Confirmation of the Luminous Blue Variable nature of AFGL 2298

¹ Department of Physics and Astronomy, University College London, Gower Street, London, WC1E 6BT, England, UK
² Astronomical Institute of St. Petersburg University, Petrodvorets, Universitetsky pr. 28, 198504 St. Petersburg, Russia
³ Isaac Newton Institute of Chile, St. Petersburg Branch
⁴ US Air Force Research Laboratory, Space Vehicles Directorate, 29 Randolph Road, Hanscom AFB, MA 01731-3010, USA
⁵ Central Astronomical Observatory, 196140 St. Petersburg, Russia

Corresponding author: J. S. Clark, jsc@star.ucl.ac.uk

Received: 22 January 2003
Accepted: 13 March 2003

Abstract

We present new photometric and spectroscopic observations of the stellar source AFGL 2298 (= IRAS 18576+0341) that has recently been proposed as a candidate Luminous Blue Variable (LBV). Our data confirm that the star is a highly luminous B supergiant which is both spectroscopically and photometrically variable. Assuming a distance of 10 kpc, comparison of the 2001 June data to synthetic spectra suggest stellar parameters of kK, log and yr^-1. Data obtained in 2002 August indicate an increase in both temperature (=15 kK) and mass loss rate (= yr^-1) at constant bolometric luminosity. These physical parameters place AFGL 2298 at the Humphreys-Davidson limit for the most luminous stars known. We conclude that the position of AFG 2298 in the HR diagram, the significant variability observed between 1999-2002 and presence of a massive ejection nebula are consistent with a classification of AFGL 2298 as a bona fide LBV.