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J/AJ/122/1486       NGC 2451A proper motions and membership  (Platais+, 2001)

WIYN open cluster study. VII. NGC 2451A and the Hipparcos distance scale. Platais I., Kozhurina-Platais V., Barnes S., Girard T.M., Demarque P., van Altena W.F., Deliyannis C.P., Horch E. <Astron. J. 122, 1486 (2001)> =2001AJ....122.1486P
ADC_Keywords: Clusters, open ; Proper motions ; Radial velocities ; Photometry, UBV Keywords: astrometry - color-magnitude diagrams - open clusters and associations: individual (NGC 2451A) Abstract: We provide new evidence that NGC 2451A is undoubtedly a young open cluster, although sparsely populated. New cluster membership has been derived from relative proper motions of 5868 stars. In total, 136 stars down to V∼15 5 have membership probability Pµ≥2%. New CCD BV photometry indicates that about 70 stars are indeed main-sequence stars of NGC 2451A. This is also supported by our measurements of radial velocities. A total of 34 very likely cluster members yield a mean heliocentric radial velocity for NGC 2451A equal to +22.9km/s. The high quality of our BV photometry, a confirmation of cluster membership from proper motions and radial velocities, and a recently obtained metallicity estimate for several cluster stars allow us to perform a precise isochrone fit. The Yale isochrones, updated by the latest available input physics, have been fitted to the cluster's color-magnitude diagram, yielding a distance modulus V0-MV in the range 6.35 to 6.38, which is in excellent agreement with the distance modulus (m-M)0=6.38 derived from the Hipparcos data recently by van Leeuwen and Robichon et al. (1998, Cat. J/A+AS/130/157). We have used the high-resolution spectra acquired using the Hydra multiobject spectrograph at the WIYN telescope (Kitt Peak, Arizona) in 1997 November and 1998 October. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 65 136 Astrometry and photometry for probable cluster members in NGC 2451A table3.dat 34 67 Radial velocities spm.dat 129 5868 Catalog of positions, relative proper motions and BV photographic photometry in the region of open cluster NGC 2451 ccd.dat 71 14836 Catalog of CCD BV photometry in the region of open cluster NGC 2451
See also: : SPM Home Page I/252 : The USNO-A2.0 Catalogue (Monet+ 1998) I/277 : SPM catalog 2.0 (Platais+, 1998) J/AJ/124/601 : WIYN Open Cluster Study. VIII (Platais+, 2002) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 4 I4 --- PKB Running identification number, Cl* NGC 2451 PKB NNNNN in Simbad 6- 8 I3 --- Will ? The Williams (1967MNSSA..26...30W) number, NGC 2451 NNN in Simbad 10 I1 h RAh Right Ascension (J2000, epoch J2000) (1) 12- 13 I2 min RAm Right Ascension (J2000, epoch J2000) (1) 15- 20 F6.3 s RAs Right Ascension (J2000, epoch J2000) (1) 22 A1 --- DE- Declination sign (J2000, epoch J2000) (1) 23- 24 I2 deg DEd Declination (J2000, epoch J2000) (1) 26- 27 I2 arcmin DEm Declination (J2000, epoch J2000) (1) 29- 33 F5.2 arcsec DEs Declination (J2000, epoch J2000) (1) 35- 39 F5.1 mas/yr pmX Relative proper motion along X (2) 41- 44 F4.1 mas/yr pmY Relative proper motion along Y (2) 46- 51 F6.3 mag Vmag The Johnson V band magnitude 53 A1 --- r_Vmag [aeu] Source of Vmag (3) 55- 60 F6.3 mag B-V The (B-V) color 62 I1 --- o_Vmag Number of observations for Vmag 64- 65 I2 % Prob Cluster membership probability
Note (1): Epoch and equinox J2000. Note (2): Relative proper motions to X, Y directions, specified in spm.dat file. Note (3): Reference for photometry: a = B and V photometry adopted from Hipparcos, Cat. I/239 e = B and V photometry from SPM photometry (see Sec.2.2) u = B and V photometry from Williams (1967MNSSA..26...30W)
Byte-by-byte Description of file: table3.dat
Bytes Format Units Label Explanations
1- 4 I4 --- PKB Running identification number, Cl* NGC 2451 PKB NNNNN in Simbad 6- 16 F11.3 d HJD Heliocentric Julian date 18- 23 F6.2 km/s HRV Heliocentric radial velocity 24 A1 --- n_HRV [a] indicates a broad cross-correlation peak 27- 30 A4 --- Memb Membership status based on membership probability (2)
Note (2): Membership status: ms: star located on the main sequence of NGC 2451A or up to 0.75mag above B-cl: probable NGC 2451B members fld: star located below or well above the main sequence of NGC 2451A, considered as field star
Byte-by-byte Description of file: spm.dat
Bytes Format Units Label Explanations
2- 5 I4 --- PKB Running identification number, Cl* NGC 2451 PKB NNNNN in Simbad 7- 12 F6.2 mm Xpos X position (1) 14- 19 F6.2 mm Ypos Y position (1) 21- 30 F10.7 rad RArad Right ascension for the epoch 1991.25 and in the ICRS reference system (i.e. equinox 2000.0) 32- 41 F10.7 rad DErad Declination for the epoch 1991.25 and equinox 2000.0 43- 45 I3 mas e_RArad Estimated standard error in right ascension multiplied by cos(DE) 47- 49 I3 mas e_DErad Estimated standard error in declination 51- 56 F6.1 mas/yr pmRA Relative proper motion in right ascension multiplied by cos(DE) 58- 63 F6.1 mas/yr pmDE Relative proper motion in declination 65- 66 I2 --- o_Bmag The number of grating images per star detected on blue plates (grating image pairs are counted as one image) 68- 69 I2 --- o_Vmag The number of grating images per star on visual plates 71- 74 F4.1 mas/yr e_pmRA Estimated standard error in right ascension's proper motion 76- 79 F4.1 mas/yr e_pmDE Estimated standard error in declination's proper motion 81- 85 F5.2 mag Bmag ?=0.00 Photographic B-magnitude (if missing then set to 0.00) 87- 90 F4.2 mag e_Bmag Estimated standard error of B-magnitude 92- 96 F5.2 mag Vmag ?=0.00 Photographic V-magnitude (if missing then set to 0.00) 98-101 F4.2 mag e_Vmag Estimated standard error of V-magnitude 103-108 F6.3 mag Vmagc ?=-1.000 CCD V-magnitude (if missing then set to -1.000) 110-115 F6.3 mag B-Vc ?=-1.000 CCD B-V color (if missing then set to -1.000) 117-121 F5.3 mag e_Vmagc IRAF generated error in CCD V-magnitude 123-127 F5.3 mag e_B-Vc IRAF generated error in CCD B-V color 129 I1 --- Nframe [0/4]? Number of frames per star (G1)
Note (1): Approximate rectangular coordinates on the SPM plate #18. The scale of SPM plates is 55.1"/mm. East is in the direction of increasing X, North is in the direction of Y.
Byte-by-byte Description of file: ccd.dat
Bytes Format Units Label Explanations
1- 9 I9 --- Seq Object identifier (1) 11- 19 F9.5 deg RAdeg Right ascension (mean epoch=1996.6, equinox J2000.0) 21- 29 F9.5 deg DEdeg Declination (mean epoch=1996.6, equinox J2000.0) 31- 36 F6.3 mag Vmag CCD V magnitude 38- 43 F6.3 mag B-V CCD B-V magnitude 45- 49 F5.3 mag e_Vmag IRAF generated error in CCD V-magnitude 51- 55 F5.3 mag e_B-V IRAF generated error in CCD B-V color 57- 62 F6.3 arcsec DRA "CCD-USNOA2.0" (I/252) coordinate difference in right ascension multiplied by cos(DE) 64- 69 F6.3 arcsec DDE "CCD-USNOA2.0" (I/252) coordinate difference in declination 71 I1 --- Nframe [1/4] Number of frames per star (G1)
Note (1): Normally, first four digits indicate the probable NGC 2451A member which usually was placed at the center of CCD chip
Global notes: Note (G1): Number of frames per star: If it is 2, 3, or 4 then mean CCD BV magnitudes have been averaged from 2, 3, or 4 frames. (Note that for spm.dat, many entries entirely miss this item!)
History: From electronic version of the journal References: Von Hippel & Sarajedini, Paper I 1998AJ....116.1789V Sarajedini et al., Paper II 1999AJ....118.2894S Sarajedini, Paper III 1999AJ....118.2321S Barrado y Navascues et al., Paper V 2001ApJ...549..452B Sills & Sarajedini, Paper VI 2000ApJ...544..944S Platais et al., Paper VIII 2002AJ....124..601P, Cat. J/AJ/124/601 Grocholski & Sarajedini Paper X 2002AJ....123.1603G von Hippel et al., Pap XI 2002AJ....124.1555V Kafka & Honeycutt, Pap XV 2003AJ....126..276K Grocholski & Sarajedini, Pap XVI 2003MNRAS.345.1015G Platais et al., Pap XVII 2003AJ....126.2922P, Cat. J/AJ/126/2922 Mathieu et al., Pap XVIII 2004ApJ...602L.121M Sarajedini, et al., Pap XIX 2004AJ....127..991S Kafka et al., Pap XX 2004AJ....127.1622K Hole et al. Pap XXIV 2009AJ....138..159H, Cat. J/AJ/138/159 Platais et al., Pap XXVI 2007A&A...461..509P, Cat. J/A+A/461/509 Geller et al., Pap XXXII 2008AJ....135.2264G, Cat. J/AJ/135/2264 Geller et al., Pap XXXVI 2009AJ....137.3743G, Cat. J/AJ/137/3743 Geller et al., Pap XXXVIII 2010AJ....139.1383G, Cat. J/AJ/139/1383 Anthony-Twarog et al., Pap XXXIX 2010AJ....139.2034A, Cat. J/AJ/139/2034 Geller & Mathieu Pap XLVIII 2012AJ....144...54G Yang et al., Pap LII 2013ApJ...762....3Y Platais et al., Pap LV 2013AJ....146...43P, Cat. J/AJ/146/43 Maderak et al., Pap LVII 2013AJ....146..143M Tofflemire et al., Pap LIX 2014AJ....148...61T, Cat. J/AJ/148/61 Milliman et al., Pap LX 2014AJ....148...38M, Cat. J/AJ/148/38 Anthony-Twarog et al., Pap LXI 2014AJ....148...51A, Cat. J/AJ/148/51 Thompson et al., Pap LXII 2014AJ....148...85T, Cat. J/AJ/148/85
(End) Greg Schwarz [AAS], Patricia Bauer [CDS] 14-Jan-2002
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