! Hubble Space Telescope Cycle 6 (1996) Phase II Proposal Template ! $Id: 6427,v 10.1 1996/04/22 17:33:53 pepsa Exp $ Proposal_Information Title: Direct measurement of the BE Ursae Majoris sdO primary star mass-a critical test case for common envelope evolution Proposal_Category: GO Scientific_Category: BINARIES AND STAR FORMATION Cycle: 6 Investigators PI_name: Donald H. Ferguson PI_Institution: Ferguson Enterprises CoI_Name: James Liebert CoI_Institution: Steward Observatory, University of Arizona Contact: N CoI_Name: Thomas James CoI_Institution: Chaffey High School Contact: N Abstract: BE UMa is a post-common envelope, pre-cataclysmic binary system with nearly unique properties. The primary is a very hot ~100,000 K sdO, about to become a white dwarf, separated by 8 solar radii from a G9V-K5V secondary. With most of its energy distribution emitted in the extreme ultraviolet, it produces a spectacular reprocessing spectrum on the facing side of the cool main sequence companion. This spectrum includes strong optical continuum and emission lines, which have been used to determine the radial velocity of the secondary star. It is also one of the few evolved systems which eclipses, so that tight constaints on the orbital inclination are available, as is the spectrum of the cool secondary star. It is one of the few to have an associated planetary nebula. Most importantly, the parameters derived for the primary star suggest that the binary has been ``uncloaked'' from the common envelope for only 1E6 years. But has the primary star evolved as a normal post-AGB objects, as the atmospheric parameters and mass (0.6 solar) inferred from analyzing its spectrum suggest? Our model of the reprocessed envelope suggests instead that the primary has a substantially higher mass. We propose here to obtain GHRS spectra to measure the velocity of the He II 1640A absorption line in the helium-rich primary especially at orbital quadratures in order to measure directly the mass, from the orbital solution and well as from any detectable gravitational redshift. The orbital separation, another key parameter of the modeling, is also determined. If the result validates the reflection effect models of Ferguson and James (1994), this would allow masses and separations for a broader selection of stars in a similar evolutionary phase (including non-eclipsers or those with less energetic reflection effects); e.g. certain planetary nebulae central stars. Questions Observing_Description: Three sets of exposures at binary phases 0.0, 0.25, and 0.75 required. Each exposure set requires 56 min. Hence, 3 full orbits are required. The first observation MUST be at phase=0 with the offset saved to ensure the exposures at quadrature have the longest integrations. Each exposure set consists of placing the star in the SSA and collecting several exposures with a wavelength calibration on either end. Real_Time_Justification: The observations must be timed to the binary ephemeris for optimum value. The current best ephemeris for BE UMa is that of Wood et al. 1995: minimum light corresponding to eclipse of the hot sdO by the secondary star occurs at HJD 2444998.2810 + 2.2911658(7) days. We require one observation each at minimum phase and opposite quadratures, all within a delta-phase of 0.08, in order to obtain spectra near maximum radial velocity shifts. These observations need not be obtained during hte same binary orbit cycle, however. Calibration_Justification: !None Additional_Comments: (Answer to the TAC question of how we'll remove the emission peak) The 1640A feature consists of a broad absorption line from the high-gravity sdO and a narrow emission line from a reflection effect on the side of the main sequence-like secondary facing the sdO. Note first that the emission feature is in near-eclipse around phase =0 and so has greatly reduced intensity. With the spectrum at phase 0, we will fit the outer wings of the absorption line using the models of Liebert et al 1994 as far toward the central wavelength as possible until a deviation in slope of the profile upward is detected using least-squares fitting. Now at quadrature, the emission line will be displaced from zero due to orbit-induced Doppler shifting by +- 102 km/s and the sdO lines will of course be Doppler shifted in the opposite direction, increasing the magnitude of the emission peak movement away from the central wavlength of the absorption line. We will fit the entire absorption line profile (including the uncontaminated half opposite the emission peak) with the results from the zero phase absorption line profile, allowing removal of the central peak. Fixed_Targets Target_Number: 1 Target_Name: BE-UMa Alternate_Names: PG1155+492 Description: STAR, SDO Position: RA = 11H 57M 44.78S +/- 0.05S, DEC = 48D 56' 18.7" +/- 0.5", PLATE-ID = 024C Equinox: J2000 RV_or_Z: V = -67 RA_PM: ! N/A --object at 1-2 kpc Dec_PM: ! N/A --object too far away Epoch: ! N/A Annual_Parallax: ! N/A Flux: V = 14.7 +/- 1.5 B-V = 0.13 +/- 0.13 F-CONT(1640) = 5 +/- 1 1E-14 Comments: Coordinates are from an inventory GASP measurement by Karla Visits ! Section 6 Visit_Number: 1 Visit_Requirements: PERIOD 54.98798H AND ZERO-PHASE JD2449980.2810 Visit_Comments: This visit is at phase 0. Exposure_Number: 10 Target_Name: BE-UMa Config: HRS Opmode: ACQ Aperture: 2.0 Sp_Element: MIRROR-N2 Optional_Parameters: BRIGHT=RETURN, SEARCH-SIZE=3 Number_of_Iterations: 1 Time_Per_Exposure: 7.2s Special_Requirements: ONBOARD ACQ FOR 20 SEQ 10-50 NON-INT Comments: assuming 500 counts/s Exposure_Number: 20 Target_Name: BE-UMa Config: HRS Opmode: ACQ/PEAKUP Aperture: 0.25 Sp_Element: MIRROR-N2 Optional_Parameters: SEARCH-SIZE=5 Number_of_Iterations: 1 Time_Per_Exposure: 20s Special_Requirements: ONBOARD ACQ FOR 30-50 Exposure_Number: 30 Target_Name: WAVE Config: HRS Opmode: ACCUM Aperture: SC2 Sp_Element: G160M Wavelength: 1623-1657 Optional_Parameters: Number_of_Iterations: 1 Time_Per_Exposure: 54.4s Special_Requirements: PHASE 0.96 TO 0.04 Exposure_Number: 40 Target_Name: BE-UMa Config: HRS Opmode: ACCUM Aperture: 0.25 Sp_Element: G160M Wavelength: 1623-1657 Optional_Parameters: DOPPLER=DEF, CENSOR=YES Number_of_Iterations: 3 Time_Per_Exposure: 326.4s Exposure_Number: 50 Target_Name: WAVE Config: HRS Opmode: ACCUM Aperture: SC2 Sp_Element: G160M Wavelength: 1623-1657 Optional_Parameters: Number_of_Iterations: 1 Time_Per_Exposure: 54.4s Visit_Number: 2 Visit_Requirements: PERIOD 54.98798H AND ZERO-PHASE JD2449980.2810 Visit_Comments: This visit is at phase .25. Exposure_Number: 10 Target_Name: BE-UMa Config: HRS Opmode: ACQ Aperture: 2.0 Sp_Element: MIRROR-N2 Optional_Parameters: BRIGHT=RETURN, SEARCH-SIZE=3 Number_of_Iterations: 1 Time_Per_Exposure: 7.2s Special_Requirements: ONBOARD ACQ FOR 20 SEQ 10-50 NON-INT Comments: assuming 500 counts/s Exposure_Number: 20 Target_Name: BE-UMa Config: HRS Opmode: ACQ/PEAKUP Aperture: 0.25 Sp_Element: MIRROR-N2 Optional_Parameters: SEARCH-SIZE=5 Number_of_Iterations: 1 Time_Per_Exposure: 20s Special_Requirements: ONBOARD ACQ FOR 30-80 Exposure_Number: 30 Target_Name: WAVE Config: HRS Opmode: ACCUM Aperture: SC2 Sp_Element: G160M Wavelength: 1623-1657 Optional_Parameters: Number_of_Iterations: 1 Time_Per_Exposure: 54.4s Special_Requirements: PHASE 0.21 TO 0.29 Exposure_Number: 40 Target_Name: BE-UMa Config: HRS Opmode: ACCUM Aperture: 0.25 Sp_Element: G160M Wavelength: 1623-1657 Optional_Parameters: DOPPLER=DEF, CENSOR=YES Number_of_Iterations: 3 Time_Per_Exposure: 326.4s Exposure_Number: 50 Target_Name: WAVE Config: HRS Opmode: ACCUM Aperture: SC2 Sp_Element: G160M Wavelength: 1623-1657 Optional_Parameters: Number_of_Iterations: 1 Time_Per_Exposure: 54.4s Exposure_Number: 60 Target_Name: WAVE Config: HRS Opmode: ACCUM Aperture: SC2 Sp_Element: G160M Wavelength: 1623-1657 Optional_Parameters: Number_of_Iterations: 1 Time_Per_Exposure: 54.4s Special_Requirements: SEQ 60-80 NON-INT Exposure_Number: 70 Target_Name: BE-UMa Config: HRS Opmode: ACCUM Aperture: 0.25 Sp_Element: G160M Wavelength: 1623-1657 Optional_Parameters: DOPPLER=DEF, CENSOR=YES Number_of_Iterations: 7 Time_Per_Exposure: 326.4s Special_Requirements: Exposure_Number: 80 Target_Name: WAVE Config: HRS Opmode: ACCUM Aperture: SC2 Sp_Element: G160M Wavelength: 1623-1657 Optional_Parameters: Number_of_Iterations: 1 Time_Per_Exposure: 54.4s Special_Requirements: Visit_Number: 3 Visit_Requirements: PERIOD 54.98798H AND ZERO-PHASE JD2449980.2810 Visit_Comments: This visit is at phase .75. Exposure_Number: 10 Target_Name: BE-UMa Config: HRS Opmode: ACQ Aperture: 2.0 Sp_Element: MIRROR-N2 Optional_Parameters: BRIGHT=RETURN, SEARCH-SIZE=3 Number_of_Iterations: 1 Time_Per_Exposure: 7.2s Special_Requirements: ONBOARD ACQ FOR 20 SEQ 10-50 NON-INT Comments: assuming 500 counts/s Exposure_Number: 20 Target_Name: BE-UMa Config: HRS Opmode: ACQ/PEAKUP Aperture: 0.25 Sp_Element: MIRROR-N2 Optional_Parameters: SEARCH-SIZE=5 Number_of_Iterations: 1 Time_Per_Exposure: 20s Special_Requirements: ONBOARD ACQ FOR 30-80 Exposure_Number: 30 Target_Name: WAVE Config: HRS Opmode: ACCUM Aperture: SC2 Sp_Element: G160M Wavelength: 1623-1657 Optional_Parameters: Number_of_Iterations: 1 Time_Per_Exposure: 54.4s Special_Requirements: PHASE 0.71 TO 0.79 Exposure_Number: 40 Target_Name: BE-UMa Config: HRS Opmode: ACCUM Aperture: 0.25 Sp_Element: G160M Wavelength: 1623-1657 Optional_Parameters: DOPPLER=DEF, CENSOR=YES Number_of_Iterations: 3 Time_Per_Exposure: 326.4s Exposure_Number: 50 Target_Name: WAVE Config: HRS Opmode: ACCUM Aperture: SC2 Sp_Element: G160M Wavelength: 1623-1657 Optional_Parameters: Number_of_Iterations: 1 Time_Per_Exposure: 54.4s Exposure_Number: 60 Target_Name: WAVE Config: HRS Opmode: ACCUM Aperture: SC2 Sp_Element: G160M Wavelength: 1623-1657 Optional_Parameters: Number_of_Iterations: 1 Time_Per_Exposure: 54.4s Special_Requirements: SEQ 60-80 NON-INT Exposure_Number: 70 Target_Name: BE-UMa Config: HRS Opmode: ACCUM Aperture: 0.25 Sp_Element: G160M Wavelength: 1623-1657 Optional_Parameters: DOPPLER=DEF, CENSOR=YES Number_of_Iterations: 7 Time_Per_Exposure: 326.4s Special_Requirements: Exposure_Number: 80 Target_Name: WAVE Config: HRS Opmode: ACCUM Aperture: SC2 Sp_Element: G160M Wavelength: 1623-1657 Optional_Parameters: Number_of_Iterations: 1 Time_Per_Exposure: 54.4s Special_Requirements: Data_Distribution Medium: 8MM Blocking_Factor: 10 Ship_To: PI_Address Ship_Via: UPS