J/AJ/145/125ivo://CDS.VizieR/J/AJ/145/125doi:10.26093/cds/vizier.51450125CDSVargas Alvarez C.A.Kobulnicky H.A.Bradley D.R.Kannappan S.J.,Norris M.A.Cool R.J.Miller B.P.2017-07-04T07:08:18Z2014-05-22T07:09:01ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.fropen-star-clustersearly-type-starshst-photometryastronomical-object-identificationextinctionstellar-spectral-typesWe 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 2.2013AJ....145..125Vhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/AJ/145/125CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toIII/195 : Atlas of Optical Spectral Classification OB Stars (Walborn+ 1990)J/A+A/555/A50 : UBVIc photometry of stars in Westerlund 2 (Carraro+, 2013)J/A+A/466/137 : Westerlund 2 JHKs photometry (Ascenso+, 2007)J/A+A/463/981 : BV CCD photometry in Westerlund 2 (Rauw+, 2007)J/ApJ/663/320 : IR-through-UV extinction curve (Fitzpatrick+, 2007)J/A+AS/127/423 : VI photometry of Westerlund 1 and 2 (Piatti+ 1998)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/AJ/145/125https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/AJ/145/125http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/AJ/145/125https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/AJ/145/125https://vizier.iucaa.in/viz-bin/votable?-source=J/AJ/145/125http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/AJ/145/125GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/AJ/145/125/table2 (HST photometry)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/AJ/145/125/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/AJ/145/125/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/AJ/145/125/table2?GETtext/xml+votable180.050000true155.93865-57.757190.0055555555555555566/373432.0401237512456292e-19 6.367785378457404e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/AJ/145/125?format=asciiOpticaldefaultJ/AJ/145/125/table2HST photometryrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintStar[1/1136] Running star number (<[VKB2013] NNNN> in Simbad)meta.id;meta.mainintprimarySSimbad column added by the CDSmeta.ref.urlcharM+91? Moffat et al. (1991AJ....102..642M) identifiermeta.idintnullablem_M+91Multiplicity flag on M+91 (a, b, c, d) (G1)meta.code.multipcharRAJ2000Right Ascension in decimal degrees (J2000)degpos.eq.ra;meta.mainDEJ2000Declination in decimal degrees (J2000)degpos.eq.dec;meta.mainF336W? HST/WFPC2 F336W band magnitudemagphot.mag;em.opt.Ufloatnullablee_F336W? The 1{sigma} uncertainty in F336Wmagstat.errorfloatnullableF439W? HST/WFPC2 F439W band magnitudemagphot.mag;em.opt.Bfloatnullablee_F439W? The 1{sigma} uncertainty in F439Wmagstat.errorfloatnullableF555W? HST/WFPC2 F555W band magnitudemagphot.mag;em.opt.Vfloatnullablee_F555W? The 1{sigma} uncertainty in F555Wmagstat.errorfloatnullableF814W? HST/WFPC2 F814W band magnitudemagphot.mag;em.opt.Ifloatnullablee_F814W? The 1{sigma} uncertainty in F814Wmagstat.errorfloatnullableUmag? Standard U band magnitudemagphot.mag;em.opt.UfloatnullableBmag? Standard B band magnitudemagphot.mag;em.opt.BfloatnullableVmag? Standard V band magnitudemagphot.mag;em.opt.VfloatnullableImag? Standard I band magnitudemagphot.mag;em.opt.IfloatnullableS/NSignal-to-Noise ratiostat.snrfloatD[sl] Detection of the star (s=on short exposure image, l=on long exposure image) (1)meta.codecharSimbadSimbad column added by the CDSmeta.ref.urlcharJ/AJ/145/125/table3New spectral classificationrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintGrGroup of stars (A, OB, F, U) (1)meta.code.classcharStar[137/1031] Running star numbermeta.id;meta.mainintf_StarSpectroscopic flag on Star (a, b, or/and c) (2)meta.codecharM+91? Moffat et al. (1991AJ....102..642M) identifiermeta.idintnullablem_M+91Multiplicity flag on M+91 (a, b, c) (G1)meta.code.multipcharVmag[13.464/18.982] The V band magnitudemagphot.mag;em.opt.VfloatB-V[0.373/1.66] The B-V color indexmagphot.color;em.opt.B;em.opt.Vfloatl_EWII[<] Upper limit flag on EWIImeta.code.errorcharEWII? Measured equivalent width for HeII lines ({lambda}5411); in {AA} (3)0.1nmspect.line.eqWidthfloatnullablee_EWII? Uncertainty in EWII0.1nmstat.errorfloatnullableEWI? Measured equivalent width for HeI lines ({lambda}5876); in {AA} (3)0.1nmspect.line.eqWidthfloatnullablee_EWI? Uncertainty in EWI0.1nmstat.errorfloatnullableREW? EWII/EWI Ratio (4)spect.line.eqWidthfloatnullablee_REW? Uncertainty in REWstat.errorfloatnullableTeff? Stellar effective temperature (5)Kphys.temperature.effectiveintnullablee_Teff? Uncertainty in TeffKstat.error;phys.temperature.effectiveintnullableSpTMK spectral type (6)src.spTypecharTelTelescope (7)meta.id;instr.telcharJ/AJ/145/125/reddeningReddening summarye_Av3Uncertainty in Av3magstat.errorfloatrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintStar[137/1039]? Running star number, as in table2 (blank for average)meta.recordintnullablef_Star[ab] Photometric flag on Star (a or b) (G2)meta.codecharSpTAdopted MK spectral typesrc.spTypecharA[A] A=the following columns give the Average R_V_ and A_V_ values for the clusterphys.absorptioncharRv1Best-fitting ratio of selective to total extinction using the method of Cardelli et al. (1989ApJ...345..245C) (R_V_=A_V_/E(B-V))magphys.absorptionfloate_Rv1Uncertainty in Rv1magstat.errorfloatRv2Best-fitting ratio of selective to total extinction using the method of Fitzpatrick (2004ASPC..309...33F) (R_V_=A_V_/E(B-V))magphys.absorptionfloate_Rv2Uncertainty in Rv2magstat.errorfloatRv3Best-fitting ratio of selective to total extinction using the method of Fitzpatrick & Massa (2007, J/ApJ/663/320) (R_V_=A_V_/E(B-V))magphys.absorptionfloate_Rv3Uncertainty in Rv3magstat.errorfloatRv4Best-fitting ratio of selective to total extinction using the method of Fitzpatrick & Massa (2009ApJ...699.1209F) (R_V_=A_V_/E(B-V))magphys.absorptionfloate_Rv4Uncertainty in Rv4magstat.errorfloat<Rv>The average ratio of selective to total extinctionmagphys.absorption.gal;arith.ratio;stat.meanfloate_<Rv>Uncertainty in <Rv>magstat.errorfloatAv1Best-fitting extinction using the method of Cardelli et al. (1989ApJ...345..245C)magphys.absorptionfloate_Av1Uncertainty in Av1magstat.errorfloatAv2Best-fitting extinction using the method of Fitzpatrick (2004ASPC..309...33F)magphys.absorptionfloate_Av2Uncertainty in Av2magstat.errorfloatAv3Best-fitting extinction using the method of Fitzpatrick & Massa (2007, cat. J/ApJ/663/320)magphys.absorptionfloatAv4Best-fitting extinction using the method of Fitzpatrick & Massa (2009ApJ...699.1209F)magphys.absorptionfloate_Av4Uncertainty in Av4magstat.errorfloat<Av>[5.75/7.49] The average extinctionmagphys.absorptionfloate_<Av>Uncertainty in <Av>magstat.errorfloatA1The F336W filter extinction for Cardelli et al. (1989ApJ...345..245C)magphys.absorptionfloate_A1Uncertainty in A1magstat.errorfloatA2The F336W filter extinction for Fitzpatrick (2004ASPC..309...33F)magphys.absorptionfloate_A2Uncertainty in A2magstat.errorfloatA3The F336W filter extinction for Fitzpatrick & Massa (2007, cat. J/ApJ/663/320)magphys.absorptionfloate_A3Uncertainty in A3magstat.errorfloat<A336>[8.7/11.35] The F336W filter average extinctionmagphys.absorptionfloate_<A336>Uncertainty in <A336>magstat.errorfloatA4The F439W filter extinction for Cardelli et al. (1989ApJ...345..245C)magphys.absorptionfloate_A4Uncertainty in A4magstat.errorfloatA5The F439W filter extinction for Fitzpatrick (2004ASPC..309...33F)magphys.absorptionfloate_A5Uncertainty in A5magstat.errorfloatA6The F439W filter extinction for Fitzpatrick & Massa (2007, cat. J/ApJ/663/320)magphys.absorptionfloate_A6Uncertainty in A6magstat.errorfloat<A439>[7.46/9.79] The F439W filter average extinctionmagphys.absorptionfloate_<A439>Uncertainty in <A439>magstat.errorfloatA7The F555W filter extinction for Cardelli et al. (1989ApJ...345..245C)magphys.absorptionfloate_A7Uncertainty in A7magstat.errorfloatA8The F555W filter extinction for Fitzpatrick (2004ASPC..309...33F)magphys.absorptionfloate_A8Uncertainty in A8magstat.errorfloatA9The F555W filter extinction for Fitzpatrick & Massa (2007, cat. J/ApJ/663/320)magphys.absorptionfloate_A9Uncertainty in A9magstat.errorfloat<A555>[5.85/7.68] The F555W filter average extinctionmagphys.absorptionfloate_<A555>Uncertainty in <A555>magstat.errorfloatA10The F814W filter extinction for Cardelli et al. (1989ApJ...345..245C)magphys.absorptionfloate_A10Uncertainty in A10magstat.errorfloatA11The F814W filter extinction for Fitzpatrick (2004ASPC..309...33F)magphys.absorptionfloate_A11Uncertainty in A11magstat.errorfloatA12The F814W filter extinction for Fitzpatrick & Massa (2007, cat. J/ApJ/663/320)magphys.absorptionfloate_A12Uncertainty in A12magstat.errorfloat<A814>[3.65/6.62] The F814W filter average extinctionmagphys.absorptionfloate_<A814>Uncertainty in <A814>magstat.errorfloatJ/AJ/145/125/table6Distance calculationSpTMK spectral typesrc.spTypecharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintStar[137/1039] Running star numbermeta.id;meta.mainintM+91? Moffat et al. (1991AJ....102..642M) numbermeta.idintnullablem_M+91Multiplicity flag on M+91 (a, b, c, d) (G1)meta.code.multipcharf_SpT[*] Determined by Rauw et al. (2007, cat. J/A+A/463/981; 2011A&A...535A..40R)meta.codecharF555Observed apparent HST/WFPC2 F555W magnitudemagphot.mag;em.opt.Vfloate_F555Uncertainty in F555Wmagstat.errorfloat(B-V)The observed (F439W-F555W) color indexmagphot.color;em.opt.B;em.opt.Vfloate_(B-V)Uncertainty in 439-555magstat.errorfloatM555absolute HST/WFPC2 F555W magnitudemagphot.mag;em.opt.Vfloate_M555Uncertainty in 555Magmagstat.errorfloat(B-V)0The intrinsic (F439W-F555W) color indexmagphot.color;em.opt.B;em.opt.Vfloate_(B-V)0Uncertainty in 439-555imagstat.errorfloatA555The F555W filter extinction (A_F555W_)magphys.absorptionfloate_A555Uncertainty in A555magstat.errorfloatDM[11.177/14.526] Distance modulusmagphot.mag.distModfloate_DMUncertainty in DMmagstat.errorfloatd[1.72/8.04] Distancekpcpos.distance;pos.heliocentricfloate_dUncertainty in dkpcstat.errorfloat