SIMBAD references

2013AJ....145..125V - Astron. J., 145, 125 (2013/May-0)

The distance to the massive Galactic cluster Westerlund 2 from a spectroscopic and HST photometric study.

VARGAS ALVAREZ C.A., KOBULNICKY H.A., BRADLEY D.R., KANNAPPAN S.J., NORRIS M.A., COOL R.J. and MILLER B.P.

Abstract (from CDS):

We present a spectroscopic and photometric determination of the distance to the young Galactic open cluster Westerlund 2 using WFPC2 imaging from the Hubble Space Telescope (HST) and ground-based optical spectroscopy. HST imaging in the F336W, F439W, F555W, and F814W filters resolved many sources previously undetected in ground-based observations and yielded photometry for 1136 stars. We identified 15 new O-type stars, along with two probable binary systems, including MSP 188 (O3 + O5.5). We fit reddened spectral energy distributions based on the Padova isochrones to the photometric data to determine individual reddening parameters RV and AVfor O-type stars in Wd2. We find average values < RV > = 3.77±0.09 and < AV > = 6.51 ±0.38 mag, which result in a smaller distance than most other spectroscopic and photometric studies. After a statistical distance correction accounting for close unresolved binaries (factor of 1.08), our spectroscopic and photometric data on 29 O-type stars yield that Westerlund 2 has a distance < d > = 4.16±0.07 (random) +0.26 (systematic) kpc. The cluster's age remains poorly constrained, with an upper limit of 3 Myr. Finally, we report evidence of a faint mid-IR polycyclic aromatic hydrocarbon ring surrounding the well-known binary candidate MSP 18, which appears to lie at the center of a secondary stellar grouping within Westerlund 2.

Abstract Copyright:

Journal keyword(s): open clusters and associations: individual: Westerlund 2 - stars: early-type - stars: fundamental parameters

VizieR on-line data: <Available at CDS (J/AJ/145/125): table2.dat table3.dat table4.dat table5.dat table6.dat>

Nomenclature: Table 2: [VKB2013] NNNN (Nos 1-1136).

Status at CDS:   being processed
// All or part of tables of objects will be ingested in SIMBAD with priority 1.

CDS comments: HESS J1023-5746 not identified (not in the HESS Source Catalog).

Simbad objects: 1156

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2020.04.03-22:22:31

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