Proposal_Information ! Section 4 Title: Understanding the Simplest Symbiotic System(s) II. The 1996 eclipse of RW Hydrae Proposal_Category: GO Scientific_Category: BINARIES AND STAR FORMATION Cycle: 6 Investigators PI_name: Werner Schmutz PI_Institution: Institute of Astronomy CoI_Name: Urs Muerset CoI_Institution: Institute of Astronomy, ETH Zuerich Contact: N ! Y or N (designate at most one contact) CoI_Name: Harry Nussbaumer CoI_Institution: Institute of Astronomy, ETH Zuerich Contact: N ! Y or N (designate at most one contact) CoI_Name: Hans Schild CoI_Institution: Institute of Astronomy, ETH Zuerich Contact: N ! Y or N (designate at most one contact) CoI_Name: Hans Martin Schmid CoI_Institution: Mount Stromlo and Siding Spring Observatories Contact: N ! Y or N (designate at most one contact) CoI_Name: Steven Shore CoI_Institution: Indiana University South Bend Contact: N ! Y or N (designate at most one contact) CoI_Name: Rolf Walder CoI_Institution: Institute of Astronomy, ETH Zuerich Contact: N ! Y or N (designate at most one contact) Abstract: ! Free format text (please update) We propose to observe the symbiotic system RW Hya during eclipse. The observations will be compared to approved cycle 5 HST observations at quadrature. The comparison will yield a stringent test of our model for S-type symbiotic systems. The proposed target, RW Hya, is a typical S-type system and carefully selected for its characteristics: eclipsing, line profile variations that repeat with orbital phase, absence of outbursts, and UV bright. We postulate three different emission regions: wind lines from the hot star, nebular emission from the wind of the red giant facing the hot star, and most interesting, features emerging from the wind-wind interaction zone. We predict a different eclipse behavior for each of these regions. The GHRS observations are focused on weak low density intercombination lines that are suspected to be formed in a shock zone between the two stars and on broad line wings and P Cygni features emergent from the stellar wind of the hot object. These features are too weak to be accessible by IUE. If our model is confirmed qualitatively by the proposed test we will apply in a later HST cycle to cover a full orbit. Doppler tomography of optically thin intercombination lines will allow to map the interaction zone in the binary system. The results will be used for a quantitative comparison with sophisticated hydrodynamic calculations. Observational constraints are desperately needed to validate our understanding of the hydrodynamics. Questions ! Free format text (please update) Observing_Description: For cycle 6 we ask for 1 visit of the system RW Hya. The following five lines should be observed with the GHRS grating G140M using the large science aperture: Nv L1240, Ov L1371, Niv LL1483.3,1486.5, Oiv L1400, and Heii L1640. According to the flux observed by IUE during eclipse we expose each wavelength region for 33 min. The five wavelength settings require 165 min or 4 orbits including the first acquisition and re-acquisition. With the small science aperture and G140M we intend to observe Ov LL 1213.9,1218.4 with an exposure time of 40 min or one orbit including a peak up acquisition. The Ov LL 1213.9,1218.4 lines are close to LyAlpha and one could suspect that the interstellar absorption by the hydrogen line prevents the observation of the oxygen lines. However, the Hi column density towards RW Hya is only ~ 5,10^19 cm^-2. The oxygen lines have been seen with IUE in a long exposure of RR Tel that has a larger Hi column density (~ 10^20 cm^-2). Another matter of concern with the Ov LambdaLambda 1213.9,1218.4 lines is the geocoronal LyAlpha. Out of eclipse we will have a count rate in the continuum of 0.43 counts/diode/sec. The geocoronal total count rate will be (out of earth shadow) 20 counts/sec. The geocoronal line will have a FWHM of 8 diodes (LSA) or 0.6 Angstrom. The closer Ov line is at DeltaLambda = 1.8A and assuming a width of 200 km/s for the Ov Lambda 1213.9 its red side will be contaminated by a count rate of 0.09 counts/diode/sec. Thus this contamination can still be corrected by subtracting the geocoronal contribution. However, in eclipse the flux from RW Hya will be considerably lower and therefore, we will use the small science aperture for the observation proposed here. With the GHRS grating G140L we will cover the region (1150--1800) with three wavelength settings. The purpose of this observation is threefold: First, we will get an absolute flux for the SSA G140M exposure of the 1215A setting, second, the low resolution exposure will detect the continuum during eclipse that is at most 1/30 of the level outside eclipse, and third, with a complete coverage of the wavelength region we may detect other lines from the wind-wind interaction zone. In the absence of the hot stellar continuum and most of the nebula continuum, a deep exposure during eclipse provides a good opportunity to detect unexpected features beside the (strong) nebular lines known from IUE exposures: Civ Lambda1550, Oiii Lambda1660, Niv Lambda1718 and Niii Lambda1750. In one orbit each of the three wavelength settings can be exposed for 11 min. In total we apply for 6 HST orbits. Exposure times are calculated from IUE low resolution observations. Real_Time_Justification: The observations have to be taken during eclipse. Mid eclipse in 1996 is June 19. From IUE observations we know that the eclipse lasts at least up to phase 0.05, i.e. the eclipse duration is from June 1st to July 7. Thus, if the nominal start of cycle 6 is taken into account then the observations have to be obtained in the window July 1st to July 7 1996. Calibration_Justification: ! Move appropriate text from Real_Time_Justification Additional_Comments: Fixed_Targets ! Section 5.1 Target_Number: 1 Target_Name: HD117970 Alternate_Names: RW-HYA, GSC6718-01146 Description: STAR, SYMBIOTIC STAR, NOVA-LIKE, INTERACTING BINARY, EMISSION LINE STAR Position: RA = 13H 34M 18.17S +/- 0.04S, DEC = -25D 22' 48.9" +/- 0.5", PLATE-ID = 04LM Equinox: J2000 RV_or_Z: V=13 RA_PM: -0.0025 ! Units are seconds of time per year Dec_PM: 0.014 ! Units are seconds of arc per year Epoch: 1976.417 Annual_Parallax: Flux: V=9.2+/-0.3, F-CONT(1400)=1+/-1 E-13, F-LINE(1240)=60+/-60, W-LINE(1240)=2+/-2 Comments: Coordinates from GSC Visits ! Section 6 Visit_Number: 01 Visit_Requirements: BETWEEN 1-JUN-1996 AND 7-JUL-1996 Visit_Comments: Exposure_Number: 1 ! Section 6.5 Target_Name: HD117970 Config: HRS Opmode: ACQ Aperture: 2.0 Sp_Element: MIRROR-N1 Wavelength: Optional_Parameters: BRIGHT=RETURN,SEARCH-SIZE=3 Number_of_Iterations: 1 Time_Per_Exposure: 36S Special_Requirements: ONBOARD ACQ FOR 2-8 Comments: STEP-TIME=4S, EXPECT 700 COUNTS IN STEP-TIME, UNCERTAINTY OF EXPECTED COUNTS IS 100 TO 2000 Exposure_Number: 2 Target_Name: HD117970 Config: HRS Opmode: ACCUM Aperture: 2.0 Sp_Element: G140L Wavelength: 1620 Optional_Parameters: FP-SPLIT=STD Number_of_Iterations: 1 Time_Per_Exposure: 652.8S Comments: S/N=30 in continuum Exposure_Number: 3 Target_Name: HD117970 Config: HRS Opmode: ACCUM Aperture: 2.0 Sp_Element: G140L Wavelength: 1320 Optional_Parameters: FP-SPLIT=STD Number_of_Iterations: 1 Time_Per_Exposure: 761.6S Comments: S/N=30 in continuum Exposure_Number: 4 Target_Name: HD117970 Config: HRS Opmode: ACCUM Aperture: 2.0 Sp_Element: G140M Wavelength: 1640 Optional_Parameters: FP-SPLIT=STD Number_of_Iterations: 1 Time_Per_Exposure: 1414.4S Comments: S/N=10 in continuum Exposure_Number: 5 Target_Name: HD117970 Config: HRS Opmode: ACCUM Aperture: 2.0 Sp_Element: G140M Wavelength: 1550 Optional_Parameters: FP-SPLIT=STD Number_of_Iterations: 1 Time_Per_Exposure: 1305.6S Comments: S/N=10 in continuum Exposure_Number: 6 Target_Name: HD117970 Config: HRS Opmode: ACCUM Aperture: 2.0 Sp_Element: G140M Wavelength: 1484 Optional_Parameters: FP-SPLIT=STD Number_of_Iterations: 1 Time_Per_Exposure: 1196.8S Comments: S/N=10 in continuum Exposure_Number: 7 Target_Name: HD117970 Config: HRS Opmode: ACCUM Aperture: 2.0 Sp_Element: G140M Wavelength: 1400 Optional_Parameters: FP-SPLIT=STD Number_of_Iterations: 1 Time_Per_Exposure: 1196.8S Comments: S/N=10 in continuum Exposure_Number: 8 Target_Name: HD117970 Config: HRS Opmode: ACCUM Aperture: 2.0 Sp_Element: G140M Wavelength: 1240 Optional_Parameters: FP-SPLIT=STD Number_of_Iterations: 1 Time_Per_Exposure: 1414.4S Comments: S/N=10 in continuum EXPAND TO FILL ORBIT IF POSSIBLE Visit_Number: 02 Visit_Requirements: BETWEEN 10-JUL-1996 AND 10-AUG-1996 Visit_Comments: Exposure_Number: 11 ! Section 6.5 Target_Name: HD117970 Config: HRS Opmode: ACQ Aperture: 2.0 Sp_Element: MIRROR-N1 Wavelength: Optional_Parameters: BRIGHT=RETURN,SEARCH-SIZE=3 Number_of_Iterations: 1 Time_Per_Exposure: 18S Special_Requirements: ONBOARD ACQ FOR 12-17 Comments: STEP-TIME=2S, EXPECT 1500 COUNTS IN STEP-TIME, UNCERTAINTY OF EXPECTED COUNTS IS APPROX 500 TO 3000 Exposure_Number: 12 Target_Name: HD117970 Config: HRS Opmode: ACCUM Aperture: 2.0 Sp_Element: G140L Wavelength: 1320 Optional_Parameters: FP-SPLIT=STD Number_of_Iterations: 1 Time_Per_Exposure: 435.2S Comments: S/N=30 in continuum Exposure_Number: 13 Target_Name: HD117970 Config: HRS Opmode: ACCUM Aperture: 2.0 Sp_Element: G140L Wavelength: 1620 Optional_Parameters: FP-SPLIT=STD Number_of_Iterations: 1 Time_Per_Exposure: 435.2S Comments: S/N=30 in continuum Exposure_Number: 14 Target_Name: HD117970 Config: HRS Opmode: ACCUM Aperture: 2.0 Sp_Element: G140M Wavelength: 1640 Optional_Parameters: FP-SPLIT=STD Number_of_Iterations: 1 Time_Per_Exposure: 544.0S Comments: S/N=10 in continuum Exposure_Number: 15 Target_Name: HD117970 Config: HRS Opmode: ACCUM Aperture: 2.0 Sp_Element: G140M Wavelength: 1550 Optional_Parameters: FP-SPLIT=STD Number_of_Iterations: 1 Time_Per_Exposure: 435.2S Comments: S/N=10 in continuum Exposure_Number: 16 Target_Name: HD117970 Config: HRS Opmode: ACCUM Aperture: 2.0 Sp_Element: G140M Wavelength: 1400 Optional_Parameters: FP-SPLIT=STD Number_of_Iterations: 1 Time_Per_Exposure: 435.2S Comments: S/N=10 in continuum Exposure_Number: 17 Target_Name: HD117970 Config: HRS Opmode: ACCUM Aperture: 2.0 Sp_Element: G140M Wavelength: 1240 Optional_Parameters: FP-SPLIT=STD Number_of_Iterations: 1 Time_Per_Exposure: 544.0S Comments: S/N=10 in continuum EXPAND TO FILL ORBIT IF POSSIBLE Data_Distribution ! 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