17072( 5) - 15-Jul-2023 18:20:03 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 17072 Version: 5 Check-in Time: 15-Jul-2023 18:20:03 STScI Edit Number: 2 Title From atomic physics to stellar evolution: decoding the heavy-metal subdwarfs with HST ------------------------------------------------------------------------------------ Type Cycle GO 30 ------------------------------------------------------------------------------------ Investigators Contact? PI: Matti Dorsch Universitat Potsdam Y CoI: Prof. C Simon Jeffery Armagh Observatory and Planetarium N CoI: Prof. Ulrich Heber Universitat Erlangen-Nurnberg N CoI: Laura Scott Armagh Observatory and Planetarium N ------------------------------------------------------------------------------------ Abstract Hot subdwarf stars are helium-burning stars that are believed to form either via stripping of red giants' envelopes in binaries or by helium white dwarf mergers. They display a large variety of chemical peculiarities. Helium poor sdBs are found at Teff<35kK while extremely helium rich sdOs dominate at Teff>40kK. Particularly interesting are the rare mixed H/He composition iHe-sdOBs which bridge the gap. They may either be in a process of transition from red giant core to He-poor sdB, simply have insufficient hydrogen to quench the helium, or be the product of some other history. Several iHe-sdOBs show peculiar surface compositions with extraordinarily large enrichments of heavy elements (e.g. Zr, Pb by 4-6 dex). With two exceptions, these stars are completely unexplored in the space ultraviolet. We selected three "extreme chemistry" iHe-sdOBs that from a sequence of increasing Teff and helium abundance. This includes the recently discovered EC22536-5304, which resides in a binary with a very metal poor sdF-type companion, and likely formed via stripping by mass transfer to the sdF. UV spectra will allow us to determine 1) the abundances of a dozen or more species not observable in the optical, including the iron group, 2) the degree of stratification in the atmosphere (how thick is the enhanced layer?), 3) lead isotope ratios in the bright, lead-rich star HD127493. The results will allow us to explore the processes that may lead to heavily stratified envelopes and to study the transformation of red giant cores or white dwarf mergers with a helium-enriched surface into helium-poor sdBs. In addition, they will test alternative scenarios, such as pollution by SN ejecta. ------------------------------------------------------------------------------------ Observations Description ------------------------ First visit (LS IV -14 116): The goal is a high S/N spectrum with the medium-resolution echelle E140M grism (using the standard 0.2x0.2 aperture). TIME-TAG is used when possible - for two out of three orbits, to limit the number of dumps. The ACCUM mode is used for the remaining orbit. Second visit (EC22536-5304): A STIS/E140M (0.2x0.2) spectrum with about S/N = 40 at 1350 AA is the goal. TIME-TAG is used when possible - for two out of three orbits, to limit the 17072( 5) - 15-Jul-2023 18:20:03 - [ 2] number of dumps. The ACCUM mode is used for the remaining orbit. Third visit (HD127493): A high-S/N (~100) observation with E140H/1271 using the 0.2x0.09 slit is the goal. The star is bright (V=10.08mag, Teff~41000K), and the ACCUM mode will be used. ------------------------------------------------------------------------------------ 17072( 5) - 15-Jul-2023 18:20:03 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 LS-IV--14-11 STAR, SDO RA=20H57M38.8828S +/- 0.00005", J2000 V = 12.956 +/- 0.02 6 DEC=-14D25'46.04" +/- 0.00003" Reference Frame: ICRS Extended: NO Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2016.0 5.099996238111805E-4 -0.12826540998821423 0.0023405666220228413 ------------------------------------------------------------------------------------------------------------------------------------ 2 EC-22536-530 STAR, SDO RA=22H56M35.9285S +/- 0.00005", J2000 V = 13.323 +/- 0.03 4 DEC=-52D48'36.77" +/- 0.00005" Reference Frame: ICRS Extended: NO Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2016.0 2.705866240348549E-4 -0.0443410887137311 0.0013682472167333315 ------------------------------------------------------------------------------------------------------------------------------------ 3 HD-127493 STAR, SDO RA=14H32M21.4560S +/- 0.00005", J2000 V = 10.01 +/- 0.03 DEC=-22D39'25.93" +/- 0.00004" Reference Frame: ICRS Extended: NO Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2016.0 -0.0022916316705357516 -0.017683558256879475 0.005692375042818344 ------------------------------------------------------------------------------------------------------------------------------------ 17072( 5) - 15-Jul-2023 18:20:03 - [ 4] Visit: 01 (LSIV-14 116) 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 LS-IV--14-1 STIS/CCD ACQ F28X50LP MIRROR 1 1 S (1 S) 16 ------------------------------------------------------------------------------------------------------------------------------------ 2 LS-IV--14-1 STIS/FUV TIME-TA 0.2X0.2 E140M 1425 BUFFER-TIME=174 1 2270.3 S 16 -MAMA G (2270.3 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 LS-IV--14-1 STIS/FUV TIME-TA 0.2X0.2 E140M 1425 BUFFER-TIME=174 1 2726.3 S 16 -MAMA G (2726.3 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 LS-IV--14-1 STIS/FUV ACCUM 0.2X0.2 E140M 1425 1 2726.3 S 16 -MAMA (2726.3 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 | ------------------------------------------------------------------------------------------------------------------------------------ LS-IV--14-116 1 STIS/CCD ACQ F28X50LP MIRROR none none none none 1 N/A LS-IV--14-116 2 STIS/FUV TIME-TA 0.2X0.2 E140M 1425 none none none none 1 N/A -MAMA G LS-IV--14-116 3 STIS/FUV TIME-TA 0.2X0.2 E140M 1425 none none none none 2 N/A -MAMA G LS-IV--14-116 4 STIS/FUV ACCUM 0.2X0.2 E140M 1425 none none none none 3 N/A -MAMA 17072( 5) - 15-Jul-2023 18:20:03 - [ 5] Visit: 02 (EC-22536-5304) 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 EC-22536-53 STIS/CCD ACQ F28X50LP MIRROR 1 1 S (1 S) 04 ------------------------------------------------------------------------------------------------------------------------------------ 2 EC-22536-53 STIS/FUV ACCUM 0.2X0.2 E140M 1425 1 2513 S 04 -MAMA (2513 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 EC-22536-53 STIS/FUV TIME-TA 0.2X0.2 E140M 1425 BUFFER-TIME=263 1 2910.3 S 04 -MAMA G (2910.3 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 EC-22536-53 STIS/FUV TIME-TA 0.2X0.2 E140M 1425 BUFFER-TIME=263 1 2910.3 S 04 -MAMA G (2910.3 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 | ------------------------------------------------------------------------------------------------------------------------------------ EC-22536-5304 1 STIS/CCD ACQ F28X50LP MIRROR none none none none 1 N/A EC-22536-5304 2 STIS/FUV ACCUM 0.2X0.2 E140M 1425 none none none none 1 N/A -MAMA EC-22536-5304 3 STIS/FUV TIME-TA 0.2X0.2 E140M 1425 none none none none 2 N/A -MAMA G EC-22536-5304 4 STIS/FUV TIME-TA 0.2X0.2 E140M 1425 none none none none 3 N/A -MAMA G 17072( 5) - 15-Jul-2023 18:20:03 - [ 6] Visit: 03 (HD127493) 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 HD-127493 STIS/CCD ACQ F28X50LP MIRROR 1 0.1 S (0.1 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 HD-127493 STIS/CCD ACQ/PEA 0.2X0.09 MIRROR 1 0.1 S (0.1 K S) ------------------------------------------------------------------------------------------------------------------------------------ 3 HD-127493 STIS/FUV ACCUM 0.2X0.09 E140H 1271 1 1891.6 S -MAMA (1891.6 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 HD-127493 STIS/FUV ACCUM 0.2X0.09 E140H 1271 1 2734.6 S -MAMA (2734.6 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 | ------------------------------------------------------------------------------------------------------------------------------------ HD-127493 1 STIS/CCD ACQ F28X50LP MIRROR none none none none 1 N/A HD-127493 2 STIS/CCD ACQ/PEA 0.2X0.09 MIRROR none none none none 1 N/A K HD-127493 3 STIS/FUV ACCUM 0.2X0.09 E140H 1271 none none none none 1 N/A -MAMA HD-127493 4 STIS/FUV ACCUM 0.2X0.09 E140H 1271 none none none none 2 N/A -MAMA 17072( 5) - 15-Jul-2023 18:20:03 - [ 7] Visit: 04 (LSIV-14 116 (redo)) Visit Requirements: On Hold Comments: Additional Comments: This is a new visit to repeat one orbit of Visit 01 of LS IV -14 116. During the original orbit HST failed to acquire the guide stars. Following HOPR 92568 for this HST program (17072), this single repeat orbit was approved by the TTRB. 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 LS-IV--14-1 STIS/CCD ACQ F28X50LP MIRROR 1 1 S (1 S) 16 ------------------------------------------------------------------------------------------------------------------------------------ 2 LS-IV--14-1 STIS/FUV TIME-TA 0.2X0.2 E140M 1425 BUFFER-TIME=174 1 2270.3 S 16 -MAMA G (2270.3 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 | ------------------------------------------------------------------------------------------------------------------------------------ LS-IV--14-116 1 STIS/CCD ACQ F28X50LP MIRROR none none none none 1 N/A LS-IV--14-116 2 STIS/FUV TIME-TA 0.2X0.2 E140M 1425 none none none none 1 N/A -MAMA G 17072( 5) - 15-Jul-2023 18:20:03 - [ 8] Summary Form for Proposal 17072 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 0.2X0.09, 0.2X0.2, F28X50LP ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD, STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM, ACQ, ACQ/PEAK, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=174, BUFFER-TIME=263 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements E140H, E140M, MIRROR ------------------------------------------------------------------------------------------------------------------------------------ Target Names EC-22536-5304, HD-127493, LS-IV--14-116 ------------------------------------------------------------------------------------------------------------------------------------