J/AJ/145/134 Radial velocities of 108 stars in Ruprecht 147 (Curtis+, 2013)
Ruprecht 147: the oldest nearby open cluster as a new benchmark for stellar
astrophysics.
Curtis J.L., Wolfgang A., Wright J.T., Brewer J.M., Johnson J.A.
<Astron. J., 145, 134 (2013)>
=2013AJ....145..134C 2013AJ....145..134C
ADC_Keywords: Clusters, open ; Stars, variable ; Stars, giant ; Proper motions ;
Radial velocities ; Photometry, ugriz ;
Keywords: open clusters and associations: general -
open clusters and associations: individual: Ruprecht 147
Abstract:
Ruprecht 147 is a hitherto unappreciated open cluster that holds great
promise as a standard in fundamental stellar astrophysics. We have
conducted a radial velocity survey of astrometric candidates with
Lick, Palomar, and MMT observatories and have identified over 100
members, including 5 blue stragglers, 11 red giants, and 5
double-lined spectroscopic binaries (SB2s). We estimate the cluster
metallicity from spectroscopic analysis, using Spectroscopy Made Easy
(SME), and find it to be [M/H]=+0.07±0.03. We have obtained deep
CFHT/MegaCam g'r'i'z' photometry and fit Padova isochrones to the
(g'-i') and Two Micron All Sky Survey (J-KS) color-magnitude
diagrams, using the τ2 maximum-likelihood procedure of Naylor,
and an alternative method using two-dimensional cross-correlations
developed in this work. We find best fits for Padova isochrones at age
t=2.5±0.25Gyr, m-M=7.35±0.1, and AV=0.25±0.05, with additional
uncertainty from the unresolved binary population and possibility of
differential extinction across this large cluster. The inferred age is
heavily dependent on our choice of stellar evolution model: fitting
Dartmouth and PARSEC models yield age parameters of 3Gyr and 3.25Gyr,
respectively. At ∼300pc and ∼3Gyr, Ruprecht 147 is by far the oldest
nearby star cluster.
Description:
Our initial list of candidate members was drawn from the NOMAD (Naval
Observatory Merged Astrometric Data; Zacharias et al., 2005, cat.
I/297) and UCAC-3 (Third USNO CCD Astrograph Catalog; Zacharias et
al., 2009, cat. I/315, obsoleted by cat. I/322) catalogs.
We performed initial radial velocity confirmation of suspected members
to verify the existence of the cluster with the Hamilton echelle
spectrometer on the 120inch Shane telescope at Lick Observatory
(R∼50000). We observed candidate cluster members on UT 2007 July
31-August 1 and August 22-23, including the members identified by
Kharchenko et al. (2005, cat. J/A+A/438/1163). We observed on 2008
August 5 and 18 with the East-Arm Echelle (R∼33000) on the Hale
200inch at Palomar.
Spectra of four cluster members were obtained on 2008 September 12
(Stars 72 and 78 in Table3) and 18 (Stars 21 and 22) and for two
members on 2011 October 17 (Stars 44 and 91) with the High Resolution
Echelle Spectrometer (HIRES) on the 10m telescope at Keck Observatory
(R∼50000). The stars were kindly observed by the California Planet
Survey team (CPS, http://exoplanets.org/cps.html).
We obtained high-resolution spectra (UT 2010 July 4-5) with
MMT/Hectochelle in the vicinity of the CaII H & K lines for 48 members
(as determined from Lick/Palomar radial velocities), 10 candidate
members (from astrometry and photometry alone), and 23 potential
astrometric reference stars. MMT is a 6.5m telescope located at the
Fred Lawrence Whipple Observatory on Mt. Hopkins, AZ. Hectochelle is a
high-resolution (R∼32000-40000) fiber-fed spectrograph
We imaged a 4deg2 field in the optical g'r'i'z' bands in 2008 April
and May with Canada-France-Hawaii Telescope (CFHT)/MegaCam.
Other observing projects are underway, including deep NIR imaging with
UKIRT/WFCAM (PI: Adam Kraus), a 260ks exposure of the cluster core
with Chandra/ACIS (PI: Steve Saar), and RV surveys for K and M dwarf
members with (PIs: Jason Curtis and Steve Saar).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 91 108 Radial velocities, proper motions and
membership in Ruprecht 147
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See also:
B/ocl : Optically visible open clusters and Candidates (Dias+ 2002-2013)
I/322 : UCAC4 Catalogue (Zacharias+, 2012)
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
I/317 : The PPMXL Catalog (Roeser+ 2010)
I/297 : NOMAD Catalog (Zacharias+ 2005)
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
I/239 : The Hipparcos and Tycho Catalogues (ESA 1997)
J/A+A/564/A79 : Optically visible open clusters proper motions (Dias+, 2014)
J/PAZh/38/571 : Astrophysical parameters of 593 open clusters (Gozha+, 2012)
J/A+A/548/A97 : Catalogue of variable stars in open clusters (Zejda+, 2012)
J/MNRAS/407/2109 : Kinematic study of open clusters (Vande Putte+, 2010)
J/A+A/446/949 : Open clusters proper motions based on UCAC2 (Dias+, 2006)
J/A+A/438/1163 : Catalogue of Open Cluster Data (COCD) (Kharchenko+, 2005)
J/ApJS/141/503 : Radial Velocities for 889 late-type stars (Nidever+, 2002)
J/A+A/376/441 : Absolute proper motions of 112 open clusters (Dias+, 2001)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Star [1/108] Running star number (1)
5- 20 A16 --- 2MASS 2MASS identifier (HHMMSSss+DDMMSSs)
22- 25 F4.1 mas/yr pmRA Proper motion in Right Ascension (2)
27- 29 F3.1 mas/yr e_pmRA 1-σ uncertainty in pmRA (2)
31- 35 F5.1 mas/yr pmDE Proper motion in Declination (2)
37- 39 F3.1 mas/yr e_pmDE 1-σ uncertainty in pmDE (2)
41- 45 F5.2 mag g'mag ? CFHT/MegaCam g' magnitude
47- 51 F5.2 mag g'-i' ? CFHT/MegaCam (g'-i') color index
53- 57 F5.2 mag Jmag 2MASS J magnitude (from cat. II/246) (3)
58 A1 --- f_Jmag [e] Probable binary (star #51) (4)
60- 64 F5.2 mag J-K 2MASS (J-Ks) color index (from cat. II/246) (3)
66- 69 F4.1 km/s RV1 ? Lick/Palomar radial velocity
71- 74 F4.1 km/s RV2 ? Hectochelle radial velocity
76 A1 --- Mm [NPY] Overall membership probability (5)
78 A1 --- Mpm [NPY] Membership probability assigned to proper
motion radial distance from cluster value (5)
79 A1 --- Mv1 [NPY] Membership probability assigned to
Lick/Palomar radial velocities (5)
80 A1 --- Mv2 [NPY] Membership probability assigned to
Hectochelle radial velocities (5)
81 A1 --- Mjk [NPYB] Membership probability assigned to 2MASS
(J-Ks) color-magnitude diagram (5)
82 A1 --- Mgi [NPYB] Membership probability assigned to
CFHT/MegaCam (g'-i') color-magnitude diagram (5)
84 A1 --- u_Type [?] Uncertainty flag on Type (?)
85- 91 A7 --- Type Star classification (6)
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Note (1): Sorted by V magnitude (provided by NOMAD, cat. I/297).
The stars are <[CWW2013] NNN> in Simbad.
Note (2): From PPMXL catalog (Roeser et al., 2010, cat. I/317).
Note (3): We use 2MASS aperture photometry instead of the default PSF photometry
for 18 stars, based on our analysis that these stars, and only these stars,
shift position on the (J-Ks) Color-Magnitude Diagram (CMD) and that they
all move toward the cluster locus. No neighbors are resolved in our optical
imaging within 5". The stars are 22, 24, 27, 28, 30, 37, 38, 43, 48, 49,
57, 59, 67, 68, 90, 91, 94, and 100.
Note (4): e = Our MegaCam imaging shows Star 51 is an optical double, with
a star 1.65" away with a similar g'r'i'z' SED. Assuming a cluster
distance of 300pc this angular separation translates into a minimum
physical separation of 495AU. This suggests that the pair actually
form a wide binary, although their angular proximity could also be
explained by a chance alignment. This double was not resolved in the
2MASS Point Source Catalog (cat. II/246). Adding 0.75mag to the J band
magnitude (halving the brightness, to reflect just the one star) moves
Star 51 in the (J-Ks) Color-Magnitude Diagram (CMD) to its neighbors
in the (g'-i') CMD. Despite this realization, we quote the 2MASS Point
Source Catalog photometry here. See Section 3.4.2.
Note (5): Membership confidence level of the star in Ruprecht 147 as follows:
Y = Yes, highest confidence member;
P = Possible/Probable member;
N = Not likely/Non-member;
B = photometry consistent with Blue stragglers.
Note (6): Type as follows:
BS = Blue Straggler;
RG = Red Giant;
SB1 = single-lined Spectroscopic Binary;
SB1? = Inconsistent radial velocities between multiple epochs;
SB2 = Spectroscopic double line Binary.
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History:
From electronic version of the journal
(End) Sylvain Guehenneux [CDS] 22-May-2014