7613( 7) - 01/29/98 15:35 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 7613 Version: 7 Check-in Date: 29-Jan-1998 15:34:12 1.Proposal Title: Structure and evolution of the globular cluster low mass X-ray binary AC211 in M15 ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO/CAR 7 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Tim Naylor Keele University CoI: Lydie Koch-Miramond CEN SACLAY N CoI: Michel Auriere Observatoire de Pic-du-Midi N CoI: Phil Charles University of Oxford N CoI: Sergio Ilovaisky Observatoire de Haute Provence N CoI: Claude Chevalier Observatoire de Haute Provence N CoI: Jan van Paradijs University of Amsterdam N CoI: Bruce Margon University of Washington N ------------------------------------------------------------------------------------ 5. Abstract AC211 is optically the brightest counterpart of any globular cluster X-ray binary, and one of the brightest amongst all LMXBs. Given its large UV excess and high orbital inclination (evident from its large UV eclipse) this object is a prime target for HST. We are proposing to carry out phase resolved spectrophotometry of AC211 using the temporal and UV spectral resolutions offered by the FOS. We will model the observed eclipses to define the mechanism responsible for the optical and UV luminosity of this system. This is widely believed to be the heating of the accretion disc by X-rays from the corona. A large flux of X-rays scattered down onto the disc produces a large UV luminosity, and thus a flatter radial disc temperature distribution than pure accretion. The behaviour of the spectral lines with orbital phase will allow us to define the geometry of the wind and the accretion disc. The optical line profiles already infer significant mass loss, implying that the UV resonance lines will show phase modulated P Cyg profiles. From these we can estimate the mass loss rate, and hence the mass transfer and wind mechanisms which are related to the evolutionary state of the binary (predicted to be unique to globular clusters). Only with Space Telescope will we be able to obtain line profiles and continuum measurements which are uncontaminated by light from other cluster members. The results have implications for LMXBs in general and globular cluster X-ray sources in particular. ------------------------------------------------------------------------------------ 7613( 7) - 01/29/98 15:35 - [ 2] Observations Description ------------------------ All our exposures are with the FOS 0.3 arcsec aperture, and so require 3 orbits per visit to get the target into the aperture. Our requirement is then for the following. 1) Four orbits with FOS/RD + PRISM to carry out our eclipse modelling making a total of 7 orbits for the eclipse visit. 2) We also wish to cover an entire orbit interleaving G130H and G190H exposures, obtaining one exposure in each grating. Some of these exposures will cover eclipse, and so their continuum measurements will be used to extend our wavelength range available for eclipse modelling. To obtain a complete orbitalcycle will require 10 orbits, which will have to be split into two groups of 5 orbits if no one observation is to be more than 9 orbits. Thus we require a further 16 orbits for the complete orbital cycle. 0.3cm Signal-to-noise 0.1cm 1) G190H. In our IUE spectra the HeII 1640A has a peak flux of about 1 * 10^-14 ergs cm^-2 s^-1 ang^-1. A 10 minute integration will provide a signal-to-noise of about 20. 2) G130H. After HeII the next strongest line we expect to see is either CIV or NV. From our IUE spectra we can place an upper limit of about 0.5 * 10^-14 ergs cm^ -2 s^-1 ang^-1 at peak. After obtaining the G190H spectrum, and allowing for overheads, we will probably be left with about 30 minutes of unocculted time pre orbit for the G130H. This would yield a signal-to-noise of about 10 at CIV. 3) PRISM. In four minutes the prism will give a peak signal-to-noise of about 100 and should yield usable data (S:N of 10) right down to the short wavelength limit. Real Time Justification ----------------------- The eclipse visit will clearly have to be time critical. if a complete orbital cycle cove be covered in 1 visit (takes 13 orbits) then it would not be time critical (and would save us 3 orbits in setup time). If the observation has to be split, however, the scheduling would have to be such as to ensure the two observations covered separate parts of the orbital cycle. Calibration Justification ------------------------- Real_Time_Justification Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 7613( 7) - 01/29/98 15:35 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC7078- STAR RA=21H 29M 56.556S +/- 2000 V = 14.1+/-0.2 OFFSET 0.01S,DEC=12D 10' 7.270" +/- U-V = 1.3+/-0.2 0.1" Comments: Offset star. Position updated based on early-acq WF/PC image obtained in prior cycle 3 proposal. 2 NGC7078-STAR STAR, LMXB RA-OFF=1.796S+/- 0.01S,DEC-OFF=- 2000 V = 17.0+/-0.2 3.879"+/- 0.1",FROM 1 B-V = +0.4+/-0.2 V = 15.0+/-0.2 Comments: Variable star. Position updated based on early-acq WF/PC image obtained in prior cycle 3 proposal. 7613( 7) - 01/29/98 15:35 - [ 4] Visit: 01 Visit Priority: Visit Requirements: PERIOD 0.713014 D AND ZERO-PHASE JD2447790.963000 PCS MODE FINE On Hold Comments: Additional Comments: Ephemeris from Ilovaisky et al A&A 270, 139. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC7078-OFF STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 0.3 S ONBOARD ACQ FOR 2 SET CD P Comments: Star will saturate in around 5 seconds, and give S:N of 80 in about 0.1 seconds. ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC7078-STA STIS/F ACCUM 52X0.5 G140L 1425 1 421 S EXPAND MAX DUR 10 M MIN R UV-MAM DUR 5 M SEQ 2-3 NON-INT A PHASE 0.70 TO 0.80 ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC7078-STA STIS/F ACCUM 52X0.5 G140L 1425 2 421 S EXPAND MAX DUR 10 M MIN R UV-MAM DUR 5 M SEQ 2-3 NON-INT A ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC7078-STA STIS/F ACCUM 52X0.5 G140L 1425 4 421 S EXPAND MAX DUR 10 M MIN R UV-MAM DUR 5 M SEQ 4 NON-INT A ------------------------------------------------------------------------------------------------------------------------------------ 5 NGC7078-STA STIS/F ACCUM 52X0.5 G140L 1425 4 421 S EXPAND MAX DUR 10 M MIN R UV-MAM DUR 5 M SEQ 5 NON-INT A ------------------------------------------------------------------------------------------------------------------------------------ 6 NGC7078-STA STIS/F ACCUM 52X0.5 G140L 1425 4 421 S EXPAND MAX DUR 10 M MIN R UV-MAM DUR 5 M SEQ 6 NON-INT A ------------------------------------------------------------------------------------------------------------------------------------ 7613( 7) - 01/29/98 15:35 - [ 5] Visit: 02 Visit Priority: Visit Requirements: PERIOD 0.713014 D AND ZERO-PHASE JD2447790.963000 PCS MODE FINE On Hold Comments: Additional Comments: Ephemeris from Ilovaisky et al A&A 270, 139. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 11 NGC7078-OFF STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 0.3 S ONBOARD ACQ FOR 12 SET CD P Comments: Star will saturate in around 5 seconds, and give S:N of 80 in about 0.1 seconds. ------------------------------------------------------------------------------------------------------------------------------------ 12 NGC7078-STA STIS/F ACCUM 52X0.5 G140L 1425 1 421 S EXPAND MAX DUR 10 M MIN R UV-MAM DUR 5 M SEQ 12-13 NON-INT A PHASE 0.90 TO 0.10 ------------------------------------------------------------------------------------------------------------------------------------ 13 NGC7078-STA STIS/F ACCUM 52X0.5 G140L 1425 2 421 S EXPAND MAX DUR 10 M MIN R UV-MAM DUR 5 M SEQ 12-13 NON-INT A ------------------------------------------------------------------------------------------------------------------------------------ 14 NGC7078-STA STIS/F ACCUM 52X0.5 G140L 1425 4 421 S EXPAND MAX DUR 10 M MIN R UV-MAM DUR 5 M SEQ 14 NON-INT A ------------------------------------------------------------------------------------------------------------------------------------ 15 NGC7078-STA STIS/F ACCUM 52X0.5 G140L 1425 4 421 S EXPAND MAX DUR 10 M MIN R UV-MAM DUR 5 M SEQ 15 NON-INT A ------------------------------------------------------------------------------------------------------------------------------------ 16 NGC7078-STA STIS/F ACCUM 52X0.5 G140L 1425 4 421 S EXPAND MAX DUR 10 M MIN R UV-MAM DUR 5 M SEQ 16 NON-INT A ------------------------------------------------------------------------------------------------------------------------------------ 7613( 7) - 01/29/98 15:35 - [ 6] Summary Form for Proposal 7613 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO/CAR ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PERIOD 0.713014 D AND ZERO-PHASE JD2447790.963000 PCS MODE FINE ONBOARD ACQ FOR 2 EXPAND MAX DUR 10 M MIN DUR 5 M SEQ 2-3 NON-INT PHASE 0.70 TO 0.80 EXPAND MAX DUR 10 M MIN DUR 5 M SEQ 2-3 NON-INT EXPAND MAX DUR 10 M MIN DUR 5 M SEQ 4 NON-INT EXPAND MAX DUR 10 M MIN DUR 5 M SEQ 5 NON-INT EXPAND MAX DUR 10 M MIN DUR 5 M SEQ 6 NON-INT ONBOARD ACQ FOR 12 EXPAND MAX DUR 10 M MIN DUR 5 M SEQ 12-13 NON-INT PHASE 0.90 TO 0.10 EXPAND MAX DUR 10 M MIN DUR 5 M SEQ 12-13 NON-INT EXPAND MAX DUR 10 M MIN DUR 5 M SEQ 14 NON-INT EXPAND MAX DUR 10 M MIN DUR 5 M SEQ 15 NON-INT EXPAND MAX DUR 10 M MIN DUR 5 M SEQ 16 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G140L ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC7078-OFFSET NGC7078-STAR ------------------------------------------------------------------------------------------------------------------------------------