6414( 5) - 06/21/96 10:46 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6414 Version: 5 Check-in Date: 21-Jun-1996 10:43:48 1.Proposal Title: Doppler mapping of chromospheric and transition region UV emission lines in BW Dra. ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle BINARIES AND STAR FOR GO 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: SIMON ROSEN University of Leicester CoI: John Pye University of Leicester N CoI: Simon Hodgkin University of Leicester N CoI: Martin Barstow University of Leicester N CoI: Steve Howell Planetary Sciences Institute N CoI: Paul McGale University of Leicester N ------------------------------------------------------------------------------------ 6. Abstract The gravitationally distorted stellar components in contact binaries power a wealth of chromospheric and transition region lines in the UV, the profiles of which are known to vary on the binary period. However, whilst it is clear that there is spatial structure associated with this emission, its distribution within each region is poorly defined. Since most contact binaries are at least partially eclipsing, they are very amenable to eclipse mapping studies, but if combined with radial velocity information, Doppler imaging can also be employed, providing a powerful, complementary tool to probe such structure. To date, the combination of both high S/N and well phase-resolved spectra required to exploit this technique has not been possible with IUE. Our objective is to take advantage of both the enhanced sensitivity and temporal resolution available with HST to secure highly phase resolved (<=6 %) high dispersion (0.1Angstrom) HRS spectra of the bright, late (W- type) contact binary, BW Dra, to reconstruct emissivity maps in two key UV lines which trace out temperature structure over the surface of the two stars. Specifically, we aim to compare the chromospheric and transition region emissivity patterns associated with the connecting neck between the stars, temperature gradients across the binary and with active regions. ------------------------------------------------------------------------------------ 6414( 5) - 06/21/96 10:46 - [ 2] Observations Description ------------------------ Our observations will make use of the GHRS with the large aperture (for maximum throughput). We will employ the G160M and G270M gratings to centre on the CIV 1550A and MgII 2800A lines respectively. Observations will be performed using ACCUM mode and we will record sequences of exposures with individual integration times of about 500s duration to maximize flexibility during the analysis stage. Given our allocation of 10 HST orbits, each line will be observed for the equivalent of one binary orbit (i.e. 2 binary cycles in total). Since BW~Dra is in the northern CVZ, this can be achieved with one visit. Starting the visit at the beginning of the 8 orbits that are uninterrupted by the SAA will then provide 8 orbits of clear data and will extend into only two of the 8 orbits affected by the SAA. To provide the best coverage of a given binary cycle in BOTH lines whilst maintaining good observing efficiency, we will alternate the gratings every HST orbit. This will provide alternating sequences of about 11x500s exposures for each line, each sequence spanning roughly one fifth of the binary cycle. In the absence of previous UV data on BW Dra, our feasibility estimates for the star are based on scaling the previous IUE spectra of 44i Boo (CIV line) and VW Cep (MgII line) by the respective optical V band flux ratios of 0.1 and 0.33. From the measured fluxes at half-height of the CIV and MgII lines in these stars of about 30 and 6 e-14 ergs/s/cm2/A respectively, we predict 3 and 2 e-14 ergs/s/cm2/A in the CIV and MgII lines in BW Dra. Using the HST HRS sensitivity information we can expect around 0.012 (CIV) and 0.08 (MgII) counts/s/diode (remembering that 1 diode corresponds to a wavelength range of about 0.07 Angstroms and 0.09 Angstroms in the G160M and G270M gratings respectively). Within a 500s integration (2% of the binary period) we would expect fluxes of about 6 and 40 counts/diode per exposure at the half-height of each line (the disparity in flux between the two lines is largely due to the different sensitivities of the gratings). For the low S/N CIV line, we will bin in wavelength by a factor 4 (giving a velocity resolution of about 50 km/s) and in phase by a factor about 3 so as to achieve a phase resolution of about 6%. Thus for CIV we anticipate a flux of about 70 counts or a S/N of about 6.1 (including the dark current) per bin. For the MgII line we will fare much better and should achieve a flux of about 40 counts/diode (S/N of about 6) in each 500s exposure without any wavelength binning. Binning by a factor 2 in wavelength (27 km/s resolution) and phase (4% phase resolution) would double the S/N. We aim to augment these observations with ground based data. Photometry and moderate dispersion optical spectroscopy will be obtained from the US (with reasonable flexibility in scheduling). We note from the HST schedulability information that the star is visible to HST during three intervals before the servicing mission. These are from Jul 25 - 28 1996, Sep 20-22 and Nov 15-17 1996. As far as ground based observing is concerned, the earliest of these is by far the best since the star sets too early from mid-August onwards. If at all possible, we therefore ask that the HST observation of BW Dra be scheduled in the July window. Fortuitously, this slot will also allow us to underpin the observations with high dispersion H alpha spectroscopy from the 4.2m William Hershel Telescope (WHT) on La Palma since there is a WHT service night allocated on the night of July 27. If the HST observation could then be scheduled to at least partially cover the night (UT) of the 27th/28th, this would be very beneficial. NEVERTHELESS, our overriding requirement for the HST observations is that they use all 8 CVZ orbits that are unaffected by the SAA so if this constraint conflicts with the ground based timing, the HST requirements are the ones that should be fulfilled. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 6414( 5) - 06/21/96 10:46 - [ 3] Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 6414( 5) - 06/21/96 10:46 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 BW-DRA STAR, INTERACTING RA=15H 11M 50.03S +/- 0.04S, J2000 V = 8.8+/-0.2 BINARY, W UMa star DEC=+61D 51' 40.5" +/- 0.30" B-V = 0.61+/-0.2 TYPE=G3V F-LINE(1550)=6+/-3e-14 W-LINE(1550)=6.0+/-2.0 F-LINE(2795)=4+/-2e-14 W-LINE(2795)=4.0+/-1.0 Comments: Line flux and width estimates are based on those predicted for BW Dra based on measurements of IUE spectra of VW Cep and 44i Boo. The coordinates come from the Hipparcos INCA Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) J2000 -0.024 0.089 0.0 6414( 5) - 06/21/96 10:46 - [ 5] Visit: 01 Visit Requirements: CVZ On Hold Comments: Additional Comments: Our aim is to acquire the most continuous coverage possible of BW Dra during one HST visit. Two of our 10 CVZ orbits will intersect the SAA. To enable us to back these HST observations with ground based optical coverage, a scheduling during the CVZ slot in July 96 (25th-28th) would be appreciated (see Observing Description section). Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 BW-DRA HRS ACQ 2.0 MIRROR-N2 BRIGHT=RETURN,SEARCH-SIZE=3, 1 2.7 S ONBOARD ACQ FOR 2-6 SAA-CONTOUR=HIGH-NOISE Comments: STEP-TIME = 0.3S; EXPECTED COUNT RATE = 19300 COUNTS/S ------------------------------------------------------------------------------------------------------------------------------------ 2 BW-DRA HRS ACCUM 2.0 G160M 1550 SAA-CONTOUR=HIGH-NOISE 10 489.6 S ------------------------------------------------------------------------------------------------------------------------------------ 3 BW-DRA HRS ACCUM 2.0 G270M 2800 SAA-CONTOUR=HIGH-NOISE 10 489.6 S ------------------------------------------------------------------------------------------------------------------------------------ 4 BW-DRA HRS ACCUM 2.0 G160M 1550 SAA-CONTOUR=HIGH-NOISE 10 489.6 S ------------------------------------------------------------------------------------------------------------------------------------ 5 BW-DRA HRS ACCUM 2.0 G270M 2800 SAA-CONTOUR=HIGH-NOISE 10 489.6 S ------------------------------------------------------------------------------------------------------------------------------------ 6 BW-DRA HRS ACCUM 2.0 G160M 1550 SAA-CONTOUR=HIGH-NOISE 10 489.6 S ------------------------------------------------------------------------------------------------------------------------------------ 7 BW-DRA HRS ACQ/PEA 2.0 MIRROR-N2 SAA-CONTOUR=HIGH-NOISE 1 30.6 S ONBOARD ACQ FOR 8-12 KUP Comments: STEP-TIME = 0.3S; peakup midway through observation. ------------------------------------------------------------------------------------------------------------------------------------ 8 BW-DRA HRS ACCUM 2.0 G270M 2800 SAA-CONTOUR=HIGH-NOISE 10 489.6 S ------------------------------------------------------------------------------------------------------------------------------------ 9 BW-DRA HRS ACCUM 2.0 G160M 1550 SAA-CONTOUR=HIGH-NOISE 10 489.6 S ------------------------------------------------------------------------------------------------------------------------------------ 10 BW-DRA HRS ACCUM 2.0 G270M 2800 SAA-CONTOUR=HIGH-NOISE 10 489.6 S ------------------------------------------------------------------------------------------------------------------------------------ 11 BW-DRA HRS ACCUM 2.0 G160M 1550 SAA-CONTOUR=HIGH-NOISE 11 489.6 S ------------------------------------------------------------------------------------------------------------------------------------ 12 BW-DRA HRS ACCUM 2.0 G270M 2800 SAA-CONTOUR=HIGH-NOISE 12 489.6 S ------------------------------------------------------------------------------------------------------------------------------------ 6414( 5) - 06/21/96 10:46 - [ 6] Summary Form for Proposal 6414 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations HRS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ACQ/PEAKUP ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BRIGHT=RETURN SEARCH-SIZE=3 SAA-CONTOUR=HIGH-NOISE ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category BINARIES AND STAR FORMATION ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements CVZ ONBOARD ACQ FOR 2-6 ONBOARD ACQ FOR 8-12 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR-N2 G160M G270M ------------------------------------------------------------------------------------------------------------------------------------ Target Names BW-DRA ------------------------------------------------------------------------------------------------------------------------------------