J/ApJ/814/35 Flare events in M dwarf of M37 (Chang+, 2015)
Photometric study on stellar magnetic activity.
I. Flare variability of red dwarf stars in the open cluster M37.
Chang S.-W., Byun Y.-I., Hartman J.D.
<Astrophys. J., 814, 35 (2015)>
=2015ApJ...814...35C 2015ApJ...814...35C (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Stars, flare ; Clusters, open ; Photometry, RI
Keywords: open clusters and associations: individual: M37;
stars: activity; stars: flare; stars: low-mass; stars: statistics
techniques: photometric
Abstract:
Based on one-month long MMT time-series observations of the open
cluster M37, we monitored light variations of nearly 2500 red dwarfs
and successfully identified 420 flare events from 312 cluster M dwarf
stars. For each flare light curve, we derived observational and
physical parameters, such as flare shape, peak amplitude, duration,
energy, and peak luminosity. We show that cool stars produce
serendipitous flares energetic enough to be observed in the r-band,
and their temporal and peak characteristics are almost the same as
those in traditional U-band observations. We also found many
large-amplitude flares with inferred Δu>6mag in the cluster
sample which had been rarely reported in previous ground-based
observations. Following the ergodic hypothesis, we investigate in
detail statistical properties of flare parameters over a range of
energy (Er~=1031-1034erg). As expected, there are no statistical
differences in the distributions of flare timescales, energies, and
frequencies among stars of the same age and mass group. We note that
our sample tend to have longer rise and decay timescales compared to
those seen in field flare stars of the same spectral type and be more
energetic. Flare frequency distributions follow power-law
distributions with slopes β∼0.62-1.21 for all flare stars and
β∼0.52-0.97 for stars with membership information (Pmem≥0.2).
These are in general agreement with previous works on flare statistics
of young open clusters and nearby field stars. Our results give
further support to the classical age-activity relations.
Description:
We used the archival imaging data of the M37 taken by MMT 6.5m
telescope (see Hartman et al. 2008, J/ApJ/675/1233 for details:
observations spanning 24 nights between 2005 Dec 21 and 2006 January
21). The archive contains almost 5000 images obtained in r'-band over
one-month period. We refer the reader to Chang et al.
(2015AJ....149..135C 2015AJ....149..135C) for a detailed description of our new
photometric reduction and light curve production.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table6.dat 87 604 Observational parameters of 604 flare events
detected in the whole sample
table7.dat 65 420 Physical parameters of 420 flare events detected
in the cluster sample
stars.dat 12 419 List of flare stars; table added by CDS
--------------------------------------------------------------------------------
See also:
B/ocl : Optically visible open clusters and Candidates (Dias+ 2002-2015)
II/131 : Tonantzintla Pleiades Flare Stars (Haro+ 1982)
J/ApJ/809/161 : X-ray obs. and membership probabilities of M37 (Nunez+, 2015)
J/AJ/150/27 : New catalog of variable stars in M37 field (Chang+, 2015)
J/ApJS/209/5 : Superflares of Kepler stars. I. (Shibayama+, 2013)
J/ApJS/207/15 : M dwarf flare spectra (Kowalski+, 2013)
J/ApJ/754/4 : HST monitoring of flaring stars in the bulge (Osten+, 2012)
J/other/Nat/485.478 : Superflares on solar-type stars (Maehara+, 2012)
J/AJ/141/97 : SDSS DR7 M dwarfs (West+, 2011)
J/AJ/141/50 : White-light flares on cool Kepler stars (Walkowicz+, 2011)
J/AJ/140/1402 : M dwarf flares from SDSS spectra (Hilton+, 2010)
J/AJ/140/483 : Flares of UV Cet type stars (Dal+, 2010)
J/ApJ/675/1233 : gri photometry in M37 (NGC 2099) (Hartman+, 2008)
J/AJ/135/785 : SDSS-DR5 low-mass star spectroscopic sample (West+, 2008)
J/AJ/134/2398 : Stellar SEDs in SDSS and 2MASS filters (Covey+, 2007)
J/ApJ/606/466 : X-ray variability in NGC 2516 (Wolk+, 2004)
J/A+A/327/1114 : Optical flares on EV Lac in 1967-1977 (Leto+ 1997)
Byte-by-byte Description of file: stars.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- VarID Variable star ID (among V42 to V2306) (G1)
7- 12 F6.3 mag rmag [16.7/24.5] r band magnitude
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table6.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- VarID Variable star ID (among V42 to V2306) (G1)
7- 12 F6.3 mag rmag [16.7/24.5] r band magnitude
14- 15 A2 --- FlID Flare event ID (F1-F6) (2)
17- 27 F11.5 d tpeak ? Modified Julian Date at flare peak
29- 33 F5.3 mag mpeak [0.01/3.8]? The incremental magnitude
at flare peak
35- 39 F5.3 mag mbase [0/1.1]? The magnitude difference (3)
41- 44 F4.2 min t0.9r ? The flare timescale; q=0.9, rise part
46- 49 F4.2 min t0.9d ? The flare timescale; q=0.9, decay part
51- 55 F5.2 min t0.5r ? The flare timescale; q=0.5, rise part
57- 61 F5.2 min t0.5d ? The flare timescale; q=0.5, decay part
63- 67 F5.2 min t0.2r ? The flare timescale; q=0.2, rise part
69- 74 F6.2 min t0.2d ? The flare timescale; q=0.2, decay part
76- 80 F5.2 min t0.0r ? The flare timescale; q=0, rise part
82- 87 F6.2 min t0.0d ? The flare timescale; q=0, decay part
--------------------------------------------------------------------------------
Note (2): For each star, the identification number (FlID) of each flare
event is listed in time order.
Note (3): Between the first epoch data and the last epoch data of
flare observations.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table7.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- VarID Variable star ID (among V78 to V2306) (G1)
7- 12 F6.3 mag rmag [18/24.5] r band magnitude
14- 15 A2 --- FlID Flare event ID (F1-F5)
17 A1 --- l_Tau0 Limit flag on Tau0
19- 24 F6.2 min Tau0 [3.5/508] Flare duration
26 A1 --- l_Pr Limit flag on Pr
28- 32 I5 s Pr [2/13416] The equivalent duration
34- 39 F6.3 [10-7W] logLr [29.5/32.1]? The quiescent luminosity
of the star
41 A1 --- l_logLrpk Limit flag on logLrpk
43- 48 F6.3 [10-7W] logLrpk [28.9/31.9] The flare luminosity
at maximum brightness
50 A1 --- l_logEr Limit flag on logEr
52- 57 F6.3 [10-7J] logEr [31.4/35.3] The Flare energy
61- 65 F5.3 % Pmem ? Cluster membership probability from
Nunez et al. (2015, J/ApJ/809/161)
--------------------------------------------------------------------------------
Global note:
Note (G1): The identification number (VarID) is a number uniquely identifying
each flare star (notations are taken from Paper II, in prep).
Star identification numbers come from Chang+, 2015, J/AJ/150/27;
<[CBH2015] VNNNN> in Simbad.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 22-Feb-2016