17793( 3) - 20-Jun-2025 16:30:27 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 17793 Version: 3 Check-in Time: 20-Jun-2025 16:30:27 STScI Edit Number: 1 Title Stellar Rotation and Winds for Old Sun-like Stars ------------------------------------------------------------------------------------ Type Cycle GO 32 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Brian Erland Wood Naval Research Laboratory Y CoI: Dr. Travis S. Metcalfe White Dwarf Research Corporation N CoI: Dr. Hans-Reinhard Mueller Dartmouth College N CoI: Prof. Seth Redfield Wesleyan University N ------------------------------------------------------------------------------------ Abstract We propose to use STIS to study the H I Lyman-alpha spectra of four nearby old Sun-like coronal GK stars, to search for signs of astrospheric absorption. The Lyman-alpha astrospheric absorption signature is currently the only means of detecting the coronal winds of cool main sequence stars, and HST is the only observatory that has ever been capable of observing it. The project will allow us to explore the future of our own Sun's wind. In addition, one of our targets, HD 166620, appears to have an interrupted activity cycle, possibly analogous to the "Maunder minimum" state that the Sun went through in the 1600s. Thus, the HD 166620 data could tell us what the solar wind was like then. A particular area of scientific interest is the phenomenon of "weakened magnetic braking", recently discovered from analyses of Kepler data, indicating a significant change in stellar rotation evolution at late stellar ages. All of our chosen targets have existing or expected ground-based spectropolarimetric constraints, which when combined with HST mass loss measurements will allow us to determine if the weakened magnetic braking is due to dramatically weaker winds or fundamental changes in stellar magnetic morphology. ------------------------------------------------------------------------------------ Observations Description ------------------------ Table 1 in the proposal lists the 4 GK dwarfs that we plan to observe with STIS for 1-2 orbits each. Note that COS cannot be used for Lyman-alpha studies due to obscuration by geocoronal Lyman-alpha caused by the large COS aperture, so STIS is our only option. Our project is focused on detecting and measuring astrospheric absorption in the H I Ly-alpha line, but confidence in this analysis is significantly improved with information provided by observations of the MgII h & k lines near 2800 A, so we will be obtaining an E230H spectrum of the 2574-2851A wavelength range for each of our targets, through the 0.2"x0.09" aperture. Such an observation already exists for Tau Ceti, so we will not make the E230H exposure for this star. The Mg II lines provide two benefits. The first is that the ISM Mg II absorption lines are much narrower than the ISM H I and D I lines, allowing us to discern multiple velocity components in the ISM towards our stars, which we can then account for in our analysis of the Lyman-alpha line. The second benefit is that the Mg II emission lines are highly opaque chromospheric lines 17793( 3) - 20-Jun-2025 16:30:27 - [ 2] like Lyman-alpha, and so provide useful guidance for what the intrinsic stellar Lyman-alpha lines should look like. This is useful considering that the stellar Lyman-alpha profile is always greatly obscured by the broad ISM absorption (see Figure 2). After the E230H exposure (if done), the rest of the observing time will be used for an E140M spectrum of the 1150-1700 A wavelength range through the 0.2"x0.2" aperture, which will contain the primary line of interest: H I Ly-alpha at 1216 A. All but one of our targets are comfortably in compliance with STIS/MAMA bright object limits, as verified using both Table 13.45 in the STIS Instrument Handbook and the online STIS exposure time calculator. The exception is Beta Hyi. The E230H exposure for this star exceeds the total image count rate limit unless we replace the 0.2"X0.09" aperture with the tiny 0.1"x0.03" slit. The E230H observation will provide the highest resolution (R= \lambda/\Delta\lambda = 110, 000) spectrum of the Mg II lines. After target acquisition we will perform an ACQ/PEAK peakup observation to accurately center the target in the narrow 0.2"x 0.09" slit (or the smaller slit for Beta Hyi), thereby maximizing the accuracy of our wavelength calibration, important for both this spectrum and the following E140M spectrum. The E140M grating does not have quite the resolution of E230H, but its R=45, 800 resolution is good enough to study the H I Ly-alpha line profile in the detail that we require. Previous studies provide many examples of Mg II and Ly-alpha spectra of inactive GK dwarfs (Wood et al. 2021). The chromospheric Mg II and H I Ly-alpha lines are very bright even for inactive GK dwarfs, so we have high confidence that we can acquire high-quality Mg II and Ly-alpha spectra in only 2 orbits, or just 1 in the case of Tau Ceti where we do not need Mg II. ------------------------------------------------------------------------------------ 17793( 3) - 20-Jun-2025 16:30:27 - [ 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=01H44M4.0831S +/- 0.01", J2000 V = V = 3.50 +/- 0.01 G8-V, B-V=0.72 DEC=-15D56'14.93" +/- 0.01" -16.6 Reference Frame: ICRS Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 -0.11937023269799406 0.8549629999999999 0.2738097 ------------------------------------------------------------------------------------------------------------------------------------ 2 HD2151 STAR, G V-IV RA=00H25M45.0704S +/- 0.01", J2000 V = 23.1 V = 2.79 +/- 0.01 G0-V, B-V=0.62 DEC=-77D15'15.29" +/- 0.01" Reference Frame: ICRS Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 0.6706821226467173 0.32409 0.13407 ------------------------------------------------------------------------------------------------------------------------------------ 3 HD185144 STAR, K V-IV RA=19H32M21.5902S +/- 0.01", J2000 V = 26.7 V = 4.68 +/- 0.01 K0-V, B-V=0.78 DEC=+69D39'40.24" +/- 0.01" Reference Frame: ICRS Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 0.11458261141964486 -1.738286 0.1734939 ------------------------------------------------------------------------------------------------------------------------------------ 4 HD166620 STAR, K V-IV RA=18H09M37.4162S +/- 0.01", J2000 V = V = 6.40 +/- 0.01 K2-V, B-V=0.87 DEC=+38D27'28.00" +/- 0.01" -19.3 Reference Frame: ICRS Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 -0.026941426210242495 -0.468348 0.0901234 ------------------------------------------------------------------------------------------------------------------------------------ 17793( 3) - 20-Jun-2025 16:30:27 - [ 4] Visit: 01 Visit Requirements: BETWEEN 02-MAR-2025:00:00:00 AND 15-NOV-2025:00:00:00; BETWEEN 02-MAR-2026:00:00:00 AND 15-NOV-2026:00:00:00; BETWEEN 02-MAR-2027:00:00:00 AND 15-NOV-2027:00:00:00 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 HD10700 STIS/CCD ACQ F25ND5 MIRROR 1 1.0 S (1 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 HD10700 STIS/FUV TIME-TA 0.2X0.2 E140M 1425 BUFFER-TIME=600 1 2000 S -MAMA G see below (2093 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 | ------------------------------------------------------------------------------------------------------------------------------------ HD10700 1 STIS/CCD ACQ F25ND5 MIRROR none none none none 1 N/A HD10700 2 STIS/FUV TIME-TA 0.2X0.2 E140M 1425 none none none none 1 2093.0 S -MAMA G 17793( 3) - 20-Jun-2025 16:30:27 - [ 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 HD2151 STIS/CCD ACQ F25ND5 MIRROR 1 0.5 S (0.5 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 HD2151 STIS/CCD ACQ/PEA 0.2X0.09 G430M 4451 1 0.5 S (0.5 K S) ------------------------------------------------------------------------------------------------------------------------------------ 3 HD2151 STIS/CCD ACQ/PEA 0.1X0.03 G430M 4451 1 0.5 S (0.5 K S) ------------------------------------------------------------------------------------------------------------------------------------ 4 HD2151 STIS/NUV ACCUM 0.1X0.03 E230H 2713 1 600 S -MAMA see below (1325 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 HD2151 STIS/FUV TIME-TA 0.2X0.2 E140M 1425 BUFFER-TIME=600 1 2000 S -MAMA G see below (2808 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 | ------------------------------------------------------------------------------------------------------------------------------------ HD2151 1 STIS/CCD ACQ F25ND5 MIRROR none none none none 1 N/A HD2151 2 STIS/CCD ACQ/PEA 0.2X0.09 G430M 4451 none none none none 1 N/A K HD2151 3 STIS/CCD ACQ/PEA 0.1X0.03 G430M 4451 none none none none 1 N/A K HD2151 4 STIS/NUV ACCUM 0.1X0.03 E230H 2713 none none none none 1 1325.0 S -MAMA HD2151 5 STIS/FUV TIME-TA 0.2X0.2 E140M 1425 none none none none 2 2808.0 S -MAMA G 17793( 3) - 20-Jun-2025 16:30:27 - [ 6] Visit: 03 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 HD185144 STIS/CCD ACQ F25ND5 MIRROR 1 3.0 S (3 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 HD185144 STIS/CCD ACQ/PEA 0.2X0.09 G430M 4451 1 0.5 S (0.5 K S) ------------------------------------------------------------------------------------------------------------------------------------ 3 HD185144 STIS/NUV ACCUM 0.2X0.09 E230H 2713 1 600 S -MAMA see below (1693 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 HD185144 STIS/FUV TIME-TA 0.2X0.2 E140M 1425 BUFFER-TIME=600 1 2000 S -MAMA G see below (2741 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 | ------------------------------------------------------------------------------------------------------------------------------------ HD185144 1 STIS/CCD ACQ F25ND5 MIRROR none none none none 1 N/A HD185144 2 STIS/CCD ACQ/PEA 0.2X0.09 G430M 4451 none none none none 1 N/A K HD185144 3 STIS/NUV ACCUM 0.2X0.09 E230H 2713 none none none none 1 1693.0 S -MAMA HD185144 4 STIS/FUV TIME-TA 0.2X0.2 E140M 1425 none none none none 2 2741.0 S -MAMA G 17793( 3) - 20-Jun-2025 16:30:27 - [ 7] Visit: 04 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 HD166620 STIS/CCD ACQ F25ND5 MIRROR 1 5.0 S (5 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 HD166620 STIS/CCD ACQ/PEA 0.2X0.09 G430M 4451 1 2.0 S (2 K S) ------------------------------------------------------------------------------------------------------------------------------------ 3 HD166620 STIS/NUV ACCUM 0.2X0.09 E230H 2713 1 600 S -MAMA see below (1543 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 HD166620 STIS/FUV TIME-TA 0.2X0.2 E140M 1425 BUFFER-TIME=600 1 2000 S -MAMA G see below (2629 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 | ------------------------------------------------------------------------------------------------------------------------------------ HD166620 1 STIS/CCD ACQ F25ND5 MIRROR none none none none 1 N/A HD166620 2 STIS/CCD ACQ/PEA 0.2X0.09 G430M 4451 none none none none 1 N/A K HD166620 3 STIS/NUV ACCUM 0.2X0.09 E230H 2713 none none none none 1 1543.0 S -MAMA HD166620 4 STIS/FUV TIME-TA 0.2X0.2 E140M 1425 none none none none 2 2629.0 S -MAMA G 17793( 3) - 20-Jun-2025 16:30:27 - [ 8] Visit: 53 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 HD185144 STIS/CCD ACQ F25ND5 MIRROR 1 3.0 S (3 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 HD185144 STIS/CCD ACQ/PEA 0.2X0.09 G430M 4451 1 0.5 S (0.5 K S) ------------------------------------------------------------------------------------------------------------------------------------ 3 HD185144 STIS/NUV ACCUM 0.2X0.09 E230H 2713 1 600 S -MAMA see below (1693 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 HD185144 STIS/FUV TIME-TA 0.2X0.2 E140M 1425 BUFFER-TIME=600 1 2000 S -MAMA G see below (2741 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 | ------------------------------------------------------------------------------------------------------------------------------------ HD185144 1 STIS/CCD ACQ F25ND5 MIRROR none none none none 1 N/A HD185144 2 STIS/CCD ACQ/PEA 0.2X0.09 G430M 4451 none none none none 1 N/A K HD185144 3 STIS/NUV ACCUM 0.2X0.09 E230H 2713 none none none none 1 1693.0 S -MAMA HD185144 4 STIS/FUV TIME-TA 0.2X0.2 E140M 1425 none none none none 2 2741.0 S -MAMA G 17793( 3) - 20-Jun-2025 16:30:27 - [ 9] Summary Form for Proposal 17793 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 0.1X0.03, 0.2X0.09, 0.2X0.2, F25ND5 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD, STIS/FUV-MAMA, STIS/NUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM, ACQ, ACQ/PEAK, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=600 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BETWEEN 02-MAR-2025:00:00:00 AND 15-NOV-2025:00:00:00, BETWEEN 02-MAR-2026:00:00:00 AND 15-NOV-2026:00:00:00, BETWEEN 02-MAR-2027:00:00:00 AND 15-NOV-2027:00:00:00 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements E140M, E230H, G430M, MIRROR ------------------------------------------------------------------------------------------------------------------------------------ Target Names HD10700, HD166620, HD185144, HD2151 ------------------------------------------------------------------------------------------------------------------------------------