Characterizing four massive post-interaction binaries with HST/COS

0 Assigned ID: 3355 ----- Attempting Submission 1 (Fri Mar 25 17:34:10 GMT 2022) ----- HST Phase I Proposal 3355 successfully submitted. Receipt: # 3355-1 ----- Attempting Submission 2 (Fri Mar 25 19:38:30 GMT 2022) ----- HST Phase I Proposal 3355 successfully submitted. Receipt: # 3355-2 ----- Attempting Submission 3 (Fri Mar 25 21:30:38 GMT 2022) ----- HST Phase I Proposal 3355 successfully submitted. Receipt: # 3355-3 ----- Attempting Submission 4 (Fri Mar 25 21:55:40 GMT 2022) ----- HST Phase I Proposal 3355 successfully submitted. Receipt: # 3355-4 Because target 4 is located close to a bright star, we have updated the acquisition image such that it targets to a different, nearby star (target 5), hopefully avoiding confusion when later pointing to target 4 to obtain spectra. -918327246 ----- Attempting Submission 1 (Tue Jul 12 14:31:53 GMT 2022) ----- ----- Attempting Submission 2 (Thu Dec 08 14:33:43 GMT 2022) ----- Characterizing four massive post-interaction binaries with HST/COS Massive stars stripped of their hydrogen-rich envelopes should be one of the most common types of binary products and the progenitors of stripped-envelope supernovae and binary neutron star mergers. Yet, no such system descending directly from stable mass transfer has been published. We propose to characterize a set of four binaries containing ~2-5 Msun stripped stars (originating from stars with initial masses ~7-20 Msun) that orbit B-type companions and that were recently discovered in the Large Magellanic Cloud. Because stripped stars are the exposed helium cores of their progenitors, they are very hot and emit most of their light in the ionizing extreme ultraviolet. As a result, their main-sequence companions dominate the optical output, making HST/COS UV spectroscopy necessary for characterizing the properties of the stripped stars. Using a set of HeII and HI lines combined with NIV and NV lines in the UV, we will be able to measure the effective temperature, surface gravity, surface hydrogen/helium content, and wind mass loss. In turn, these will lead to estimates for the bolometric luminosity, stellar radius, and mass. Combined with the properties of the companion star, we will provide the first stringent constraints on the outcomes of stable mass transfer in massive binary stars. This program will obtain UV spectra for 4 targets in the LMC that are newly discovered double-lined spectroscopic binaries, where one of the components is an intermediate mass stripped helium star candidate. These stripped stars are hot stars that are more luminous than subdwarfs, but lack the wind emission lines of Wolf-Rayet stars. The goal is to obtain UV spectra that can be modeled to both obtain stellar parameters and to constrain their wind parameters. The UV is essential for this study both because the optical spectra are obscured by the companion main-sequence star and the UV contains valuable spectral lines sensitive to wind parameters. Spectra will be obtained in the FUV with the G140L grism and a center wavelength of 800 Angstrom, providing continuous wavelength coverage between ~900-1950 Angstrom. We use the maximum exposure time avalible in between 2-3 orbits allocated per star, using all four FP positions for each target. The impacts of a reduced gyro operations on this program would primarily be reduced schedualability due to the smaller field of regard, as well as possible impacts of roll angle constraints when avoiding placement of bright field objects in the second COS aperture. Slightly longer acquisition times would have only a small effect on the S/N of our observations. All investigators on this proposal are experts in various aspects of massive star evolution. Dr. Ylva Gotberg is an expert in theoretical studies using stellar evolution models and radiative transfer models to investigate products of mass stripping in close binary evolution, their predicted observational signatures, and their contribution to the radiation budget of stellar populations. Dr. Maria Drout is an expert in observational studies of evolved stellar populations in nearby galaxies, a wide range of supernova explosions, and other transients including kilonovae. These studies of transients include a particular emphasis on supernovae that have experienced significant mass stripping. Bethany Ludwig is a PhD student at the University of Toronto and expert at UV phototmetry in crowded stellar regions. Dr. Selma de Mink is an expert on theoretical studies of a wide range of problems in massive binary star evolution, mass transfer and stellar mergers, binary vs. single star population synthesis, and a variety of implications for observational studies of massive stars. Dr. Jose Groh conducts both observational and theoretical studies of massive stars and the impact of mass loss on their evolution. This includes stellar evolution models, and CMFGEN radiative transfer models to derive accurate physical properties of stars, their wind mass loss, and radiative transfer models of supernova explosions. Eoin Farrell is a PhD student at Trinity College Dublin and an expert in stellar structure modelling of post main sequence stars. Dr. Nathan Smith concentrates on observational studies of mass loss from massive stars, including winds, eruptions, and binary mass loss, implications for the late evolution of massive stars and stellar populations, and studies of supernovae from massive stars with significant mass loss. Stellar Physics and Stellar Types 6 false false false false false false false SUPPORTED EXT-STAR ALGOL SYSTEM COMPOSITE SPECTRAL TYPE INTERACTING BINARY SDO NO J2000 J2000 UVW2: 17.87 (ABmag), UVM2: 17.93 (ABmag) EXT-STAR ALGOL SYSTEM COMPOSITE SPECTRAL TYPE SDO NO J2000 J2000 UVW2: 17.47 (ABmag), UVM2: 17.57 (ABmag) EXT-STAR ALGOL SYSTEM COMPOSITE SPECTRAL TYPE SDO NO J2000 J2000 UVW2: 17.09 (ABmag), UVM2: 17.19 (ABmag) EXT-STAR ALGOL SYSTEM COMPOSITE SPECTRAL TYPE SDO NO J2000 J2000 UVW2: 17.67 (ABmag), UVM2: 17.76 (ABmag) EXT-STAR UNDESIGNATED NO This star is to make the acquisition of target 4 easier. We aim to first point at this star, then offset the telescope to target 4 and obtain the spectrum of star 3. J2000 UVW2: 17.73 (ABmag), UVM2: 17.49 (ABmag), UVW1: 17.61 (ABmag) COS/FUV Spectroscopic No No G140L 800 COS/FUV Spectroscopic No No G140L 800 COS/FUV Spectroscopic No No G140L 800 COS/FUV Spectroscopic No No G140L 800 1670444000996 The scheduling data was generated by CASM 30.3. 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