Miras around the Galactic Center

TL;DR

This study uses near-IR observations of Miras to determine the distance to the Galactic Center and analyze its variable extinction, employing a new method for simultaneous distance and extinction estimation.

Contribution

The paper introduces a method for estimating distances and extinctions of Miras using period-luminosity relations in multiple bands, applicable to a wide period range.

Findings

Estimated the distance modulus of the Galactic Center as 14.58 mag.

Detected 1364 long-period variables in the surveyed field.

Found large, highly variable extinction towards the Galactic Center.

Abstract

We report results of our near-IR survey for variables in a field of view of 20 arcmin by 30 arcmin towards the Galactic Center (GC), where we detected 1364 long-period variables. We have established a method for the simultaneous estimation of distances and extinctions using the period-luminosity relations for the JHKs bands. Our method is applicable to Miras with periods in the range 100-350 days and mean magnitudes available in two or more filters. Here we discuss 143 Miras whose distances and extinctions were obtained based on their periods and H- and Ks-band magnitudes. We find that almost all of them are located at the same distance to within our accuracy, and the distance modulus of the GC is estimated to be 14.58+-0.02+-0.11 mag. The former error corresponds to the statistical error and the latter to the systematic one which includes the uncertainty of our assumed distance modulus of the LMC (18.45+-0.05 mag). We also discuss the large and highly variable extinction towards the GC.