10479(  7) - 05/20/05 13:48  - [  1]

    PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS   ST ScI Use Only
                                                       ID:      10479
                                                       Version: 7
                                                       Check-in Date: 20-May-2005
                                                                      17:47:20

1.Proposal Title:
The Distance and Mass of the Neutrino-Luminous White Dwarf PG 0122+200
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2. Proposal For  3. Cycle  4. Parallel Pointing Tolerance
GO               14        <none>
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5. Investigators
                                                                                     Contact?
    PI: Dr. M. Sean O'Brien               Yale University
   CoI: Dr. Howard E. Bond                Space Telescope Science Institute             N
   CoI: Dr. Edmund Nelan                  Space Telescope Science Institute             N

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6. Abstract

PG 0122+200 is a pulsating hot white dwarf that is believed to radiate more energy
as neutrinos than it does as photons. We propose to measure with FGS the
trigonometric parallax of PG 0122+200 and thereby determine its distance,
luminosity, and mass. Ongoing investigations from the ground will infer the neutrino
luminosity through its effect on the pulsation periods, thus testing standard and
non-standard lepton theory, but the stellar mass must first be known. The pulsation
spectrum of PG 0122+200 admits two alternative seismological interpretations, each
implying a different mass, luminosity, and distance. Measurement of an accurate
distance will resolve the matter once and for all and precisely determine the
stellar mass. This project represents the first test of lepton physics in dense (log
rho = 6) plasma and is relevant to the many areas of stellar physics in which
neutrino interactions are important, including recent theories intended to solve the
solar-neutrino problem.
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                                                10479(  7) - 05/20/05 13:48  - [  2]

  Observations Description
  ------------------------

     The proposed observations consist of astrometric measurements of PG 0122+200,
     along with about half a dozen reference stars surrounding it. The target will
     be observed with FGS1R at five epochs of maximum parallax factor, i.e., at 6,
     12, 18, and 24 months after the initial observation. At each epoch we will
     observe the target and its reference field during two HST visits separated by
     about two weeks. Each one-orbit visit will consist of repeated measurements of
     our science target and the reference stars in the field of view. This will
     yield the relative positions of the stars for the visit and allow us to define
     the visit's "plate." The 24-month baseline will allow a robust determination of
     the proper motions of the targets, an essential ingredient in the parallax
     solution. Once the observations from all 5 epochs have been completed, the
     observations will be combined with a "plate-overlay" technique to define a
     common reference frame (a "virtual plate") onto which the positions of the
     individual stars can be mapped. By comparing the position of the science target
     to the reference frame in the 10 independent observations obtained during the 5
     epochs, we can solve for both the proper motion and the trigonometric parallax
     of the object, relative to the comparison stars. Our request is thus for 10
     orbits (5 visits 2 orbits per visit). This is a Long-Term proposal, since the
     observations must extend 24 months past the first visit. We request 4 orbits in
     Cycle 12, 4 in Cycle 13, and 2 in Cycle 14. The derived FGS parallaxes will, of
     course, be relative to the reference frame of the fainter surrounding stars. In
     order to convert the relative parallax to absolute with the highest accuracy,
     we need an estimated parallax of each individual reference star. We therefore
     plan to obtain photometry and spectroscopy of each of the reference stars and
     determine spectroscopic parallaxes for them. We are applying herewith (see the
     Coordinated Observations section below) for the modest amount of NOAO observing
     time needed to obtain the data for the spectroscopic parallaxes of the
     reference stars. FGS3, the original FGS used for HST astrometry, was capable of
     excellent parallax accuracy. For example, based on a series of FGS3
     observations obtained in 1995-97, Benedict et al. (2002a, b) obtained absolute
     parallax accuracies of ?0.15 and ?0.20 mas for Cep and RR Lyr, respectively.
     For comparison, the Hipparcos accuracies for the same stars were ?0.58 and
     ?0.59 mas. FGS1R, installed in 1997, has replaced FGS3 as the "astrometry" FGS.
     The performance of FGS1R should exceed that of FGS3 for two reasons. (1) FGS1R
     displays a temporal stability of its interferograms never achieved by FGS3, an
     attribute that greatly improves the measurement repeatability. (2) FGS1R
     benefits from a more robust calibration program. In particular, the observing
     technique employed to calibrate its geometric distortions (the dominant source
     of astrometric error) has resulted in residuals that are about 1/3 those of
     FGS3. The instrument's lateral color and cross-filter calibrations are also
     better characterized. Indications of FGS1R's excellent performance are becoming
     available. A recently completed program (McGrath et al. 2002) used FGS1R to
     search for the astrometric wobble of rho-1 Cnc due to its planetary companion.
     Fourteen orbits of FGS data were taken near one epoch of maximum parallax
     factor to search for the short-period wobble. To determine the proper motion
     and parallax, one additional orbit each was used 6 and 12 months later, so that
     the parallax error budget is essentially that of a 3-orbit program. Our team
     member Nelan, who is the STScI FGS Instrument Scientist, designed the observing
     strategy, and has done an unpublished analysis of the rho-1 Cnc parallax. The
     result shows a 1-sigma parallax error of ?0.4 mas. We thus adopt ?0.4 mas as
                                                10479(  7) - 05/20/05 13:48  - [  3]

     the error in an FGS1R parallax based on three one-orbit HST visits at 6-month
     intervals. This error can be reduced to ?0.4/(n/3)^1/2 mas, where n is the
     number of HST orbits, down to a systematic-error floor that we estimate to be <
     0.15 mas. These considerations suggest that FGS1R should be able to measure the
     relative parallax of PG 0122+200 with an accuracy of at least 0.2 mas based on
     10 HST orbits over the next three scheduling cycles. Benedict, G.F. et al.
     2002a, AJ, 123, 473 Benedict, G.F. et al. 2002b, AJ, 124, 1695 McGrath, M.A. et
     al. 2002, ApJ, 564, L27

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


  Calibration Justification
  -------------------------


  Additional Comments
  -------------------

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                                                10479(  7) - 05/20/05 13:48  - [  4]

TARGET LIST    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   PG0122+200   EXT-STAR, PG1159 STAR   RA=01H25M22.4800S +/- 0.5",      J2000             V = 16.3+/-0.2
                                         DEC=+20D17'56.94" +/- 0.5",
                                         PLATE-ID=021K
    Coordinate Source: GUIDE_STAR_CATALOG

2   REF1         CALIBRATION,            RA=01H25M20.4800S +/- 0.1",      J2000             V = 13.6+/-0.2
                 ASTROMETRIC             DEC=+20D17'53.05" +/- 0.1",
                                         PLATE-ID=021K
    Coordinate Source: GUIDE_STAR_CATALOG

3   REF2         CALIBRATION,            RA=01H25M40.2000S +/- 0.1",      J2000             V = 15.3+/-0.3
                 ASTROMETRIC             DEC=+20D19'10.90" +/- 0.1",
                                         PLATE-ID=021K
    Coordinate Source: GUIDE_STAR_CATALOG

4   REF3         CALIBRATION,            RA=01H25M40.2000S +/- 0.1",      J2000             V = 14.52+/-0.2
                 ASTROMETRIC             DEC=+20D19'10.88" +/- 0.1"
    Coordinate Source: GUIDE_STAR_CATALOG

5   REF4         CALIBRATION,            RA=01H25M51.0000S +/- 0.1",      J2000             V = 13.42+/-0.2
                 ASTROMETRIC             DEC=+20D19'59.16" +/- 0.1"
    Coordinate Source: GUIDE_STAR_CATALOG

6   REF5         CALIBRATION,            RA=01H25M40.0100S +/- 0.1",      J2000             V = 14.9+/-0.2
                 ASTROMETRIC             DEC=+20D16'50.12" +/- 0.1",
                                         PLATE-ID=021K
    Coordinate Source: GUIDE_STAR_CATALOG

7   REF6         CALIBRATION,            RA=01H25M32.1000S +/- 0.1",      J2000             V = 14.22
                 ASTROMETRIC             DEC=+20D16'24.02" +/- 0.1",
                                         PLATE-ID=021K
    Coordinate Source: GUIDE_STAR_CATALOG

8   REF7         CALIBRATION,            RA=01H25M25.9500S +/- 0.1",      J2000             V = 13.81+/-0.2
                 ASTROMETRIC             DEC=+20D16'20.50" +/- 0.1",
                                         PLATE-ID=021K
    Coordinate Source: GUIDE_STAR_CATALOG

                                                10479(  7) - 05/20/05 13:48  - [  5]

Visit: 01
     Visit Priority:      <none>
     Visit Requirements:  PCS MODE FINE; SCHED 30%; ORIENT 249.0D TO 255.0 D; BETWEEN 10-JUL-
                          2005:00:00:00 AND 13-JUL-2005:00:00:00
     On Hold Comments:    <none>
     Additional Comments: <none>


Exposures
------------------------------------------------------------------------------------------------------------------------------------
Exp |   Target  | Instr  | Oper. | Aper    |Spectral|Central|           Optional           |Num|   Time   |       Special
Num |    Name   | Config | Mode  | or FOV  |Element |Waveln.|          Parameters          |Exp|          |     Requirements
------------------------------------------------------------------------------------------------------------------------------------
1    PG0122+200  FGS      POS     1         F583W                                           1   45 S       POS TARG -99,-55; GSPAIR
                                                                                                           0120301621F20120300898F3;
                                                                                                           GS ACQ SCENARIO BASE13GO;
                                                                                                           SEQ 1-16 NON-INT
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2    REF1        FGS      POS     1         F583W                                           1   10 S       SAME POS AS 1
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3    REF7        FGS      POS     1         F583W                                           1   10 S       SAME POS AS 1
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4    REF6        FGS      POS     1         F583W                                           1   10 S       SAME POS AS 1
------------------------------------------------------------------------------------------------------------------------------------
5    REF5        FGS      POS     1         F583W                                           1   10 S       SAME POS AS 1
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6    PG0122+200  FGS      POS     1         F583W                                           1   45 S       SAME POS AS 1
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7    REF1        FGS      POS     1         F583W                                           1   10 S       SAME POS AS 1
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8    REF7        FGS      POS     1         F583W                                           1   10 S       SAME POS AS 1
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9    REF2        FGS      POS     1         F583W                                           1   10 S       SAME POS AS 1
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10   REF3        FGS      POS     1         F583W                                           1   10 S       SAME POS AS 1
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11   REF4        FGS      POS     1         F583W                                           1   10 S       SAME POS AS 1
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12   REF5        FGS      POS     1         F583W                                           1   10 S       SAME POS AS 1
------------------------------------------------------------------------------------------------------------------------------------
13   PG0122+200  FGS      POS     1         F583W                                           1   45 S       SAME POS AS 1
------------------------------------------------------------------------------------------------------------------------------------
14   REF1        FGS      POS     1         F583W                                           1   10 S       SAME POS AS 1
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15   REF7        FGS      POS     1         F583W                                           1   10 S       SAME POS AS 1
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16   REF6        FGS      POS     1         F583W                                           1   10 S       SAME POS AS 1
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                                                10479(  7) - 05/20/05 13:48  - [  6]
Sub Exposures
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Target             | Exp |Instr   | Oper. |  Aper  |Spectral|Cent.|Primary     |Secondary   |Iteration |CR-SPLIT  |Orbit  |Duration
Name               | Num |Config  | Mode  | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num       |Num       |Number |
------------------------------------------------------------------------------------------------------------------------------------

Sub Exposures
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Target             | Exp |Instr   | Oper. |  Aper  |Spectral|Cent.|Primary     |Secondary   |Iteration |CR-SPLIT  |Orbit  |Duration
Name               | Num |Config  | Mode  | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num       |Num       |Number |
------------------------------------------------------------------------------------------------------------------------------------
PG0122+200          1     FGS      POS     1        F583W          none         none         none       none       1       N/A
REF1                2     FGS      POS     1        F583W          none         none         none       none       1       N/A
REF7                3     FGS      POS     1        F583W          none         none         none       none       1       N/A
REF6                4     FGS      POS     1        F583W          none         none         none       none       1       N/A
REF5                5     FGS      POS     1        F583W          none         none         none       none       1       N/A
PG0122+200          6     FGS      POS     1        F583W          none         none         none       none       1       N/A
REF1                7     FGS      POS     1        F583W          none         none         none       none       1       N/A
REF7                8     FGS      POS     1        F583W          none         none         none       none       1       N/A
REF2                9     FGS      POS     1        F583W          none         none         none       none       1       N/A
REF3                10    FGS      POS     1        F583W          none         none         none       none       1       N/A
REF4                11    FGS      POS     1        F583W          none         none         none       none       1       N/A
REF5                12    FGS      POS     1        F583W          none         none         none       none       1       N/A
PG0122+200          13    FGS      POS     1        F583W          none         none         none       none       1       N/A
REF1                14    FGS      POS     1        F583W          none         none         none       none       1       N/A
REF7                15    FGS      POS     1        F583W          none         none         none       none       1       N/A
REF6                16    FGS      POS     1        F583W          none         none         none       none       1       N/A
                                                10479(  7) - 05/20/05 13:48  - [  7]

Visit: 02
     Visit Priority:      <none>
     Visit Requirements:  PCS MODE FINE; SCHED 30%; ORIENT 249.0D TO 255.0 D; AFTER 01 BY 1 D TO 3 D
     On Hold Comments:    <none>
     Additional Comments: <none>


Exposures
------------------------------------------------------------------------------------------------------------------------------------
Exp |   Target  | Instr  | Oper. | Aper    |Spectral|Central|           Optional           |Num|   Time   |       Special
Num |    Name   | Config | Mode  | or FOV  |Element |Waveln.|          Parameters          |Exp|          |     Requirements
------------------------------------------------------------------------------------------------------------------------------------
1    PG0122+200  FGS      POS     1         F583W                                           1   45 S       POS TARG -99,-55; GSPAIR
                                                                                                           0120301621F20120300898F3;
                                                                                                           GS ACQ SCENARIO BASE13GO;
                                                                                                           SEQ 1-16 NON-INT
------------------------------------------------------------------------------------------------------------------------------------
2    REF1        FGS      POS     1         F583W                                           1   10 S       SAME POS AS 1
------------------------------------------------------------------------------------------------------------------------------------
3    REF7        FGS      POS     1         F583W                                           1   10 S       SAME POS AS 1
------------------------------------------------------------------------------------------------------------------------------------
4    REF6        FGS      POS     1         F583W                                           1   10 S       SAME POS AS 1
------------------------------------------------------------------------------------------------------------------------------------
5    REF5        FGS      POS     1         F583W                                           1   10 S       SAME POS AS 1
------------------------------------------------------------------------------------------------------------------------------------
6    PG0122+200  FGS      POS     1         F583W                                           1   45 S       SAME POS AS 1
------------------------------------------------------------------------------------------------------------------------------------
7    REF1        FGS      POS     1         F583W                                           1   10 S       SAME POS AS 1
------------------------------------------------------------------------------------------------------------------------------------
8    REF7        FGS      POS     1         F583W                                           1   10 S       SAME POS AS 1
------------------------------------------------------------------------------------------------------------------------------------
9    REF2        FGS      POS     1         F583W                                           1   10 S       SAME POS AS 1
------------------------------------------------------------------------------------------------------------------------------------
10   REF3        FGS      POS     1         F583W                                           1   10 S       SAME POS AS 1
------------------------------------------------------------------------------------------------------------------------------------
11   REF4        FGS      POS     1         F583W                                           1   10 S       SAME POS AS 1
------------------------------------------------------------------------------------------------------------------------------------
12   REF5        FGS      POS     1         F583W                                           1   10 S       SAME POS AS 1
------------------------------------------------------------------------------------------------------------------------------------
13   PG0122+200  FGS      POS     1         F583W                                           1   45 S       SAME POS AS 1
------------------------------------------------------------------------------------------------------------------------------------
14   REF1        FGS      POS     1         F583W                                           1   10 S       SAME POS AS 1
------------------------------------------------------------------------------------------------------------------------------------
15   REF7        FGS      POS     1         F583W                                           1   10 S       SAME POS AS 1
------------------------------------------------------------------------------------------------------------------------------------
16   REF6        FGS      POS     1         F583W                                           1   10 S       SAME POS AS 1
------------------------------------------------------------------------------------------------------------------------------------

Sub Exposures
------------------------------------------------------------------------------------------------------------------------------------
Target             | Exp |Instr   | Oper. |  Aper  |Spectral|Cent.|Primary     |Secondary   |Iteration |CR-SPLIT  |Orbit  |Duration
Name               | Num |Config  | Mode  | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num       |Num       |Number |
------------------------------------------------------------------------------------------------------------------------------------
                                                10479(  7) - 05/20/05 13:48  - [  8]
Sub Exposures
------------------------------------------------------------------------------------------------------------------------------------
Target             | Exp |Instr   | Oper. |  Aper  |Spectral|Cent.|Primary     |Secondary   |Iteration |CR-SPLIT  |Orbit  |Duration
Name               | Num |Config  | Mode  | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num       |Num       |Number |
------------------------------------------------------------------------------------------------------------------------------------
PG0122+200          1     FGS      POS     1        F583W          none         none         none       none       1       N/A
REF1                2     FGS      POS     1        F583W          none         none         none       none       1       N/A
REF7                3     FGS      POS     1        F583W          none         none         none       none       1       N/A
REF6                4     FGS      POS     1        F583W          none         none         none       none       1       N/A
REF5                5     FGS      POS     1        F583W          none         none         none       none       1       N/A
PG0122+200          6     FGS      POS     1        F583W          none         none         none       none       1       N/A
REF1                7     FGS      POS     1        F583W          none         none         none       none       1       N/A
REF7                8     FGS      POS     1        F583W          none         none         none       none       1       N/A
REF2                9     FGS      POS     1        F583W          none         none         none       none       1       N/A
REF3                10    FGS      POS     1        F583W          none         none         none       none       1       N/A
REF4                11    FGS      POS     1        F583W          none         none         none       none       1       N/A
REF5                12    FGS      POS     1        F583W          none         none         none       none       1       N/A
PG0122+200          13    FGS      POS     1        F583W          none         none         none       none       1       N/A
REF1                14    FGS      POS     1        F583W          none         none         none       none       1       N/A
REF7                15    FGS      POS     1        F583W          none         none         none       none       1       N/A
REF6                16    FGS      POS     1        F583W          none         none         none       none       1       N/A
                                                10479(  7) - 05/20/05 13:48  - [  9]

            Summary Form for Proposal  10479

  Item                         Used in this proposal
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  Apertures                    1
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  Configurations               FGS
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  Opmodes                      POS
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  Proposal Category            GO
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  Special Requirements         PCS MODE FINE; SCHED 30%; ORIENT 249.0D TO 255.0 D; BETWEEN 10-JUL-2005 00 00 00 AND 13-JUL-2005 00
                               00 00 POS TARG -99,-55; GSPAIR 0120301621F20120300898F3; GS ACQ SCENARIO BASE13GO; SEQ 1-16 NON-INT
                               SAME POS AS 1 PCS MODE FINE; SCHED 30%; ORIENT 249.0D TO 255.0 D; AFTER 01 BY 1 D TO 3 D
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  Spectral Elements            F583W
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  Target Names                 PG0122+200 REF1 REF7 REF6 REF5 REF2 REF3 REF4
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