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.
Description
Signatures of unresolved binaries in stellar spectra: implications for
spectral fitting
%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
}