Analysis of the WN star WR 102c, its WR nebula, and the associated cluster of massive stars in the Sickle Nebula^⋆

¹ Institute of Physics and Astronomy, University of Potsdam, 14476 Potsdam, Germany
e-mail: msteinke@astro.physik.uni-potsdam.de; lida@astro.physik.uni-potsdam.de
² I. Physikalisches Institut der Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany
³ Leibniz Institute for Astrophysics Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany

Received: 3 November 2015
Accepted: 13 January 2016

Abstract

Context. The massive Wolf-Rayet type star WR 102c is located near the Quintuplet Cluster, one of the three massive star clusters in the Galactic centre region. Previous studies indicated that WR 102c may have a dusty circumstellar nebula and is among the main ionising sources of the Sickle Nebula associated with the Quintuplet Cluster.

Aims. The goals of our study are to derive the stellar parameters of WR 102c from the analysis of its spectrum and to investigate its stellar and nebular environment.

Methods. We obtained observations with the ESO VLT integral field spectrograph SINFONI in the K-band, extracted the stellar spectra, and analysed them by means of stellar atmosphere models.

Results. Our new analysis supersedes the results previously reported for WR 102c. We significantly decrease its bolometric luminosity and hydrogen content. We detect four early OB type stars close to WR 102c. These stars have radial velocities similar to that of WR 102c. We suggest that together with WR 102c these stars belong to a distinct star cluster with a total mass of ~ 1000 M_⊙. We identify a new WR nebula around WR 102c in the SINFONI map of the diffuse Brγ emission and in the HST Paα images. The Brγ line at different locations is not significantly broadened and similar to the width of nebular emission elsewhere in the H ii region around WR 102c.

Conclusions. The massive star WR 102c located in the Galactic centre region resides in a star cluster containing additional early-type stars. The stellar parameters of WR 102c are typical for hydrogen-free WN6 stars. We identify a nebula surrounding WR 102c that has a morphology similar to other nebulae around hydrogen-free WR stars, and propose that the formation of this nebula is linked to interaction of the fast stellar wind with the matter ejected at a previous evolutionary stage of WR 102c.