/ftp/cats/aliases/V//VKB2013



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J/AJ/145/125   Spectroscopy and HST photometry in Westerlund 2   (Vargas+, 2013)
The following files can be converted to FITS (extension .fit or fit.gz)
	table2.dat table3.dat table4.dat table5.dat table6.dat
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Query from: http://vizier.cds.unistra.fr/viz-bin/VizieR?-source=J/AJ/145/125
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Beginning of ReadMe : J/AJ/145/125 Spectroscopy and HST photometry in Westerlund 2 (Vargas+, 2013) ================================================================================ 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., Miller B.P. <Astron. J., 145, 125 (2013)> =2013AJ....145..125V ================================================================================ ADC_Keywords: Clusters, open ; Stars, early-type ; Photometry, HST ; Cross identifications ; Extinction ; Spectral types Keywords: open clusters and associations: individual: Westerlund 2 - stars: early-type - stars: fundamental parameters Abstract: 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 MSP188 (O3+O5.5). We fit reddened spectral energy distributions based on the Padova isochrones to the photometric data to determine individual reddening parameters R_V_ and A_V_for O-type stars in Wd2. We find average values <R_V_>=3.77+/-0.09 and <A_V_>=6.51+/-0.38mag, 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 3Myr. 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. Description: The cluster Westerlund 2 was observed on 2005 May 19 and on 2005 May 20 using the Wide-Field Planetary Camera 2 (WFPC2) on board HST (with the filters F336W, F439W, F555W, and F814W; Table2). The observations were performed during Cycle 13, proposal ID 10276, PI H. Kobulnicky, and HST program 8zt. In Table2, UBVI magnitudes are transformed from the HST to Johnson system. Longslit spectra were obtained for 10 sources from Moffat et al. (1991AJ....102..642M) with the 6.5m Magellan I Walter Baade Telescope (located at Las Campanas Observatory, Chile) and the 4.1m SOAR (Southern Astrophysical Research) telescope, using the Inamori-Magellan Areal Camera and Spectrograph (IMACS) and the Goodman High Throughput Spectrograph (GHTS), respectively. Spectra for six stars (528, 640, 714, 738, 857, and 906 in our numeration system) were obtained on 2011 April 6/7 with the Magellan Telescope. The sources 137, 549, 1004, and 1031 were observed on 2011 June 9 and 10 with SOAR. We obtained spectra of stars 714 and 738 with the Magellan Inamori Kyocera Echelle (MIKE) spectrograph on the Magellan II Clay telescope on 2011 November 14.