The first known Mira-type variable star in IC 1613

¹ Department of Astronomy, Sofia University, and Isaac Newton Institute of Chile, Bulgarian Branch, 1164 Sofia, Bulgaria
² Instituto de Astronomía, Universidad Nacional Autónoma de México, Apartado postal 70-264, 04510 México, D.F., México e-mail: georgiev@astroscu.unam.mx
³ Institute of Astronomy, Bulgarian Academy of Sciences, and Isaac Newton Institute of Chile, Bulgarian Branch, 72 Tsarigradsko Chaussèe, 1784 Sofia, Bulgaria e-mail: jura@haemimont.bg
⁴ Department of Astronomy, University of California, Berkeley, CA 94720 -3411, USA e-mail: (wli, alex, rtreffers)@astro.berkeley.edu

Corresponding author: R. Kurtev, kurtev@phys.uni-sofia.bg

Received: 2 May 2001
Accepted: 14 August 2001

Abstract

King et al. (1999) discovered Nova 1999 in IC 1613 at the Lick Observatory. Both Fugazza et al. ([CITE]) and Borissova et al. ([CITE]) questioned this classification, because they were able to detect the star on images obtained in previous years. In infrared frames taken on Oct. 15, 1998, Nova 1999 has and mag. Our light curve study, based primarily on 92 unfiltered Lick images, suggested that the object could be a Mira-type variable with a period of 640.7 days. This period is very close to that obtained by Fugazza et al. ([CITE]) - 631 days. The star is overluminous with respect to the period-luminosity (PL) relation derived by Feast et al. ([CITE]) for Mira variables in the LMC. At longer periods , many LMC Miras show such behavior and the PL relation appears to break down. It is possible that the situation in IC 1613 is similar. An optical spectrum obtained with the Keck-II telescope shows features typical of M3Ie or M3IIIe stars. We conclude that the star is a normal long-period M-type Mira variable, the first such star confirmed in IC 1613.