J/ApJ/830/44 X-ray luminosity functions of M37 low-mass stars (Nunez+, 2016)
The X-ray luminosity function of M37 and the evolution of coronal activity
in low-mass stars.
Nunez A., Agueros M.A.
<Astrophys. J., 830, 44-44 (2016)>
=2016ApJ...830...44N 2016ApJ...830...44N (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Stars, masses ; X-ray sources
Keywords: open clusters and associations: individual: M37;
stars: activity; stars: coronae; stars: low-mass;
X-rays: individual: M37
Abstract:
We use a 440.5ks Chandra observation of the ∼500Myr old open cluster
M37 to derive the X-ray luminosity functions of its ≤1.2M☉
stars. Combining detections of 162 M37 members with upper limits for
160 non-detections, we find that its G, K, and M stars have a similar
median (0.5-7keV) X-ray luminosity LX=1029.0erg/s, whereas the
LX-to-bolometric-luminosity ratio (LX/Lbol) indicates that M
stars are more active than G and K stars by ∼1 order of magnitude at
500Myr. To characterize the evolution of magnetic activity in low-mass
stars over their first ∼600Myr, we consolidate X-ray and optical data
from the literature for stars in six other open clusters: from
youngest to oldest they are, the Orion Nebula Cluster (ONC), NGC 2547,
NGC 2516, the Pleiades, NGC 6475, and the Hyades. For these, we
homogenize the conversion of instrumental count rates to LX by
applying the same one-temperature emission model as for M37, and
obtain masses using the same empirical mass-absolute magnitude
relation (except for the ONC). We find that for G and K stars X-ray
activity decreases ∼2 orders of magnitude over their first 600Myr, and
for M stars, ∼1.5. The decay rate of the median LX follows the
relation LX∝tb, where b=-0.61±0.12 for G stars,
-0.82±0.16 for K stars, and -0.40±0.17 for M stars. In LX/Lbol
space, the slopes are -0.68±0.12, -0.81±0.19, and -0.61±0.12,
respectively. These results suggest that for low-mass stars the
age-activity relation steepens after ∼625Myr, consistent with the
faster decay in activity observed in solar analogs at t>1Gyr.
Description:
In Nunez+ (2015, J/ApJ/809/161; Paper I), we described our 440.5ks
Chandra observation of M37 (NGC 2099). We combined the MMT/Megacam gri
photometry compiled by Hartman+ (2008, J/ApJ/675/1233) and distance
from the cluster core to generate membership probabilities (Pmem)
for cluster stars. Our final catalog included 561 Chandra X-ray
sources with optical counterparts, 278 of which had Pmem≥0.2. Here,
we add to these detections LX upper limit (UL) measurements for
undetected members to determine the X-ray luminosity functions (XLFs)
for M37's G, K, and M stars. We also compute bolometric luminosities
(Lbol).
To characterize the evolution of X-ray activity, we compare the M37
XLFs and LX/Lbol functions (LLFs) to those of other open clusters
in the approximate age range 6-625Myr: the ONC, NGC 2547, NGC 2516,
the Pleiades, NGC 6475, and the Hyades (see table 2 for the X-ray data
references).
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 32 565 M37 (NGC 2099) low-mass members in the
field of view of Chandra
table2.dat 81 7 Cluster characteristics and number of X-ray
detections/non-detections
table3.dat 88 1441 Clusters members characteristics for the 6 other
open clusters
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See also:
B/chandra : The Chandra Archive Log (CXC, 1999-2014)
IX/50 : XMM-Newton Serendipitous Source Catalogue 3XMM-DR6 (XMM-SSC, 2016)
J/ApJ/822/47 : K2 rotation periods for 65 Hyades members (Douglas+, 2016)
J/ApJ/809/161 : X-ray obs. and membership probabilities of M37 (Nunez+, 2015)
J/ApJ/804/146 : Atmospheric parameters for nearby B-F stars (David+, 2015)
J/A+A/566/A132 : Teff and L for stars in 7 open clusters (Silaj+, 2014)
J/A+A/559/A43 : Pan-STARRS1 (PS1) observations of the Hyades (Goldman+, 2013)
J/MNRAS/431/2063 : UV/X-ray activity of M dwarfs within 10pc (Stelzer+, 2013)
J/MNRAS/407/465 : Fast-rotating M dwarfs in NGC2516 (Jackson+, 2010)
J/A+A/490/113 : X-ray sources in NGC 752 (Giardino+, 2008)
J/ApJ/675/1254 : M37 variable stars (Hartman+, 2008)
J/ApJ/675/1233 : gri photometry in M37 (NGC 2099) (Hartman+, 2008)
J/A+A/453/101 : UBV(RI)c photometry of 4 open clusters (Lyra+, 2006)
J/A+A/450/993 : XMM survey of NGC 2516 (Pillitteri+, 2006)
J/MNRAS/367/781 : XMM observations of NGC 2547 (Jeffries+, 2006)
J/ApJS/160/319 : COUP: observations and source lists (Getman+, 2005)
J/MNRAS/358/13 : Faint dwarfs in NGC 2547 (Jeffries+, 2005)
J/ApJ/601/979 : vsini of Orion low-mass stars (Wolff+, 2004)
J/ApJ/588/1009 : Chandra X-ray observations of NGC 2516 (Damiani+, 2003)
J/ApJ/584/911 : X-rays in the Orion nebula cluster (Feigelson+, 2003)
J/A+A/397/147 : Activity-rotation relationship in stars (Pizzolato+ 2003)
J/AJ/123/290 : UBVI CCD photometry of NGC 2516 (Sung+, 2002)
J/A+A/345/471 : Memberships of open clusters (Robichon+, 1999)
J/A+A/341/751 : ROSAT HRI observations of the Pleiades (Micela+ 1999)
J/A+A/335/183 : Pleiades low-mass stars rotational velocities (Queloz+ 1998)
J/A+A/331/81 : Hyades membership (Perryman+ 1998)
J/AJ/110/1229 : ROSAT X-ray survey in NGC 6475 (Prosser+ 1995)
J/ApJ/448/683 : Hyades RASS observations (Stern+ 1995)
J/ApJS/91/625 : ROSAT survey of the Pleiades (Stauffer+ 1994)
J/ApJ/315/687 : X-Ray emission from solar-type stars: F and G (Maggio+, 1987)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 I6 --- ID [30118/340096] Optical ID from
Hartman+ (2008, J/ApJ/675/1233;
<Cl* NGC 2099 HGH NNNNNN> in Simbad)
8- 11 F4.2 --- Pmem [0.3/1] Probability that object is member (1)
13 I1 --- Bin Binarity flag (1=likely a binary member) (2)
15- 18 F4.2 Msun Mass [0.2/1.2] Stellar mass
20- 24 F5.2 [10-7W] logLbol [31.7/34] Log bolometric luminosity, erg/s (2)
26 I1 --- f_logLX Detection flag (0=X-ray upper limit only) (3)
28- 32 F5.2 [10-7W] logLX [28.4/30.5] Log X-ray luminosity
(or upper limit luminosity), erg/s (G1)
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Note (1): Probability recalculated from Paper I, Nunez+ (2015, J/ApJ/809/161)
Note (2): From Paper I, Nunez+ (2015, J/ApJ/809/161)
Note (3): Detection flag
0 = object has only X-ray upper limit measurement;
1 = object has X-ray measurement.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- Cluster Open cluster name
10 A1 --- f_Cluster [e] Flag on Cluster (1)
12- 19 A8 --- Ref Reference(s) (2)
21- 26 A6 --- Inst Instrument(s) (3)
28- 32 F5.2 [10-7W] logLX [27.4/29] Minimum log X-ray luminosity
detected in 0.5-7keV band, in erg/s
34- 35 I2 --- GDet [10/74] Number of G stars (0.8-1.2M☉)
detected
37- 38 I2 --- GnDet [0/59] Number of G stars non-detected
40- 41 I2 --- KDet [7/58] Number of K stars (0.6-0.8M☉)
detected
43- 44 I2 --- KnDet [0/89] Number of K stars non-detected
46- 48 I3 --- MDet [6/138] Number of M stars (0.1-0.6M☉)
detected
50- 52 I3 --- MnDet [0/174] Number of M stars non-detected
54- 57 F4.2 [yr] logAge [6.4/8.8] Log Age
58 A1 --- f_logAge [f] Flag on logAge (1)
60- 65 F6.1 pc Dist [47/1490] Distance
66 A1 --- f_Dist [f] Flag on Dist (1)
68 A1 --- l_logNH Limit flag on NH
69- 73 F5.2 [cm-2] logNH [20/22] Atomic neutral hydrogen column density
74 A1 --- f_logNH [f] Flag on logNH (1)
76- 80 F5.3 mag E(B-V) [0/0.3]? Reddening
81 A1 --- f_E(B-V) [g] Flag on E(B-V) (1)
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Note (1): Flag as follows:
e = We combine these two to create the representative ∼120Myr old cluster
used in our analysis.
f = Mean value for cluster stars.
g = No reddening value adopted.
Note (2): Reference for X-ray data as follows:
1 = Getman et al. (2005, J/ApJS/160/319)
2 = Jeffries & Tolley (1998MNRAS.300..331J 1998MNRAS.300..331J)
3 = Jeffries & Oliveira (2005, J/MNRAS/358/13)
4 = Pillitteri et al. (2006, J/A+A/450/993)
5 = Stauffer et al. (1994, J/ApJS/91/625)
6 = Micela et al. (1999, J/A+A/341/751)
7 = Stelzer et al. (2000A&A...356..949S 2000A&A...356..949S)
8 = Prosser et al. (1995, J/AJ/110/1229)
9 = James & Jeffries (1997MNRAS.292..252J 1997MNRAS.292..252J)
10 = Obs. ID 0300690101 in 3XMM-DR5 Catalog (IX/46, superseded by IX/50);
11 = Paper I; Nunez et al. 2015, J/ApJ/809/161
12 = Stern et al. (1995, J/ApJ/448/683).
Note (3): X-ray instrument as follows:
CA = Chandra ACIS;
X = XMM EPIC;
RP = ROSAT PSPC;
RH = ROSAT HRI.
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Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 25 A25 --- Name Identifier
27- 36 F10.6 deg RAdeg Right ascension of object (J2000)
38- 47 F10.6 deg DEdeg Declination of object (J2000)
49- 56 A8 --- Cluster Open cluster to which object belongs (the ONC,
NGC 2547, NGC 2516, NGC 6475, the Pleiades
and the Hyades)
58- 61 F4.2 Msun Mass [0.1/1.2] Stellar mass (1)
63- 67 F5.2 [10-7W] logLbol [30/35] Log of Bolometric luminosity,
erg/s (2)
69- 73 F5.1 pc Dist [31/414] Distance to object
75- 80 F6.2 10+20cm-2 NH [1/912.1]? Atomic neutral hydrogen
column density (3)
82 I1 --- f_logLX Detection flag (0=X-ray upper limit only)
84- 88 F5.2 [10-7W] logLX [27.5/31.5] Log of X-ray luminosity
(or upper limit luminosity), erg/s (G1)
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Note (1): Stellar mass derived from JHK or ugriz photometry using the
mass-absolute magnitude relation of Kraus & Hillenbrand
(2007, J/AJ/134/2340) and extended for BRI photometry by
Agueros et al. (in prep).
Note (2): Lbol derived from a linear interpolation between the stellar mass-Lbol
relation in M37 stars, as described in Section 2.2.
Note (3): Atomic neutral hydrogen column density;
null if assumed to be negligible.
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Global notes:
Note (G1): Calculated in the 0.5-7keV energy band for detected (undetected)
objects calculated using the method in Section 2.3.
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History:
17-Feb-2017: From electronic version of the journal
28-Jan-2025: units of logAge in table2 corrected ([yr] instead of Myr).
References:
Nunez et al. Paper I. 2015ApJ...809..161N 2015ApJ...809..161N Cat. J/ApJ/809/161
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 17-Jan-2017