7785( 3) - 08/06/97 16:47 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 7785 Version: 3 Check-in Date: 06-Aug-1997 16:46:43 1.Proposal Title: The Nature of GRB970228 and Its Surrounding Nebulosity ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle COSMOLOGY GO/DD 7 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: ANDREW FRUCHTER SPACE TELESCOPE SCIENCE INSTITUTE CoI: Elena Pian ITESRE-CNR Bologna N CoI: F. Frontera ITESRE-CNR N CoI: M. Tavani Columbia University N CoI: S. Thorsett Princeton N ------------------------------------------------------------------------------------ 6. Abstract We propose to observe the Gamma Ray Burster GRB 970228 with the STIS CCD. Although four orbits have already been devoted to observing this object with WFPC2 in PC mode, no clear detection of the reported nebulosity surrounding the point source burster has been obtained. Using the WF mode of the WFPC2 to image this source would only marginally improve the sensitivity of the observation, as this source is near the ecliptic, and the image noise is dominated, even in the PC, by sky background. The use of the STIS CCD, near zodiacal light minimum, would produce a gain in S/N of two magnitudes over the observations previously taken due to the high throughput of the STIS camera and the availability of an unusually broad red filter. This improvement in sensitivity will allow us to obtain the magnitude and position of the source at 6 months after the initial burst, constraining emission mechanisms and possible proper motion, and will provide a clear detection of the "galaxy" should it really exist. If instead the nebulosity is variable, the STIS images will give us the S/N to show that the variability is not due to statistical uncertainty. If the nebulosity is undetectable in these STIS images, the conclusion that the burst was non-cosmological will be nearly inescapable. ------------------------------------------------------------------------------------ 7785( 3) - 08/06/97 16:47 - [ 2] Observations Description ------------------------ Observations will be taken with STIS CCDs for 2 orbits ( no filter ). Real Time Justification ----------------------- This candidate gamma ray burster is declining rapidly in brightness; however, the sky is also bright in the summer due to the location of the object in the ecliptic. The optimum observing time is early September. Calibration Justification ------------------------- None Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 7785( 3) - 08/06/97 16:47 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 GRB970228 STAR,GAMMA RAY BURSTER RA=05H 1M 46.69S +/- J2000 V = 28+/-2 0.01S,DEC=11D 46' 53.1" +/- 0.2" 7785( 3) - 08/06/97 16:47 - [ 4] Visit: 01 Visit Requirements: SCHED 100% BETWEEN 20-Aug-1997 AND 15-Sep-1997 On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 10 GRB970228 STIS/C ACCUM 50CCD MIRROR CR-SPLIT=2 1 1150 S MAX DUR MIN DUR CD ------------------------------------------------------------------------------------------------------------------------------------ 20 GRB970228 STIS/C ACCUM 50CCD MIRROR CR-SPLIT=2 1 1150 S POS TARG 0.0,0.125 MAX CD DUR MIN DUR ------------------------------------------------------------------------------------------------------------------------------------ 30 GRB970228 STIS/C ACCUM 50CCD MIRROR CR-SPLIT=2 1 1150 S POS TARG 0.125,0.0 MAX CD DUR MIN DUR ------------------------------------------------------------------------------------------------------------------------------------ 40 GRB970228 STIS/C ACCUM 50CCD MIRROR CR-SPLIT=2 1 1150 S POS TARG 0.175,0.175 MAX CD DUR MIN DUR ------------------------------------------------------------------------------------------------------------------------------------ 7785( 3) - 08/06/97 16:47 - [ 5] Summary Form for Proposal 7785 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=2 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO/DD ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category COSMOLOGY ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements SCHED 100% BETWEEN 20-Aug-1997 AND 15-Sep-1997 MAX DUR MIN DUR POS TARG 0.0,0.125 MAX DUR MIN DUR POS TARG 0.125,0.0 MAX DUR MIN DUR POS TARG 0.175,0.175 MAX DUR MIN DUR ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR ------------------------------------------------------------------------------------------------------------------------------------ Target Names GRB970228 ------------------------------------------------------------------------------------------------------------------------------------