J/ApJ/862/33 Improved & expanded membership catalog for NGC752 (Agueros+, 2018)
A new look at an old cluster: the membership, rotation, and magnetic activity of
low-mass stars in the 1.3 Gyr old open cluster NGC 752.
Agueros M.A., Bowsher E.C., Bochanski J.J., Cargile P.A., Covey K.R.,
Douglas S.T., Kraus A., Kundert A., Law N.M., Ahmadi A., Arce H.G.
<Astrophys. J., 862, 33 (2018)>
=2018ApJ...862...33A 2018ApJ...862...33A
ADC_Keywords: Clusters, open; Photometry, infrared; Radial velocities;
Spectral types; Stars, masses; Photometry, RI
Keywords: open clusters and associations: individual (NGC 752); stars: activity;
stars: rotation
Abstract:
The nearby open cluster NGC 752 presents a rare opportunity to study
stellar properties at ages >1Gyr. However, constructing a membership
catalog for it is challenging; most surveys have been limited to
identifying its giants and dwarf members earlier than mid-K. We
supplement past membership catalogs with candidates selected with
updated photometric and proper-motion criteria, generating a list of
258 members, a >50% increase over previous catalogs. Using a Bayesian
framework to fit MESA Isochrones & Stellar Tracks evolutionary models
to literature photometry and the Tycho-Gaia Astrometric Solution data
available for 59 cluster members, we infer the age of and distance to
NGC 752: 1.34±0.06Gyr and 438-6+8pc. We also report the results
of our optical monitoring of the cluster using the Palomar Transient
Factory. We obtain rotation periods for 12 K and M cluster members,
the first periods measured for such low-mass stars with a
well-constrained age >1Gyr. We compare these new periods to data from
the younger clusters Praesepe and NGC 6811, and to a theoretical model
for angular momentum loss, to examine stellar spin-down for low-mass
stars over their first 1.3Gyr. While on average NGC 752 stars are
rotating more slowly than their younger counterparts, the difference
is not significant. Finally, we use our spectroscopic observations to
measure Hα for cluster stars, finding that members earlier than
∼M2 are magnetically inactive, as expected at this age. Forthcoming
Gaia data should solidify and extend the membership of NGC 752 to
lower masses, thereby increasing its importance for studies of
low-mass stars.
Description:
Our work has added 125 new stars (using astrometric and photometric
data from 2MASS and UCAC3) to the nearby open cluster NGC 752,
reclassified five stars listed as nonmembers in the literature as
cluster members, and extended NGC 752's membership to the mid-M stars.
Conversely, we have removed 32 stars, or one-fifth of the merged
Daniel+ (1994, J/PASP/106/281) and Mermilliod+ (1998, J/A+A/339/423)
catalog, from the list of cluster members (see Table 2). The 258
cluster members are presented in Tables 3 and 4.
We had access to RV measurements for 123 candidate cluster members.
These include RVs published by Daniel+ (1994, J/PASP/106/281) for 92
stars, as well as measurements for 76 stars shared with us by
C. Pilachowski. For each of these 76 stars, ∼15 spectra were obtained
as part of a long-term monitoring campaign with the Hydra spectrograph
on the WIYN 3.5m telescope, Kitt Peak, AZ.
We monitored NGC 752 from 2010 August 22 to 2011 January 19 using time
allocated to two PTF Key Projects: the PTF Open Cluster Survey and the
PTF/M-dwarfs survey. We used the robotic 48-inch Oschin (P48)
telescope at Palomar Observatory, CA equipped with the modified CFH12K
mosaic camera. Under typical conditions (1.1" seeing), it delivered 2"
FWHM images that reached a 5σ limiting RPTF ∼21mag in 60s. We
imaged two overlapping 3.5°x2.31° fields covering the center
of NGC 752. In total, we obtained close to 400 observations for each
field. See section 4.1.
We observed NGC 752 with the Hydra multi-object spectrograph the WIYN
3.5m telescope during the nights of 2011 February 7 and 8 (range
between 6050 to 8950Å; R∼4000) to obtain spectra for 96 stars.
See section 5.1.
We used the MDM Observatory Modular Spectrograph (ModSpec) on the 2.4m
Hiltner telescope to obtain spectra of 180 candidate cluster members
over the course of five observing runs between 2010 December 1 and
2012 February 20 (range 4500-7500Å and R∼3300). See section 5.2.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 58 32 Stars identified as members in the literature and
as non-members in this Work
table3.dat 95 208 Membership probability (Pmem)-selected
NGC 752 members
table4.dat 86 50 Other NGC 752 members
table6.dat 58 12 NGC 752 rotators (section 4.3)
lcs/* . 12 *Individual PTF light curves for the 12 rotators
in ASCII format (Figure 9)
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Note on lcs/*: These light curves were generated from the close to 400
observations of NGC 752 obtained with PTF from 2010 Aug 22 to 2011 Jan 19.
In addition to the standard data reduction for PTF images described in
Law+ (2011ASPC..448.1367L 2011ASPC..448.1367L), we applied a version of the SYSREM algorithm
to remove systematic trends from these data. The 90 PTF light curves
for NGC 752 members were then cleaned of unreliable data points (those
with errors >0.5 mag or >6 sigma removed from the mean magnitude)
before computing a Lomb-Scargle periodogram for them. Using an
injection/recovery test, we then determined a threshold power for the
most significant peak in our periodograms for identifying robust period
measurements. We also cleaned the periodograms of any aliases and beat
periods between the candidate period and a one-day sampling frequency
before removing stars for which there were secondary peaks with power
>60% of the primary peak's. These 12 stars are those that passed these
tests.
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See also:
B/ocl : Optically visible open clusters & Candidates (Dias+ 2002-2015)
I/177 : Proper motions in NGC 752 (Platais 1992)
I/259 : The Tycho-2 Catalogue (Hog+ 2000)
I/284 : The USNO-B1.0 Catalog (Monet+ 2003)
I/315 : UCAC3 Catalogue (Zacharias+ 2009)
I/337 : Gaia DR1 (Gaia Collaboration, 2016)
VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)
J/PASP/106/281 : Photometry and radial velocities in NGC752 (Daniel+, 1994)
J/A+A/339/423 : Velocities of red giants in NGC 752 (Mermilliod+ 1998)
J/A+A/416/125 : RI photometry in alpha Per and Pleiades (Deacon+, 2004)
J/A+A/417/557 : Rotation & variability of PMS Stars in NGC 2264 (Lamm, 2004)
J/AJ/132/1517 : Spectroscopy of M dwarfs in Praesepe (Kafka+, 2006)
J/AJ/134/2398 : Stellar SEDs in SDSS and 2MASS filters (Covey+, 2007)
J/AJ/134/2340 : Membership of Praesepe & Coma Ber clusters (Kraus+, 2007)
J/A+A/490/113 : X-ray sources in NGC 752 (Giardino+, 2008)
J/ApJ/687/1264 : Age estimation for solar-type dwarfs (Mamajek+, 2008)
J/AJ/135/785 : SDSS-DR5 low-mass star spectroscopic sample (West+, 2008)
J/BaltA/19/35 : NGC 752 Vilnius photometry (Zdanavicius+, 2010)
J/BaltA/20/27 : NGC 752 Vilnius photometry (Bartasiute+, 2011)
J/MNRAS/413/2218 : Stellar rotation in Hyades and Praesepe (Delorme+, 2011)
J/ApJ/733/L9 : Stellar rotation for 71 NGC 6811 members (Meibom+, 2011)
J/AJ/141/97 : SDSS DR7 M dwarfs (West+, 2011)
J/AJ/145/134 : Radial velocities of 108 stars in Ruprecht 147 (Curtis+, 2013)
J/AJ/145/7 : UBVRI CCD photom. of the open cluster NGC 6811 (Janes+, 2013)
J/A+A/558/A53 : MW global survey of star clusters. II. (Kharchenko+, 2013)
J/ApJ/795/161 : Activity & rotation in Praesepe & the Hyades (Douglas+, 2014)
J/MNRAS/442/2081 : Praesepe members light curves (Kovacs+, 2014)
J/MNRAS/446/3562 : Abundances of red giants in NGC752 (Bocek Topcu+, 2015)
J/AJ/150/134 : uvbyCaHβ photometry of NGC 752 (Twarog+, 2015)
J/ApJ/822/81 : PTF stellar rot. periods for Pleiades members (Covey+, 2016)
J/ApJ/822/47 : K2 rotation periods for 65 Hyades members (Douglas+, 2016)
J/ApJ/830/44 : X-ray luminosities of M37 low-mass stars (Nunez+, 2016)
J/ApJ/831/L6 : Eclipsing binary parallaxes with Gaia data (Stassun+, 2016)
J/AJ/152/115 : Pleiades members with K2 light curves. III. (Stauffer+, 2016)
J/ApJ/842/83 : Praesepe members rot. periods from K2 LCs (Douglas+, 2017)
J/ApJ/838/25 : Hectochelle spectroscopy for 776 Kepler stars (Guo+, 2017)
J/ApJ/845/72 : The factory & the beehive. III. (Kraus+, 2017)
J/ApJ/834/176 : Spectroscopic survey of M37 candidate members (Nunez+, 2017)
J/MNRAS/470/3937 : 1876 open clusters multimembership catalog (Sampedro+, 2017)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 16 A16 --- 2MASS 2MASS ID (HHMMSSss+DDMMSSs; J2000)
18 A1 --- Bin [1] Candidate binary flag
20 I1 --- Set [1/2] Set (1)
22- 25 I4 --- P91 Platais (1991A&AS...87...69P 1991A&AS...87...69P, I/177) catalog
number; <CL* NGC 752 PLA NNNN> in Simbad
27- 31 F5.2 mag Jmag [8.4/13.9] 2MASS J band magnitude
33- 36 F4.2 mag e_Jmag [0.02/0.03] Uncertainty in Jmag
38- 41 F4.1 % Pmem [0/99.9]? Membership probability (2)
43- 48 F6.2 km/s RVel [-31.5/16.3]? Radial velocity (3)
50- 53 F4.2 km/s eRVel1 [0.1/5]? First uncertainty in RVel (4)
55- 58 F4.2 km/s eRVel2 [0.08/1]? Second uncertainty in RVel (5)
--------------------------------------------------------------------------------
Note (1): Subset of demoted stars as follows:
1 = these 11 stars have RVs >2σ from the cluster value of
5.5±0.6 km/s from Daniel+ (1994, J/PASP/106/281);
2 = 21 stars have Pmem< 50%. Four of these have RVs consistent with
membership but Pmem<10% and are therefore excluded from our catalog.
Note (2): Pmem is presented for all of the stars for which it was calculated,
even though for those with J<9.5 mag, its value (or absence) does
not impact our membership decision as the classification of
Daniel+ (1994, J/PASP/106/281) and Mermilliod+ (1998, J/A+A/339/423)
takes precedence.
Note (3): The RV data are from the WIYN long-term monitoring campaign
(C. Pilachowshi, priv. comm.). Most stars were observed multiple
times on multiple nights, and an average RV and σ were computed
for each star on each night.
Note (4): The first RV uncertainty corresponds to the σ in the RV computed
from the set of nightly average RVs (and is used for single stars,
for which we define this σ_1 <3km/s).
Note (5): The second uncertainty is the average of the nightly σ (and is
used for binaries).
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Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 24 A24 --- ID Member ID
26 A1 --- f_ID Flag on ID (1)
28- 31 I4 --- P91 ? Platais (1991A&AS...87...69P 1991A&AS...87...69P, I/177) catalog
number; <CL* NGC 752 PLA NNNN> in Simbad
33- 38 F6.3 mag Jmag [9.5/16.3]? 2MASS J band magnitude
40- 43 F4.2 mag e_Jmag [0.02/0.1]? Uncertainty in Jmag
45- 50 F6.3 mag Ksmag [9.3/15.7]? 2MASS Ks band magnitude
52- 55 F4.2 mag e_Ksmag [0.01/0.2]? Uncertainty in Ksmag
57- 60 F4.2 Msun Mass [0.2/1.4]? Derived stellar mass, solar units
62- 65 A4 --- SpT Spectral type
67- 70 F4.2 mag DM [6.5/8.5] Derived distance modulus
72- 75 F4.2 mag e_DM [0.03/2.6] Uncertainty in DM
77- 81 F5.2 mag Mbol [10.2/18.1] Derived bolometric magnitude
83- 86 F4.2 mag e_Mbol [0.02/0.9] Uncertainty in Mbol
88- 90 A3 --- Bin Binary flag(s) (G1)
92- 95 F4.1 % Pmem [51.2/99.9] Membership probability
--------------------------------------------------------------------------------
Note (1):
b = 2MASS photometry does not exist for WISE J015743.22+374417.6 due to
confusion with a persistence artifact in the 2MASS image. Based on a
fit to its optical SED, we classify the source as a probable
(Pmem=89.5%) cluster member; the source does not factor in to our
subsequent analysis, so we do not attempt to derive a separate
non-K-band based mass estimate.
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Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 16 A16 --- 2MASS 2MASS member ID (HHMMSSss+DDMMSSs; J2000)
18- 21 I4 --- P91 ? Platais (1991A&AS...87...69P 1991A&AS...87...69P, I/177) catalog
number; <CL* NGC 752 PLA NNNN> in Simbad
23- 27 F5.2 mag Jmag [7/14.1]? 2MASS J band magnitude
29- 32 F4.2 mag e_Jmag [0.01/0.02]? Uncertainty in Jmag
34- 38 F5.2 mag Ksmag [6.4/13.7]? 2MASS Ks band magnitude
40- 43 F4.2 mag e_Ksmag [0.02/0.04]? Uncertainty in Ksmag
45- 48 F4.2 Msun Mass [0.7/1.3]? Derived stellar mass, solar units
50- 53 A4 --- SpT Spectral type
55- 58 F4.1 km/s RVelD [-7.6/7.4]? Radial velocity (1)
60- 63 F4.1 km/s e_RVelD [0.1/19]? Uncertainty in RVelD
65- 70 F6.2 km/s RVelP [-11/22.4]? Radial velocity (2)
72- 76 F5.2 km/s eRVelP1 [0.06/34]? First uncertainty in RVelP (3)
78- 82 F5.2 km/s eRVelP2 [0.1/36.7]? Second uncertainty in RVelP (4)
84- 86 A3 --- Bin Binary flag(s) (G1)
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Note (1): RV measurements published by Daniel+ (1994, J/PASP/106/281) or
Mermilliod+ (1998, J/A+A/339/423);
Note (2): RV measurements collected by C. Pilachowski, priv. comm.
Note (3): The first RV uncertainty corresponds to the σ in the RV computed
from the set of nightly average RVs (and is used for single stars,
for which we define this σ_1 <3km/s).
Note (4): The second uncertainty is the average of the nightly σ (and is
used for binaries).
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Byte-by-byte Description of file: table6.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 16 A16 --- 2MASS 2MASS member ID (HHMMSSss+DDMMSSs; J2000)
18- 21 A4 --- SpT Spectral type (1)
23- 26 F4.1 % Pmem [52.8/96.5] Membership probability
28- 31 F4.2 mag KMag [4.3/5.9] Absolute K band magnitude (2)
33- 36 F4.2 Msun Mass [0.4/0.8] Derived stellar mass (3)
38- 42 F5.2 mag Rmag [13.9/17.3] Median PTF R band magnitude (4)
44- 46 I3 --- Nobs [303/695] Number of observations
48- 52 F5.2 d Per [5.2/35] Derived period
54- 58 F5.2 d e_Per [0.3/25.1] Uncertainty in Per
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Note (1): The formal uncertainty for the SpTs is 0.1 spectral classes.
However, the systematic uncertainty in the underlying definition is ∼0.5
spectral classes for M dwarfs, and this systematic uncertainty will be
reflected in the color-spectral type relations used for SED fits.
Note (2): KMag is calculated for each star using the best-fit distance
modulus determined from the SED fit, and in turn is used to obtain
masses.
Note (3): Masses for sources brighter than KMag=5.5mag are assigned using the
theoretical model of Dotter et al. (2008ApJS..178...89D 2008ApJS..178...89D), while masses
for fainter sources are assigned using the empirical mass-luminosity
relation measured by Delfosse et al. (2000A&A...364..217D 2000A&A...364..217D). Although the
Delfosse et al. (2000A&A...364..217D 2000A&A...364..217D) relation extends to stars with
MK=4.5 mag, the predicted mass values diverge by up to about 5% from
those of Dotter et al. (2008ApJS..178...89D 2008ApJS..178...89D) for stars brighter than
MK=5.5 mag.
Note (4): We provide the median RPTF magnitude of each light curve after
filtering on flags and correcting for the (generally very small)
photometric offset between fields for stars that were in both. The
uncertainty on these magnitudes is of order 1%.
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Byte-by-byte Description of file: lcs/*
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 F9.5 d Epoch [598.2/748.2] Number of Julian days
since 2009 Jan 1
11- 17 F7.4 mag Rmag [13.9/19.8] PTF R band magnitude
19- 24 F6.4 mag e_Rmag [0.0005/0.2] Uncertainty in Rmag
26- 34 F9.6 deg RAdeg [28.2/29.8] Right Ascension (J2000)
36- 44 F9.6 deg DEdeg [37.3/38.1] Declination (J2000)
46 I1 --- sflag [0/3] S-extractor flag (1)
48- 53 I6 --- PTFfield [110005/110006] PTF Field (2)
55- 56 I2 --- Chip [2/10] PTF camera CCD Chip
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Note (1): S-extractor flags as follows:
0 = no flag;
3 = the object was originally blended with another one, has neighbors,
bright and close enough to significantly bias the photometry, or bad
pixels (more than 10% of the integrated area affected).
Note (2): PTF observations of NGC 752 (Table 5):
-----------------------------------------------
PTFfield Field center (J2000) Number of
observations
-----------------------------------------------
110005 01:53:35+37:19:00 377
110006 01:53:53+38:19:00 413
-----------------------------------------------
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Global notes:
Note (G1): Binary flag based on RV measurements as follows:
D = published by Daniel+ (1994, J/PASP/106/281) or
Mermilliod+ (1998, J/A+A/339/423);
P = collected by C. Pilachowski, private communication
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 22-Jul-2019