8143( 4) - 05/02/00 09:36 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 8143 Version: 4 Check-in Date: 08-Nov-1999 12:12:09 1.Proposal Title: A Search for Acoustic Heating in the Chromospheres of Low Activity Dwarfs ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 8 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Steven Saar Harvard-Smithsonian Center for Astrophysics CoI: Dr. Philip Judge High Altitude Observatory, National Center N for Atmospheric Research CoI: Dr. Mats Carlsson Institute of Theoretical Astrophysics, N Oslo Univ. ------------------------------------------------------------------------------------ 5. Abstract Recent observations cast doubt on the importance of acoustic waves for chromospheric heating, at least in inactive giant stars, and have set small upper limits to their contribution to upper layers of the Solar chromosphere. These findings contradict the widely accepted picture that acoustic heating accounts for a significant fraction, the ``basal component'', of chromospheric heating in inactive stars across the HR diagram. To help resolve this issue, we propose to observe an extremely inactive (basal) dwarf star (Tau Ceti) to search for specific signatures of upward propagating acoustic waves: blue-shifts and enhanced blue wings in chromospheric lines. Solar data show that the strength of blue-shift can be used to estimate the acoustic contribution to chromospheric heating. We will also analyze archival HST data of an active dwarf of the same spectral type, and solar spectra from the SUMER instrument on SOHO, for comparison with the new data. Lack of a significant acoustic signature in Tau Ceti would indicate that magnetic heating generated by a local (turbulent, non- cycling) dynamo is responsible for the basal component of chromospheric heating in main sequence stars. Tau Cet may be in a phase analogous to the solar Maunder minimum, and HST spectra might serve as a proxy for the solar spectrum in this state. The spectra will also be used for emission measure analysis differentially between the Sun and solar-like stars. ------------------------------------------------------------------------------------ 8143( 4) - 05/02/00 09:36 - [ 2] Observations Description ------------------------ Since Tau Ceti is bright, we use the narrowband O III filter to acquire, where 0.1 s yields S/N = 270 (4.4e4 electrons in brightest pixel). To obtain the most accurate wavelengths, we peakup in a smaller slit (0.3x0.5ND) than the science slit (0.2x0.2) and be sure to get autowavecals for every orbit. A 0.1s peakup yields S/N = 160 (1.6e4 electrons in the peak). The resulting spectrum should show e.g., S/N = 25 per resolution element in the Si IV line (1393 A). Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- NUV spectra of Tau Ceti from Dr. Ayres' large program (ID 8280) will also be analyzed in this program. ------------------------------------------------------------------------------------ Data Distribution Paper Products: NO Media: ELECTRONIC Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 8143( 4) - 05/02/00 09:36 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 HD10700 STAR, G V-IV RA = 1H 44M 04.09S +/- 0.001S, J2000 V=-16 V = 3.50+/-0.01 DEC = -15D 56' 14.9" +/- 0.02" B-V = +0.72+/-0.01 F(1393)=0.15+/-0.07e-12 TYPE=G8V Coordinate Source: Comments: Coordinates and Proper Motions from PPM Catalog via VizieR (NOTE: calculated to EPOCH J2000); UV Fluxes from low-res IUE spectra Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) J2000 -0.1191 0.856 0.274 8143( 4) - 05/02/00 09:36 - [ 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 HD10700 STIS/C ACQ F28X50O MIRROR ACQTYPE=POINT 1 0.1 S CD III ------------------------------------------------------------------------------------------------------------------------------------ 2 HD10700 STIS/C ACQ/PEA 0.3X0.0 MIRROR 1 0.1 S CD K 5ND ------------------------------------------------------------------------------------------------------------------------------------ 3 HD10700 STIS/F ACCUM 0.2X0.2 E140M 1425 1 1862 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 4 HD10700 STIS/F ACCUM 0.2X0.2 E140M 1425 4 2897 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 8143( 4) - 05/02/00 09:36 - [ 5] Summary Form for Proposal 8143 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50OIII 0.3X0.05ND 0.2X0.2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACQ/PEAK ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR E140M ------------------------------------------------------------------------------------------------------------------------------------ Target Names HD10700 ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 1425 ------------------------------------------------------------------------------------------------------------------------------------