! File: 2450C.PROP
! Database: PEPDB
! Date: 17-FEB-1994:06:46:48
coverpage:
title_1: UV-SPECTROSCOPY OF THE UNIQUE HOT RCRB STAR V348 SGR
sci_cat: STELLAR ASTROPHYSICS
sci_subcat: LATE EVOLUTION
proposal_for: GO
pi_title: PROF.
pi_fname: K.
pi_lname: HUNGER
pi_inst: KIEL UNIVERSITY
pi_country: FRG
pi_phone: 431-880-4110
keywords_1: STARS: CHEMICALLY PECULIAR STAR; SPECTRAL ANALYSIS
keywords_2: 1.5
hours_pri: 2.20
num_pri: 1
hrs: X
pi_position: DIRECTOR
off_fname: D.
off_mi: K.
off_lname: HUNGER
off_title: DIRECTOR
off_inst: INSTITUT F. THEOR. PHYSIK U. STERNW.
off_addr_1: OLSHAUSENSTRASSE 40
off_city: KIEL
off_state: S-H
off_zip: D2300
off_country: FRG
! end of coverpage
abstract:
line_1: V348 is a unique object: it is classified as i) the hottest known RCrB star
line_2: (with Teff=20000K); ii) a very-late Wolf-Rayet type (WC10) central star of a
line_3: planetary nebula; iii) a hydrogen-deficient star whose photospheric composition
line_4: resembles those of extreme helium stars.
line_6: This unusual combination opens the possibility to attack the following problems
line_7: concerning late phases of stellar evolution:
line_9: a) formation of planetaries with He-enriched central stars;
line_10: b) formation of RCrB stars and extreme helium stars,
line_11: c) mass loss processes and the RCrB phenomenon.
line_13: In the present proposal, the following problems shall be addressed:
line_15: i) position of V348 Sgr in the HR-diagram
line_16: ii) chemical composition of the photosphere
line_17: iii) mass-loss rate of V348 Sgr.
line_19: The final aim is to determine the mass of the original H-rich shell and to
line_20: derive the time when the nebular was expelled (onset of superwind).
!
! end of abstract
general_form_proposers:
lname: KAUFMANN
fname: J.
title: DR.
mi: P.
inst: BERLIN TECHNICAL UNIVERSITY
country: FRG
esa: X
!
lname: KILKENNY
fname: D.
title: DR.
inst: SOUTH AFRICAN ASTRONOMICAL OBSERVATORY
country: S AFRICA
!
lname: HUNGER
fname: K.
title: P.I.
inst: KIEL UNIVERSITY
country: FRG
esa: X
!
lname: RAO
fname: N.
title: DR.
mi: K.
inst: INDIAN INSTITUTE OF ASTROPHYSICS
country: INDIA
!
lname: HOUZIAUX
fname: L.
title: DR.
inst: LIEGE UNIVERSITY
country: BELGIUM
esa: X
!
lname: MANFROID
fname: J.
title: DR.
inst: LIEGE UNIVERSITY
country: BELGIUM
esa: X
!
lname: NEMRY
fname: F.
title: MME.
inst: LIEGE UNIVERSITY
country: BELGIUM
esa: X
!
lname: NANDY
fname: K.
title: DR.
inst: ROYAL OBSERVATORY, EDINBURGH
country: UK
esa: X
!
lname: HILL
fname: P.
title: DR.
mi: W.
inst: ST ANDREWS, UNIVERSITY OF
country: UK
esa: X
!
lname: JEFFERY
fname: C.
title: DR.
mi: S.
inst: ST ANDREWS, UNIVERSITY OF
country: UK
esa: X
!
lname: POLLACCO
fname: D.
title: MR.
inst: ST ANDREWS, UNIVERSITY OF
country: UK
esa: X
!
lname: CLEGG
fname: R.E.S.
title: DR.
inst: LONDON, UNIVERSITY COLLEGE
country: UK
esa: X
!
lname: DRILLING
fname: J.
title: DR.
mi: S.
inst: LOUISIANA STATE UNIVERSITY
country: USA
!
lname: HAMANN
fname: W.-R.
title: DR.
inst: KIEL UNIVERSITY
country: FRG
esa: X
!
lname: HEBER
fname: U.
title: DR.
inst: KIEL UNIVERSITY
country: FRG
esa: X
!
lname: HECK
fname: A.
title: DR.
inst: STRASBOURG OBSERVATORY
country: FRANCE
esa: X
!
lname: KLINGLESMITH
fname: D.
title: DR.
inst: NASA, GODDARD
country: USA
!
lname: LYNAS-GRAY
fname: A.
title: DR.
mi: E.
inst: OXFORD, UNIVERSITY OF
country: UK
esa: X
!
lname: SCHOENBERNER
fname: D.
title: DR.
inst: KIEL UNIVERSITY
country: FRG
esa: X
!
lname: WALKER
fname: H.
title: DR.
mi: J.
inst: NASA, AMES
country: USA
!
! end of general_form_proposers block
general_form_text:
question: 3
section: 1
line_1: Drilling et al. (1984) and Schoenberner and Heber (1986) compared IUE low-
line_2: resolution spectra of MV Sgr and V348 Sgr with those of the well-studied extreme
line_3: helium stars HD 124448 and BD +10D 2179. All four stars are found to have
line_4: similare IUE spectra, suggesting that the photosphere of V348 Sgr is observable
line_5: with HST. Accordingly, it is proposed that the ST High-Resolution Spectrograph
line_6: (HRS) be used to obtain ultraviolet spectroscopy of V348 Sgr at maximum light.
line_8: Coordinates of V348 Sgr taken from Allen et al. (1982) are alpha(1950) =
line_9: 18h37m18.2s, delta(1950) = -22D57'20". These are used for Anglo Australian
line_10: Telescope acquisition and are claimed to be accurate to 2 - 3 arcseconds. While
line_11: a high coordinate precision is desirable for HST observations, especially in
line_12: view of the variable magnitude, these should suffice if it can be confirmed from
line_13: groundbased photometry that V348 Sgr is at maximum light at the time of HST
line_14: observations. The HRS operates in acquisition mode using a 2 x 2 arcsecond
line_15: aperture. It is not possible to use the Wide Field Camera/Planetary Camera as
line_16: V348 Sgr would be too bright; the N2 mirror will give a count rate in the
line_17: recommended range and the standard acquisition time (5 minutes) will result.
line_18: Scientific spectra to be obtained with the HRS are as follows:
line_19: 1. Low resolution spectrum in the wavelength range 120 nm - 148.8 nm.
line_20: 2. Low resolution spectrum in the wavelength range 141.2 nm - 170 nm.
line_21: 3. Medium resolution spectrum in the wavelength range (280.7 nm - 285.3 nm).
line_22: The intention is to study the HeI line at 282.9 nm and the CII doublet
line_23: 283.671 nm, 283.76 nm.
!
question: 3
section: 2
line_1: 4. Medium resolution spectrum in the range (292.2 nm - 296.8 nm) for studying
line_2: the HeI line at 294.5 nm.
line_3: It is expected that the HRS low-resolution spectra will be adequate for studying
line_4: the expected strong lines 124.7 nm (CIII), 130 nm (SiIII, SiII), 135.5 nm (CII),
line_5: 140 nm (SiIV), 155 nm (CIV), 164 nm (HeII).
!
question: 4
section: 1
line_1: High-resolution optical spectra have been obtained with the ESO-CASPEC (see
line_2: sect. 2) . Direct images and long-slit spectroscopy of the nebula have been
line_3: obtained at the ESO 2.2 m telescope and the AAT. Infrared photometry is
line_4: available both from the ground (Kilkenny and Whittet, 1984) and with the IRAS
line_5: satellite (Walker, 1985). Well-exposed low-resolution spectra (obtained with
line_6: the Short Wavelength Prime and Long Wavelength Redundant Cameras of IUE)
line_7: require about 40 minutes of exposure when V348 Sgr is at maximum light (Heck et
line_8: al., 1982). Unfortunately, low-resolution spectra obtained with IUE are not of
line_9: an adequate resolution for an abundance analysis, and high-resolution spectra
line_10: would require prohibitively long exposures. The HST is therefore needed if an
line_11: ultraviolet spectrum of V348 Sgr is to be obtained at a resolution sufficient
line_12: for an abundance analysis of the photosphere. IUE spectra suggest that it is
line_13: only in the ultraviolet (lambda .LE. 300 nm) that there is any chance of
line_14: obtaining a photospheric spectrum with comparatively little contamination
line_15: from the chromosphere, nebula or shell.
!
question: 5
section: 1
line_1: It is estimated from Figure 4-2 in the HRS Handbook the standard time for
line_2: acquisition (about 5 minutes) can be adopted.
line_3: Dark counts rates observed in both detectors (D1 and D2) are negligible in
line_4: comparison with the count rate produced by V348 Sgr at maximum light. Dead-time
line_5: effects can be neglected, as can scattered light since the echelle is not being
line_6: used. Both D1 and D2 suffer from granularity and fixed-pattern noise, but D2 is
line_7: better than D1 and so D2 is selected for this program. Worst blemishes in D2
line_8: deviate by 10% from the mean local response; this is a problem for weak line
line_9: work and the applicants suggest that it be overcome by breaking each exposure
line_10: into 4 parts (using the FP-SPLIT option) with the central wavelengths being
line_11: slightly altered in each case.
line_13: Possible nebular contributions to the ultraviolet spectrum cannot be excluded in
line_14: the case of V348 Sgr. It is therefore important to measure the background in the
line_15: science diodes. Exposure times listed in the table below correspond to the
line_16: exposures requested in section 3; they are based on IUE fluxes observed by Heck
line_17: et al. (1982) and HRS sensitivity curves. It has been assumed that 1600 counts
line_18: are needed in each diode for a signal/noise (S/N) of 40, and each exposure is
line_19: increased by 6% because of the need for background measurements.
!
question: 5
section: 2
line_1:
line_2: Continuum IUE flux 1E14 Grating Counts S/N t
line_3: Lambda (nm) erg/cm/cm/sec/0.1nm diode/sec (min.)
line_4: 130 2.9 G140L 0.250 30 22
line_5: 147.5 6.5 G140L 1.800 30 9
line_6: 283 4.4 G270M 0.260 20 28
line_7: 293.9 5.5 G270M 0.230 20 31
!
question: 7
section: 1
line_1: Reduction and calibration of HRS spectra can be carried out with the program
line_2: DIPSO (Howarth, 1984). Heber et al. (1984) have identified CIII, 124.7 nm, SiIII
line_3: 130 nm, CII, 133.5 nm, SiIV, 140 nm and CIV, 155 nm in the low resolution IUE
line_4: spectrum of V348 Sgr; these are similar to BD+10D 2179 and HD 124448.
line_5: Accordingly, a scheme for analysing the HRS spectra of V348 Sgr is suggested,
line_6: assuming they are similar to the IUE high-resolution spectra of BD+10D 2179. The
line_7: analysis will be carried out in a similar way as that of BD+10D 2179 (Heber,
line_8: 1983). Details of model atmosphere and line profile calculation can be found in
line_9: Heber (1983) and Drilling et al. (1984). The ionization equilibria of CII/CIII
line_10: and SiIII/SiIV will be used to derive the effective temperature. Surface gravity
line_11: will be determined by matching the line profiles of the pressure-broadened HeI
line_12: lines, 282.9 nm and 294.5 nm. After having fixed Teff and log g, abundances for
line_13: C, N, Al, Si, P, Ti, Cr, Mn, Fe and Ni can be determined as demonstrated in the
line_14: case of BD+10D 2179 (Heber, 1983).
line_15: Low resolution IUE spectra of V348 Sgr indicate that the CIV resonance line at
line_16: 155 nm is affected by an expanding envelope. This line can be used to determine
line_17: the mass-loss rate. The comoving frame method (Hamann et al., 1982) will be
line_18: used to estimate the mass-loss rate.
!
question: 8
section: 1
line_1: Photometric monitoring of V348 Sgr for more than fifty years suggests that it
line_2: spends approximately half of the time at maximum light. Deep obscurational
line_3: minima, however,can occur abruptly and at unpredictable times.
line_4: As it is necessary to observe V348 Sgr with the HST at maximum light, so that
line_5: ultraviolet photospheric spectra will be obtained, it is suggested that HST time
line_6: be scheduled as though observations were not time-critical; the chance that
line_7: V348 Sgr would be at maximum light, and remain there during the scheduled
line_8: observations, is about 50%.
line_9: The applicants further suggest that HST time be scheduled during the months when
line_10: V348 Sgr is observable from the ground (April to August inclusive). It would
line_11: then be possible to conduct nightly monitoring of V348 Sgr, from the South
line_12: African Astronomical Observatory (SAAO) in advance of HST observations. Should
line_13: it transpire that V348 Sgr is unlikely to be at maximum at the time of HST
line_14: observations, a postponement could be requested and the HST time used for
line_15: another program.
!
question: 10
section: 1
line_1: Computer resources:
line_2: i) Starlink computer at the University College London, at the University of
line_3: Oxford and at the University of St. Andrews will be used to reduce the
line_4: HRS spectra.
line_5: ii) CRAY X-MP 216 of the "Rechenzentrum der Universitaet Kiel"
line_6: will be used to compute model atmospheres.
!
!end of general form text
general_form_address:
lname: HUNGER
fname: KURT
title: PROF.
category: PI
inst: INST.F. THEOR. PHYSIK UND STERNWARTE DER UNIV. KIEL
addr_1: OLSHAUSENSTRASSE 40
city: KIEL D-2300
country: F.R. GERMANY
!
! end of general_form_address records
fixed_targets:
targnum: 1
name_1: V348-SGR
descr_1: STAR; TYPE=RCRB
pos_1: RA = 18H 40M 19.923S +/- 0.013S,
pos_2: DEC = -22D 54' 28.63" +/- 0.2",
pos_3: PLATE-ID=067T
equinox: 2000
pos_epoch_bj: J
rv_or_z: V = 174
fluxnum_1: 1
fluxval_1: V = 12.3 +/- 0.3
fluxnum_2: 2
fluxval_2: F-CONT(1300) = 2.9 +/- 0.3 E-14
fluxnum_3: 3
fluxval_3: F-CONT(1475) = 6.5 +/- 0.6 E-14
fluxnum_4: 4
fluxval_4: F-CONT(2830) = 4.4 +/- 0.5 E-14
fluxnum_5: 5
fluxval_5: F-CONT(2939) = 5.5 +/- 0.6 E-14
!
! end of fixed targets
! No solar system records found
! No generic target records found
exposure_logsheet:
linenum: 1.000
targname: V348-SGR
config: HRS
opmode: ACQ
aperture: 2.0
sp_element: MIRROR-N2
num_exp: 1
time_per_exp: 144.5S
fluxnum_1: 2
fluxnum_2: 3
fluxnum_3: 4
fluxnum_4: 5
priority: 1
param_1: FAINT=700,BRIGHT=8000,
param_2: MAP=END-POINT,
param_3: SEARCH-SIZE=5
req_1: ONBOARD ACQ FOR 2-5
comment_1: STEP-TIME=0.5S
!
linenum: 2.000
targname: V348-SGR
config: HRS
opmode: ACCUM
aperture: 2.0
sp_element: G140L
wavelength: 1200-1488
num_exp: 1
time_per_exp: 24.5M
s_to_n: 30
fluxnum_1: 2
priority: 1
param_1: STEP-PATT=5
!
linenum: 3.000
targname: V348-SGR
config: HRS
opmode: ACCUM
aperture: 2.0
sp_element: G140L
wavelength: 1478-1766
num_exp: 2
time_per_exp: 12.25M
s_to_n: 30
fluxnum_1: 3
priority: 1
param_1: STEP-PATT=5
!
linenum: 4.000
targname: V348-SGR
config: HRS
opmode: ACCUM
aperture: 2.0
sp_element: G270M
wavelength: 2807-2853
num_exp: 2
time_per_exp: 15.5M
s_to_n: 20
fluxnum_1: 4
priority: 1
param_1: STEP-PATT=5
!
linenum: 5.000
targname: V348-SGR
config: HRS
opmode: ACCUM
aperture: 2.0
sp_element: G270M
wavelength: 2922-2968
num_exp: 2
time_per_exp: 16M
s_to_n: 20
fluxnum_1: 5
priority: 2
param_1: STEP-PATT=5
!
! end of exposure logsheet
! No scan data records found