Resubmission with minor typo corrections to the main proposal text 827099461 Assigned ID: 245 ----- Attempting Submission 1 (Thu Apr 04 19:28:49 GMT 2019) ----- HST Phase I Proposal 245 (m31-wr-hst-tool.apt) successfully submitted. Receipt: # 245-1 ----- Attempting Submission 2 (Fri Apr 05 14:48:38 GMT 2019) ----- HST Phase I Proposal 245 (m31-wr-hst-tool.apt) successfully submitted. Receipt: # 245-2 ----- Attempting Submission 3 (Fri Apr 05 22:55:53 GMT 2019) ----- Resubmission of the Phase II proposal to account for all four FP-POS in Visit 01 as discussed with Ravi Sankrit -820324217 ----- Attempting Submission 1 (Tue Jul 09 02:06:19 GMT 2019) ----- ----- Attempting Submission 2 (Thu Mar 12 17:01:31 GMT 2020) ----- Anchoring mass-loss and metallicity for the WR population in M31 - A prototype study A major uncertainty in modern day astrophysics is the metallicity-dependence of massive star winds. The huge mass-loss of massive stars, enriching the interstellar medium with processed metals, as well as their significant ionizing flux define them as key players of galactic evolution throughout the cosmic ages. Their energetic influence integrated over their lifetime is comparable to supernova explosions, thus providing important constraints to other astrophysical fields. Among the massive stars, Wolf-Rayet (WR) stars are a keystone. Their strong winds lead to broad emission lines, making them easy to discover even in unresolved stellar populations and distant galaxies. Their mass-loss rates exceed those of other massive stars by at least one order of magnitude. Massive black holes form during the core collapse of WR stars, possibly even without an accompanying supernova explosion. Studying the WR population of a galaxy is therefore vital for our current understanding of the Universe. To constrain the metallicity-dependence of wind mass-loss and its drastic impact on stellar evolution, studies have been carried out for the WR populations in the Milky Way (MW) and the Magellanic Clouds (MCs). The WR population of M31 would be the next milestone, but recent analyses using optical data revealed puzzling differences between M31 and the MW, despite apparently similar metallicities. We propose COS UV observations of four prototypical WR stars in M31 in order to obtain the crucial diagnostics necessary to properly anchor the metallicity and the mass-loss rates of their WR winds, setting a fundament for a theoretical framework of metallicity-dependent wind driving. We propose to observe four prototypical WR stars in M31 with FUV spectroscopy, aiming at a S/N of lager than 20 at 1310 Angstroem. This requires a total of 15 orbits, three for our brigtest target and four each for the dimmer WR stars. The spectral observations will be performed with the G140L grating with pass band 700 to 1950. It covers most of the far UV range, including the line forest of iron ions (e.g. Fe VI around 1260 to 1290 Angstroem, Fe v around 1450 to 1490 Angstroem and Fe IV around 1660 to 1700 Angstroem). Furthermore, this spectral range contains important wind lines, such as the resonance lines of Si iv, Civ, and Nv which act as crucial indicators in order to determine the correct wind parameters. For our spectral analyses with stellar atmospheres, the resolution of the G140L grating is fully sufficient, while a relatively high S/N of about 30 is required to reliably determine the iron abundance. Therefore, we will require in total 15 orbits to achieve our science goals. Our brightest target has a magnitude of mV = 18.09 and an estimated reddening of EBV approx 0.25, bringing the object safely below the brightness limit of the COS detector. This is confirmed by ETC calculations with a PoWR model spectrum used in our previous analysis of the optical data of this star in Sander et al. (2014). As an additional layer of security, we also cross-checked this with a much hotter 150 kK black body input. We will follow the recommended observing strategy and request that the default wavelength-calibration procedure is applied. The observations shall be performed in TIME-TAG mode, changing to a new FP-POS position each orbit. While all four FP-POS positions will be used for three of the targets, the first target will use only three FP-POS since its observation requires only three orbits. Compared to the original plan in the Phase I proposal, the target coordinates have been updated with Gaia DR2 results. Moreover, we have switched from the COS G140L 1105 central wavelength (1121 - 2148 window) to the new 800 option. The ETC calculations using WR model atmospheres show that we do not really gain a lot of photons at the larger wavelengths of the 1105 setting while we have the chance to catch emission lines of additonal elements (e.g. O VI for early WR types) at lower wavelengths around 1100 Angstroems with the 800 setting. New ETC calculations linked in the Phase II proposal have been performed with this option. The proposing team consists of experts from both the theoretical and the observational side with several members having long-time HST experience. The CoIs R. Hainich, L. Oskinova, T. Shenar, W-R. Hamann and R. Ignace have extensive experience with HST UV data with more than half a dozen accepted proposals in the last decade. W-R. Hamann, R. Hainich, A. Sander, H. Todt, and T. Shenar have long-time experience with analysing Wolf-Rayet stars and have published various papers about this matter with multiple of them being now a standard reference in the field. L. Oskinova and R. Ignace add further expertise in the field of wind clumping to the team. A. Sander, H. Todt, and W.-R. Hamann are lead developers of PoWR, one of the most advanced expanding non-LTE stellar atmosphere code, especially designed to properly cope with the complex winds of hot Wolf-Rayet stars. Moreover, A. Sander and J. Vink are experts in the theoretical modelling and hydrodynamically consistent simulation of radiation-driven winds of hot stars. Stellar Populations Stellar Physics 6 false false true false false false false SUPPORTED EXT-STAR EMISSION LINE STAR WOLF RAYET WOLF RAYET - WN NO This object was generated by the targetselector and retrieved from the SIMBAD database. Coordinates updated with Gaia DR2 M31WR-27 LGGS-J004056.49+410308.7 J2000 J2000 EBV 0.25, U: 17.010+/-0.008, SpT WN9 EXT-STAR EMISSION LINE STAR WOLF RAYET WOLF RAYET - WN NO This object was generated by the targetselector and retrieved from the SIMBAD database. Coordinates updated with Gaia DR2 M31WR-36 LGGS-J004114.95+404448.2 J2000 J2000 EBV 0.1, U: 19.322+/-0.007, SpT WN6 EXT-STAR EMISSION LINE STAR WOLF RAYET WOLF RAYET - WN NO This object was generated by the targetselector and retrieved from the SIMBAD database. Coordinates updated with Gaia DR2 M31WR-101 LGGS-J004420.58+415412.5 J2000 J2000 EBV 0.1, U: 19.377+/-0.017, SpT WN3 EXT-STAR EMISSION LINE STAR WOLF RAYET WOLF RAYET - WC NO This object was generated by the targetselector and retrieved from the SIMBAD database. Coordinates updated with Gaia DR2 M31WR-96 LGGS-J004412.44+412941.7 J2000 J2000 EBV 0.2, U: 18.858+/-0.004, SpT WC6 COS/FUV Spectroscopic No No G140L 1105 COS/FUV Spectroscopic No No G140L 1105 COS/FUV Spectroscopic No No G140L 1105 COS/FUV Spectroscopic No No G140L 1105 C:\Users\General Mengsk\AppData\Local\Temp\OPVisit14276733939784480752.xml The scheduling data was generated by CASM 28.0. CASM was run in Phase II mode. 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