability of filter wheel motions.

{Intflat sequences tied to decons, visits 1-18 in prop 10363, have been

moved to the cycle 15 decon proposal xxxx for easier scheduling.} Note:

long-exposure WFPC2 intflats must be scheduled during ACS anneals to

prevent stray light from the WFPC2 lamps from contaminating long ACS

external exposures.

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: (None)

COMPLETED OPS NOTES: (None)

                        SCHEDULED      SUCCESSFUL 

FGS GSacq                08                 08 

FGS REacq                02                 02                      

OBAD with Maneuver 20                 20                                 

SIGNIFICANT EVENTS: (None)