6525( 7) - 04/02/96 10:04 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6525 Version: 7 Check-in Date: 02-Apr-1996 10:02:08 1.Proposal Title: The B/UV Colors of Geminga Suggest Spectral Feature on Hot Continuum. ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle HOT STARS GO 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Giovanni F. Bignami Istituto di Fisica Cosmica del CNR CoI: Patrizia A. Caraveo Istituto di Fisica Cosmica del CNR N CoI: Roberto P. Mignani Istituto di Fisica Cosmica del CNR N ------------------------------------------------------------------------------------ 6. Abstract Among middle age neutron stars, Geminga is, no doubt, the best studied. Many years of efforts aimed at the identification of the optical counterpart of the X/Gamma ray source yielded the I,R,V,B and more recently F555W and F342W colors of G". When plotted in a flux vs wavelength diagram, the colors of G" do not appear to follow completely a planckian distribution. While the F342W and B fluxes, as well as I upper limit, lie on the extrapolation of the planckian measured by EUVE and ROSAT, the F555W, V and R appear to be well above it. In fact, they seem to define a spectral feature superimposed on the thermal emission. This is the first observational evidence of a spectral feature on an Isolated Neutron Star and as such is in need of confirmation. Aim of this proposal is to provide this by better constraining the underlying planckian, measuring the flux of Geminga with filters F430W and F275W. While F275W would be a new piece of information, the F430W will allow a cross check of the difficult and uncertain B point, measured from the ground to be 26.5. ------------------------------------------------------------------------------------ 6525( 7) - 04/02/96 10:04 - [ 2] Observations Description ------------------------ To estimate the exposure times we used FOCSIM and our previous FOC observation of Geminga, gathered during Cycle 4. According to FOCSIM, exposure times of 5400 and 5000 sec in the F430W and F275W filters, respectively, should be adequate to detect the target with a S/N 30. Therefore, we ask for two exposures: one of 5400 sec. (F430W filter) and the other of 5000 sec (F275W filter). These observations, split in shorter chunks to minimize cosmic rays contamination, should cover five orbits. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 6525( 7) - 04/02/96 10:04 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 01 STAR-0633- STAR,NEUTRON STAR RA=6H 33M 54.13S +/- 0.0006S, J2000 V = 25.5 1746 DEC=17D 46' 12.56" +/- 0.1" B-V = 1 Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1994.03 0.01 0.109 0.006 6525( 7) - 04/02/96 10:04 - [ 4] Visit: 01 Visit Requirements: PCS MODE F 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 STAR-0633- FOC/96 IMAGE 512X512 F430W 3940 1 2500S 1746 ------------------------------------------------------------------------------------------------------------------------------------ 2 STAR-0633- FOC/96 IMAGE 512X512 F430W 3940 1 2500S 1746 ------------------------------------------------------------------------------------------------------------------------------------ 3 STAR-0633- FOC/96 IMAGE 512X512 F430W 3940 1 2500S 1746 ------------------------------------------------------------------------------------------------------------------------------------ 4 STAR-0633- FOC/96 IMAGE 512X512 F195W 2110 1 1100S 1746 ------------------------------------------------------------------------------------------------------------------------------------ 5 STAR-0633- FOC/96 IMAGE 512X512 F195W 2110 1 1100S 1746 ------------------------------------------------------------------------------------------------------------------------------------ 6 STAR-0633- FOC/96 IMAGE 512X512 F195W 2110 1 1100S 1746 ------------------------------------------------------------------------------------------------------------------------------------ 7 STAR-0633- FOC/96 IMAGE 512X512 F195W 2110 1 1100S 1746 ------------------------------------------------------------------------------------------------------------------------------------ 6525( 7) - 04/02/96 10:04 - [ 5] Summary Form for Proposal 6525 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FOC/96 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category HOT STARS ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PCS MODE F ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F430W F195W ------------------------------------------------------------------------------------------------------------------------------------ Target Names STAR-0633-1746 ------------------------------------------------------------------------------------------------------------------------------------