18336( 2) - 17-Aug-2026 16:29:39 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 18336 Version: 2 Check-in Time: 17-Aug-2026 16:29:39 STScI Edit Number: 0 Title A Multiwavelength Campaign to Characterize the Astrosphere of a Nearby Debris Disk Hosting Star ------------------------------------------------------------------------------------ Type Cycle GO 34 ------------------------------------------------------------------------------------ Investigators Contact? PI: Prof. Seth Redfield Wesleyan University Y CoI: Dr. Carey Michael Lisse The Johns Hopkins University Applied N Physics Laboratory CoI: Dr. Brian Erland Wood Naval Research Laboratory N CoI: Dr. Jeffrey L. Linsky University of Colorado at Boulder N CoI: Dr. Konrad O. Dennerl Max Planck Institute for Extraterrestrial N Physics CoI: Dr. Dimitra Koutroumpa LATMOS N CoI: Dr. Hans Moritz Guenther Massachusetts Institute of Technology N CoI: Dr. Scott J. Wolk Smithsonian Institution Astrophysical N Observatory ------------------------------------------------------------------------------------ Abstract Stellar mass loss is a ubiquitous property of stars, as are planets and circumstellar dusty debris disks. In the case of our own star, the Sun, the unique properties of its particle wind shape the structure of our debris disks, dictate the thermal and chemical structure of planetary atmospheres, and ultimately push against the confining plasma of our surrounding interstellar medium, producing the heliosphere. The detection of astrospheres, the result of the relatively weak winds of solar-like, cool, stars can be made with high-resolution spectra of Lyman-alpha, a unique capability of HST. Charge exchange in the interaction zone of stellar winds with their surrounding interstellar medium produces detectable HI Lyman-alpha absorption, where the amount of absorption allows for a determination of the mass loss rate. A well-known nearby young debris disk, HD61005, (also known as The Moth due to the captivating morphology of the scattered light of its disk) was recently discovered to have extended X-ray emission that is associated with its astrosphere. We propose UV spectroscopy in order measure Lyman-alpha profile and detect or constrain the astrospheric signature of hot, excess hydrogen at the interface of the astrosphere and local interstellar medium. These observations would provide a comprehensive view of HD61005's astrosphere and provide a valuable model for our own Sun's heliosphere early in its main-sequence lifetime. ------------------------------------------------------------------------------------ Observations Description ------------------------ Desired Spectral Coverage and Resolution: The high spectral resolution capabilities of STIS are necessary to adequately model potentially blended LISM absorption line profiles and resolve the critical DI line. We propose to use the E230H (R ~ 110, 000) grating, in the 2574-2851 A wavelength range, which encompasses MgII h & k near 2800 A and FeII at 2600 A to resolve the velocity structure of the ISM along the line of sight. Because the hydrogen at the astrospheric interface is hot (T ~ 100, 000 K), it has a broad absorption 18336( 2) - 17-Aug-2026 16:29:39 - [ 2] profile, and does not necessarily require the highest spectral resolution. To maximize the S/N we plan to use the E140M setting. Desired Signal-to-Noise and Exposure Times: Estimating the S/N for our planned spectra requires first estimating the expected Lyman-alpha and MgII fluxes of HD61005. Chromospheric line fluxes (such as MgII and Lyman-alpha) are correlated to X-ray fluxes. Lyman-alpha spectra of similar stars are used as the comparison stars for our purposes here, scaled by their X-ray flux. After acquisition, peakup, and observational overhead are considered, we expect at least 28 minutes to be available in the first orbit for the E230H exposure. We expect a S/N of ~25 per resolution element at MgII. We expect at least 41 minutes of exposure time to be available in the second orbit for the E140M exposure, and 48 minutes in subsequent orbits. For 4 orbits we expect to reach S/N > 15 in the Lyman-alpha profile, which is sufficient to detect astrospheric absorption. Brightness Limits: HD61005 has been previously observed at medium resolution (E230M) which is insufficient to detect and model interstellar or circumstellar absorption but provides an excellent basis to evaluate the brightness limit at MgII. The global count rate is only 1, 900 counts per second, about 100 times less than the global brightness limit. The two emission lines of interest in the HST observations (Lyman-alpha and MgII) are also the brightest, and the procedure given above for estimating the S/N is also used to test for brightness limit violations. In the strongest lines, the brightest pixel only generates 0.1 counts per second. ------------------------------------------------------------------------------------ 18336( 2) - 17-Aug-2026 16:29:39 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 HD61005 STAR, DISK, EMISSION RA=07H35M47.4624S, J2000 V = 8.22 LINE STAR, G V-IV DEC=-32D12'14.05" Reference Frame: ICRS Extended: NO Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. SIMBAD listed proper motion for this target. When retrieving targets with PM from SIMBAD, APT requests the coordinates be calculated with an epoch of the year 2000. Do not modify this epoch. Always review coordinates using the Target Confirmation tool, which graphically displays the PM. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 -0.00433725724495945 0.074319 0.0274344 ------------------------------------------------------------------------------------------------------------------------------------ 18336( 2) - 17-Aug-2026 16:29:39 - [ 4] Visit: 01 Visit Requirements: BETWEEN 25-JUN-2026:00:00:00 AND 26-FEB-2027:00:00:00; BETWEEN 25-JUN-2027:00:00:00 AND 26-FEB-2028:00:00:00; BETWEEN 25-JUN-2028:00:00:00 AND 26-FEB-2029:00:00:00 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 HD61005 STIS/CCD ACQ F25ND3 MIRROR ACQTYPE=POINT 1 1.7 S (1.7 S) Comments: SNR = 152.6861 Brightest Pixel = 9, 707.79 e ------------------------------------------------------------------------------------------------------------------------------------ 2 HD61005 STIS/CCD ACQ/PEA 0.2X0.09 G430L 4300 1 0.5 S (0.5 K S) Comments: SNR = 80.0255 Brightest Pixel = 2, 855.23 e Global Source Counts = 14, 130.055 e ------------------------------------------------------------------------------------------------------------------------------------ 3 HD61005 STIS/NUV TIME-TA 0.2X0.09 E230H 2713 BUFFER-TIME=1020 1 1515 S -MAMA G (1515 S) Comments: SNR = 31.9650 Brightest Pixel = 451.46 e ------------------------------------------------------------------------------------------------------------------------------------ 4 HD61005 STIS/FUV TIME-TA 0.2X0.2 E140M 1425 BUFFER-TIME=17770 1 2577 S -MAMA G (2577 S) Comments: SNR = 13.8863 Brightest Pixel = 94.44 e ------------------------------------------------------------------------------------------------------------------------------------ 5 HD61005 STIS/FUV TIME-TA 0.2X0.2 E140M 1425 BUFFER-TIME=17770 1 2577 S -MAMA G (2577 S) Comments: SNR = 13.8863 Brightest Pixel = 94.44 e ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ HD61005 1 STIS/CCD ACQ F25ND3 MIRROR none none none none 1 N/A HD61005 2 STIS/CCD ACQ/PEA 0.2X0.09 G430L 4300 none none none none 1 N/A K HD61005 3 STIS/NUV TIME-TA 0.2X0.09 E230H 2713 none none none none 1 N/A -MAMA G HD61005 4 STIS/FUV TIME-TA 0.2X0.2 E140M 1425 none none none none 2 N/A -MAMA G HD61005 5 STIS/FUV TIME-TA 0.2X0.2 E140M 1425 none none none none 3 N/A -MAMA G 18336( 2) - 17-Aug-2026 16:29:39 - [ 5] Visit: 02 Visit Requirements: BETWEEN 25-JUN-2026:00:00:00 AND 26-FEB-2027:00:00:00; BETWEEN 25-JUN-2027:00:00:00 AND 26-FEB-2028:00:00:00; BETWEEN 25-JUN-2028:00:00:00 AND 26-FEB-2029:00:00:00 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 HD61005 STIS/CCD ACQ F25ND3 MIRROR ACQTYPE=POINT 1 1.7 S (1.7 S) Comments: SNR = 152.6861 Brightest Pixel = 9, 707.79 e ------------------------------------------------------------------------------------------------------------------------------------ 2 HD61005 STIS/CCD ACQ/PEA 0.2X0.09 G430L 4300 1 0.5 S (0.5 K S) Comments: SNR = 80.0255 Brightest Pixel = 2, 855.23 e Global Source Counts = 14, 130.055 e ------------------------------------------------------------------------------------------------------------------------------------ 3 HD61005 STIS/FUV TIME-TA 0.2X0.2 E140M 1425 BUFFER-TIME=17770 1 1532 S -MAMA G (1532 S) Comments: SNR = 10.7068 Brightest Pixel = 56.14 e ------------------------------------------------------------------------------------------------------------------------------------ 4 HD61005 STIS/FUV TIME-TA 0.2X0.2 E140M 1425 BUFFER-TIME=17770 1 2577 S -MAMA G (2577 S) Comments: SNR = 13.8863 Brightest Pixel = 94.44 e ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ HD61005 1 STIS/CCD ACQ F25ND3 MIRROR none none none none 1 N/A HD61005 2 STIS/CCD ACQ/PEA 0.2X0.09 G430L 4300 none none none none 1 N/A K HD61005 3 STIS/FUV TIME-TA 0.2X0.2 E140M 1425 none none none none 1 N/A -MAMA G HD61005 4 STIS/FUV TIME-TA 0.2X0.2 E140M 1425 none none none none 2 N/A -MAMA G 18336( 2) - 17-Aug-2026 16:29:39 - [ 6] Summary Form for Proposal 18336 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 0.2X0.09, 0.2X0.2, F25ND3 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD, STIS/FUV-MAMA, STIS/NUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ, ACQ/PEAK, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT, BUFFER-TIME=1020, BUFFER-TIME=17770 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BETWEEN 25-JUN-2026:00:00:00 AND 26-FEB-2027:00:00:00, BETWEEN 25-JUN-2027:00:00:00 AND 26-FEB-2028:00:00:00, BETWEEN 25-JUN-2028:00:00:00 AND 26-FEB-2029:00:00:00 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements E140M, E230H, G430L, MIRROR ------------------------------------------------------------------------------------------------------------------------------------ Target Names HD61005 ------------------------------------------------------------------------------------------------------------------------------------