%0 Generic %1 elbadry2017signatures %A El-Badry, Kareem %A Rix, Hans-Walter %A Ting, Yuan-Sen %A Weisz, Daniel R. %A Bergemann, Maria %A Cargile, Phillip %A Conroy, Charlie %A Eilers, Anna-Christina %D 2017 %K multiplicity %T Signatures of unresolved binaries in stellar spectra: implications for spectral fitting %U http://arxiv.org/abs/1709.03983 %X The observable spectrum of an unresolved binary star system is a superposition of two single-star spectra. Even without a detectable velocity offset between the two stellar components, the combined spectrum of a binary system is in general different from that of either component, and fitting it with single-star models may yield inaccurate stellar parameters and abundances. We perform simple experiments with synthetic spectra to investigate the effect of unresolved main-sequence binaries on spectral fitting, modeling spectra similar to those collected by the APOGEE, GALAH, and LAMOST surveys. We find that fitting unresolved binaries with single-star models introduces systematic biases in the derived stellar parameters and abundances that are modest but certainly not negligible, with typical systematic errors of $300\,K$ in $T_eff$ and $0.1\,dex$ in $Fe/H$ for APOGEE-like spectra of solar-type stars. These biases are smaller for spectra at optical wavelengths than in the near-infrared. We show that biases can be corrected by fitting spectra with a binary model, which adds only two labels to the fit and includes single-star models as a special case. Our model provides a promising new method to constrain the Galactic binary population, including systems with single-epoch spectra and no detectable velocity offset between the two stars.

@misc{elbadry2017signatures, abstract = {The observable spectrum of an unresolved binary star system is a superposition of two single-star spectra. Even without a detectable velocity offset between the two stellar components, the combined spectrum of a binary system is in general different from that of either component, and fitting it with single-star models may yield inaccurate stellar parameters and abundances. We perform simple experiments with synthetic spectra to investigate the effect of unresolved main-sequence binaries on spectral fitting, modeling spectra similar to those collected by the APOGEE, GALAH, and LAMOST surveys. We find that fitting unresolved binaries with single-star models introduces systematic biases in the derived stellar parameters and abundances that are modest but certainly not negligible, with typical systematic errors of $300\,\rm K$ in $T_{\rm eff}$ and $0.1\,\rm dex$ in $[\rm Fe/H]$ for APOGEE-like spectra of solar-type stars. These biases are smaller for spectra at optical wavelengths than in the near-infrared. We show that biases can be corrected by fitting spectra with a binary model, which adds only two labels to the fit and includes single-star models as a special case. Our model provides a promising new method to constrain the Galactic binary population, including systems with single-epoch spectra and no detectable velocity offset between the two stars.}, added-at = {2017-09-14T23:56:14.000+0200}, author = {El-Badry, Kareem and Rix, Hans-Walter and Ting, Yuan-Sen and Weisz, Daniel R. and Bergemann, Maria and Cargile, Phillip and Conroy, Charlie and Eilers, Anna-Christina}, biburl = {https://www.bibsonomy.org/bibtex/209f0f10bfe9a3313058cb7d581f5f047/superjenwinters}, description = {Signatures of unresolved binaries in stellar spectra: implications for spectral fitting}, interhash = {a0a106ebab552f1437a0cdb20506bc65}, intrahash = {09f0f10bfe9a3313058cb7d581f5f047}, keywords = {multiplicity}, note = {cite arxiv:1709.03983Comment: Submitted to MNRAS. 7 pages, 5 figures}, timestamp = {2017-09-14T23:56:14.000+0200}, title = {Signatures of unresolved binaries in stellar spectra: implications for spectral fitting}, url = {http://arxiv.org/abs/1709.03983}, year = 2017 }