9798( 5) - 03/30/04 11:22 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 9798 Version: 5 Check-in Date: 30-Mar-2004 11:18:09 1.Proposal Title: What's The Point? Deep NICMOS Imaging of the Central X-ray Point Source in Cas A ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 12 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Dr. George G. Pavlov The Pennsylvania State University CoI: Dr. Robert A. Fesen Dartmouth College N CoI: Dr. Divas Sanwal The Pennsylvania State University N ------------------------------------------------------------------------------------ 5. Abstract First-light Chandra X-ray Observatory images revealed an enigmatic central point source in Cas A, the Galaxy's youngest known supernova remnant (SN 1680). The object lies within 7 arcsec of the remnant's expansion center and is presumably the remnant's neutron star with unusual properties. Deep Cycle 9 STIS observations and Keck's near-IR imaging detected only one object within the Chandra positional error circle, and this appears to be a foreground star. These optical and NIR upper limits already prove that the X-ray source cannot be a field star, an AGN, an ordinary pulsar, or an X-ray binary with any known type of optical companion. A likely possibility is that it is a very young magnetar that will evolve into an Anomalous X-ray Pulsar or a Soft Gamma-ray Repeater. Due to the high extinction to Cas A, deep NICMOS imaging offers the best way to search for a counterpart. Here we propose obtaining NIC2 H band images which will go to H=25.7 -- almost 6 mags deeper than the previous searches and about 2 mags deeper than is realistically possible with Keck or Subaru. The high-resolution capability of NIC2 will also limit potential source confusion in this galactic plane region. We will obtain matching J images (to 27.2 mag) to provide color information on the candidate objects. These ultra-deep NICMOS images will either detect the counterpart and hence determine its nature, or place severe constraints on the properties of the point source. ------------------------------------------------------------------------------------ 9798( 5) - 03/30/04 11:22 - [ 2] Observations Description ------------------------ Since the proposed program requires very deep imaging (at least 15 regular orits), we request CVZ observations (8 orbits) to maximize HST efficiency. To obtain the deepest H-band imaging, we propose to use NIC2 so as to provide good photometric accuracy (compared to NIC3) while providing a large enough FOV to include several other adjacent stars for calibration and for which we already have deep JHK photometry. We plan to use the NIC2 filter F160W for H-band, which the NICMOS Handbook describes as having the lowest background. With a 6 min target ACQ, and taking the data in Multiple-Accum mode to get the best S/N on faint sources, we estimate a total available exposure time of just over 16, 000 sec during three (3) CVZ orbits. According to the NICMOS exposure calculator, we should achieve H = 25.7 with a S/N of 5 for the brightest pixel in 15, 000--16, 000 sec. Inputs were a power-law spectrum f_lambda \propto lambda^{-alpha} with alpha=2--4, an E(B-V) = 1.8, and average zodiacal light. To obtain additional color information, we propose to use the F110W (J) filter because it can detect the target with a shorter exposure than the F205W (K) and F187W (Ks) filters, assuming the (de-reddened) source spectrum grows with frequency similar to the AXP spectra. Estimates with the NICMOS ETC show that a total exposure of 26, 000 s (5 CVZ orbits) will give a limiting J magnitude of 27.2. We break the 8 orbit exposure in two visits of 5 orbits (F110W observation) and 3 orbits (F160W observation). To permit the removal of dead pixels and estimate the background, we will use dithering. We choose the NIC- SPIRAL-DITH pattern (9 points, 2.318 point spacing, 0.4696 pattern orientation, step32, nsamp=25) sucessfully used in a similar observation of the RCW 103 CCO (GO-9467). Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 9798( 5) - 03/30/04 11:22 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 CASA-CCO STAR, NEUTRON STAR RA=23H23M27.9S +/- 1.0", J2000 V = 30.0 DEC=+58D48'43.0" +/- 1.0" Coordinate Source: Other_Source: Chandra Observations Comments: The target position is known from Chandra observations with an accuracy of about 1 arcsec. 9798( 5) - 03/30/04 11:22 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type NIC-SPIRAL-DITH Pattern_Purpose DITHER Number_Of_Points 9 Point_Spacing 2.318 Coordinate_Frame POS-TARG Pattern_Orient 0.4696 Center_Pattern YES ------------------------------------------------------------------------------------------------------------------------------------ 9798( 5) - 03/30/04 11:22 - [ 5] Visit: 01 Visit Priority: Visit Requirements: CVZ; BETWEEN 01-MAR-2004:00:00:00 AND 10-MAR-2004:00:00:00 On Hold Comments: Additional Comments: Observation of the Cas A CCO with F110W. We request this 5 CVZ orbit observation to be carried out in the schedulability window of January 2004 (11 Jan - 14 Jan), not to interfere with another program (monitoring observation of the Cas A SNR; PI: Fesen) that also requires CVZ orbits. Note: The between was changed to March to allow for a ToO. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 CASA-CCO NIC2 MULTIAC NIC2 F110W SAMP-SEQ=STEP32,NSAMP=25, 1 DEF PATTERN 1 1 CUM OFFSET=SAM ------------------------------------------------------------------------------------------------------------------------------------ 2 CASA-CCO NIC2 MULTIAC NIC2 F110W SAMP-SEQ=STEP32,NSAMP=25, 1 DEF PATTERN 1 2 CUM OFFSET=SAM ------------------------------------------------------------------------------------------------------------------------------------ 3 CASA-CCO NIC2 MULTIAC NIC2 F110W SAMP-SEQ=STEP32,NSAMP=25, 1 DEF PATTERN 1 3 CUM OFFSET=SAM ------------------------------------------------------------------------------------------------------------------------------------ 4 CASA-CCO NIC2 MULTIAC NIC2 F110W SAMP-SEQ=STEP32,NSAMP=25, 1 DEF PATTERN 1 4 CUM OFFSET=SAM ------------------------------------------------------------------------------------------------------------------------------------ 5 CASA-CCO NIC2 MULTIAC NIC2 F110W SAMP-SEQ=STEP32,NSAMP=25, 1 DEF PATTERN 1 5 CUM OFFSET=SAM ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Visit Id| Exp Id |Primary |Secondary |Iteration |CR-SPLIT |Orbit Num |Duration | |Pattern Pos |Pattern Pos |Num |Num | | ------------------------------------------------------------------------------------------------------------------------------------ 01 1 1 none none none tbd tbd 01 1 2 none none none tbd tbd 01 1 3 none none none tbd tbd 01 1 4 none none none tbd tbd 01 1 5 none none none tbd tbd 01 1 6 none none none tbd tbd 01 1 7 none none none tbd tbd 01 1 8 none none none tbd tbd 01 1 9 none none none tbd tbd 01 2 1 none none none tbd tbd 01 2 2 none none none tbd tbd 01 2 3 none none none tbd tbd 01 2 4 none none none tbd tbd 01 2 5 none none none tbd tbd 01 2 6 none none none tbd tbd 01 2 7 none none none tbd tbd 9798( 5) - 03/30/04 11:22 - [ 6] Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Visit Id| Exp Id |Primary |Secondary |Iteration |CR-SPLIT |Orbit Num |Duration | |Pattern Pos |Pattern Pos |Num |Num | | ------------------------------------------------------------------------------------------------------------------------------------ 01 2 8 none none none tbd tbd 01 2 9 none none none tbd tbd 01 3 1 none none none tbd tbd 01 3 2 none none none tbd tbd 01 3 3 none none none tbd tbd 01 3 4 none none none tbd tbd 01 3 5 none none none tbd tbd 01 3 6 none none none tbd tbd 01 3 7 none none none tbd tbd 01 3 8 none none none tbd tbd 01 3 9 none none none tbd tbd 01 4 1 none none none tbd tbd 01 4 2 none none none tbd tbd 01 4 3 none none none tbd tbd 01 4 4 none none none tbd tbd 01 4 5 none none none tbd tbd 01 4 6 none none none tbd tbd 01 4 7 none none none tbd tbd 01 4 8 none none none tbd tbd 01 4 9 none none none tbd tbd 01 5 1 none none none tbd tbd 01 5 2 none none none tbd tbd 01 5 3 none none none tbd tbd 01 5 4 none none none tbd tbd 01 5 5 none none none tbd tbd 01 5 6 none none none tbd tbd 01 5 7 none none none tbd tbd 01 5 8 none none none tbd tbd 01 5 9 none none none tbd tbd 9798( 5) - 03/30/04 11:22 - [ 7] Visit: 02 Visit Priority: Visit Requirements: CVZ; BETWEEN 01-MAR-2004:00:00:00 AND 10-MAR-2004:00:00:00 On Hold Comments: Additional Comments: Observation of the Cas A CCO with F160W. We request this 3 CVZ orbit observation to be carried out in the schedulabilty window of January 2004 (11 Jan - 14 Jan), not to interfere with another program (monitoring observations of the Cas A SNR; PI: Fesen) that also requires CVZ orbits. Note: The between was changed to March to allow for a ToO. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 CASA-CCO NIC2 MULTIAC NIC2 F160W SAMP-SEQ=STEP32,NSAMP=25, 1 DEF PATTERN 1 1 CUM OFFSET=SAM ------------------------------------------------------------------------------------------------------------------------------------ 2 CASA-CCO NIC2 MULTIAC NIC2 F160W SAMP-SEQ=STEP32,NSAMP=25, 1 DEF PATTERN 1 2 CUM OFFSET=SAM ------------------------------------------------------------------------------------------------------------------------------------ 3 CASA-CCO NIC2 MULTIAC NIC2 F160W SAMP-SEQ=STEP32,NSAMP=25, 1 DEF PATTERN 1 3 CUM OFFSET=SAM ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Visit Id| Exp Id |Primary |Secondary |Iteration |CR-SPLIT |Orbit Num |Duration | |Pattern Pos |Pattern Pos |Num |Num | | ------------------------------------------------------------------------------------------------------------------------------------ 02 1 1 none none none tbd tbd 02 1 2 none none none tbd tbd 02 1 3 none none none tbd tbd 02 1 4 none none none tbd tbd 02 1 5 none none none tbd tbd 02 1 6 none none none tbd tbd 02 1 7 none none none tbd tbd 02 1 8 none none none tbd tbd 02 1 9 none none none tbd tbd 02 2 1 none none none tbd tbd 02 2 2 none none none tbd tbd 02 2 3 none none none tbd tbd 02 2 4 none none none tbd tbd 02 2 5 none none none tbd tbd 02 2 6 none none none tbd tbd 02 2 7 none none none tbd tbd 02 2 8 none none none tbd tbd 02 2 9 none none none tbd tbd 02 3 1 none none none tbd tbd 02 3 2 none none none tbd tbd 02 3 3 none none none tbd tbd 02 3 4 none none none tbd tbd 9798( 5) - 03/30/04 11:22 - [ 8] Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Visit Id| Exp Id |Primary |Secondary |Iteration |CR-SPLIT |Orbit Num |Duration | |Pattern Pos |Pattern Pos |Num |Num | | ------------------------------------------------------------------------------------------------------------------------------------ 02 3 5 none none none tbd tbd 02 3 6 none none none tbd tbd 02 3 7 none none none tbd tbd 02 3 8 none none none tbd tbd 02 3 9 none none none tbd tbd 9798( 5) - 03/30/04 11:22 - [ 9] Visit: 51 Visit Priority: Visit Requirements: CVZ On Hold Comments: Additional Comments: Observation of the Cas A CCO with F110W. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 CASA-CCO NIC2 MULTIAC NIC2 F110W SAMP-SEQ=STEP32,NSAMP=25, 1 DEF PATTERN 1 1 CUM OFFSET=SAM ------------------------------------------------------------------------------------------------------------------------------------ 2 CASA-CCO NIC2 MULTIAC NIC2 F110W SAMP-SEQ=STEP32,NSAMP=25, 1 DEF PATTERN 1 2 CUM OFFSET=SAM ------------------------------------------------------------------------------------------------------------------------------------ 3 CASA-CCO NIC2 MULTIAC NIC2 F110W SAMP-SEQ=STEP32,NSAMP=25, 1 DEF PATTERN 1 3 CUM OFFSET=SAM ------------------------------------------------------------------------------------------------------------------------------------ 4 CASA-CCO NIC2 MULTIAC NIC2 F110W SAMP-SEQ=STEP32,NSAMP=25, 1 DEF PATTERN 1 4 CUM OFFSET=SAM ------------------------------------------------------------------------------------------------------------------------------------ 5 CASA-CCO NIC2 MULTIAC NIC2 F110W SAMP-SEQ=STEP32,NSAMP=25, 1 DEF PATTERN 1 5 CUM OFFSET=SAM ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Visit Id| Exp Id |Primary |Secondary |Iteration |CR-SPLIT |Orbit Num |Duration | |Pattern Pos |Pattern Pos |Num |Num | | ------------------------------------------------------------------------------------------------------------------------------------ 51 1 1 none none none tbd tbd 51 1 2 none none none tbd tbd 51 1 3 none none none tbd tbd 51 1 4 none none none tbd tbd 51 1 5 none none none tbd tbd 51 1 6 none none none tbd tbd 51 1 7 none none none tbd tbd 51 1 8 none none none tbd tbd 51 1 9 none none none tbd tbd 51 2 1 none none none tbd tbd 51 2 2 none none none tbd tbd 51 2 3 none none none tbd tbd 51 2 4 none none none tbd tbd 51 2 5 none none none tbd tbd 51 2 6 none none none tbd tbd 51 2 7 none none none tbd tbd 51 2 8 none none none tbd tbd 51 2 9 none none none tbd tbd 51 3 1 none none none tbd tbd 51 3 2 none none none tbd tbd 9798( 5) - 03/30/04 11:22 - [ 10] Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Visit Id| Exp Id |Primary |Secondary |Iteration |CR-SPLIT |Orbit Num |Duration | |Pattern Pos |Pattern Pos |Num |Num | | ------------------------------------------------------------------------------------------------------------------------------------ 51 3 3 none none none tbd tbd 51 3 4 none none none tbd tbd 51 3 5 none none none tbd tbd 51 3 6 none none none tbd tbd 51 3 7 none none none tbd tbd 51 3 8 none none none tbd tbd 51 3 9 none none none tbd tbd 51 4 1 none none none tbd tbd 51 4 2 none none none tbd tbd 51 4 3 none none none tbd tbd 51 4 4 none none none tbd tbd 51 4 5 none none none tbd tbd 51 4 6 none none none tbd tbd 51 4 7 none none none tbd tbd 51 4 8 none none none tbd tbd 51 4 9 none none none tbd tbd 51 5 1 none none none tbd tbd 51 5 2 none none none tbd tbd 51 5 3 none none none tbd tbd 51 5 4 none none none tbd tbd 51 5 5 none none none tbd tbd 51 5 6 none none none tbd tbd 51 5 7 none none none tbd tbd 51 5 8 none none none tbd tbd 51 5 9 none none none tbd tbd 9798( 5) - 03/30/04 11:22 - [ 11] Summary Form for Proposal 9798 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures NIC2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations NIC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes MULTIACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters SAMP-SEQ=STEP32 NSAMP=25 OFFSET=SAM ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements CVZ; BETWEEN 01-MAR-2004 00 00 00 AND 10-MAR-2004 00 00 00 PATTERN 1 1 PATTERN 1 2 PATTERN 1 3 PATTERN 1 4 PATTERN 1 5 CVZ; BETWEEN 01-MAR-2004 00 00 00 AND 10-MAR-2004 00 00 00 CVZ ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F110W F160W ------------------------------------------------------------------------------------------------------------------------------------ Target Names CASA-CCO ------------------------------------------------------------------------------------------------------------------------------------