# Massive Stars

## Summary

Spectra of massive stars: OB dwarfs and red supergiants

## Finding Targets

An object whose APOGEE_TARGET1 value includes one or more of the bitmasks in the following table was targeted for spectroscopy as part of this ancillary target program. See SDSS-III bitmasks to learn how to use these values to identify objects in this ancillary target program.

APOGEE_TARGET1
bit name
Bit Target Description
APOGEE_MASSIVE_STAR 25 OB or red supergiant star

## Description

This ancillary project is targeting OB stars and red supergiants (RSGs) in a two-pronged study of obscured massive stars. The first goal is to compile a spectral library of known OB stars. These objects’ young ages imply that they reflect the present properties of the ISM, and their rapid evolution means that even a relatively small sample of these stars provides us with multiple snapshots of different evolutionary phases. As the progenitors of supernovae, OB stars are some of the primary drivers of galactic chemical evolution.

The second goal of this ancillary program is to observe a number of main-sequence stars and RSGs located in the massive star-forming regions near Galactic longitude ~ 30°. These regions, often referred to collectively as the Scutum Complex (e.g., Davies et al. 2007; Negueruela et al. 2012), contain a large number of massive (M ≥ 105 M) but highly-obscured clusters in which only the RSGs have been observed spectroscopically. Multiple theories to explain this high concentration of massive clusters have been proposed, but the lack of absolute luminosity or robust distance estimates has so far prevented clear discrimination amongst these scenarios.

## Primary contact

Artemio Herrero Davó
Instituto de Astrofisica de Canarias
ahd -at- iac.es

## Other contacts

M. Garcia, S. Ramirez Alegria

## Target Selection Details

The early-type stars for this ancillary program are drawn from the Galactic O-Stars Spectroscopic Survey (Sota et al. 2011), in which all of the stars have a well-established spectral type and luminosity class. Cluster RSGs are selected to have 8 ≤ H ≤ 10 mag (Vega), (J-K) > 0.75, and color index 0.1 < QIR < 0.4 (following Comerón et al. 2002), while the unevolved stars are selected using the IR pseudo-color technique of Negueruela et al. (2010) and have magnitudes as faint as H ~ 14.8 mag.

## REFERENCES

Comerón, F., Pasquali, A., Rodighiero, G., et al. 2002, A&A, 389, 874
Davies, B., Figer, D. F., Kudritzki, R.-P., et al. 2007, ApJ, 671, 781
Negueruela, I., Clark, J. S., & Ritchie, B. W. 2010, A&A, 516, A78
Negueruela, I., Marco, A., González-Fernández, C., et al. 2012, A&A, 547, A15
Sota, A., et al. 2011, Bulletin de la Societe Royale des Sciences de Liege, 80, 519