6136(  7) - 08/23/95 11:14  - [  1]

    PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS   ST ScI Use Only
                                                       ID:      6136
                                                       Version: 7
                                                       Check-in Date: **********

1.Proposal Title:
Positioning and proper motion measurement of the PSR0656+14 optical counterpart.
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2. Scientific Category   3. Proposal For  4. Cycle
Hot Stars                   GO               5
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5. Investigators
                                                                                     Contact?
    PI: Roberto Mignani                   Universita degli Studi di Milano and
                                          Istituto di Fisica Cosmica del CNR
   CoI: Giovanni F. Bignami               Istituto di Fisica Cosmica del CNR            N
   CoI: Patrizia A. Caraveo               Istituto di Fisica Cosmica del CNR            N
   CoI: Sandro Mereghetti                 Istituto di Fisica Cosmica del CNR            N

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6. Abstract

PSR0656+14, is one of the few radio pulsars for which an optical counterpart has
been proposed. Two ground based ESO (1989 and 1991) observations detected a m_V ~ 25
object at the radio position. This detection seems confirmed by the HST/FOC and by
EUVE data. We now propose to image the field of PSR0656+14 with the PC to perform
very accurate relative astrometry of the suggested optical counterpart, both as a
reference for future observations, and in order to compare its present position with
those measured in our 1989 and 1991 frames. Since the radio pulsar exhibits a proper
motion towards the SE of ~ 70 mas /year, the corresponding angular displacement of
the optical counterpart over 6 years (>= 0sec point 4) could be measurable. If
observed, this will confirm the proposed identification, and yield interesting
constraints on the emission mechanism(s), expecially in comparison with EUVE and X-
ray data.
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  Observations Description
  ------------------------

     We plan to do deep imaging of the region around PSR0656+14 in order to position
     accurately the candidate counterpart. To estimate the exposure time needed to
     detected our target (m_V <= 25) we take advantage of the experience wa have now
     gathered during Cycle 4 with the program 5484 focussed on the Geminga optical
     counterpart, a target of comparable brightness. In order to clearly detect such
     a faint target with the PC and reduce contamination from cosmic ray hits 6
     images of 7-800 secs are required, split in two exposures per orbit, to fulfill
     our science goal with the necessary overheads. We choose the F555W filter since
     the target has been observed close to this passband from the ground.

  Real Time Justification
  -----------------------

     Our previous ground based observations represent the only accurate reference
     both to  the target position in the PC field and to sufficient nearby stars.

  Calibration Justification
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  Additional Comments
  -------------------

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  Data Distribution

  Media:           8MM
  Blocking Factor: 10
  Ship To:         PI_Address
  Ship Via:        UPS
  Email:                                                              ,
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                                                6136(  7) - 08/23/95 11:14  - [  3]

TARGET LIST    a) Fixed Targets
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Tar|   Target   |         Target        |            Target              |Coord   | Radial |             Flux data
No |    Name    |       Description     |           Position             |Eqnx    |  Vel.  |
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1   STAR-        STAR,NEUTRON STAR       RA=6H 59M 48.12S +/- 0.001S,     J2000             V=25
    065948+14142                         DEC=14D 14' 29.53" +/- 0.01"
    1

   Epoch of Position    RA proper motion (seconds of time/yr)    DEC Proper Motion (arcsec/yr)    Annual Parallax (arcsec)
   J1995.03             0.0044                                   -0.028                           0.0

                                                6136(  7) - 08/23/95 11:14  - [  4]

Visit: 01
     Visit Requirements:  ORIENTation 45.0D TO 45.0D PCS MODE F
     On Hold Comments:    <none>
     Additional Comments: <none>


Exposures
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Exposure|   Target  |Instr | Oper. | Aper  |Spectral|Central|   Optional    |Num|  Time |               Special
 Number |    Name   |Config| Mode  |or FOV |Element |Waveln.|  Parameters   |Exp|       |             Requirements
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1        STAR-       WFPC2  IMAGE   PC1-FIX F555W    5407    CR-SPLIT=0.5,CR 1   1600S
         065948+1414                                         -TOLERANCE=0.2
         21
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2        STAR-       WFPC2  IMAGE   PC1-FIX F555W    5407    CR-SPLIT=0.5,CR 1   1600S
         065948+1414                                         -TOLERANCE=0.2
         21
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3        STAR-       WFPC2  IMAGE   PC1-FIX F555W    5407    CR-SPLIT=0.5,CR 1   1600S
         065948+1414                                         -TOLERANCE=0.2
         21
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4        STAR-       WFPC2  IMAGE   PC1-FIX F555W    5407    CR-SPLIT=0.5,CR 1   1400S
         065948+1414                                         -TOLERANCE=0.2
         21
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                                                6136(  7) - 08/23/95 11:14  - [  5]

            Summary Form for Proposal  6136

  Item                         Used in this proposal
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  Configurations               WFPC2
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  Opmodes                      IMAGE
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  Optional Parameters          CR-SPLIT=0.5 CR-TOLERANCE=0.2
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  Proposal Category            GO
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  Scientific Category          Hot Stars
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  Special Requirements         ORIENTation 45.0D TO 45.0D PCS MODE F
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  Spectral Elements            F555W
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  Target Names                 STAR-065948+141421
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