J/ApJ/909/106 R-band LC and spectrum of a superstellar flare (Xin+, 2021)
A ΔR∼9.5mag superflare of an ultracool star detected by the SVOM/GWAC
system.
Xin L.P., Li H.L., Wang J., Han X.H., Xu Y., Meng X.M., Cai H.B., Huang L.,
Lu X.M., Qiu Y.L., Wang X.G., Liang E.W., Dai Z.G., Wang X.Y., Wu C.,
Zhang J.B., Li G.W., Turpin D., Feng Q.C., Deng J.S., Sun S.S., Zheng T.C.,
Yang Y.G., Wei J.Y.
<Astrophys. J., 909, 106 (2021)>
=2021ApJ...909..106X 2021ApJ...909..106X
ADC_Keywords: Stars, flare; Photometry, RI; Spectra, optical; Stars, M-type
Keywords: Flare stars ; M dwarf stars ; Stellar flares ; Spectroscopy
Abstract:
We report the detection and follow-up of a superstellar flare
GWAC181229A with an amplitude of ΔR∼9.5mag on an M9-type star by
SVOM/GWAC and the dedicated follow-up telescopes. The estimated
bolometric energy Ebol is (5.56-9.25)x1034erg, which makes the event
one of the most powerful flares seen on ultracool stars. The magnetic
strength is inferred to be 3.6-4.7kG. Thanks to sampling with a
cadence of 15s, a new component near the peak time with a very steep
decay is detected in the R-band light curve, followed by the
two-component flare template given by Davenport+ (2014ApJ...797..122D 2014ApJ...797..122D).
An effective temperature of 5340±40K is measured by fitting a
blackbody shape to the spectrum in the shallower phase during the
flare. The filling factors of the flare are estimated to be ∼30% and
19% at the peak time and at 54 minutes after the first detection. The
detection of this particular event with large amplitude, huge emitted
energy, and a new component demonstrates that high-cadence sky
monitoring cooperation with fast follow-up observations is very
important for understanding the violent magnetic activity.
Description:
On 2018 December 29 UT10:42:51, an alert was generated by the
Ground-based Wide Angle Cameras (GWAC) online pipelines for a very
bright optical transient (GWAC 181229A) during a survey for one
predefined field from 10:03:07.8 to 14:55:21.0 UT on the same night.
The GWAC system located at Xinglong observatory of the National
Astronomical Observatories of China (NAOC) is an optical transient
survey that images the sky in the optical down to R∼16.0mag.
When the flare was triggered by the GWAC real-time pipeline, it was
immediately followed-up by the Guangxi-NAOC 60cm optical telescope
(F60A) in the standard Johnson-Cousins R band. See Section 3.1.
One long-slit spectrum was obtained by the NAOC 2.16m telescope by
using the Beijing Faint Object Spectrograph and Camera (BFOSC) via a
Target of Opportunity request. The observation start time for the
spectrum was at 11:21:51.0 UT, 39 minutes after the trigger time. The
exposure time was 30 minutes. The spectral resolution is ∼10Å for a
wavelength coverage of 3850-8000Å. See Section 3.2.
Objects:
---------------------------------------------------------
RA (ICRS) DE Designation(s)
---------------------------------------------------------
01 33 33.08 +00 32 23.0 GWAC 181229A = GWAC 181229A
---------------------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
fig2.dat 36 57 R-band light curve of GWAC181229A
fig6.dat 30 1801 The spectrum obtained by the 2.16m telescope at
Xinglong observatory, China
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See also:
V/154 : Sloan Digital Sky Surveys (SDSS), Release 16 (DR16) (Ahumada+, 2020)
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
J/A+A/333/231 : O-M stars model atmospheres (Bessell+ 1998)
J/A+A/487/293 : Em. lines in a giant flare of CN Leo (Fuhrmeister+, 2008)
J/AJ/141/97 : SDSS DR7 M dwarfs (West+, 2011)
J/MNRAS/435/2161 : Catalogue of bright (K<9) M dwarfs (Frith+, 2013)
J/ApJS/207/15 : M dwarf flare spectra (Kowalski+, 2013)
J/ApJ/794/120 : Sloan Digital Sky Survey coadd. Stripe 82 (Annis+, 2014)
J/AJ/149/158 : The BUD sample. I. L dwarf activity sample (Schmidt+, 2015)
J/ApJ/829/23 : Stellar flares from Q0-Q17 Kepler LCs (Davenport, 2016)
J/ApJ/858/55 : K2 ultracool dwarfs survey. III. Flares (Paudel+, 2018)
J/A+A/623/A127 : Homogeneous sample of 34000 M7-M9.5 dwarfs (Ahmed+, 2019)
J/ApJ/876/115 : Optical follow-up of ASAS-SN M dwarf flares (Schmidt+, 2019)
Byte-by-byte Description of file: fig2.dat
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Bytes Format Units Label Explanations
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1- 14 F14.6 d JD Julian Date of the observation
16- 18 I3 s Exp [10/150] Exposure time
20- 25 F6.3 mag Rmag [13.49/19.1] Apparent R band magnitude
27- 31 F5.3 mag e_Rmag [0.03/0.6] Uncertainty in Rmag
33- 36 A4 --- Tel Telescope code (1)
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Note (1): Telescope as follows:
GWAC = Ground-based Wide Angle Cameras at Xinglong observatory;
F60A = Guangxi-NAOC 60cm optical "A" telescope.
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Byte-by-byte Description of file: fig6.dat
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Bytes Format Units Label Explanations
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1- 16 F16.11 0.1nm lambda [3731.84/8691.75] Wavelength; Angstroms
18- 30 E13.6 cW/m2/nm Flux [-3.42e-16/1.6e-15] Flux;
in erg/s/cm2/Angstrom units
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 09-Aug-2022