NOAO >   Observing Info >   Approved Programs >   2016A-0287

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Program Information for 2016A-0287


PI: Nathan Smith, U. of Arizona, nathans@as.arizona.edu
Address: Department of Astronomy and Steward Observatory, 933 AVENUE, TUCSON, AZ 85721-0065 USA

Title: [Fe II] Kinematics of Galactic Luminous Blue Variables

Abstract: We propose to use the Phoenix spectrograph on Gemini South to obtain infrared high-resolution spectra of the [Fe II] 1.644 micron line in circumstellar nebulae of Galactic luminous blue variables (LBVs). The goal of the observations is to provide a high precision (few km/s) measurement of the systemic velocities of these stars using the centroid velocities of slow-moving circumstellar nebulae. Visual-wavelength spectra of the central stars are not suitable to derive a precise systemic velocity because the stellar spectra are dominated by wind emission with strong P Cygni profiles and even photospheric lines are contaminated by significant stellar variability. We have shown from previous low-resolution spectra that LBV nebulae have bright emission from [Fe II] in the near-IR. The reason we are interested in the systemic velocities is because LBVs have anomolous environments: A recent study found that LBVs, which are the most luminous stars in any star-forming galaxy, actually show a surprising degree of isolation from other massive stars. They seem to avoid clusters of O-type stars. This contradicts standard scenarios of massive star evolution that place LBVs in a brief transitional phase between O stars and Wolf-Rayet stars. The alternative hypothesis is that LBVs are preferentially the product of massive binary evolution, and that they are isolated from other massive stars because they have received a kick when their companion exploded in a supernovae. Our proposed observations will be a simple and direct test of this hypothesis, because if LBVs are runaway stars, some of them should have anomalous radial velocities compared to Galactic rotation and their surrounding stars.

Program Type: Standard/Galactic

Scheduled Nights:
Run 1 (2016A):  GEM-S-SVC/PHNX -- 20hrs band 1 (GS-2016A-Q-4)


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NOAO >   Observing Info >   Approved Programs >   2016A-0287

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