! 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