J/ApJS/173/673 M dwarf UV flares in GALEX (Welsh+, 2007)
The detection of M dwarf UV flare events in the GALEX data archives.
Welsh B.Y., Wheatley J.M., Seibert M., Browne S.E., West A.A.,
Siegmund O.H.W., Barlow T.A., Forster K., Friedman P.G., Martin D.C.,
Morrissey P., Small T., Wyder T., Schiminovich D., Neff S., Rich R.M.
<Astrophys. J. Suppl. Ser., 173, 673-681 (2007)>
=2007ApJS..173..673W 2007ApJS..173..673W
ADC_Keywords: Stars, variable ; Magnitudes ; Ultraviolet
Keywords: stars: variables: other - ultraviolet: stars
Abstract:
We present the preliminary results from implementing a new software
tool that enables inspection of time-tagged photon data for the
astronomical sources contained within individual GALEX ultraviolet
(UV) images of the sky. We have inspected the photon data contained
within 1802 GALEX images to reveal rapid, short-term (≲500s) UV
source variability in the form of stellar "flares." The mean
associated change in near-UV (NUV) magnitude due to this flaring
activity is 2.7±0.3mag. A list of 49 new UV variable star
candidates is presented (associated with 52 separate flare events),
together with their associated Sloan Digital Sky Survey (SDSS)
photometric magnitudes. From these data we can associate the main
source of these UV flare events with magnetic activity on M dwarf
stars. Photometric parallaxes have been determined for 32 of these
sources, placing them at distances ranging from approximately 25 to
1000pc. The average UV flare energy for these flare events is
2.5x1030ergs, which is of a similar energy to that of U-band, X-ray,
and EUV flares observed on many local M dwarf stars. We have found
that stars of classes M0 to M5 flare with energies spanning a far
larger range and with an energy approximately 5 times greater than
those of later (M6 to M8) spectral type.
Description:
Our initial search for variability within the time-tagged source
photon lists was performed with data generated from 1802 individual
sky-field images contained in the GALEX data release IR1.1+GR1.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 132 52 List of short-term UV variable objects
table2.dat 50 33 M dwarf distances, NUV luminosities and
flare energies
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See also:
J/AJ/130/825 : GALEX ultraviolet variability catalog (Welsh+, 2005)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 6 F6.2 deg RAdeg Right Ascension in degrees (J2000)
8- 13 F6.2 deg DEdeg Declination in degrees (J2000)
15- 33 A19 --- SDSS SDSS-DR4 ID (JHHMMSS.ss+DDMMSS.s) (1)
35- 56 A22 --- Field GALEX Field (MAST Identifier)
58- 60 I3 --- Nobs Number of observations
62- 66 F5.2 mag NUVm NUV (175-275nm) magnitude maximum
68- 71 F4.2 mag NUVv NUV (175-275nm) magnitude variation
73- 77 F5.2 mag gmag ?=- SDSS g band magnitude
78 A1 --- f_gmag [b] magnitude uncertain due to CCD saturation
80- 84 F5.2 mag rmag ?=- SDSS r band magnitude
85 A1 --- f_rmag [b] magnitude uncertain due to CCD saturation
87- 91 F5.2 mag imag ?=- SDSS i band magnitude
92 A1 --- f_imag [b] magnitude uncertain due to CCD saturation
94- 98 F5.2 mag zmag ?=- SDSS z band magnitude
99 A1 --- f_zmag [b] magnitude uncertain due to CCD saturation
101-131 A31 --- Notes Probable spectral Type (or Simbad identifier)
132 A1 --- f_Notes [c] Spectral type based on USNOB data
134-152 A19 --- SDSS-DR6 Exact name from SDSS-DR6 (column added at CDS)
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Note (1): Format is sometimes rounded: JHHMMSS.ss+DDMMSS;
CR = SDSS image cosmic-ray contaminated.
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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- 19 A19 --- SDSS SDSS-DR4 Identifier
21- 25 A5 --- SpType Spectral Type
27- 29 I3 pc Dist Heliocentric distance
31- 35 F5.2 [solLum] Lbol Log of bolometric luminosity
37- 43 E7.2 10-7J ENUV Total NUV flare energy
44 A1 --- n_ENUV [a] Note when two flares observed
46- 49 F4.1 [-] Lfl/Lbol log of NUV flare luminosity referenced to
the stellar bolometric luminosity
50 A1 --- n_Lfl/Lbol [a] 'a' when two flares observed
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History:
* 28-May-2009: from electronic version of the journal
* 07-Jul-2009: added column "SDSS-DR6" in table1, in order to
give the accurate SDSS name
(End) Emmanuelle Perret [CDS] 28-May-2009