The ACS LCID Project. II. Faint Variable Stars in the Isolated Dwarf Irregular Galaxy IC1613
Edouard J. Bernard, Matteo Monelli, Carme Gallart, Antonio Aparicio, Santi Cassisi, Igor Drozdovsky, Sebastian L. Hidalgo, Evan D. Skillman, Peter B. Stetson
备注：
20 pages, 17 figures, in emulateapj format. Accepted for publication in ApJ. Several figures degraded. See http://www.iac.es/project/LCID/?p=publications for a version with full resolution figures
(Abridged) We present the results of a new search for variable stars in the Local Group (LG) isolated dwarf galaxy IC1613, based on 24 orbits of F475W and F814W photometry from the ACS camera onboard the HST. We detected 259 candidate variables in this field, of which only 13 (all of them bright Cepheids) were previously known. Out of the confirmed variables, we found 90 RR Lyrae stars, 49 classical Cepheids (including 36 new discoveries), and 38 eclipsing binary stars for which we could determine a period. The RR Lyrae include 61 fundamental (RRab) and 24 first-overtone (RRc) pulsators, and 5 pulsating in both modes simultaneously (RRd). As for the majority of LG dwarfs, the mean periods of the RRab and RRc (0.611 and 0.334 day, respectively) as well as the fraction of overtone pulsators (f_c=0.28) place this galaxy in the intermediate regime between the Oosterhoff types. From their position on the period-luminosity diagram and light-curve morphology, we can unambiguously classify 25 and 14 Cepheids as fundamental and first-overtone mode pulsators, respectively. Another two are clearly second-overtone Cepheids, the first ones to be discovered beyond the Magellanic Clouds. We estimate the distance to IC1613 using various methods based on the photometric and pulsational properties of the Cepheids and RR Lyrae stars. The values we find are in very good agreement with each other and with previous estimates based on independent methods. When corrected to a common reddening of E(B-V)=0.025 and true LMC distance modulus of (m-M)_{LMC,0}=18.515+-0.085, we find that all the distance determinations from the literature converge to a common value of (m-M)_0=24.400+-0.014 (statistical), or 760 kpc.
Galaxy UV Legacy Project: Survey Description and First Insights Into NGC 4449 Recent History of Star Formation
Gemini Observatory/NSFs NOIRLab（双子座天文台/美国国家光学红外天文研究实验室）；Space Telescope Science Institute（太空望远镜科学研究所）；AURA for the European Space Agency (ESA), ESA Office, Space Telescope Science Institute（欧洲航天局（ESA）办公室，太空望远镜科学研究所）；Dept. of Astronomy, University of Massachusetts, Amherst（马萨诸塞大学阿默斯特分校天文学系）；Department of Physics, The University of Auckland（奥克兰大学物理系）；Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg（海德堡大学天文学计算研究所）；University of Arizona（亚利桑那大学）；Astrophysics Research Cluster, School of Mathematical and Physical Sciences, University of Sheffield（谢菲尔德大学数理科学学院天体物理学研究集群）；Department of Astronomy, O（天文学系）
