0 Assigned ID: 4109 ----- Attempting Submission 1 (Tue May 23 14:47:44 GMT 2023) ----- ORBITAL VISIBILITY OVERRUN ORBITAL VISIBILITY OVERRUN ORBITAL VISIBILITY OVERRUN ORBITAL VISIBILITY OVERRUN This submission is in order to repeat visit 6, which failed. A new visit, 7, has been added. 620630703 ----- Attempting Submission 1 (Fri Sep 08 17:21:40 GMT 2023) ----- ----- Attempting Submission 2 (Mon Sep 23 23:30:34 GMT 2024) ----- ----- Attempting Submission 3 (Tue Nov 26 17:04:19 GMT 2024) ----- Visits 1, 2, 3, and 4 all have orbital visibility overruns because they have already been completed. Visit 6 failed, and my HOPR has been approved. This resubmission is now for Visit 7, a duplicate of 6. Neugent has no affiliation listed because she has no affilliation. Weighing the Most Massive Binary Understanding massive star evolution requires understanding massive binaries, as many massive stars are members of binary systems. In addition, orbit solutions provide the one direct measurement of a star's most fundamental property, its mass. We are proposing to measure accurate masses for NGC3603-A1, the most massive binary known, and the most luminous star in its rich cluster. Although identified as an eclipsing binary in 1984, the extreme crowding in the center of the cluster has made follow-up work difficult. An orbit using AO in the NIR on the VLT found masses of 116 Mo and 89 Mo for the two components. If correct, the primary would have a mass 50% larger than that of any other directly measured unevolved star. However, the uncertainties on these masses are quite large as the spectral features are mainly very broad, blended emission lines. An attempt to get better velocities was carried out by a competing group in Cycle 19, but the data were never published. We have analyzed these spectra, discovering that the upper Balmer lines are in absorption, and that at orbital phases near quadrature, the lines are readily resolved into two components: one from the primary and one from the secondary. Only two of their observations were taken at such phases, and the data have poor S/N. Here we propose to obtain much better data on the upper Balmer lines taken at times where we know the two components will be well resolved. This provides an efficient way to obtain accurate orbital parameters and masses for the most massive binary known. Such a system is the unevolved progenitor of the sort of merging massive black hole pairs indicated by recent gravitational wave detections. The goal of this program is to obtain high S/N (~100) sspectrum of the star NGC 3601-A1, two at phase ~0.25, and two at a phase of 0.75. The star is crowded, and so the observing plan is to do the ACQ on a nearby (20" sepaeration) offset star. A SAM then takes us to A1, where we perform a peakup with the 52x0.1E1 aperture. We then do a 7-point dither-along-slit centered on the 52x0.1E1. Special requirements include the timing given the 3.8 day orbital period of the binary, and the need to have ORIENT angles that avoid nearby bright stars from contaminating our spectrum. Dr. Philip Massey has studied massive binaries for most of his career, and has used STIS data to determine the orbits of several very massive stars in the R136 cluster. Massey has extensive experience in analysis of photometry and spectroscopic data. Dr. Laura Penny is an expert in the analysis of light-curve data from massive binaries, and is responsible for the analysis used in this proposal. Dr. Nidia Morrell is also a leading expert in the measurement of radial velocities from the spectra of massive binaries. Dr. Kathryn Neugent is also an expert on massive stars, including the study of massive binaries; she is currently a Hubble Fellow at the CfA. When Ms. Sarah Bodansky was an undergraduate at Carleton College, she performed the photometry and radial velocity measurements of the archival HST data used in this proposal. Now that she is a graduate student at UMass, she will continue working on the project under the supervision of Massey. Examples of the work by our team on massive binaries (including the use of STIS data) can be found for example in Massey, Penny, & Vukovich 2002, ApJ, 565, 982; Massey, Morrell, Neugent, Penny et al. 2012, ApJ, 748, 96, and Morrell, Massey, Neugent, Penny, & Gies 2014, ApJ, 789, 139. Stellar Physics and Stellar Types 6 false false false false false false false false SUPPORTED STAR B0-B2 III-I NO Proper motion has been applied to bring the coordinates to circa Cycle 31 from Gaia 2016 epoch. J2000 J2000 B-V=1.42 STAR EMISSION LINE STAR SUPERGIANT O WOLF RAYET - WN NO Positions have been measured on numerous HST/STIS images as the Gaia position is affected by crowded. Similarly the Gaia proper motion cannot be trusted. Instead, the average cluster proper motion has been adopted and applied to the Cycle 31 time frame. V-band magnitude measured from ACS/HRC frame J9EU05040 taken at phase 0.25, i.e., out of eclipse, and thus a good representation of the brightness for our observations here. J2000 J2000 B-V=1.03 STIS/CCD Imaging No No F28X50LP STIS/CCD Imaging No No 50CCD STIS/CCD Spectroscopic No No G430M 3843 STIS/CCD Imaging No No F28X50LP STIS/CCD Imaging No No 50CCD STIS/CCD Spectroscopic No No G430M 3843 STIS/CCD Imaging No No F28X50LP STIS/CCD Imaging No No 50CCD STIS/CCD Spectroscopic No No G430M 3843 STIS/CCD Imaging No No F28X50LP STIS/CCD Imaging No No 50CCD STIS/CCD Spectroscopic No No G430M 3843 POS-TARG DITHER 0.50 LINE false true 7 90.0 STIS-ALONG-SLIT 1 false /private/var/folders/qw/xgykb7fs39jct5h1_24mydq80000gn/T/OPVisit9902801817263204608.xml Timing link suitability includes constraints ([02 After 01 by 3.0 to 500.0 days] [05 After 01 by 3.0 to 500.0 days]) The scheduling data was generated by CASM 32.1.3. 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