15904( 3) - 24-Sep-2019 13:59:23 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 15904 Version: 3 Check-in Time: 24-Sep-2019 13:59:23 STScI Edit Number: 0 Title Spatially Resolving the Winds of Red Giant Stars ------------------------------------------------------------------------------------ Type Cycle GO 27 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Brian Erland Wood Naval Research Laboratory Y CoI: Dr. Graham M. Harper University of Colorado at Boulder N CoI: Dr. Hans-Reinhard Mueller Dartmouth College N ------------------------------------------------------------------------------------ Abstract We propose to use long-slit STIS/G140M spectroscopy to spatially resolve red giant winds for the first time. Specifically, we will study the H I Lyman-alpha wind scattering around two red giant stars, Alpha Tau (K5 III) and Gamma Cru (M3.5 III). This project is stimulated by the very recent realization that in existing STIS/E140M spectra of these giants and others, the Lyman-alpha emission is to a large extent uniformly filling the 0.2x0.2 arcsecond STIS aperture, especially for the M giants. The only obvious way to explain this surprising result is to propose that H is actually ionized close to the stars, only becoming neutral far from the star (>10 R_star). Such a picture could dramatically alter our understanding of red giant winds, potentially increasing mass loss rate estimates for such stars by over an order of magnitude. Our proposed new observations will determine exactly how far the Lyman-alpha scattering region truly extends around K and M giants. In combination with constraints on the winds from existing STIS echelle spectra, we will be able to make more accurate mass loss rate measurements, involving better constrained assessments of wind temperature and ionization structure. Finally, as these winds are known to be variable, we could potentially be able to detect and study spatial structure in red giant winds for the first time. ------------------------------------------------------------------------------------ Observations Description ------------------------ We propose to observe the Lyman-alpha lines of alpha Tau (K5 III) and gamma Cru (M3.5 III) for 4 orbits each with the G140M grating (1222 setting) through the 52" x 0.2" long slit. Both targets are comfortably in compliance with STIS/MAMA bright object limits, as verfied using both Table 13.44 in the STIS Instrument Handbook and the online STIS exposure time calculator. After acquisition and overheads are considered, we expect our 4-orbit G140M exposures to amount to about 180 minutes of total exposure per target. This information can be combined with the Lyman-alpha scattering model shown in Figure 4 to estimate expected signal-to-noise (S/N) for our planned observations, as a function of distance along the slit. The STIS exposure time calculator predicts S/N=10 for a surface brightness of sigma_lambda=2e-13 ergs/cm2/s/A/arcsec2, corresponding to distances from the star of roughly 20 AU (0.98") and 30 AU (1.11") for alpha Tau and gamma Cru, respectively, according to Figure 4. These two distances correspond to roughly 85 R_* for both stars, meaning that it is entirely possible that we may actually be able to detect 15904( 3) - 24-Sep-2019 13:59:23 - [ 2] scattered wind emission at >100 R_* from each star. The exposure time calculator suggests a detectable S/N=3 down to sigma_lambda=2.5e-14 ergs/cm2/s/A/arcsec2, though at that point the limiting factor may be the brightness of the extended wings of the PSF of the bright emission from close to the star. We considered using the 0.5" occulting bar available with the 52" x 0.2" slit in order to block the stellar chromospheric flux, but ultimately decided against it. The PSF wings of the chromospheric emission will be a potentially significant contaminant for the circumstellar wind-scattered flux in which we are interested. Blocking this emission would simplify the analysis and maximize the spatial extent to which we might detect the scattered flux, but it would also obscure the spatial flux profile close to the star, which is a region that is very much of interest. Thus, we ultimately decided not to use the occulter, meaning we will have to utilize deconvolution procedures to derive a true spatial flux profile from the observed one, which is convolved with the spatial PSF. We note that there is already a G140M Lyman-alpha spectrum of a white dwarf (WD1056-384) in the HST archives made through the 52" x 0.2" long slit, which will provide an excellent empirical point source PSF for our purposes. ------------------------------------------------------------------------------------ 15904( 3) - 24-Sep-2019 13:59:23 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 HD29139 STAR, K III-I, WIND RA=04H35M55.2391S +/- 0.1", J2000 V = V = 0.86 +/- 0.01 TYPE=K5III, DEC=+16D30'33.49" +/- 0.1" 54.26 F-LINE(1216)=4.7+/-0.5E-11, W-LINE(1216)=2.5 Reference Frame: ICRS Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000.0 0.004411886146252058 -0.18894 0.04894 ------------------------------------------------------------------------------------------------------------------------------------ 2 HD108903 STAR, M III-I, WIND RA=12H31M9.9596S +/- 0.1", J2000 V = 21.0 V = 1.64 +/- 0.01 TYPE=M3.5III, DEC=-57D06'47.57" +/- 0.1" F-LINE(1216)=1.2+/-0.2E-11, W-LINE(1216)=3.0 Reference Frame: ICRS Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000.0 0.0034660525912681654 -0.26508 0.03683 ------------------------------------------------------------------------------------------------------------------------------------ 15904( 3) - 24-Sep-2019 13:59:23 - [ 4] Visit: 01 Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 HD29139 STIS/CCD ACQ F25ND5 MIRROR 1 0.1 S (0.1 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 HD29139 STIS/FUV TIME-TA 52X0.2 G140M 1222 BUFFER-TIME=1045 1 2100 S -MAMA G see below (2106 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 HD29139 STIS/FUV TIME-TA 52X0.2 G140M 1222 BUFFER-TIME=1045 1 2100 S -MAMA G see below (2824 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 HD29139 STIS/FUV TIME-TA 52X0.2 G140M 1222 BUFFER-TIME=1045 1 2100 S -MAMA G see below (2824 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 HD29139 STIS/FUV TIME-TA 52X0.2 G140M 1222 BUFFER-TIME=1045 1 2100 S -MAMA G see below (2824 S) ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ HD29139 1 STIS/CCD ACQ F25ND5 MIRROR none none none none 1 N/A HD29139 2 STIS/FUV TIME-TA 52X0.2 G140M 1222 none none none none 1 2106.0 S -MAMA G HD29139 3 STIS/FUV TIME-TA 52X0.2 G140M 1222 none none none none 2 2824.0 S -MAMA G HD29139 4 STIS/FUV TIME-TA 52X0.2 G140M 1222 none none none none 3 2824.0 S -MAMA G HD29139 5 STIS/FUV TIME-TA 52X0.2 G140M 1222 none none none none 4 2824.0 S -MAMA G 15904( 3) - 24-Sep-2019 13:59:23 - [ 5] Visit: 02 Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 HD108903 STIS/CCD ACQ F25ND5 MIRROR 1 0.1 S (0.1 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 HD108903 STIS/FUV TIME-TA 52X0.2 G140M 1222 BUFFER-TIME=1050 1 2100 S -MAMA G see below (2339 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 HD108903 STIS/FUV TIME-TA 52X0.2 G140M 1222 BUFFER-TIME=1050 1 2100 S -MAMA G see below (3057 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 HD108903 STIS/FUV TIME-TA 52X0.2 G140M 1222 BUFFER-TIME=1050 1 2100 S -MAMA G see below (3057 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 HD108903 STIS/FUV TIME-TA 52X0.2 G140M 1222 BUFFER-TIME=1050 1 2100 S -MAMA G see below (3057 S) ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ HD108903 1 STIS/CCD ACQ F25ND5 MIRROR none none none none 1 N/A HD108903 2 STIS/FUV TIME-TA 52X0.2 G140M 1222 none none none none 1 2339.0 S -MAMA G HD108903 3 STIS/FUV TIME-TA 52X0.2 G140M 1222 none none none none 2 3057.0 S -MAMA G HD108903 4 STIS/FUV TIME-TA 52X0.2 G140M 1222 none none none none 3 3057.0 S -MAMA G HD108903 5 STIS/FUV TIME-TA 52X0.2 G140M 1222 none none none none 4 3057.0 S -MAMA G 15904( 3) - 24-Sep-2019 13:59:23 - [ 6] Summary Form for Proposal 15904 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 52X0.2, F25ND5 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD, STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=1045, BUFFER-TIME=1050 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G140M, MIRROR ------------------------------------------------------------------------------------------------------------------------------------ Target Names HD108903, HD29139 ------------------------------------------------------------------------------------------------------------------------------------