6637( 3) - 02/16/96 10:41 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6637 Version: 3 Check-in Date: 16-Feb-1996 10:19:03 1.Proposal Title: Determining the Morphology of the Intense Magnetic Field in the Hot DA White Dwarf RE J0317-853 ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle HOT STARS GO 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Matthew Burleigh XRA Astronomy Group, University of Leicester, Leicester LE1 7RH, United CoI: Dr. Martin Barstow XRA Astronomy Group, University of N Leicester CoI: Dr. Stefan Jordan Institut fur Astronomie und Astrophysik N der Universitat, Kiel, Germany ------------------------------------------------------------------------------------ 6. Abstract We propose to observe RE J0317-853 with the FOS to obtain time resolved spectra to model the morphology of the intense magnetic field present in the star. RE J0317-853 is at T~ 50,000K the hottest highly magnetic (B~ 340MG) DA white dwarf known. It is varying optically with a period of ~ 725s, almost certainly due to the rotation of the star. If it lies at the same distance as a cool white dwarf only 16 arcsecs away, it must have a mass approaching the Chandrasekhar limit, making it the most massive white dwarf yet discovered. The intense magnetic field broadens and shifts the Balmer lines beyond recognition, while the IUE SWP spectrum shows two unusual large absorption features near 1300Angstrom \ which are almost certainly components of the hydrogen Lyman Alpha line. Weaker features present in the UV data may be due to heavy elements in the circumstellar environment. By taking spectra at different phases of the spin period, we can monitor and measure the large expected shifts in the Lyman Alpha components' line positions to study the structure of the magnetic field. In addition, we want to confirm the identifications of the metal lines in the IUE spectrum and search for any weak splitting of these features. These metal lines have not been seen in any other magnetic white dwarf, and little is known of the behaviour of heavy elements in an intense magnetic field. ------------------------------------------------------------------------------------ 6637( 3) - 02/16/96 10:41 - [ 2] Observations Description ------------------------ We propose to observe RE0317-853 with the blue filter, G130H grating and the 1" aperture, giving approximately 1 Angstrom resolution and a count rate in the Lyman Alpha sigma component of about 1.8 counts/sec per diode. By acquiring the target with ACQ/BINARY and taking into account guide star acquisition and instrument overhead, we calculate that we can achieve our scientific objectives within two HST orbits. We will be able to observe the target for a total for more than seven 725.4+/-0.9s cycles, in order to look for any subtle variations from cycle to cycle. By using the RAPID mode we can divide each cycle into 20 bins of 36.25s duration each. Observing across over seven cycles will allow us to achieve a signal/noise ratio of 20 (400counts/bin), enabling us to see subtle changes in line strength and accurately measure line positions throughout the rotation period. After target acquisition and overheads, the total exposure in the two HST orbits is 5727.5s (95m 27.5s). Real Time Justification ----------------------- none Calibration Justification ------------------------- none Additional Comments ------------------- none ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 6637( 3) - 02/16/96 10:41 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 REJ0317-853 STAR,DA,REGULAR RA=03H 17M 17.74S +/- 0.7",DEC=- J2000 V = 14.90+/-0.15 VARIABLE, 85D 32' 26.0" +/- 0.7",PLATE- B-V = -0.16+/-0.02 ID=04BO TYPE=DA Comments: REJ0317-853 has a DA companion (V=14.11+/-0.02, B- V=0.07+/-0.02) only 4.2 arcsecs away at position (J2000) 03 17 19.86 -85 32 29.7. On the DSS plates these two stars merge into one another. In the GSC they are blended together as one object - GSC9495.01022 - flagged as not single and non stellar. The GSC co-ord of GSC9495.01022 is 03 17 19.02 -85 32 28.4 - this co-ord MUST NOT BE TRUSTED. Use only our measured co-ords for REJ0317-853 and its brighter DA companion. REJ0317-853 varies by ~+/- 0.1 mag every ~725secs. 6637( 3) - 02/16/96 10:41 - [ 4] Visit: 01 Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 REJ0317-853 FOS/BL ACQ/BIN 4.3 MIRROR BRIGHT=6600 1 1.277S ONBOARD ACQ FOR 2 ARY Comments: REJ0317-853 varies by ~+/- 0.1 mag every 725secs. BRIGHT has been set to 1.5x the expected Vmag (14.90+/-0.15) of the target, due to the close proximity of another DA (V=14.11+/-0.02) only 4.2 arcsecs away. The exp. time was calculated using Table 2.5 of the FOS instument handbook, assuming this to be a 50,000K star (it is in fact a ~50,000K DA white dwarf). ------------------------------------------------------------------------------------------------------------------------------------ 2 REJ0317-853 FOS/BL RAPID 1.0 G130H READ-TIME=36.25 1 2537.5S ------------------------------------------------------------------------------------------------------------------------------------ 3 REJ0317-853 FOS/BL RAPID 1.0 G130H READ-TIME=36.25 1 3190S ------------------------------------------------------------------------------------------------------------------------------------ 6637( 3) - 02/16/96 10:41 - [ 5] Summary Form for Proposal 6637 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FOS/BL ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/BINARY RAPID ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BRIGHT=6600 READ-TIME=36.25 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category HOT STARS ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 2 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G130H ------------------------------------------------------------------------------------------------------------------------------------ Target Names REJ0317-853 ------------------------------------------------------------------------------------------------------------------------------------