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Abstract: We report the results of a near-infrared survey for long-period variables ina field of view of 20 arcmin by 30 arcmin towards the Galactic Centre GC. Wehave detected 1364 variables, of which 348 are identified with those reportedin Glass et al. 2001. We present a catalogue and photometric measurements forthe detected variables and discuss their nature. We also establish a method forthe simultaneous estimation of distances and extinctions using theperiod-luminosity relations for the JHKs bands. Our method is applicable toMiras with periods in the range 100-350 d and mean magnitudes available in twoor more filter bands. While J-band means are often unavailable for our objectsbecause of the large extinction, we estimated distances and extinctions for 143Miras whose H- and Ks-band mean magnitudes are obtained. We find that most arelocated at the same distance to within our accuracy. Assuming that thebarycentre of these Miras corresponds to the GC, we estimate its distancemodulus to be 14.58+-0.02stat.+-0.11syst. mag, corresponding to8.24+-0.08stat.+-0.42syst. kpc. We have assumed the distance modulus to theLMC to be 18.45 mag, and the uncertainty in this quantity is included in thesystematic error above. We also discuss the large and highly variableextinction. Its value ranges from 1.5 mag to larger than 4 mag in AKs excepttowards the thicker dark nebulae and it varies in a complicated way with theline of sight. We have identified mid-infrared counterparts in the Spitzer-IRACcatalogue of Ramirez et al. 2008 for most of our variables and find that theyfollow rather narrow period-luminosity relations in the 3.6 to 8.0 micrometrewavelength range.



Author: Noriyuki Matsunaga 1 and 2, Takahiro Kawadu 2, Shogo Nishiyama 2, Takahiro Nagayama 3 and 2, Hirofumi Hatano 3, Motohide Tamura 4

Source: https://arxiv.org/







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