An equatorial ultra iron-poor star identified in BOSS

¹ Instituto de Astrofísica de Canarias, Vía Láctea, 38205 La Laguna, Tenerife, Spain
e-mail: callende@iac.es
² Universidad de La Laguna, Departamento de Astrofísica, 38206 La Laguna, Tenerife, Spain
³ Consejo Superior de Investigaciones Científicas, Spain
⁴ Department of Astronomy and Space Science, Chungnam National University, 305-764 Daejeon, Republic of Korea
⁵ Dept. of Physics and JINA Center for the Evolution of the Elements, University of Notre Dame, Notre Dame, IN 46556, USA
⁶ UCO/Lick Observatory, University of California, Santa Cruz, CA 95064, USA
⁷ Department of Astronomy, University of Florida, Bryant Space Science Center, Gainesville, FL 32611-2055, USA

Received: 15 February 2015
Accepted: 13 May 2015

Abstract

We report the discovery of SDSS J131326.89−001941.4, an ultra iron-poor red giant star ([Fe/H] ≃ −4.3) with a very high carbon abundance ([C/Fe] ≃ +2.5). This object is the fifth star in this rare class, and the combination of a fairly low effective temperature (T_eff ≃ 5300 K), which enhances line absorption, with its brightness (g = 16.9), makes it possible to measure the abundances of calcium, carbon and iron using a low-resolution spectrum from the Sloan Digital Sky Survey. We examine the carbon and iron abundance ratios in this star and other similar objects in the light of predicted yields from metal-free massive stars, and conclude that they are consistent. By way of comparison, stars with similarly low iron abundances but lower carbon-to-iron ratios deviate from the theoretical predictions.