Cepheids and other short-period variables near the Galactic Centre

TL;DR

This study conducted a near-infrared survey of short-period variable stars near the Galactic Centre, discovering various types including Cepheids and eclipsing binaries, and used these to estimate the distance to the Galactic Centre.

Contribution

First near-infrared survey of short-period variables in the Galactic Centre, classifying new variables and refining distance estimates using Cepheids and reddening law validation.

Findings

Discovered 45 variable stars, including 16 type II Cepheids and 24 eclipsing binaries.

Estimated the distance to the Galactic Centre consistent with previous kinematic measurements.

Supported the reddening law A(Ks)/E(H-Ks)=1.44 based on distance estimates.

Abstract

We report the result of our near-infrared survey of short-period variable stars (P<60d) in a field-of-view of 20'x30' towards the Galactic Centre. Forty-five variables are discovered and we classify the variables based on their light curve shapes and other evidence. In addition to 3 classical Cepheids reported previously, we find 16 type II Cepheids, 24 eclipsing binaries, one pulsating star with P=0.265d (RR Lyr or delta Sct) and one Cepheid-like variable whose nature is uncertain. Eclipsing binaries are separated into the foreground objects and those significantly obscured by interstellar extinction. One of the reddened binaries contains an O-type supergiant and its light curve indicates an eccentric orbit. We discuss the nature and distribution of type II Cepheids as well as the distance to the Galactic Centre based on these Cepheids and other distance indicators. The estimates of R0(GC) we obtained based on photometric data agree with previous results obtained with kinematics of objects around the GC. Furthermore, our result gives a support to the reddening law obtained by Nishiyama and collaborators, A(Ks)/E(H-Ks)=1.44, because a different reddening law would result in a rather different distance estimate.