! Proposal 6777, submission 1 ! PI: Richard Rothschild ! Received Fri Feb 2 12:23:34 EST 1996 ! From: ross@cassfos04.UCSD.EDU ! Hubble Space Telescope Cycle 6 (1996) Phase II Proposal Template ! $Id: 6777,v 3.1 1996/02/06 19:28:57 pepsa Exp $ ! Hubble Space Telescope Cycle 6 (1996) Phase II Proposal Template ! $Id: 6777,v 3.1 1996/02/06 19:28:57 pepsa Exp $ ! ! Refer to the HST Phase II Proposal Instructions to fill this out ! ! Anything after a "!" is ignored, and may be deleted ! ! All keywords with multiple entries are comma delimited except the ! Visit_Requirements and Special_Requirements keywords which can be ! delimited with carriage returns or semi-colons, but not commas ! ! For help call your Program Coordinator: Bremmer ! Phone: 410-338-4458 , E-mail: bremmer@stsci.edu ! ! This partially completed template was generated from a Phase I proposal. ! Name of Phase I Proposal: archive-0997.rothschild.prop ! Date generated: Fri Dec 22 15:46:53 EST 1995 ! Proposal_Information ! Section 4 Title: A Counterpart Search for SGR 0526-66 Proposal_Category: GO Scientific_Category: HOT STARS Cycle: 6 Investigators PI_name: Richard Rothschild PI_Institution: University of California, San Diego CoI_Name: David Marsden CoI_Institution: University of California, San Diego Contact: ! Y or N (designate at most one contact) CoI_Name: Ross Cohen CoI_Institution: University of California, San Diego Contact: ! Y or N (designate at most one contact) Abstract: ! Free format text (please update) Soft gamma-ray repeaters are a class of bursting X-ray sources which are characterized by short durations, relatively soft spectra, and lack of spectral evolution during outburst. Thought to be due to neutron stars, optical counterparts have yet to be confirmed for any of the three known SGRs. We propose to use the WFPC2 to search for an optical counterpart to the X-ray point source which is coincident with the gamma- ray error box for SGR 0526-66. Detection of an optical counterpart is crucial to advancing our understanding of these remarkable objects. The proposed search will be made possible by the fine resolution of the WFPC2, which will allow for significantly more sensitive searches than presently available. Questions ! Free format text (please update) Observing_Description: The observation will take one orbit in the CVZ, and will use the PC and F814W. After quide star acquisition and overhead, time remains for 4 exposures of 1100s each. This allows for two exposures (to remove cosmic rays) at each of two locations separated by 11 pixels (to correct for hot pixels and other defects). To calculate the expected optical flux of a typical low mass X-ray binary (LMXRB) in the field of view, we use a relationship between the optical and X-ray fluxes for these systems F_optsimF_x/500, where F_opt and F_x are the integrated optical (3000-7000Angstrom) and X-ray (2-11 keV) fluxes, respectively (Van Paradijs, 1995). To obtain the X-ray flux we integrated a power law model with photon index 1.4 (White et al, 1988) and neutral hydrogen column density of 10^22 cm^2 (Dickel, 1995) over the 2-11 keV range using the PIMMS software package and the normalization from the ROSAT HRI observations of the N49 point source (Rothschild et al, 1994). The X-ray flux found was 8.5 X 10^-12 erg cm^ -2 s^-1, which yielded an integrated optical flux of 3.0 X 10^-14 erg cm^-2 s^-1. Because the optical flux per frequency f_nu of LMXRB is approximately flat over the wavelengths of interest (Van Paradijs, 1995), we then obtained the predicted (unreddened) differential flux F_nu=3 X 10^-29 erg cm^-2 s^-1 hz^-1 for a putative LMXRB in the N49 point source. Because the X-ray point source coincides with the N49 supernova remnant, the background is dominated by emission lines and nebular continuum emission. To minimize both the background due to emission lines and the extinction, we will use the PC with the F814W filter for the proposed observation. We estimate the reddening using N_H= 10^22 cm^2 derived from the ROSAT PSPC observations of the N49 point source (Dickel, 1995) and the relationship between neutral H column and extinction (Diplas & Savage, 1994). We derive 3.6 magnitudes of extinction at 8140 Angstroms, for an estimated observed magnitude m_nu(8140)=26.35. The mean nebular background was estimated from data in Vancura et al (1992) as m_nu=21.2 per square arcsecond. Object count rates, nebular and sky background (at the south ecliptic pole), dark count rates, and read noise were estimated from "Exposure Time Estimation for WFPC2 Images of Stellar Targets". The count rates are 0.13 counts/sec, 0.031 counts/sec/pixel, and 0.0075 counts/sec/pixel for the source, nebula, and sky, respectively. For the PC, in a 4680 s exposure we obtain a S/N of 8 on the target, assuming that the object falls at a pixel corner (sharpness=0.045). Because read noise is not dominant, we can split the exposures to allow cosmic ray removal. Real_Time_Justification: Continuous viewing zone observation (CVZ) Calibration_Justification: ! Move appropriate text from Real_Time_Justification Additional_Comments: Fixed_Targets ! Section 5.1 Target_Number:1 Target_Name:N49-052601-660435 Alternate_Names:SGR0526-66 Description:Unidentified,X-ray Emitter,Gamma Ray Emitter,Star,X-ray Burster,X-ray Transient,Gamma Ray Burster,Neutron Star Position:RA=5H 26M 0.44S +/- 1.72S, DEC=-66D 4' 35.56"+/-5.0" Equinox:2000 Flux:I=25.6,F(8140)=5e-20,SURF-BKG(8140)=5.5e-18 Comments: These fluxes are calculated for the filter F814W Visits ! Section 6 Visit_Number:1 Visit_Requirements: ! Section 7.1 ! Uncomment or copy visit level special requirements needed ! Most of these requirements (including ORIENT) will limit scheduling ! PCS MODE [Fine | Gyro] ! GUIDing TOLerance ! DROP TO GYRO IF NECESSARY [NO REACQuisition] ! ORIENTation TO ! ORIENTation TO FROM ! ORIENTation TO FROM NOMINAL ! SAME ORIENTation AS CVZ ! PARallel ! SCHEDulability ! AFTER [BY [TO ]] ! AFTER ! BEFORE ! BETWEEN AND ! GROUP WITHIN