! Hubble Space Telescope Cycle 5 (1995) Phase II Proposal Template ! $Id: 6090,v 4.1 1995/08/11 18:09:14 pepsa Exp $ ! ! Refer to the HST Phase II Proposal Instructions to fill this out ! ! Anything after a "!" is ignored, and may be deleted ! ! All keywords with multiple entries are comma delimited except the ! Visit_Requirements and Special_Requirements keywords which can be ! delimited with carriage returns or semi-colons, but not commas ! ! For help call your Program Coordinator: Dustin Manning ! Phone: 410 338-4456 , E-mail: manning@stsci.edu ! ! This partially completed template was generated from a Phase I proposal. ! Date generated: Sun Dec 18 19:28:49 EST 1994 ! Proposal_Information ! Section 4 Title: UV spectroscopy of two ultra-hot white dwarf candidates Proposal_Category: GO Scientific_Category: Hot Stars Cycle: 5 Investigators PI_name: Klaus Werner PI_Institution: Institut fuer Theoretische Physik und Sternwarte, Universitaet Kiel CoI_Name: Ulrich Heber CoI_Institution: Sternwarte Bamberg, Astronomisches Institut der Universitaet Erlangen-Nuernberg Contact: N ! Y or N (designate at most one contact) CoI_Name: Stefan Dreizler CoI_Institution: Sternwarte Bamberg, Astronomisches Institut der Universitaet Erlangen-Nuernberg Contact: N ! Y or N (designate at most one contact) CoI_Name: Dieter Reimers CoI_Institution: Sternwarte Hamburg Contact: N ! Y or N (designate at most one contact) Abstract: ! Free format text (please update) We propose GHRS UV spectroscopy of two outstanding stars which define a completely new spectroscopic class. The optical spectra are dominated by ultra-high ionization absorption (!) lines of carbon and oxygen (CVI, OVII, OVIII). In comparison, the very hot (T(eff)>100 000 K) PG 1159 stars exhibit lines from CIV and OVI. First exploratory non- LTE model calculations indicate that the effective temperature of these objects must exceed half a million degrees! Thus the temperatures by far exceed those of the hottest stars known. The surface gravities are high (log g>8), hence these object are probably compact post-AGB stars which are just about to enter the white dwarf cooling sequence. Comparison with evolutionary tracks suggests masses just below the Chandrasekhar limit. The proposed HST observations are needed to verify the nature of these stars by detailed spectrum synthesis in order to precisely determine the stellar parameters. Questions ! Free format text (please update) Observing_Description: We propose to observe HE0504-2408 and HS0713+3958 with the GHRS. For the brighter star (HE0504-2408) three different wavelength regions shall be covered by the spectra. In the case of the fainter star we restrict ourselves to the bluest wavelength region. Generally, a resolution of about 1 Angstrom is sufficient, because the lines are expected to be broad like the optical lines. We therefore want to use the low resolution grating G140L. For one exposure centered near 3000 Angstrom we must use the medium resolution grating G270M since G140L is not sensitive there. A S/N of 35 is aimed at. This requirement is reduced to almost 20 in the G270M case because appropriate binning can be performed. 1150-1436 Angstrom, t(exp)=28 min (HE0504-2408) and t(exp)=80 min (HS0713+3958 which has a UV flux 3 times lower than HS0713+3958) with grating G140L. According to Tab. 2 an OVIII and a CVI line will be detected. Also, the Lyman-alpha line is covered from which we can find the ISM column density towards to objects. This is required for analyses of X-ray observations which we are planning to perform. 1494-1781 Angstrom, t(exp)=48 min with grating G140L, covering numerous high ionization lines. 2956-- 3000 Angstrom, t(exp)=48 min with grating G270M. This covers the OVIII n=7-->8 line. We have recently detected this line in emission in the hot DO white dwarf KPD0005+5106 (see Fig. 3). As mentioned above, this DO also shows optical OVIII emissions. From the presence of optical OVIII absorptions in our targets we strongly expect the 2978 Angstrom line in absorption. The higher spectral resolution may be used to resolve fine structures in the line profile which might be indicative for a stellar wind. The first wavelength range can be exposed during one and two orbits for HE0504-2408 and HS0713+3958 respectively, after guide star and target aquisition. The second and third wavelength ranges are exposed for HE0504-2408 (only) during the 2nd and 3rd orbits after re-aquisition. The number of orbits for this whole proposal is then 5. Table 3 summarizes our exposure time estimates. The absolute UV fluxes of the stars are known from IUE low resolution spectra we have obtained earlier. begintableh caption Calculated exposure times to achieve S/N=35 with G140L (S/N=18 with G270M in the 3000Angstrom\ region) for HE0504-2408. centering wavelength& F_Lambda (IUE) /10^-13 & grating & sensitivity & count rate & t_ exp , Angstrom & erg/cm^2/sec/Angstrom & & 10^11 & per sec & minutes , 1150 & 3.5 & G140L &21. & 0.73 & 28 , 1700 & 1.3 & G140L &32. & 0.42 & 48. , 3000 & 0.40& G270M &27. & 0.11 & 48. , endtabular endtable !!!!!!!!!!!!!!!!!! !NOTE: accurate target coordinates are still to be determined !!---------- !!!!!!!!!!!!!!!!!! Fixed_Targets Target_Number:1 Target_Name:HE0504-2408 Description:STAR,WDO Position:RA= 05H 06M 18.16S +/- 0.1S, DEC=-24D 04' 1.9" +/- 0.1", PLATE-ID=049Y Equinox:J2000 Flux:V = 15.2 +/- 0.2, B-V=-0.3 +/-0.1 Fixed_Targets Target_Number:2 Target_Name:HS0713+3958 Description:STAR,WDO Position:RA= 07H 13M 36.00S +/- 0.1S, DEC=+39D 58' 47.0" +/- 0.1", PLATE-ID=00VU Equinox:B1950 Flux:V = 16.2 +/- 0.2, B-V=-0.3 +/-0.1 Visits Visit_Number:1 !------------------------------------------------- HE0504: ACQUISITION Exposure_Number:1 Target_Name:HE0504-2408 Config:HRS Opmode:ACQ Aperture:2.0 Sp_Element:MIRROR-N1 Wavelength: Optional_Parameters:SEARCH-SIZE=3,BRIGHT=RETURN Number_of_Iterations:1 Time_Per_Exposure:5.4S Special_Requirements:ONBOARD ACQ FOR 2 Comments:STEP-TIME=0.6S, EXPECT 400 CNTS !------------------------------------------------- HE0504: LAMBDA-RANGE 1 Exposure_Number:2 Target_Name:HE0504-2408 Config:HRS Opmode:ACCUM Aperture:2.0 Sp_Element:G140L Wavelength:1150-1436 Optional_Parameters:FP-SPLIT=STD,COMB=FOUR,DOPPLER=ON Number_of_Iterations:1 Time_Per_Exposure:1414.4S Special_Requirements: !------------------------------------------------- HE0504: LAMBDA-RANGE 2 Exposure_Number:3 Target_Name:HE0504-2408 Config:HRS Opmode:ACCUM Aperture:2.0 Sp_Element:G140L Wavelength:1494-1781 Optional_Parameters:FP-SPLIT=STD,COMB=FOUR,DOPPLER=ON Number_of_Iterations:1 Time_Per_Exposure:2611.2S Special_Requirements: !------------------------------------------------- HE0504: LAMBDA-RANGE 3 Exposure_Number:4 Target_Name:HE0504-2408 Config:HRS Opmode:ACCUM Aperture:2.0 Sp_Element:G270M Wavelength:2956-3000 Optional_Parameters:FP-SPLIT=STD,COMB=FOUR,DOPPLER=ON Number_of_Iterations:1 Time_Per_Exposure:2393.6S Special_Requirements: Visit_Number:2 !------------------------------------------------- HS0713: ACQUISITION Exposure_Number:1 Target_Name:HS0713+3958 Config:HRS Opmode:ACQ Aperture:2.0 Sp_Element:MIRROR-N1 Wavelength: Optional_Parameters:SEARCH-SIZE=3,BRIGHT=RETURN Number_of_Iterations:1 Time_Per_Exposure:11.7S Special_Requirements:ONBOARD ACQ FOR 2 Comments:STEP-TIME=1.3S, EXPECT 400 CNTS !------------------------------------------------- HS0713: LAMBDA-RANGE 1 Exposure_Number:2 Target_Name:HS0713+3958 Config:HRS Opmode:ACCUM Aperture:2.0 Sp_Element:G140L Wavelength:1150-1436 Optional_Parameters:FP-SPLIT=STD,COMB=FOUR,DOPPLER=ON Number_of_Iterations:1 Time_Per_Exposure:4243.2S Special_Requirements: Comments: Data_Distribution ! Defaults indicated; change if desired Medium: 8MM ! 8MM or 6250BPI or 1600BPI Blocking_Factor: 10 ! 10 or 1 Ship_To: PI_Address ! STSCI or PI_Address or ! PI Address from Phase I is: ! ! D-24098 Kiel, Germany ! ! Ship_Via: UPS ! UPS (2-day) or OVERNIGHT ! Overnight shipping done at PI expense Recipient_Email: ! Needed if Ship_To: is not PI_Address ! ! Let us know what you think of this template and software! ! Please send a list of your likes and dislikes to your Program Coordinator