NOAO >   Observing Info >   Approved Programs >   2016B-0274

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Program Information for 2016B-0274


PI: Guy Stringfellow, U. of Colorado, Guy.Stringfellow@colorado.edu
Address: Center for Astrophysics and Space Astronomy, 389 UCB, Boulder, CO 80309-0389 USA

Title: Variability of New Candidate and Confirmed Luminous Blue Variables

Abstract: Luminous Blue Variable (LBV) stars represent an extremely rare class and short-lived phase in the lives of very luminous massive stars with high mass loss rates. Extragalactic LBVs are responsible for producing false supernovae (SN), the SN Impostors, but also have been directly linked with the progenitors of actual SN, indicating the LBV phase can be a final endpoint for massive star evolution. Yet only a few confirmed LBVs have been identified in the Galaxy, and only a few more are known in the SMC and LMC. Their stellar evolution is poorly constrained by observations, and the physical reason for their unstable nature, both in terms of moderate spectral and photometric variability of a few magnitudes and the giant eruptions {it a la} $eta$ Car that rival SN explosions, remains a mystery. Newly discovered mid-IR shells act as signposts, pointing to the central massive stars (LBV and Wolf- Rayet [WR] stars) that produced them. My spectroscopic survey of possible progenitor stars within these shells indicate many are LBVs and WN-type WR transitional stars. This has led to a large number of new candidate LBVs which can be confirmed through photometric monitoring, where large amplitude and possible semi-periodic cycles are revealed in their light curves. The behavior displayed in the light curves provides much insight into the physics operating and the massive winds generated by these extreme stars. This proposal seeks time using ANDICAM on the SMARTS 1.3m to secure optical-IR imaging from which photometric light curves and color-magnitude diagrams will be produced. All of the stars have spectra displaying emission lines, appearing similar to LBVs, WN- transitional stars, and other types of extreme massive stars, all of which generate strong winds and have produced large mid-IR shells. These data will lead to a better understanding of the physics driving giant eruptions and LBV variability.

Program Type: Standard/Galactic

Scheduled Nights:
Run 1 (2016B):  CT-1.3m/ANDI -- 50hrs


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