0Assigned ID: 5047
----- Attempting Submission 1 (Fri Mar 22 14:28:36 GMT 2024) -----
HST Phase I Proposal 5047 successfully submitted.
Receipt: # 5047-1
----- Attempting Submission 2 (Tue Mar 26 08:30:16 GMT 2024) -----
HST Phase I Proposal 5047 successfully submitted.
Receipt: # 5047-2This is the first submitted version of the Phase II proposal.3251641----- Attempting Submission 1 (Thu Aug 01 10:08:33 GMT 2024) -----The first UV investigation of a massive stripped-envelope core-collapse progenitor at high metallicity: The WO star WR 102The WO-type Wolf-Rayet stars of the oxygen sequence represent the final stage in the life of a massive star. These stars offer a unique window to the evolutionary stages right before going supernovae and collapsing into black holes (BHs). A WO star is dominated by a strong stellar wind that further strips its outer layers. This large mass loss ultimately determines how much mass is left for a BH to form. Given the discrepancy between observed BH masses and final masses from stellar evolution, determining the wind structure and mass-loss rate is paramount.
Moreover, the evolution of these stars and their winds is poorly constrained: whether some WO stars will undergo a stripped-envelope supernova (SNIbc) is currently under debate. Optical analyses exist but cannot reveal the whole picture: mayor wind drivers and nucleosynthesis indicators can only be observed in the UV. Yet, UV spectra of WO stars at Galactic metallicities are absent. Looking at the most evolved WO star in the Milky Way, WR 102, we propose to obtain pioneering UV data to understand massive, stripped core-collapse progenitors at high metallicity and shed light on the SNIbc puzzle. Being highly evolved and stripped objects, the abundances of WO stars also yield a unique insight into the highly uncertain C-O nuclear reaction rate.
Using stellar atmosphere models with an inherent solution of the hydrodynamic equation, we will further be able to obtain consistent density stratifications for our targets and get a unique handle on the so far uncertain stellar mass. Thereby, we will be able to provide a crucial testbed for the circumstellar emvironment of highly stripped stars undergoing core collapse.The spectra of WR102 (V-V3893-SGR) will be obtained using the COS G140L (800 Angstroem) grating. As this specific grating has a pass band of 913-1940 Angstroem, the FUV range of the spectrum is well covered and without gaps. The FUV range is crucial for our target star since prominent wind features in the spectra, along with P Cygni profiles, are paramount to break parameter ambiguity resulting often from optical spectra of Wolf-Rayet stars. More specifically, expectedly strong lines like O VI 1371 Angstroem and CIV 1548-50 Angstroem are of particular importance for wind parameter and abundance determinations in our analyses.
As WR102 is quite reddened, with an E(B-V) = 1.26 (Tramper et al. 2015), the FUV regime of this star requires more exposure time than its visual magnitude of 14.20 suggests. Hence, the total of 12 orbits is necessary for our requirements. A total science exposure time of 30,078s ensures an SNR of 13.3 at 1480 Angstroem, this latter value being chosen to avoid the SNR estimate being heavily influenced by strong spectral lines. In addition, this science exposure time ensures an SNR between 10 and 11 around wavelengths around 1320 Angstroem.The proposing team consists of experts from both the theoretical and the observational side with several members having long-time HST experience. P. Massey, A. Sander, L. Oskinova, T. Shenar, and W-R. Hamann have extensive experience with HST UV data with various accepted proposals in the last decade and excellent publication records.
W-R. Hamann, L. Oskinova, P. Massey, A. Sander, V. Ramaschandran, D. Pauli, H. Todt, T. Shenar, R. Lefever, M. Bernini Peron, E. Schosser, G. Gonzalez-Tora and J. Josiek have detailed experience with non-LTE atmosphere modelling, especially in the context of analysing Wolf-Rayet stars.
A. Sander, H. Todt, and W.-R. Hamann are lead developers of PoWR, one of the most advanced non-LTE expanding stellar atmosphere code, especially designed to properly cope with the complex winds of hot Wolf-Rayet stars. Moreover, A. Sander, J.S. Vink, R. Lefever and M. Bernini Peron are experts in the theoretical modelling and hydrodynamically consistent simulation of radiation-driven winds of hot stars. E.R. Higgins is an expert in stellar evolution modelling, in particular for evolved massive stars.Stellar Physics and Stellar TypesStellar Populations and the Interstellar Medium6falsefalsefalsefalsefalsefalseSUPPORTEDSTARWOLF RAYETNOThis 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.WR102J2000J2000COS/FUVSpectroscopicNoNoG140L800The scheduling data was generated by CASM 32.1.1.CASM was run in Phase II mode.1744338104000272.63803157683924(Tic-Visit
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