5841( 11) - 10/31/95 11:34 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 5841 Version: 11 Check-in Date: ********** 1.Proposal Title: Unidentified Extreme-UV Sources and the, Isolated Neutron Stars of the Galaxy ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle Hot Stars GO 5 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Amotz Shemi Tel Aviv University CoI: Dan Maoz Tel Aviv University Y CoI: Eran O. Ofek Tel Aviv University N ------------------------------------------------------------------------------------ 6. Abstract We propose to image in the UV two fields in which bright extreme-UV (EUV) sources have been detected by the ROSAT and EUVE all-sky surveys at ~ 100 - 700Angstrom, but which have no optical identification. We have imaged these fields from the ground to a limiting magnitude of R = 23, \ B=22, and detected no blue objects that could be the optical counterparts of the EUV sources. The EUV sources could be nearby (10-100 pc) old (\sgreat 1 Gyr) isolated neutron stars, which are predicted to be abundant in the Galaxy but have never been detected before. These neutron stars rotate too slowly and their magnetic fields are too weak to make them radio pulsars. Accretion from the ISM should, however, make them bright at far-UV wavelengths. The 1200 -- 2500 Angstrom\ band that is accessible to HST is the natural bridge in which to detect and pinpoint the EUV sources, whose positions are known to only ~ 1' accuracy from the other satellite observations. The sources can then be further studied from the ground and in future HST cycles to determine if they are indeed isolated neutron stars, or some other high-energy phenomenon. The HST data will allow us to make a first measurement of the broad- band characteristics of the unidentified EUV sources. If the sources are isolated neutron stars, the HST data will constrain their accretion physics and population properties, and will have implications for the stellar evolution history of our Galaxy, its mass function, and neutron star evolution. ------------------------------------------------------------------------------------ 5841( 11) - 10/31/95 11:34 - [ 2] Observations Description ------------------------ We will observe each of the EUV-source field 1636-285 for two orbits (78 minutes exposure time) with the WFPC2 and the F218W filter, and a further two orbits (84 minutes exposure time) with the F160BW filter. The EUV source RE 0922+710, which has declination +71, can be a CVZ target, on which we can obtain very similar exposure times (79 and 85 minutes per filter) in just two orbits. The above exposure times will allow reaching a 5Sigma detection limit (100 electrons above the background, which is dominated at these wavelengths by the CCD dark current) of Nu F_Nu= 2.2* 10^-14 erg \ cm^-2 \ s^-1 in the F160BW band (F_Lambda=1.5* 10^-17 erg \ cm^-2 \ s^-1 AA^-1), and of Nu F_Nu= 6.5* 10^-15 erg \ cm^-2 \ s^- 1 in the F218W band (F_Lambda=3* 10^-18 erg \ cm^-2 \ s^-1 AA^-1). Real Time Justification ----------------------- none Calibration Justification ------------------------- Additional Comments ------------------- none ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 5841( 11) - 10/31/95 11:34 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 RE0922+710 UNIDENTIFIED, RA = 09H 17M 53.50S +/- 1S, DEC 1950 V=23 +/- 3 Ultraviolet Emitter =+71D 22' 40.5" +/- 1" Comments: Unidentified EUV source 2 EUVE1636-285 UNIDENTIFIED, RA = 16H 36M 33.89S +/- 1S, DEC 2000 V=23 +/- 3 Ultraviolet Emitter = -28D 31' 58.9" +/- 1" Comments: Unidentified EUV source 5841( 11) - 10/31/95 11:34 - [ 4] Visit: 01 Visit Requirements: CVZ 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 ------------------------------------------------------------------------------------------------------------------------------------ 11 RE0922+710 WFPC2 IMAGE WFALL- F218W CR-SPLIT=NO 1 1500S POS TARG -6, -6; SEQ 11-13 non-int FIX ------------------------------------------------------------------------------------------------------------------------------------ 12 RE0922+710 WFPC2 IMAGE WFALL- F218W CR-SPLIT=NO 1 1500S POS TARG -6, -6 FIX ------------------------------------------------------------------------------------------------------------------------------------ 13 RE0922+710 WFPC2 IMAGE WFALL- F218W CR-SPLIT=NO 1 1600S POS TARG -6, -6 FIX ------------------------------------------------------------------------------------------------------------------------------------ 21 RE0922+710 WFPC2 IMAGE WFALL- F160BW CR-SPLIT=NO 1 1600S POS TARG -6, -6; SEQ 21-23 non-int FIX ------------------------------------------------------------------------------------------------------------------------------------ 22 RE0922+710 WFPC2 IMAGE WFALL- F160BW CR-SPLIT=NO 1 1600S POS TARG -6, -6 FIX ------------------------------------------------------------------------------------------------------------------------------------ 23 RE0922+710 WFPC2 IMAGE WFALL- F160BW CR-SPLIT=NO 1 1800S POS TARG -6, -6 FIX ------------------------------------------------------------------------------------------------------------------------------------ 5841( 11) - 10/31/95 11:34 - [ 5] Visit: 02 Visit Requirements: 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 ------------------------------------------------------------------------------------------------------------------------------------ 11 EUVE1636- WFPC2 IMAGE WFALL- F218W CR-SPLIT=NO 1 1200S POS TARG -6, -6; 285 FIX ------------------------------------------------------------------------------------------------------------------------------------ 12 EUVE1636- WFPC2 IMAGE WFALL- F218W CR-SPLIT=NO 1 1200S POS TARG -6, -6 285 FIX ------------------------------------------------------------------------------------------------------------------------------------ 13 EUVE1636- WFPC2 IMAGE WFALL- F218W CR-SPLIT=NO 1 1300S POS TARG -6, -6 285 FIX ------------------------------------------------------------------------------------------------------------------------------------ 14 EUVE1636- WFPC2 IMAGE WFALL- F218W CR-SPLIT=NO 1 1300S POS TARG -6, -6 285 FIX ------------------------------------------------------------------------------------------------------------------------------------ 21 EUVE1636- WFPC2 IMAGE WFALL- F160BW CR-SPLIT=NO 1 1300S POS TARG -6, -6; 285 FIX ------------------------------------------------------------------------------------------------------------------------------------ 22 EUVE1636- WFPC2 IMAGE WFALL- F160BW CR-SPLIT=NO 1 1300S POS TARG -6, -6 285 FIX ------------------------------------------------------------------------------------------------------------------------------------ 23 EUVE1636- WFPC2 IMAGE WFALL- F160BW CR-SPLIT=NO 1 1300S POS TARG -6, -6 285 FIX ------------------------------------------------------------------------------------------------------------------------------------ 24 EUVE1636- WFPC2 IMAGE WFALL- F160BW CR-SPLIT=NO 1 1300S POS TARG -6, -6 285 FIX ------------------------------------------------------------------------------------------------------------------------------------ 5841( 11) - 10/31/95 11:34 - [ 6] Summary Form for Proposal 5841 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category Hot Stars ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements CVZ POS TARG -6, -6; SEQ 11-13 non-int POS TARG -6, -6 POS TARG -6, -6; SEQ 21-23 non-int POS TARG -6, -6; ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F218W F160BW ------------------------------------------------------------------------------------------------------------------------------------ Target Names RE0922+710 EUVE1636-285 ------------------------------------------------------------------------------------------------------------------------------------