Optical BVRI Photometry of Common Proper Motion F/G/K+M Wide Separation Binaries

TL;DR

This study provides precise optical photometry for 76 wide separation binary pairs with F/G/K primaries and M secondaries, enabling improved classification and metallicity estimation of M-type stars.

Contribution

It offers high-precision BVRI photometry for a large sample of wide binaries, distinguishing dwarf and subdwarf candidates using an improved RPM diagram.

Findings

Subdwarf candidates show larger V-R colors at a given V-I, indicating lower metallicity.

Photometry precision is approximately 0.03 mag across all bands.

The data supports models predicting metallicity differences between dwarf and subdwarf populations.

Abstract

We present optical (BVRI) photometric measurements of a sample of 76 common proper motion wide separation main sequence binary pairs. The pairs are composed of a F-, G-, or K-type primary star and an M-type secondary. The sample is selected from the revised NLTT catalog and the LSPM catalog. The photometry is generally precise to 0.03 mag in all bands. We separate our sample into two groups, dwarf candidates and subdwarf candidates, using the reduced proper motion (RPM) diagram constructed with our improved photometry. The M subdwarf candidates in general have larger $V-R$ colors than the M dwarf candidates at a given $V-I$ color. This is consistent with an average metallicity difference between the two groups, as predicted by the PHOENIX/BT-Settl models. The improved photometry will be used as input into a technique to determine the metallicities of the M-type stars.