J/ApJ/910/25 X-ray flare LCs of the RS CVn-type star GT Mus (Sasaki+, 2021)
The RS CVn-type star GT Mus shows most energetic X-ray flares throughout the
2010s.
Sasaki R., Tsuboi Y., Iwakiri W., Nakahira S., Maeda Y., Gendreau K.,
Corcoran M.F., Hamaguchi K., Arzoumanian Z., Markwardt C.B., Enoto T.,
Sato T., Kawai H., Mihara T., Shidatsu M., Negoro H., Serino M.
<Astrophys. J., 910, 25 (2021)>
=2021ApJ...910...25S 2021ApJ...910...25S
ADC_Keywords: Stars, flare; X-ray sources; Binaries, spectroscopic;
Stars, variable; Stars, double and multiple
Keywords: Stellar x-ray flares ; Stellar activity ; Time series analysis
Abstract:
We report that the RS CVn-type star GT Mus (HR 4492,
HD101379+HD101380) was the most active star in the X-ray sky in the
last decade in terms of the scale of recurrent energetic flares. We
detected 11 flares from GT Mus in 8yr of observations with the Monitor
of All-sky X-ray Image (MAXI) from 2009 August to 2017 August. The
detected flare peak luminosities were 1-4x1033erg/s in the
2.0-20.0keV band for its distance of 109.6pc. Our timing analysis
showed long durations (τr+τd) of 2-6d with long decay
times (τd) of 1-4d. The released energies during the decay
phases of the flares in the 0.1-100keV band were in the range of
1-11x1038erg, which are at the upper end of the observed stellar
flare. The released energies during the whole duration were in the
range of 2-13x1038erg in the same band. We carried out X-ray
follow-up observations for one of the 11 flares with the Neutron star
Interior Composition Explorer (NICER) on 2017 July 18 and found that
the flare cooled quasi-statically. On the basis of a quasi-static
cooling model, the flare loop length is derived to be 4x1012cm (or
60R☉). The electron density is derived to be 1x1010cm-3,
which is consistent with the typical value of solar and stellar flares
(1010-13cm-3). The ratio of the cooling timescales between
radiative (τrad) and conductive (τcond) cooling is
estimated to be τrad∼0.1τcond from the temperature; thus,
radiative cooling was dominant in this flare.
Description:
The Monitor of All-sky X-ray Image (MAXI) is an astronomical X-ray
observatory mounted on the ISS. In this analysis, we used data from
the Gas Slit Camera only, which is sensitive in the 2-30keV band.
We carried out follow-up observations of a GT Mus flare (FN 11) with
the Neutron star Interior Composition Explorer (NICER) on the ISS.
See Section 2.2.
Objects:
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RA (ICRS) DE Designation(s)
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11 39 29.59 -65 23 52.0 GT Mus = HR 4492
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 59 11 Flare epoch, photon flux, and significance of
detection with MAXI
fig2.dat 34 270 Light curves of the eleven flares of GT Mus
detected with MAXI in the 2.0-10.0keV band
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See also:
IX/10 : ROSAT All-Sky Bright Source Catalogue (1RXS) (Voges+ 1999)
I/337 : Gaia DR1 (Gaia Collaboration, 2016)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
V/76 : Chromospherically Active Binaries (Strassmeier+ 1993)
J/A+A/394/505 : UBV photometry of LQ Hya (Berdyugina+, 2002)
J/AJ/129/2798 : AR Mon photometry and radial velocities (Williamon+, 2005)
J/MNRAS/389/925 : Triple and quadruple stars (Tokovinin, 2008)
J/A+A/521/A36 : BV differential photometry of V711 Tau (Muneer+, 2010)
J/ApJ/743/48 : Stars with rot. periods & X-ray luminosities (Wright+, 2011)
J/A+A/559/A97 : II Pegasus photometry during 1979-2010 (Lindborg+, 2013)
J/A+A/614/A125 : Stellar content of the XMM-Newton slew survey (Freund+, 2018)
http://maxi.riken.jp/mxondem/ : MAXI on-demand process
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- ID Flare identifier (FN01 to FN11)
6 A1 --- r_ID Flag on ID (1)
8- 16 F9.3 d MJD [55073.69/57952.52] Modified Julian Date (2)
18- 22 F5.3 d e_MJD [0.39/1.42] MJD uncertainty
24- 40 A17 "datime" Date Date of observation (UT) (3)
42- 45 F4.2 ph/s/cm2 Flux [0.07/0.27] 2-10keV flux
in photons/s/cm2 units
47- 50 F4.2 ph/s/cm2 e_Flux [0.01/0.02] Flux uncertainty
52- 55 F4.1 --- Sig [6/25.3] Significance in σ
57- 59 A3 --- Det Detection method (4)
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Note (1): Flag as follows:
e = Nakajima+ (2010ATel.3021....1N 2010ATel.3021....1N) and Tsuboi+ (2016PASJ...68...90T 2016PASJ...68...90T)
f = Kanetou et al. (2015ATel.8285....1K 2015ATel.8285....1K)
g = Sasaki et al. (2016ATel.9251....1S 2016ATel.9251....1S)
Note (2): Detection time of the flare in the adaptive binning (see the text
for details).
Note (3): Center time of the observation.
Note (4): Here "n" and "B" are the nova-alert system and the Bayesian block,
respectively.
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Byte-by-byte Description of file: fig2.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- ID Flare identifier (FN01 to FN11)
6- 12 F7.4 d MJDr [-5.9/10] Relative time in MJD (1)
14- 19 F6.4 d e_MJDr [0.001/0.25] Uncertainty in MJDr
21- 27 F7.4 ph/s/cm2 Flux [-0.027/0.31] MAXI 2-10keV band Photon flux
29- 34 F6.4 ph/s/cm2 e_Flux [0.006/0.05] Uncertainty in Flux
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Note (1): This is time relative to a fixed point. Each Flare's set time is:
FN01 = 55073;
FN02 = 55510;
FN03 = 55912;
FN04 = 55938;
FN05 = 56052;
FN06 = 56264;
FN07 = 56602;
FN08 = 56824;
FN09 = 57341;
FN10 = 57586;
FN11 = 57952.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 11-Aug-2022