0 Assigned ID: 6523 ----- Attempting Submission 1 (Thu Apr 10 16:39:05 GMT 2025) ----- STIS SCIENCE TOO FAR FROM WAVECAL PATTERN POSITION OUTSIDE APERTURE STIS SCIENCE TOO FAR FROM WAVECAL STIS SCIENCE TOO FAR FROM WAVECAL PATTERN POSITION OUTSIDE APERTURE MISSING FRINGE FLAT CALIBRATION MISSING FRINGE FLAT CALIBRATION STIS SCIENCE TOO FAR FROM WAVECAL MISSING FRINGE FLAT CALIBRATION MISSING FRINGE FLAT CALIBRATION STIS SCIENCE TOO FAR FROM WAVECAL STIS SCIENCE TOO FAR FROM WAVECAL STIS SCIENCE TOO FAR FROM WAVECAL STIS SCIENCE TOO FAR FROM WAVECAL 0 ----- Attempting Submission 1 (Thu Aug 14 22:33:47 GMT 2025) ----- Bright source with short exposures. not sure if flats are needed for science goals. If so, another orbit is needed. VY Canis Majoris (VY CMa) is the most luminous, largest, and presumably the initially most massive red supergiant (RSG) known. It is surrounded by a spectacular asymmetric nebula that was imaged by HST over 20 years ago, and shows a complex array of knots, arcs, and large-scale axisymmetric structure. It is a key object for understanding the extreme mass loss of the most massive RSGs and a benchmark for progenitors of SNe that interact with dense circumstellar material. Spectra reveal a range of outflow velocities in these structures that are faster than typical RSG winds, suggesting blasts of uneven mass-loss episodes over the past 1000 yr. The origin of this instability is not known, but it is usually attributed to either magnetic/convective instability near the Eddington limit, or to binary interaction with an unseen companion star. Although the central source in the nebula appeared unresolved in the earlier HST/WFPC2 imaging, a recent ground-based extreme-AO image has revealed that the central core of the nebula is not a point source. Instead, the core seems to be bisected by a dark obscuring lane (a disk?), and a fainter point source (a companion star?) is resolved at about 120 mas from the core. These features would have been just at the edge of the resolution limit in dithered WFPC2 images. We propose to obtain STIS spectra of the core of VY CMa in order to (1) record the spectrum of the fainter companion candidate, to see if it is reflected RSG light or a companion star, and (2) obtain the spectrum across the central obscuring lane to determine if it is molecular/dust obscuration and estimate its column density. This program will use STIS with a 0.1 arcsec slit width to obtain spectra of the central star in VY CMa, as well as a candidate companion star located about 120mas from the star. Both with be observed in low and medium resolution settings (G750L and G750M). Dr. Nathan Smith is an expert on massive star evolution and supernovae, including massive stars with strong mass loss such as LBVs and high-mass red supergiants. He has extensive experience with high resolution imaging and spectroscopy of circumstellar nebulae around massive stars. He has written several papers about the nebula around VY CMa, including the paper presenting the first WFPC2 images of VY CMa. Dr. Emma Beasor is an expert on red supergiants, including their mass-loss rates, circumstellar dust, atmospheres, and evolution, and is also an expert in connecting red supergiant progenitors to supernovae or failed supernovae. She has significant expertise in using various radiative transfer codes to analyze RSG spectra and optical/IR spectral energy distributions. Dr. Laird Close is the PI of the MagAO-X instrument (mounted on the 6.5 Magellan/Clay telescope) that produced the extreme-AO image of VY CMa that motivated this proposal. He is an expert in high resolution adaptive optics imaging. Stellar Physics and Stellar Types 6 false false false false false false SUPPORTED EXT-STAR M V-IV YES V magnitude is variable. 8.9 is the magniutude of the star plus scattered light in the iner nebula. Central star is actually fainter than this. J2000 J2000 STIS/CCD Spectroscopic No No G750L 7751 STIS/CCD Spectroscopic No No G750M 6768 POS-TARG DITHER 0.2 LINE false false 2 90.0 STIS-ALONG-SLIT 1 false /Users/nathans/Desktop/Dropbox/PROPOSALS/HST-33/OP-cache/vy-v01.xml 1755210370004 The scheduling data was generated by CASM 33.1. CASM was run in Phase II mode. First obtain spectrum of central star (Object A; shorter exposures) with STIS slit oriented roughly east-west, and then offset 0.12 arcsec to north to obtain spectrum of Object B (longer exposures). 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