9090( 3) - 07/12/02 06:55 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 9090 Version: 3 Check-in Date: 12-Jul-2002 06:54:01 1.Proposal Title: Transition Region Emission in Very Low Mass Stars ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 10 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Suzanne Hawley University of Washington CoI: Dr. Chris Johns-Krull University of California, Berkeley N ------------------------------------------------------------------------------------ 5. Abstract The origin of the magnetic heating which produces hot outer atmospheres in late-type stars is one of the most interesting, and elusive, problems in stellar astrophysics. Our poor understanding is due in part to the lack of data for a large and varied sample of stars, which are needed to provide the basis for a general theory. Observationally, our knowledge is particularly sparse for the very low mass stars. In fact, diametrically opposed conclusions have been reached in this field: the available data has been interpreted 1.) to indicate that magnetic heating of the hot transition region and corona becomes relatively more important in stars of later spectral type (lower mass) - the pre-1999 position; and 2.) to claim that the magnetic heating is insufficient to produce these regions at all, except during flares, in very low mass objects - the current widely held view. The manifestations of magnetic activity at the stellar/brown dwarf boundary have yet to be probed in transition region diagnostics; previous IUE and HST/GHRS observations were not sensitive enough to provide constraining data. Our proposed HST/STIS observations of three very low mass stars will conclusively show if quiescent magnetic heating sufficient to produce a hot outer atmosphere still exists in these objects, or whether they are categorically different than higher mass M dwarfs. ------------------------------------------------------------------------------------ 9090( 3) - 07/12/02 06:55 - [ 2] Observations Description ------------------------ We will observe our three target stars with STIS aboard HST. We will use the G140L grating and a slightly oversized aperture (52.0 X 0.2) in order to get as much light as possible to the detector. It is important to know that we detect these stars outside of obvious flares, so we will break the total exposure of VB 8 up into 5 minute sub-exposures, and we will break the exposure of VB 10 and LHS 2065 up into 10 minute sub-exposures. Total exposure times for all three stars were determined by requiring that we be able to detect the C IV line at the greater than 4 sigma level if the flux is an order of magnitude lower than our estimates. Using the online STIS exposure time calculator and a high signal to noise FUV spectrum of AD Leo (obtained by coadding all IUE SWP spectra of AD Leo in the IUE Final Archive) scaled to the appropriate total C IV line flux, we estimated the required total exposure times to achieve this goal. Then, taking into account the various observing overheads and the visibility of each target, we estimated the total number of orbits required for each target to obtain the required total exposure time. The result is 2 orbits for VB 8 yielding a total exposure time of 3870 seconds which will detect the C IV line at the 4.2 sigma level if it is a factor of 10 lower than our initial estimate. For VB 10 and LHS 2065, 4 orbits are required, yielding a total exposure time of 8550 seconds which will produce a 4.1 sigma and 4.3 sigma detection respectively of C IV if the flux is a factor of 10 lower than originally estimated. Though not critical to the success of the science proposed here, since flares are intriguing to study in their own right, we will seek simultaneous ground based photometry and low resolution spectroscopy to support these HST observations. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 9090( 3) - 07/12/02 06:55 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 GL644C STAR, M V-IV RA=16H 55M 36.15S +/- 1.", DEC=- J2000 V = +19 V = 16.8+/-0.2 08D 23' 27.14" +/- 1.", PLATE- TYPE=M7V ID=00TN Coordinate Source: GSC_SURVEY_PLATE Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1984.25 -0.0542 -0.877 0.161 2 GL752B STAR, M V-IV, BROWN RA=19H 16M 58.29S +/- 1", J2000 V = +33 V = 17.5+/-0.2 DWARF DEC=05D 9' 25.08" +/- 1", PLATE- TYPE=M8V ID=00ZZ Coordinate Source: GSC_SURVEY_PLATE Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) B1982.56 -0.0384 -1.344 0.173 3 LHS2065 STAR, M V-IV, BROWN RA=08H 53M 36.82S +/- 1.0", J2000 V = 19.5+/-0.5 DWARF DEC=-03D 29' 29.30" +/- 1.0", TYPE=M9V PLATE-ID=03VZ Coordinate Source: GSC_SURVEY_PLATE Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1982.14 -0.036 -0.195 0.1168 9090( 3) - 07/12/02 06:55 - [ 4] Visit: 01 Visit Priority: 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 GL644C STIS/C ACQ 50CCD MIRROR ACQTYPE=POINT 1 5 S CD ------------------------------------------------------------------------------------------------------------------------------------ 20 GL644C STIS/F ACCUM 52X0.2 G140L 1425 15 5.0 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 9090( 3) - 07/12/02 06:55 - [ 5] Visit: 02 Visit Priority: 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 GL752B STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 5 S CD P ------------------------------------------------------------------------------------------------------------------------------------ 20 GL752B STIS/F ACCUM 52X0.2 G140L 1425 15 10.0 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 9090( 3) - 07/12/02 06:55 - [ 6] Visit: 03 Visit Priority: 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 LHS2065 STIS/C ACQ 50CCD MIRROR ACQTYPE=POINT 1 20 S CD ------------------------------------------------------------------------------------------------------------------------------------ 20 LHS2065 STIS/F ACCUM 52X0.2 G140L 1425 15 10.0 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 9090( 3) - 07/12/02 06:55 - [ 7] Summary Form for Proposal 9090 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 50CCD 52X0.2 F28X50LP ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G140L ------------------------------------------------------------------------------------------------------------------------------------ Target Names GL644C GL752B LHS2065 ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 1425 ------------------------------------------------------------------------------------------------------------------------------------