UBVIc photometry of stars in Westerlund 2 Virtual Observatory Resource

Authors
  1. Carraro G.
  2. Turner D.
  3. Majaess D.
  4. Baume G.
  5. Published by
    CDS
Abstract

A new X-ray, UBVIc, and JHKs study of the young cluster Westerlund 2 was undertaken to resolve discrepancies tied to the cluster's distance. Existing spectroscopic observations for bright cluster members and new multi-band photometry imply a reddening relation toward Westerlund 2 described by E(U-B)/E(B-V)=0.63+0.02E(B-V). Variable-extinction analyses for Westerlund 2 and nearby IC 2581 based upon spectroscopic distance moduli and ZAMS fitting yield values of R_V_=A_V_/E(B-V)=3.88+/-0.18 and 3.77+/-0.19, respectively, and confirm prior assertions that anomalous interstellar extinction is widespread throughout Carina. The results were confirmed by applying the color-difference method to UBVRIcJHKs data for 19 spectroscopically observed cluster members, yielding R_V_=3.85+/-0.07. The derived distance to Westerlund 2 of d=2.85+/-0.43kpc places the cluster on the far side of the Carina spiral arm. The cluster's age is no more than {tau}~2x10^6^yr as inferred from the cluster's brightest stars and an X-ray (Chandra) cleaned analysis of its pre-main-sequence demographic. Four Wolf-Rayet stars in the cluster core and surrounding corona (WR20a, WR20b, WR20c, and WR20aa) are very likely cluster members, and their inferred luminosities are consistent with those of other late-WN stars in open clusters. The color-magnitude diagram for Westerlund 2 also displays a gap at spectral type B0.5~V with associated color spread at higher and lower absolute magnitudes that might be linked to close binary mergers. These features, in conjunction with the evidence for mass loss from the WR stars, may help to explain the high flux of {gamma}-rays, cosmic rays, and X-rays from the direction toward Westerlund 2.

Keywords
  1. open-star-clusters
  2. early-type-stars
  3. ccd-photometry
Bibliographic source Bibcode
2013A&A...555A..50C
See also HTML
https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/555/A50
IVOA Identifier IVOID
ivo://CDS.VizieR/J/A+A/555/A50
Document Object Identifer DOI
doi:10.26093/cds/vizier.35550050

Access

Web browser access HTML
https://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/555/A50
https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/555/A50
http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/555/A50
IVOA Table Access TAP
https://tapvizier.cds.unistra.fr/TAPVizieR/tap
Run SQL-like queries with TAP-enabled clients (e.g., TOPCAT).
IVOA Cone Search SCS
For use with a cone search client (e.g., TOPCAT).
https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/555/A50/cluster?
https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/555/A50/cluster?
http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/555/A50/cluster?

History

2013-06-27T09:19:11Z
Resource record created
2013-06-27T09:19:11Z
Created
2013-12-29T23:00:10Z
Updated

Contact

Name
CDS support team
Postal Address
CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France
E-Mail
cds-question@unistra.fr