!  File:  4844C.PROP
!  Database:  PEPDB
!  Date:  23-FEB-1994:05:51:05

coverpage:

  title_1:         CENTRAL STARS OF PLANETARY NEBULAE: CYCLE3MED
    sci_cat:       STELLAR ASTROPHYSICS
    sci_subcat:    SUBLUMINOUS STARS
    proposal_for:  GTO/FOC
    cont_id:       1254
    pi_title:      IR.
    pi_fname:      T.
    pi_mi:         M
    pi_lname:      KAMPERMAN
    pi_inst:       SRON SPACE RESEARCH UTRECHT
    pi_country:    NETHERLANDS
    pi_phone:      3130535715
    keywords_1:    PLANETARY NEBULAE, HOT CENTRAL STARS.
    hours_pri:     5.30
    num_pri:       5
    foc:           Y
    pi_position:   PROGRAM COORDINATOR
! end of coverpage

abstract:

    line_1:        It has proved impossible to detect the very hot exciting stars of some
    line_2:        planetary neblae from the ground. This is probably because these stars emit a
    line_3:        great many ionizing photons for each visible quantum. The ionized nebula is
    line_4:        therefore so extensive that the nebular emission, both line and continuum,
    line_5:        completely dominate the visual continuum emission of the central star, which
    line_6:        becomes lost in the noise. Observing above the atmosphere increases the
    line_7:        possibility of detection of these central star by a factor of at least 400. A
    line_8:        factor ~ 100 because the light of the central star is within an image of. 1"
    line_9:        instead of the ~ 1" ground seeing limitation allowing better discrimination of
    line_10:       the star against the diffuse nebular continuum and a further factor ~ 4 occurs
    line_11:       because the star is that much brighter, relative to the nebula, in the
    line_12:       ultraviolet than it is in the visible.
    line_13:       With the spherical abberation of HST, the above mentioned factor of 100 is
    line_14:       reduced to about 15, but as the UV adventage remains, detectability is still
    line_15:       several magnitudes beyond groundobservations.

!
! end of abstract

general_form_proposers:

  lname:           POTTASCH
    fname:         S.
    title:         PROF.
    mi:            R
    inst:          GRONINGEN, UNIVERSITY OF
    country:       NETHERLANDS
    esa:           Y

!

  lname:           ZIJLSTRA
    fname:         A.
    title:         DR.
    mi:            A
    inst:          GRONINGEN, UNIVERSITY OF
    country:       NETHERLANDS
    esa:           Y

!

  lname:           WALTON
    fname:         N.
    title:         DR.
    inst:          UNIVERSITY COLLEGE LONDON
    country:       ENGLAND
    esa:           Y

!

  lname:           KAMPERMAN
    fname:         T.
    mi:            M
    inst:          SRON SPACE RESEARCH UTRECHT
    country:       NETHERLANDS
    esa:           Y

!
! end of general_form_proposers block

general_form_text:

  question:        3
    section:       1
    line_1:        In July '91 exposures have been made though different narrow band UV filters
    line_2:        of the nebula NGC7027. Fluxes through 278 and 210 nm filters
    line_3:        can be well explained, but the one through the 130 nm. filter is not compatible
    line_4:        with existing extinction models for 7027. Current approach is to continue
    line_5:        this study by using the FOC-prism mode to get an extinction profile in the UV
    line_6:        (IUE cannot discriminate between nebula and star).
    line_7:        As reference PN stars also NGC 2440 (expected low extinction, as 7027)
    line_8:        and NGC 6537 (high extinction) will be measured.
    line_9:        At least the comparison of the three should give better values of the densities
    line_10:       of the PN' and thus a better understanding in what respect, for instance,
    line_11:       PHA's have to be incorporated in the model.

!

  question:        4
    section:       1
    line_1:        The combination of ultraviolet sensitivity and the sharp central peak
    line_2:        in HST's PSF will result in a much higher detectability of central stars.
    line_3:        Where the detectability ratio HST/ground was originally at least 400,
    line_4:        the ratio is still about 70 in the same observation time.

!

  question:        5
    section:       1
    line_1:        No special scheduling requests.

!

  question:        6
    section:       1
    line_1:        All proposers have access to state-of-the-art data analysis
    line_2:        facilities at their home institutions.

!

  question:        7
    section:       1
    line_1:        All objects have been GASP-ed at the STSCI.

!

  question:        8
    section:       1
    line_1:        In CYCLE 1 NGC7027 was observed in a very small field.
    line_2:        There is little doubt anymore wheter this was a correct pointing.
    line_3:        The physics of the PN is the underlying reason for this proposal.

!

  question:        9
    section:       1
    line_1:        All three institutes have sufficient resources to support this project

!
!end of general form text

general_form_address:

  lname:           KAMPERMAN
    fname:         T.
    mi:            M
    title:         IR.
    category:      PI
    inst:          SRON SPACE RESEARCH UTRECHT
    addr_1:        SORBONNELAAN 2
    addr_2:        3584 CA
    city:          UTRECHT
    country:       NETHERLANDS
    phone:         3130535715
    telex:         NL 47224

!
! end of general_form_address records

fixed_targets:

    targnum:       1
    name_1:        NGC7027
    descr_1:       A,184
    pos_1:         RA=21H07M1.7S+/-.5S,
    pos_2:         DEC=-42D14'9.4"+/-2",
    equinox:       J2000
    rv_or_z:       V=10
    acqpr_1:       EXT
    plate_avail:   Y
    fluxnum_1:     1
    fluxval_1:     V=8.6+/-.2
    fluxnum_2:     2
    fluxval_2:     SURF(V)=14.4+/-1.
    fluxnum_3:     3
    fluxval_3:     F(4861)=6.8+/-1.0E-11
    fluxnum_4:     4
    fluxval_4:     SURF(1500)=7.6+/-2.E-16

!
! end of fixed targets

! No solar system records found

! No generic target records found

exposure_logsheet:

    linenum:       1.000
    sequence_1:    DEFINE
    sequence_2:    PRISMOBS
    targname:      #
    config:        FOC/96
    opmode:        IMAGE
    aperture:      512X512-DF
    sp_element:    PRISM1,F195W
    num_exp:       1
    time_per_exp:  60M
    fluxnum_1:     3
    priority:      1

!

    linenum:       2.000
    sequence_1:    USE
    sequence_2:    PRISMOBS
    targname:      NGC7027
    req_1:         CYCLE 3

!
! end of exposure logsheet

! No scan data records found