7479( 7) - 01/06/99 12:49 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 7479 Version: 7 Check-in Date: 06-Jan-1999 12:48:58 1.Proposal Title: Epsilon Eri: Structure and Non-Thermal Heating ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 7 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Carole Jordan University of Oxford CoI: Dr Andrew McMurry University of Oxford, Department of Y Physics (Theoretical Physics) ------------------------------------------------------------------------------------ 5. Abstract Epsilon Eri (K2 V) is the most active single K dwarf within 10 pc of the Sun, and its proximity (3.3 pc) allows studies of emission line profiles as well as fluxes. We have observed Epsilon Eri with IUE, at Lo and Hi resolution, and with ROSAT (PSPC and WFC), and have used these spectra to make models of the structure of the transition region and corona, and to establish the non-thermal energy requirements. The accuracy of the current models is limited by the available line widths and the electron density (Ne) derived from the Si III line at 1892 Angstrom. The aim of the observations with STIS is to measure the profiles and fluxes of lines formed in the chromosphere and transition region, including several lines which can yield Ne. Significantly improved models from the photosphere to the corona could then be obtained, to investigate the non-thermal heating. With Ne determined from line ratios there are sufficient lines of C and Si ions to find the C/Si abundance ratio, for co mparison with photospheric values. Epsilon Eri has a measured magnetic field and area filling factor, and together with xi Boo A (G8 V) (our Cycle 5 observations) and the Sun (G2 V), the observations will aid our understanding of the observed correlations between line fluxes, magnetic fluxes and activity indicators such as the rotation period and the Rossby number. ------------------------------------------------------------------------------------ 7479( 7) - 01/06/99 12:49 - [ 2] Observations Description ------------------------ We propose medium resolution spectrographic exposures of Epsilon Eridani covering most of the UV band from 1150A to 2380A and also high resolution exposures of the Mg II line pair at 2795 and 2802A. Given the declination of the star, it will be visible for 52 minutes each orbit. The star is within the brightness limits for using the F25X50OIII aperture (given in the STIS documentation) for acquisition. The default 8 minutes are assumed. The V- magnitude of the star (3.7) is brighter than the limit given for a K2 V star, for using the E230M. However we are only using the E230M Echelle in its shorter wavelength range, up to 2382A. An IUE Spectrum of the star has been used in the STIS exposure time calculator to calculate the total count rate for the exposure. This gives a maximum count rate of 3791 counts/sec, well below the limit. The maximum local flux in this region is around 1.0E-12 erg/cm^2/s/A, which is also well within safe limits. The Mg II h & k line fluxes may exceed th e safe limit with E230M, so we propose observations with the E230H. From observations with IUE, the peak flux is expected to be 5E-11 erg/cm^2/s/A, which is well within the safe limit. Similarly, from the existing GHRS spectrum (see below) the peak flux in H Lyman alpha is 3E-11 erg/cm^2/s/A, which is well within the limit for the E140M. The background in this region is negligible (<1E-13 erg/cm^2/s/A even at 1700A). The Mg II line will only need about 1 minute of exposure time, but we are exposing the E230H region between 2574 and 2851A for 3 minutes in order to also get a signal-to-noise of about 15 in the Al II] line at 2659A. This exposure will follow the peakup in the first orbit. The remainder of the first orbit will be used for a E230M exposure in the 2574 to 2851A tilt. The remaining two orbits will be used for the E140M exposure. This will use the only tilt available, to expose the whole 1150 to 1700A region. This exposure will get good S-to-N (>20) profiles of many l ines and will get fluxes (S-to-N of about 10) for weaker lines, so that line flux ratios can be measured accurately. Real Time Justification ----------------------- None Calibration Justification ------------------------- None Additional Comments ------------------- None ------------------------------------------------------------------------------------ Data Distribution Paper Products: Media: ELECTRONIC Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 7479( 7) - 01/06/99 12:49 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 HD22049 STAR, K V-IV, CORONA RA=3H 32M 55.852S +/- 0.00077", J2000 V=+15.5 V = 3.73+/-0.09 DEC=-9D 27' 29.744" +/- 0.00060" TYPE=K2V B-V = 0.88+/-0.01 Comments: F-LINE(2795.5)=3.3+/-0.25e-11 W-LINE(2795.5)=0.55+/- 0.06 F-LINE(1215.67)=2e-11 W-LINE(1215.67)=0.73+/-0.03 F-LINE(1816.93)=1.2+/-0.1e-12 W-LINE(1816.93)=0.14+/- 0.04 F-CONT(1600)=2.0 +/- 0.5 e-14 F-CONT(1950)=5.2 +/ - 0.2 e-14 F-CONT(2200)=2.7 +/- 0.2 e-13 F- CONT(2750)=1.2+/- 0.1 e-12 F-CONT(2050)=9.3 +/- 2.0 e- 14 Hipparcos Coordinates Used Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) J2000 -0.065096 0.01797 0.31075 7479( 7) - 01/06/99 12:49 - [ 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 HD22049 STIS/C ACQ F28X50O MIRROR ACQTYPE=POINT 1 0.1 S ONBOARD ACQ FOR 30, 40, CD II 50, 60 Comments: ETC ID=10251 ------------------------------------------------------------------------------------------------------------------------------------ 30 HD22049 STIS/N ACCUM 0.2X0.2 E230H 2713 1 180 S UV-MAM A Comments: ETC ID=399300 ------------------------------------------------------------------------------------------------------------------------------------ 40 HD22049 STIS/N ACCUM 0.2X0.2 E230M 1978 1 1800 S UV-MAM A Comments: ETC ID=399300 ------------------------------------------------------------------------------------------------------------------------------------ 50 HD22049 STIS/F ACCUM 0.2X0.2 E140M 1425 1 2460 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 60 HD22049 STIS/F ACCUM 0.2X0.2 E140M 1425 1 2800 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 7479( 7) - 01/06/99 12:49 - [ 5] Summary Form for Proposal 7479 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50OII 0.2X0.2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/NUV-MAMA STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 30, 40, 50, 60 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR E230H E230M E140M ------------------------------------------------------------------------------------------------------------------------------------ Target Names HD22049 ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 2713 1978 1425 ------------------------------------------------------------------------------------------------------------------------------------