17732( 2) - 16-Aug-2024 14:28:43 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 17732 Version: 2 Check-in Time: 16-Aug-2024 14:28:43 STScI Edit Number: 0 Title UV spectroscopy of the complete sample of Wolf-Rayet stars in the low-metallcity galaxy NGC 6822 ------------------------------------------------------------------------------------ Type Cycle GO 32 ------------------------------------------------------------------------------------ Investigators Contact? PI: Prof. Lidia Oskinova Universitat Potsdam Y CoI: Dr. Wolf-Rainer Hamann Universitat Potsdam N CoI: Dr. Andreas Sander Astronomisches Rechen-Institut Heidelberg N CoI: Dr. Varsha Ramachandran Universitat Heidelberg N CoI: Dr. Helge Todt Universitat Potsdam N CoI: Daniel Pauli Universitat Potsdam N CoI: Roel Lefever Astronomisches Rechen-Institut Heidelberg N CoI: Dr. Derck L. Massa Space Science Institute N CoI: Dr. Tomer Shenar Tel Aviv University N ------------------------------------------------------------------------------------ Abstract We propose the first UV spectroscopic study of the complete sample of four Wolf-Rayet (WR) stars in the low-metallicity galaxy NGC6822. WR stars are rare objects which represent the final evolutionary stage of most massive stars short before their collapse into black holes, and are important feedback sources. Low-metallicity WR stars are emigmatic but, arguably, the most important testbeds of the final stages of massive star evolution in conditions resembling those in the early Universe. The new COS spectra of the strategically important sample of low-metallcity WR stars are urgently needed to complement existing optical spectra, which by themselves are not sufficient to fully characterize these objects with strong winds. The HST data will be exploited to measure stellar and wind parameters using modern stellar atmosphere models. The determined mass-loss rates and wind velocities will be compared to those of WR stars in different galaxies, such as the Milky Way, the LMC, and the SMC, and used to anchor the metallicity dependence of WR wind strengths. The derived stellar parameters will test massive-star evolution models and allow a comparative study of low-metallicity WR stars in the SMC and NGC6822. If we find that WR stars in NGC6822 resemble the so far unique population of WR stars in the SMC (which fundamentally differs from the WR stars in galaxies with higher metallicity), it will disrupt the standard picture of black hole progenitors and stellar feedback at low metallicities, and by proxy in the young Universe. Obtaining the UV spectra of WR stars in NGC6822 is a necessary addtion to the HST legacy and will resonate across many areas of astrophysics. ------------------------------------------------------------------------------------ Observations Description ------------------------ COS G140L spectra of four Wolf-Rayet stars in the galaxy NGC 6822. Four visits - one per target, 5 orbits each. The targets have V~ 20. The coordinates are from Gaia DR3. 1) The targets are relatively isolated, as also confirmed by the `target confirmation' tool. The ETC suggest small exp. times for img aqc, therefore we 17732( 2) - 16-Aug-2024 14:28:43 - [ 2] use this option. We hope this is fine. 2) We could not find optimum FP-POS, the apt gives warning on inefficient use. We would be very grateful for recommendation how to improve our strategy 3) We indicate buffer time 10000 sec, ie. 2/3 of buffer time calculated by the ETC. But we are not sure this is the optimum option and would be very grateful for your recommendations. ------------------------------------------------------------------------------------ 17732( 2) - 16-Aug-2024 14:28:43 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 2 AM85-NGC-682 STAR, WOLF RAYET - WN RA=19H44M37.9598S +/- 0.003", J2000 V = 19.83 2-4 DEC=-14D51'6.80" +/- 0.003" Reference Frame: ICRS Extended: NO 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) 2016 0.0 0.0 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 1 AM85-NGC-682 STAR, WOLF RAYET - WN RA=19H44M31.9735S +/- 0.001", J2000 V = 19.69 2-3 DEC=-14D44'9.35" +/- 0.001" Reference Frame: ICRS Extended: NO 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) 2016 0.0 0.0 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 3 AM85-NGC-682 STAR, WOLF RAYET - WN RA=19H44M49.3465S +/- 0.008", J2000 V = 19.72 2-5 DEC=-14D45'40.22" +/- 0.007" Reference Frame: ICRS Extended: NO 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) 2015.5 0.0 0.0 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 4 AM85-NGC-682 STAR, WOLF RAYET - WN RA=19H45M13.4870S +/- 0.003", J2000 V = 18.96 2-12 DEC=-14D45'13.28" +/- 0.003" Reference Frame: ICRS Extended: NO 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) 2016 0.0 0.0 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 17732( 2) - 16-Aug-2024 14:28:43 - [ 4] Visit: 01 (WR 3) 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 AM85-NGC-68 COS/NUV ACQ/IMA PSA MIRRORA 1 10 S (10 22-3 GE S) ------------------------------------------------------------------------------------------------------------------------------------ 2 AM85-NGC-68 COS/FUV TIME-TA PSA G140L 800 BUFFER-TIME=10000, FLASH=YES, 1 3200 S 22-3 G FP-POS=ALL see below (9978 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 AM85-NGC-68 COS/FUV TIME-TA PSA G140L 800 FP-POS=ALL, BUFFER-TIME=3200 1 500 S 22-3 G see below (2226 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 | ------------------------------------------------------------------------------------------------------------------------------------ AM85-NGC-6822-3 1 COS/NUV ACQ/IMA PSA MIRRORA none none none none 1 N/A GE AM85-NGC-6822-3 2 COS/FUV TIME-TA PSA G140L 800 none none none 1 1 2265.0 S G AM85-NGC-6822-3 2 COS/FUV TIME-TA PSA G140L 800 none none none 2 2 2571.0 S G AM85-NGC-6822-3 2 COS/FUV TIME-TA PSA G140L 800 none none none 3 3 2571.0 S G AM85-NGC-6822-3 2 COS/FUV TIME-TA PSA G140L 800 none none none 4 4 2571.0 S G AM85-NGC-6822-3 3 COS/FUV TIME-TA PSA G140L 800 none none none 1 5 520.0 S G AM85-NGC-6822-3 3 COS/FUV TIME-TA PSA G140L 800 none none none 2 5 520.0 S G AM85-NGC-6822-3 3 COS/FUV TIME-TA PSA G140L 800 none none none 3 5 520.0 S G AM85-NGC-6822-3 3 COS/FUV TIME-TA PSA G140L 800 none none none 4 5 666.0 S G 17732( 2) - 16-Aug-2024 14:28:43 - [ 5] Visit: 02 (WR 4) 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 AM85-NGC-68 COS/NUV ACQ/IMA PSA MIRRORA 1 10 S (10 22-4 GE S) ------------------------------------------------------------------------------------------------------------------------------------ 2 AM85-NGC-68 COS/FUV TIME-TA PSA G140L 800 BUFFER-TIME=10000, FLASH=YES, 1 3200 S 22-4 G FP-POS=ALL see below (9978 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 AM85-NGC-68 COS/FUV TIME-TA PSA G140L 800 FP-POS=ALL, BUFFER-TIME=10000, 1 500 S 22-4 G FLASH=YES see below (2254 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 | ------------------------------------------------------------------------------------------------------------------------------------ AM85-NGC-6822-4 1 COS/NUV ACQ/IMA PSA MIRRORA none none none none 1 N/A GE AM85-NGC-6822-4 2 COS/FUV TIME-TA PSA G140L 800 none none none 1 1 2265.0 S G AM85-NGC-6822-4 2 COS/FUV TIME-TA PSA G140L 800 none none none 2 2 2571.0 S G AM85-NGC-6822-4 2 COS/FUV TIME-TA PSA G140L 800 none none none 3 3 2571.0 S G AM85-NGC-6822-4 2 COS/FUV TIME-TA PSA G140L 800 none none none 4 4 2571.0 S G AM85-NGC-6822-4 3 COS/FUV TIME-TA PSA G140L 800 none none none 1 5 527.0 S G AM85-NGC-6822-4 3 COS/FUV TIME-TA PSA G140L 800 none none none 2 5 527.0 S G AM85-NGC-6822-4 3 COS/FUV TIME-TA PSA G140L 800 none none none 3 5 527.0 S G AM85-NGC-6822-4 3 COS/FUV TIME-TA PSA G140L 800 none none none 4 5 673.0 S G 17732( 2) - 16-Aug-2024 14:28:43 - [ 6] Visit: 03 (WR 5) 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 AM85-NGC-68 COS/NUV ACQ/IMA PSA MIRRORA 1 10 S (10 22-5 GE S) ------------------------------------------------------------------------------------------------------------------------------------ 2 AM85-NGC-68 COS/FUV TIME-TA PSA G140L 800 BUFFER-TIME=10000, FLASH=YES, 1 3200 S 22-5 G FP-POS=ALL see below (9978 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 AM85-NGC-68 COS/FUV TIME-TA PSA G140L 800 FP-POS=ALL, BUFFER-TIME=10000, 1 500 S 22-5 G FLASH=YES see below (2254 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 | ------------------------------------------------------------------------------------------------------------------------------------ AM85-NGC-6822-5 1 COS/NUV ACQ/IMA PSA MIRRORA none none none none 1 N/A GE AM85-NGC-6822-5 2 COS/FUV TIME-TA PSA G140L 800 none none none 1 1 2265.0 S G AM85-NGC-6822-5 2 COS/FUV TIME-TA PSA G140L 800 none none none 2 2 2571.0 S G AM85-NGC-6822-5 2 COS/FUV TIME-TA PSA G140L 800 none none none 3 3 2571.0 S G AM85-NGC-6822-5 2 COS/FUV TIME-TA PSA G140L 800 none none none 4 4 2571.0 S G AM85-NGC-6822-5 3 COS/FUV TIME-TA PSA G140L 800 none none none 1 5 527.0 S G AM85-NGC-6822-5 3 COS/FUV TIME-TA PSA G140L 800 none none none 2 5 527.0 S G AM85-NGC-6822-5 3 COS/FUV TIME-TA PSA G140L 800 none none none 3 5 527.0 S G AM85-NGC-6822-5 3 COS/FUV TIME-TA PSA G140L 800 none none none 4 5 673.0 S G 17732( 2) - 16-Aug-2024 14:28:43 - [ 7] Visit: 04 (WR 12) 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 AM85-NGC-68 COS/NUV ACQ/IMA PSA MIRRORA 1 8 S (8 S) 22-12 GE ------------------------------------------------------------------------------------------------------------------------------------ 2 AM85-NGC-68 COS/FUV TIME-TA PSA G140L 800 BUFFER-TIME=10000, FLASH=YES, 1 3200 S 22-12 G SEGMENT=A, FP-POS=ALL see below (9978 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 AM85-NGC-68 COS/FUV TIME-TA PSA G140L 800 FP-POS=ALL, BUFFER-TIME=10000, 1 500 S 22-12 G FLASH=YES see below (2254 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 | ------------------------------------------------------------------------------------------------------------------------------------ AM85-NGC-6822-12 1 COS/NUV ACQ/IMA PSA MIRRORA none none none none 1 N/A GE AM85-NGC-6822-12 2 COS/FUV TIME-TA PSA G140L 800 none none none 1 1 2265.0 S G AM85-NGC-6822-12 2 COS/FUV TIME-TA PSA G140L 800 none none none 2 2 2571.0 S G AM85-NGC-6822-12 2 COS/FUV TIME-TA PSA G140L 800 none none none 3 3 2571.0 S G AM85-NGC-6822-12 2 COS/FUV TIME-TA PSA G140L 800 none none none 4 4 2571.0 S G AM85-NGC-6822-12 3 COS/FUV TIME-TA PSA G140L 800 none none none 1 5 527.0 S G AM85-NGC-6822-12 3 COS/FUV TIME-TA PSA G140L 800 none none none 2 5 527.0 S G AM85-NGC-6822-12 3 COS/FUV TIME-TA PSA G140L 800 none none none 3 5 527.0 S G AM85-NGC-6822-12 3 COS/FUV TIME-TA PSA G140L 800 none none none 4 5 673.0 S G 17732( 2) - 16-Aug-2024 14:28:43 - [ 8] Summary Form for Proposal 17732 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures PSA ------------------------------------------------------------------------------------------------------------------------------------ Configurations COS/FUV, COS/NUV ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/IMAGE, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=10000, BUFFER-TIME=3200, FLASH=YES, FP-POS=ALL, SEGMENT=A ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G140L, MIRRORA ------------------------------------------------------------------------------------------------------------------------------------ Target Names AM85-NGC-6822-12, AM85-NGC-6822-3, AM85-NGC-6822-4, AM85-NGC-6822-5 ------------------------------------------------------------------------------------------------------------------------------------