J/ApJS/207/15 M dwarf flare spectra (Kowalski+, 2013)
Time-resolved properties and global trends in dMe flares from simultaneous
photometry and spectra.
Kowalski A.F., Hawley S.L., Wisniewski J.P., Osten R.A., Hilton E.J.,
Holtzman J.A., Schmidt S.J., Davenport J.R.A.
<Astrophys. J. Suppl. Ser. 207, 15 (2013)>
=2013ApJS..207...15K 2013ApJS..207...15K (SIMBAD/NED BibCode)
ADC_Keywords: Stars, flare ; Stars, atmospheres ; Spectroscopy
Keywords: stars: flares - stars: atmospheres
Abstract:
We present a homogeneous analysis of line and continuum emission from
simultaneous high-cadence spectra and photometry covering
near-ultraviolet and optical wavelengths for 20 M dwarf flares. These
data were obtained to study the white-light continuum components at
bluer and redder wavelengths than the Balmer jump. Our goals were to
break the degeneracy between emission mechanisms that have been fit to
broadband colors of flares and to provide constraints for
radiative-hydrodynamic (RHD) flare models that seek to reproduce the
white-light flare emission. New model constraints are presented for
the time evolution among the hydrogen Balmer lines and between CaII K
and the blackbody continuum emission. We calculate Balmer jump flux
ratios and compare to the solar-type flare heating predictions from
RHD models. The model ratios are too large and the blue-optical
(λ=4000-4800Å) slopes are too red in both the impulsive and
gradual decay phases of all 20 flares. This discrepancy implies that
further work is needed to understand the heating at high column mass
during dMe flares.
Description:
The spectral data are contained in FITS files (to be read into IDL
with mrdfits.pro), and the photometry data are contained in two
column .dat files.
Spectra were obtained with the Dual-Imaging Spectrograph (DIS) on the
ARC 3.5m telescope at the Apache Point Observatory (APO) in
low-resolution. The observing log for each target star is given in
Table 2.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 159 16 *Observing log
table6.dat 89 20 Flare summary table
list.dat 53 11 List of FITS files
phot/* . 21 Individual photometry files
fits/* . 11 Individual FITS spectra
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Note on table2.dat: Note that the photometry and spectra for 2009 January 16 are
the same as those presented in Kowalski et al. (2010ApJ...714L..98K 2010ApJ...714L..98K).
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Star Star name
10- 20 A11 "YYYY/MMM/DD" Date UT date of observation (1)
22- 26 I5 d MJD ? Modified Julian date of observation
28- 32 F5.3 h Time ? Total monitoring time for the night
34- 51 A18 s Exp ? Exposure time
53- 55 I3 --- nB ? Number of exposures of sufficient quality
for blue analysis (2)
57- 59 I3 --- nT ? Total number of exposures obtained (2)
60 A1 --- f_nT [c] Flag on nT (3)
62- 64 I3 --- nR ? Number of short exposures obtained at a
lower cadence (2)
66- 68 F3.1 arcsec slit ? Slit width
70- 73 F4.1 0.1nm FWHM ? FWHM of arc line HeI4471
75- 76 I2 0.1nm Res ? Full width at 0.1max of arc line HeI4471
78- 82 A5 0.1nm FWHMg ? FWHM of Hγ for a sample target
spectrum
84- 86 F3.1 m Inst ? Instrument (4)
88- 91 A4 --- Filt Filter(s) (U or ugri)
93- 95 F3.1 m Inst2 ? 2nd Instrument (4)
97- 99 A3 --- Filt2 Filter(s) for Inst2 (ugr)
101-107 A7 --- Flare Flare(s) ID (1)
109-120 A12 --- File1 Name of the band-photometry file (first
filter) in subdirectory phot
122-133 A12 --- File2 Name of the band-photometry file (2nd
filter) in subdirectory phot
135-146 A12 --- File3 Name of the band-photometry file (3rd
filter) in subdirectory phot
148-159 A12 --- File4 Name of the band-photometry file (4th
filter) in subdirectory phot
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Note (1): In addition of 31 nights of observations, we consider the data
obtained during the large flare of 2009 October 27 on EV Lac, which
was discussed in Schmidt et al. (2012ApJ...745...14S 2012ApJ...745...14S). The blue
spectra were obtained at the Dominion Astrophysical Observatory (DAO)
and have much lower time resolution (200-300s) and only cover the
wavelength range λ=3550-4700Å with R∼750, but these data
encompass an unusually fast and large amplitude flare. We also
calculate relevant quantities from the Great Flare on AD Leo of
1985 April 12 (Hawley & Pettersen 1991ApJ...378..725H 1991ApJ...378..725H) for comparison.
The total number of flares in our sample is therefore 20.
Note (2): The data from 2010 February 14 exclude the short nR exposure data from
the nB total. The data from 2010 April 3 exclude the short nR exposure
data from the nB total. Section 2.2 for more information.
Note (3):
c = Does not include two spectra that were found to have spurious flux values
and does not include the four spectra at the beginning of the night that
had 30s exposure times and saturated red flux values.
Note (4): Instruments as follows:
0.5 = ARCSAT 0.5m telescope at the APO with the Flarecam instrument
(SDSS ugri filters)
1. = NMSU 1m telescope (continuous Johnson U-band photometry)
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- Flare Flare identifier
5 A1 --- f_Flare [bc] Flag on Flare (1)
7- 14 A8 --- Star Star name
16- 26 A11 "YYYY/MMM/DD" Date Observation date
28- 29 I2 --- Ext Extension number for the fits files (see
Note (1) of list.dat)
31- 37 F7.4 h Tpk Time from the beginning of the MJD (2)
39- 44 F6.4 h Tpk2 ? 2nd Tpk
46- 51 F6.2 --- If If, U+1 at peak photometry (3)
53- 56 F4.1 --- If2 ? 2nd If (for GF5, this is the upper range
and If is the lower range)
57 A1 --- f_If2 [d] Flag on If2 (1)
59- 63 I5 s ED Equivalent duration in U (4)
65- 69 F5.2 10-25J EU U-band energy (in 1032erg)
71 I1 10-25J uEU ? Upper EU for IF9 (in this case, EU is the
lower range)
73- 77 F5.2 10+22W LU U-band luminosity at peak photometry
79- 83 F5.2 min t1/2 t1/2, U (5)
85- 89 F5.2 --- I Impulsiveness index (6)
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Note (1): Flag as follows:
b = All properties pertain to spectral observation window except peak
amplitude of U, t1/2, U, and I.
c = U-band properties were estimated from spectra because no U-band data were
obtained. The t1/2 for GF5 estimated by smoothing the light curve over
three spectra. The energies for HF2 are lower limits because the
observations ended before the end of the gradual phase.
d = Estimated from spectra with longer integration time than the photometry.
Note (2): Time from the beginning of the MJD (tpeak) obtained from spectra
using the mid exposure of maximum C3615, except for IF1 (see note on
times in Section 3.2).
Note (3): The measure If is the familiar quantity in flare studies (Gershberg
1972Ap&SS..19...75G 1972Ap&SS..19...75G). It is the ratio of flare-only count flux
(photons/cm2/s) in a given band to the quiescent count flux in that
band. See section 3.1 for further explanations.
Note (4): The equivalent duration (ED) in a given bandpass is the integral of
If over the duration of a flare (Gershberg 1972Ap&SS..19...75G 1972Ap&SS..19...75G). The
units are in seconds and multiplying by the quiescent luminosity in
the band gives the energy of the flare.
Note (5): To describe the time evolution of a light curve, we define t1/2, the
full width of the light curve at half-maximum. See section 3.1 for
further explanations.
Note (6): To characterize the shape of the light curve, we use an "impulsiveness
index," , which is defined as I=If,peak/t1/2 (Equation (2)). The
quantity is a measure of the peak relative flux of a flare weighted by
how fast it rises to peak and decays. Both a more luminous-at-peak
flare and a smaller t1/2 (faster timescale) can give rise to larger
values of I. We find that this measure provides a way to
quantitatively sort the flares according to their light curve
evolution, while only using observables measured directly from the
light curve.
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 13 A13 --- FileName Name of the file in subdirectory fits (1)
17- 53 A37 ---- Title Title of the file
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Note (1): Notes on explanations of the FITS files:
ofluxnB.fit:
2D array of flux with dimensions of (nspec, nwave) where nspec is the number
of spectra and nwave is the number of wavelength points. This flux is the
original flux (quiescent+flare) before applying the scaling algorithm
and quiescent (or pre-flare) subtraction as described in Section 2.6 and
Appendix A. These spectra correspond to the nB subcategory of spectra, which
are suitable for blue continuum analysis (see Section 2.2).
The IDL index (starting with 0) of the nspec dimension corresponds to the S#
referred to in the text.
rfluxnB.fit:
2D array of flux with dimensions of (nspec, nwave) where nspec is the number
of spectra and nwave is the number of wavelength points. This flux is the
flare-only flux, obtained after scaling the original flux (using the
algorithm described in Section 2.6 and Appendix A) and after subtracting a
master quiescent (or pre-flare) spectrum. These spectra correspond to the nB
subcategory of spectra, which are suitable for blue continuum analysis (see
Section 2.2). The IDL index (starting with 0) of the nspec dimension
corresponds to the S# referred to in the text.
time_nB.fit:
1D array of times with dimension (nspec) corresponding to the spectra in
rfluxnB.fit and ofluxnB.fit. The units are hours elapsed on the UT
date/MJD given in Table 2, and they correspond to the midtime of the
exposure.
exp_nB.fit:
1D array of exposure times with dimension (nspec) corresponding to the
spectra in rfluxnB.fit and ofluxnB.fit.
quies.fit:
1D array of flux with dimension (nwave). This flux is the master quiescent
(or pre-flare) spectrum used to obtain the flare-only flux. The quiescent
flux has been scaled to the accepted V and B fluxes as described in
Section 2.6.
quies_t.fit
This is the approximate time interval from time_nB.fit when spectra were
co-added to form the master quiescent spectrum in quies.fit. The units are
hours elapsed on the UT date/MJD given in Table 2.
wl.fit
1D array with dimension of (nwave). This is the wavelength solution for all
spectra with the same extension.
There may be additional data with shorter exposure times that were not used
in the analysis (i.e., not in the nB subcategory of spectra). These extra
spectra are contained in the nR subcategory of spectra (see Section 2.2 and
Table 2). We also include these in the online data, but we suggest to use the
nB subcategory of spectra unless the nR spectra may be useful for a
particular need not requiring high signal-to-noise at blue wavelengths. The
formats of the following *_nR.fit files are the same as the respective
*_nB.fit files.
To read in a set of spectra, use the IDL program mrdfits.pro:
spec = mrdfits('rfluxnB.fit',extension)
where extension corresponds to the following flare events:
extension=0 : IF3
extension=1 : GF1
extension=2 : IF5
extension=3 : IF9
extension=4 : IF2
extension=5 : HF1
extension=6 : IF4
extension=7 : HF4
extension=8 : IF1/MDSF2
extension=9 : IF7
extension=10 : IF8
extension=11 : IF6
extension=12 : GF3
extension=13 : GF2
extension=14 : HF2
extension=15 : HF3
extension=16 : GF4
extension=17 : GF5
extension=18 : IF0
extension=19 : IF10
Most extensions of the *_nR.fit files have values of [-9.,-9.];
no data are stored in the FITS file corresponding to these extensions.
Values are stored in extensions=1,2,3, and 9 of the *_nR.fit files.
The value of quies_t.fit for extension=8 is [-9.,-9.] because
the quiescent spectrum was obtained from 2008 Nov 24 (see Kowalski et al.
2010 ApJL 74, L98, Section 2.2).
Notes on the photometry file naming convention:
The filename format of the aperture photometry data files is: abYYMMDD.dat
"a" is either "S" or "J", corresponding to an SDSS filter or Johnson filter,
respectively.
"b" is the filter: "U", "u", "g", "r", or "i" (lowercase indicates an SDSS
filter).
"YYMMDD" is the UT Date: year (YY), month (MM), and day (DD) as given in
Table 2.
For example, "110224" corresponds to 2011-Feb-24. The photometry available
for each night is listed in Table 2.
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Byte-by-byte Description of file(#): phot/*
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Bytes Format Units Label Explanations
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1- 8 F8.5 h Time Hours elapsed on UT date in Table 2 (1)
12- 18 F7.3 --- RFlux Aperture photometry given as relative count
flux normalized to quiescence
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Note (1): Notes on individual files:
The time in JU090116.dat is given in hours elapsed from flare start;
add 4.2483 hours to the time in JU090116.dat to obtain the hours elapsed
on the UT date from Table 2.
The blue photometry from 101011 (Uu101011.dat) is a merged light curve with
both Johnson U-band and SDSS u-band data. The Johnson U-band data (from the
NMSU 1m) extend from 1.7782 hours to 1.9613 hours and then from 2.4869 hours
to 4.5125 hours.
The SDSS u-band (from the ARCSAT 0.5m) data extend from 1.9613 hours to
2.4869 hours and then from 4.5125 hours to 8.9971 hours.
For exposure times of the photometry, see Section 2.3.
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Acknowledgements:
Adam Kowalski, adam.f.kowalski(at)nasa.gov
(End) Adam Kowalski [NASA-GSFC], Patricia Vannier [CDS] 10-Jun-2013