! $Id: 6782,v 4.1 1996/02/06 03:05:30 pepsa Exp $ ! +====================+ ! | PED OUTPUT PRODUCT | ! +====================+ ! ! /tmp_mnt/stellar/holberg/hst_phase2/rps2/6782.prop ! Generated by PREPROCESSOR, version 6.0e ! Date: Fri Jan 26 15:58:55 MST 1996 Proposal_Information Title: TESTING THE THEORY OF RADIATIVE LEVITATION IN DA WHITE DWARFS Proposal_Category: GO Scientific_Category: HOT STARS Cycle: 6 Investigators PI_Name: Dr. Jay Holberg PI_Institution: University of Arizona CoI_Name: Dr. Martin Barstow CoI_Institution: University of Leicester Contact: CoI_Name: Dr. Ivan Hubeny CoI_Institution: Goddard Space Flight Center Contact: CoI_Name: Dr. Thierry Lanz CoI_Institution: Goddard Space Flight Center Contact: Abstract: We propose GHRS observations of two H-rich DA white dwarfs with temperatures near 40,000K. This temperature defines the critical point, above which the mechanism of radiative levitation becomes efficient enough to prevent elements heavier than H or He from sinking out of the atmospheres of DA white dwarfs under the influence of gravity. Below this temperature, DA atmospheres are observed to be more or less pure hydrogen. However, measurement of photospheric abundances of stars having the same temperatures (and gravities) give quite disparate results - GD394 has a larger heavy element content than predicted, whereas the nearly identical star GD153 has an unexpectedly pure H atmosphere. Unfortunately, near 40,000K, only these two stars are bright enough to be observed at high dispersion with IUE at sufficient S/N. New observations are needed to begin providing the observational evidence necessary to establish the physical mechanisms that determine white dwarf composition, and cause departures from the predictions of radiative levitation theory. Questions Observing_Description: The proposed GHRS observation for each of the two white dwarfs is given below. The spectral coverage and exposure time are given for each spectral setup. All spectra will be obtained using the standard FP-SPLIT=4 option. This is to minimise the effects of fixed pattern detector noise and to easily identify any diode dropouts, which could produce artificial absorption features. Exposure times are set to yield an S/N ~ 20 for each wavelength range. This S/N denotes counts per data point, where each diode is quarter-stepped (each diode is used 4 times in a comb addition to produce the spectrum). This represents STEP-PATTERN=5 for the G160M grating. =5pt 0.2cm begintabbing REJ1614-085 \\=PG1057+719, o \\=1250-1285 Angstrom \\= Si II exposure \\=6 min \\=10 min, o \\=1280-1315 Angstrom \\= Si III exposure \\=5 min \\=9 min, o \\=1385-1420 Angstrom \\= Si IV exposure \\=8 min \\=15 min, o \\=1520-1555 Angstrom \\= C IV exposure \\=15 min \\=30 min, endtabbing PG 1057+719 lies in the continuous viewing zone (CVZ) and so can be complete in 2 shifts. The brighter RE J1614-085 also requires 2 shifts. Exposure times and signal-to-noise predictions were calculated using SYNPHOT procedures. Synthetic model atmosphere spectra craeted with TLUSTY were used to generate predicted count and count rate spectra using the STSDAS SYNPHOT procedures COUNTRATE and PLSPEC. Real_Time_Justification: None None Calibration_Justification: Real_Time_Justification Additional_Comments: Fixed_Targets Target_Number: 1 Target_Name: WD1057+719 Alternate_Names: PG1057+719 Description: STAR,DA Position: RA=11H 00M 34.32S +/- 0.2S,DEC=71D 38' 03.29" +/- 0.25",PLATE-ID=01L3 Equinox: J2000 RV_or_Z: RA_PM: Dec_PM: Epoch: B1984.026 Annual_Parallax: Flux: V = 14.7 +/- 0.1 B-V = -0.25 +/- 0.05 F-CONT(1400) = 4.6 +/- 0.3E-13 Comments: THIS IS A CVZ TARGET Target_Number: 2 Target_Name: REJ1614-085 Alternate_Names: WD1611-084 Description: STAR,DA Position: RA=16H 14M 19.14S +/- 0.2S,DEC=-8D 33' 26.69" +/- 0.25",PLATE-ID=00TR Equinox: J2000 RV_or_Z: RA_PM: Dec_PM: Epoch: B1983.453 Annual_Parallax: Flux: V = 14.01+/- 0.03 B-V = -0.25 +/- 0.03 F-CONT(1400) = 8.7 +/- 0.2 E-13 Comments: Solar_System_Targets Generic_Targets Scan_Data Visits Visit_Number: 01 Visit_Requirements: CVZ On_Hold_Comments: Visit_Comments: Exposure_Number: 1 Target_Name: WD1057+719 Config: HRS Opmode: ACQ Aperture: 2.0 Sp_Element: MIRROR-N2 Wavelength: Optional_Parameters: Number_of_Iterations: 1 Time_Per_Exposure: 3.6S Special_Requirements: ONBOARD ACQ FOR 2 Comments: expected counrate = 6600 c/s Exposure_Number: 2 Target_Name: WD1057+719 Config: HRS Opmode: ACQ/PEAKUP Aperture: 0.25 Sp_Element: MIRROR-N2 Wavelength: Optional_Parameters: Number_of_Iterations: 1 Time_Per_Exposure: 10.0S Special_Requirements: ONBOARD ACQ FOR 11-41 Comments: Exposure_Number: 11 Target_Name: WD1057+719 Config: HRS Opmode: ACCUM Aperture: 0.25 Sp_Element: G160M Wavelength: 1251.9 Optional_Parameters: COMB=FOUR,STEP-PATT=5,FP-SPLIT=STD Number_of_Iterations: 1 Time_Per_Exposure: 1632.0S Special_Requirements: Comments: 1260A (Si II Region) Exposure_Number: 20 Target_Name: WAVE Config: HRS Opmode: ACCUM Aperture: SC2 Sp_Element: G160M Wavelength: 1296.5 Optional_Parameters: SPYBAL=YES Number_of_Iterations: 1 Time_Per_Exposure: 54.4S Special_Requirements: Comments: WAVECAL for 1300A Region Exposure_Number: 21 Target_Name: WD1057+719 Config: HRS Opmode: ACCUM Aperture: 0.25 Sp_Element: G160M Wavelength: 1296.5 Optional_Parameters: COMB=FOUR,STEP-PATT=5,FP-SPLIT=STD Number_of_Iterations: 1 Time_Per_Exposure: 1523.2S Special_Requirements: Comments: 1300A (Si III Region) Exposure_Number: 30 Target_Name: WAVE Config: HRS Opmode: ACCUM Aperture: SC2 Sp_Element: G160M Wavelength: 1405.5 Optional_Parameters: SPYBAL=YES Number_of_Iterations: 1 Time_Per_Exposure: 54.4S Special_Requirements: Comments: WAVECAL for 1400 A Region Exposure_Number: 31 Target_Name: WD1057+719 Config: HRS Opmode: ACCUM Aperture: 0.25 Sp_Element: G160M Wavelength: 1405.5 Optional_Parameters: COMB=FOUR,STEP-PATT=5,FP-SPLIT=STD Number_of_Iterations: 1 Time_Per_Exposure: 2176.0S Special_Requirements: Comments: 1400A (Si IV Region) Exposure_Number: 41 Target_Name: WD1057+719 Config: HRS Opmode: ACCUM Aperture: 0.25 Sp_Element: G160M Wavelength: 1538.7 Optional_Parameters: COMB=FOUR,STEP-PATT=5,FP-SPLIT=STD Number_of_Iterations: 1 Time_Per_Exposure: 3155.2S Special_Requirements: Comments: 1550A (C IV Region) Visit_Number: 02 Visit_Requirements: On_Hold_Comments: Visit_Comments: Exposure_Number: 1 Target_Name: REJ1614-085 Config: HRS Opmode: ACQ Aperture: 2.0 Sp_Element: MIRROR-N2 Wavelength: Optional_Parameters: Number_of_Iterations: 1 Time_Per_Exposure: 3.6S Special_Requirements: ONBOARD ACQ FOR 2 Comments: expected counrate = 12400 c/s Exposure_Number: 2 Target_Name: REJ1614-085 Config: HRS Opmode: ACQ/PEAKUP Aperture: 0.25 Sp_Element: MIRROR-N2 Wavelength: Optional_Parameters: Number_of_Iterations: 1 Time_Per_Exposure: 10.0S Special_Requirements: ONBOARD ACQ FOR 11-41 Comments: Exposure_Number: 11 Target_Name: REJ1614-085 Config: HRS Opmode: ACCUM Aperture: 0.25 Sp_Element: G160M Wavelength: 1251.9 Optional_Parameters: COMB=FOUR,STEP-PATT=5,FP-SPLIT=STD Number_of_Iterations: 1 Time_Per_Exposure: 435.2S Special_Requirements: Comments: 1260A (Si II Region) Exposure_Number: 20 Target_Name: WAVE Config: HRS Opmode: ACCUM Aperture: SC2 Sp_Element: G160M Wavelength: 1296.5 Optional_Parameters: SPYBAL=YES Number_of_Iterations: 1 Time_Per_Exposure: 54.4S Special_Requirements: Comments: WAVECAL for 1300A Region Exposure_Number: 21 Target_Name: REJ1614-085 Config: HRS Opmode: ACCUM Aperture: 0.25 Sp_Element: G160M Wavelength: 1296.5 Optional_Parameters: COMB=FOUR,STEP-PATT=5,FP-SPLIT=STD Number_of_Iterations: 1 Time_Per_Exposure: 435.2S Special_Requirements: Comments: 1300A (Si III Region) Exposure_Number: 30 Target_Name: WAVE Config: HRS Opmode: ACCUM Aperture: SC2 Sp_Element: G160M Wavelength: 1405.5 Optional_Parameters: SPYBAL=YES Number_of_Iterations: 1 Time_Per_Exposure: 54.4S Special_Requirements: Comments: WAVECAL for 1400 A Region Exposure_Number: 31 Target_Name: REJ1614-085 Config: HRS Opmode: ACCUM Aperture: 0.25 Sp_Element: G160M Wavelength: 1405.5 Optional_Parameters: COMB=FOUR,STEP-PATT=5,FP-SPLIT=STD Number_of_Iterations: 1 Time_Per_Exposure: 761.6S Special_Requirements: Comments: 1400A (Si IV Region) Exposure_Number: 41 Target_Name: REJ1614-085 Config: HRS Opmode: ACCUM Aperture: 0.25 Sp_Element: G160M Wavelength: 1538.7 Optional_Parameters: COMB=FOUR,STEP-PATT=5,FP-SPLIT=STD Number_of_Iterations: 1 Time_Per_Exposure: 1305.6S Special_Requirements: Comments: 1550A (C IV Region) Data_Distribution ! 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