!  File:  3608C.PROP
!  Database:  PEPDB
!  Date:  19-FEB-1994:13:45:09

coverpage:

  title_1:         THE 12C TO 13C ISOTOPE RATIO IN PLANETARY NEBULAE
    sci_cat:       INTERSTELLAR MEDIUM
    sci_subcat:    PLANETARY NEBULAE
    proposal_for:  GO
    pi_fname:      ROBIN
    pi_mi:         ES
    pi_lname:      CLEGG
    pi_inst:       ROYAL GREENWICH OBSERVATORY
    pi_country:    UK
    pi_phone:      +44-223-374700
    hours_pri:     5.53
    num_pri:       3
    hrs:           Y
    off_fname:     JIM
    off_mi:        T
    off_lname:     SADLIER
    off_title:     HEAD OF ADMIN
    off_inst:      ROYAL GREENWICH OBSERVATORY
    off_addr_1:    MADINGLEY ROAD
    off_city:      CAMBRIDGE CB3 OEZ
    off_country:   UNITED KINGDOM
    off_phone:     +44 223 374700
! end of coverpage

abstract:

    line_1:        Abundances of C,N and O in red giant stars and planetary nebulae (PNs)
    line_2:        provide important diagnostics of stellar evolution theory. CNO isotope ratios
    line_3:        (eg 12C/13C, 15N/14N and 16O/18O) have given many extra constraints on all
    line_4:        the mixing processes occurring between the main sequence and PN ejection.
    line_5:        In general, observations show more mixing occurs than is predicted.
    line_6:        The CNO abundances for Galactic and Magellanic Cloud PNs show that the
    line_7:        `3rd dredge-up' of 12C is more efficient in metal-poor environments. However,
    line_8:        until now it has not been possible to measure important diagnostics such as
    line_9:        the 12C/13C ratio in nebulae so as to relate red giant & PN populations.
    line_10:       We propose to use the GHRS, Echelle and Large Science Aperture to measure
    line_11:       C12/13 ratios in 3 PNs with a novel spectroscopic method. As 12C has zero
    line_12:       nuclear spin, the normal C III 1S(J=F=0) - 3P(J=F=0,1,2) transition has only
    line_13:       two components (1906.7, 1908.7A). But the nuclear spin (I=1/2) of 13C gives
    line_14:       a finite line strength to an F=1/2-1/2 transition at 1909.6A, which is
    line_15:       absent in 12C. Measurement of all three lines will provide the C12/13 ratio.
    line_16:       In an allocation of under 9 hours we can reach 3-4 sigma limits for a C-rich
    line_17:       Galactic nebula, a C-rich SMC nebula, and a Type I (He and N-rich, and having
    line_18:       C<O) PN in the LMC. We can measure to limiting isotope ratios between
    line_19:       30 and 90. Our LMC Type I target is probably descended from the group of N-rich
    line_20:       M/MS/S stars, found by Smith & Lambert to have 12C/13C ratios between 5 and 30.

!
! end of abstract

general_form_proposers:

  lname:           CLEGG
    fname:         ROBIN
    title:         PI
    mi:            ES
    inst:          ROYAL GREENWICH OBSERVATORY
    country:       ENGLAND
    esa:           Y

!

  lname:           STOREY
    fname:         PETER
    mi:            J
    inst:          UNIVERSITY COLLEGE LONDON
    country:       ENGLAND
    esa:           Y

!

  lname:           WALSH
    fname:         JEREMY
    mi:            R
    inst:          SPACE TELESCOPE EUROPEAN COORDINATING FACILITY
    country:       GERMANY
    esa:           Y

!
! end of general_form_proposers block

general_form_text:

  question:        3
    section:       1
    line_1:        The 12C/13C isotope ratio is to be studied in three planetary nebulae using
    line_2:        the GHRS. The differing nuclear spins of the 12C and 13C nuclei create a
    line_3:        total angular momentum coupling between the C++ 3P levels of 13C, giving
    line_4:        rise to a radiative transition at the wavelength of the completely
    line_5:        forbidden "J=0-0" transition in 12C. The large aperture of GHRS and an
    line_6:        echelle grating are to be used to observe the two 12C III] lines at 1906.7
    line_7:        and 1908.7 and the 13C III] line at 1909.6A in the same echelle order. From
    line_8:        the ratio of the 1909.6A line to the 1908.7A line, and the electron density
    line_9:        (computed from the ratio of the C III] 1906.7 and 1908.7A lines), the
    line_10:       12C/13C ratio can be directly measured. We stress that measurement of the
    line_11:       1906.7/1908.7 flux ratio gives us the electron density in the C++ zone;
    line_12:       this is needed for the interpretation of the 1909.6A line. The echelle
    line_13:       provides enough dispersion that the separation of the lines will be
    line_14:       sufficient to measure the weak 1909.6A line well away from the wings of the
    line_15:       1908.7A line. From the expected range of 12C/13C ratios in possible PN
    line_16:       progenitors stars, the 1909.6A line will be several hundred times fainter
    line_17:       than the adjacent 1908.7A line. The expansion velocity of the PNs (~0.13A)
    line_18:       is a factor seven less than the separation between the 13C and 12C lines
    line_19:       (0.9A). In addition, GHRS tests show that a line observed with the GHRS+SSA
    line_20:       has no `wings' above relative intensity 3.E-4 beyond a wavelength offset of
    line_21:       0.4A from line centre. Our 13C line is offset by 0.9A from the 12C line.
    line_22:       Finally, we note that light scattered from other orders onto the detector
    line_23:       will not be a problem at this very high dispersion as there are no other

!

  question:        3
    section:       2
    line_1:        bright emission lines nearby in other orders.
    line_3:        The targets have been chosen to give a high detection probability of the
    line_4:        13C 1909.6A line by being bright in C III] emission and/or of Type I (PNs
    line_5:        with high mass progenitor star; mostly O-rich), with predicted lower
    line_6:        12C/13C ratio. NGC3918 is so bright in C III] that we can easily reach a
    line_7:        limiting ratio of 12C:13C = 90:1.

!

  question:        4
    section:       1
    line_1:        This proposal would not be scientifically feasible without the capabilites
    line_2:        of the High Resolution Spectrograph aboard HST. The 13C emission line to be
    line_3:        detected is weak, situated in the UV, and close to a brighter line
    line_4:        (1908.7A). Together these requirements necessitate the light gathering
    line_5:        power of HST, the UV capability and the high spectral resolution to
    line_6:        separate the weak line from the nearby strong line. Even allowing for these
    line_7:        advantages only a few nebulae with the highest suface brightness in the
    line_8:        C III] line (and additionally not of very high density) can feasibly be
    line_9:        observed in a reasonable time.
    line_11:       Earlier we attempted to measure the ratio of the 1909.6A line to the
    line_12:       main C III] lines, using the IUE and its small entrance aperture. However the
    line_13:       extreme slowness of the IUE+SAP, together with the very small dynamic range
    line_14:       of the IUE camera detector, enabled only a very poor result to be obtained:
    line_15:       for NGC3918, 12C/13C > 3.  The GHRS's detector has a very much better
    line_16:       dynamic range and the spectrograph gives the very high resolution we need.
    line_17:       This project cannot be done with the IUE; it needs the GHRS.

!

  question:        7
    section:       1
    line_1:        It is proposed to adopt the standard pipeline calibration. We choose not to
    line_2:        sample the inter-order background since there are no known emission lines
    line_3:        nearby in the adjacent orders at 1846 or 1974A in PN. The electron density
    line_4:        will be measured from the ratio of the C III] 1906.7 to 1908.7A lines using
    line_5:        total line fluxes as well as line fits. We will attempt to fit the 1908.7A
    line_6:        profile to that of 1909.6A (since they should be of the same shape) in
    line_7:        order to determine the 1909.6A line flux. In addition we have interactive
    line_8:        Gaussian line fitting programs which can handle constraints on line
    line_9:        wavelength as well as statistical errors. In the event of non-detection of
    line_10:       the 13C line, we expect to be able to specify useful upper limits based on
    line_11:       our extensive spectroscopic experience.

!

  question:        8
    section:       1
    line_1:        The coordinates given are from measurements on GASP frames. For NGC3918 we
    line_2:        have eyeballed the centre of the nebula ( diameter ~ 15arcsec ) and for the
    line_3:        two Magellanic Cloud nebulae have fitted a 2-D Gaussian. The coordinates
    line_4:        agree very well with those determined from our own measurements of plates.
    line_5:        All three objects - NGC3918, SMC-N2 and LMC-N122 - are bright in the UV
    line_6:        ( mostly from the many emission lines ) and so spiral search will work
    line_7:        well. For the Magellanic Cloud nebulae we have specified a LOCATE =
    line_8:        YES since we need to centre the nebulae in the large aperture.

!

  question:        10
    section:       1
    line_1:        Sufficient computing resources are already available to all three
    line_2:        investigators. Travel funds for final analysis and preparation of results
    line_3:        for publication are also readily available.

!
!end of general form text

general_form_address:

  lname:           CLEGG
    fname:         ROBIN
    mi:            ES
    category:      PI
    inst:          ROYAL GREENWICH OBSERVATORY
    addr_1:        MADINGLEY ROAD
    city:          CAMBRIDGE CB3 0EZ
    country:       ENGLAND
    phone:         +44 223 374700
    telex:         817235

!
! end of general_form_address records

fixed_targets:

    targnum:       1
    name_1:        NGC3918
    name_2:        PK294+4D1
    descr_1:       G,502
    pos_1:         PLATE-ID=06PS,
    pos_2:         RA = 11H 50M 17.88S +/- 1.5",
    pos_3:         DEC = -57D 10' 56.6" +/- 1.5"
    equinox:       J2000
    rv_or_z:       V = -20
    acqpr_1:       EXT
    comment_1:     POSITION REFERS TO THE CENTROID OF
    comment_2:     THE NEBULA AS MEASURED ON GASP
    comment_3:     FRAME.
    comment_4:     FLUX 1 IS SUM OF 1907+1909A
    comment_5:     LINES. NEBULA AREA ~ 180 SQ ARCSEC.
    comment_6:     FLUX 3 IS 13C 1910 LINE FOR
    comment_7:     12C/13C=90.
    comment_8:     FLUX 4 IS BROAD BAND 1100-3400A
    comment_9:     FOR TARGET ACQUISITI0N PASSBAND N2.
    fluxnum_1:     1
    fluxval_1:     F-LINE(1908) = 1.13 +/- 0.11 E-10
    fluxnum_2:     2
    fluxval_2:     SURF-LINE(1906) = 3.6 +/- 1.0 E-13
    fluxnum_3:     3
    fluxval_3:     SURF-LINE(1910) = 4.7 +/- 1.5 E-15
    fluxnum_4:     4
    fluxval_4:     SURF(2000) = 1.4 +/- 0.2 E-11

!

    targnum:       2
    name_1:        SMC-N2
    name_2:        SMC-SMP2
    name_3:        SMC-MG2
    descr_1:       H,502
    pos_1:         PLATE-ID=06B1,
    pos_2:         RA = 00H 32M 38.81S +/- 1.5",
    pos_3:         DEC = -71D 41' 58.9" +/- 1.5"
    equinox:       J2000
    rv_or_z:       V = 160
    comment_1:     POSITION MEASURED ON GASP FRAME.
    comment_2:     FLUX 1 IS SUM OF 1907+1908A LINES.
    comment_3:     FLUX 3 IS 13C 1910 LINE FOR
    comment_4:     12C/13C=30.
    comment_5:     FLUX 3 IS BROAD BAND 1100-3400A
    comment_6:     FOR TARGET ACQUISITI0N PASSBAND N2.
    fluxnum_1:     1
    fluxval_1:     F-LINE(1907) = 1.49 +/- 0.15 E-12
    fluxnum_2:     2
    fluxval_2:     F-LINE(1910) = 3.0 +/- 1.0 E-15
    fluxnum_3:     3
    fluxval_3:     F(2000) = 6.2 +/- 1.5 E-12

!

    targnum:       3
    name_1:        LMC-N122
    name_2:        LM1-28
    name_3:        LMC-WS18
    descr_1:       H,502
    pos_1:         PLATE-ID=05ZW,
    pos_2:         RA = 05H 19M 54.70S +/- 1.5",
    pos_3:         DEC = -69D 31' 05.1" +/- 1.5"
    equinox:       J2000
    rv_or_z:       V = 270
    comment_1:     POSITION MEASURED ON GASP FRAME.
    comment_2:     FLUX 1 IS SUM OF 1907+1908A LINES.
    comment_3:     FLUX 2 IS 13C 1910 LINE FOR
    comment_4:     12C/13C=30.
    comment_5:     FLUX 3 IS BROAD BAND 1100-3400A
    comment_6:     FOR TARGET ACQUISITI0N PASSBAND N2.
    fluxnum_1:     1
    fluxval_1:     F-LINE(1907) = 1.13 +/- 0.11 E-12
    fluxnum_2:     2
    fluxval_2:     F-LINE(1910) = 2.0 +/- 0.6 E-15
    fluxnum_3:     3
    fluxval_3:     F(2000) = 6.1 +/- 1.5 E-12

!
! end of fixed targets

! No solar system records found

! No generic target records found

exposure_logsheet:

    linenum:       1.100
    targname:      NGC3918
    config:        HRS
    opmode:        ACQ
    aperture:      2.0
    sp_element:    MIRROR-N2
    num_exp:       1
    time_per_exp:  75.0S
    fluxnum_1:     4
    priority:      1
    param_1:       SEARCH-SIZE=5
    param_2:       BRIGHT=RETURN
    req_1:         CYCLE 2;
    req_2:         ONBOARD ACQ FOR 1.2
    comment_1:     EXTENDED OBJECT. ACQ ON
    comment_2:     BRIGHTEST POINT IN CENTRE
    comment_3:     OF NEBULA. ESTIMATED COUNT
    comment_4:     RATE IS 1700 HZ.

!

    linenum:       1.200
    targname:      NGC3918
    config:        HRS
    opmode:        ACCUM
    aperture:      2.0
    sp_element:    ECH-B
    wavelength:    1908.3
    num_exp:       2
    time_per_exp:  37M
    s_to_n:        4
    s_to_n_time:   73M
    fluxnum_1:     3
    priority:      1
    param_1:       STEP-PATT=1
    param_2:       FP-SPLIT=STD
    param_3:       DOPPLER=ON
    req_1:         CYCLE 2
    comment_1:     13C 1910A LINE SEPERATED BY
    comment_2:     0.9A (43 CHANS) FROM 12C 1908.7A
    comment_3:     LINE.

!

    linenum:       2.100
    targname:      SMC-N2
    config:        HRS
    opmode:        ACQ
    aperture:      2.0
    sp_element:    MIRROR-N2
    num_exp:       1
    time_per_exp:  90.0S
    fluxnum_1:     3
    priority:      1
    param_1:       SEARCH-SIZE=3
    param_2:       BRIGHT=RETURN
    param_3:       LOCATE=YES
    req_1:         CYCLE 2;
    req_2:         ONBOARD ACQ FOR 2.2
    comment_1:     SMALL EXTENDED NEBULA.
    comment_2:     DIAMETER ~ 0.7".
    comment_3:     ESTIMATED COUNT RATE IS
    comment_4:     160 HZ.

!

    linenum:       2.200
    targname:      SMC-N2
    config:        HRS
    opmode:        ACCUM
    aperture:      2.0
    sp_element:    ECH-B
    wavelength:    1909.3
    num_exp:       2
    time_per_exp:  43.5M
    s_to_n:        3
    s_to_n_time:   81M
    fluxnum_1:     2
    priority:      1
    param_1:       STEP-PATT=1
    param_2:       FP-SPLIT=STD
    param_3:       DOPPLER=ON
    req_1:         CYCLE 2
    comment_1:     13C 1910A LINE SEPERATED BY
    comment_2:     0.9A (43 CHANS) FROM 12C 1908.7A
    comment_3:     LINE.
    comment_4:     REDSHIFT OF SMC~160KM/S

!

    linenum:       3.100
    targname:      LMC-N122
    config:        HRS
    opmode:        ACQ
    aperture:      2.0
    sp_element:    MIRROR-N2
    num_exp:       1
    time_per_exp:  90.0S
    fluxnum_1:     3
    priority:      1
    param_1:       SEARCH-SIZE=3
    param_2:       BRIGHT=RETURN
    param_3:       LOCATE=YES
    req_1:         CYCLE 2;
    req_2:         ONBOARD ACQ FOR 3.2
    comment_1:     SMALL EXTENDED NEBULA.
    comment_2:     DIAMETER ~ 0.7"
    comment_3:     ESTIMATED COUNT RATE IS
    comment_4:     180 HZ.

!

    linenum:       3.200
    targname:      LMC-N122
    config:        HRS
    opmode:        ACCUM
    aperture:      2.0
    sp_element:    ECH-B
    wavelength:    1910.0
    num_exp:       4
    time_per_exp:  49M
    s_to_n:        3
    s_to_n_time:   178M
    fluxnum_1:     2
    priority:      1
    param_1:       STEP-PATT=1
    param_2:       FP-SPLIT=STD
    param_3:       DOPPLER=ON
    req_1:         CYCLE 2
    comment_1:     13C 1910A LINE SEPERATED BY
    comment_2:     0.9A (43 CHANS) FROM 12C 1908.7A
    comment_3:     LINE.
    comment_4:     REDSHIFT OF LMC~270KM/S

!
! end of exposure logsheet

! No scan data records found