J/A+A/686/A164 Magnetic activity of radio stars (Wang+, 2024)
Magnetic activity of radio stars based on TESS and LAMOST surveys.
Wang Y., Zhang L., Su T., Han X.L., Misra P.
<Astron. Astrophys. 686, A164 (2024)>
=2024A&A...686A.164W 2024A&A...686A.164W (SIMBAD/NED BibCode)
ADC_Keywords: Stars, flare ; Stars, radio ; Magnetic fields
Keywords: stars: activity - stars: flare - stars: statistics
Abstract:
Stellar flares serve as crucial indicators for stellar magnetic
activity. Radio emissions were detectable across all stages of stellar
evolution. We defined radio stars in our paper as stars with radio
continuum emission in the frequency region of about 1.4-375GHz from
the catalogue published by Wendker (1995A&AS..109..177W 1995A&AS..109..177W, Cat. II/199,
2015 update, Cat. VIII/99). We also included detected radio stars from
the LOFAR Two-metre Sky Survey (LoTSS), Australian Square Kilometre
Array Pathfinder (ASKAP) and VLA Sky Survey (VLASS) surveys provided
by previous work, and conducted comparative discussions. We utilize
the light curves from the Transiting Exoplanet Survey Satellite (TESS)
survey, coupled with low- and medium-resolution spectra from the Large
Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) survey,
to investigate the magnetic activity and statistical properties of
radio stars.
We cross-matched the radio stars from the radio star catalogue and the
LoTSS, ASKAP and VLASS surveys with TESS survey. For the stars from
the radio star catalog, we obtained a matched sample of 1537 stars
(hereafter called "Sample 1") and downloaded their TESS light curves,
which included 4001 light curves at a 120-second cadence. For the
stars from the LoTSS, ASKAP and VLASS surveys, we obtained a matched
sample of 98 stars (hereafter called "Sample 2") and downloaded their
120-second TESS light curves, totaling 260. Subsequently, we employed
repeated fitting techniques to distinguish stellar background light
curves from flare events. For Sample 1, we successfully identified
12,155 flare events occurring on 856 stars. For the Sample 2, totally
3992 flare events were identified on 86 stars. Furthermore, by cross-
referencing our samples with the Gaia survey, TESS Input Catalog, and
LAMOST survey, we obtained additional stellar parameters, facilitating
the determination of relationships between stellar and flare
parameters.
For stars in Sample 1, within the 12155 flare events observed on the
856 flare-active radio stars, a majority more than 97% had durations
of less than 2 hours, while for stars in Sample 2, all 3992 flare
events have a duration of less than two hours. We calculated the flare
occurrence percentage for each flare-active radio star, observing a
decrease as effective temperature increased for both Sample 1 and
Sample 2. We derived values of power-law index (For Sample 1, alpha
value approximately 1.50(0.11) for single stars and 1.38(0.09) for
binary stars, for Sample 2, alpha value is about 1.47(0.11) for single
stars and 1.42(0.09) for binary stars) for the cumulative flare
frequency distribution. In both Sample 1 and Sample 2, stars with
lower effective temperatures tended to exhibit increased activity.
Utilizing LAMOST spectra and Gaia DR3 chromospheric activity index, we
noted that the Halpha equivalent width and Gaia Ca II IRT activity
index of flare-active radio stars was significantly larger than that
of non-flare stars. An intriguing finding was the potential
identification of a coronal rain candidate through the asymmetry
observed in the Halpha line.
Description:
File table1 present the stellar parameters of radio stars in both the
Sample 1 and Sample 2, encompassing crucial details such as stellar
effective temperature, radius, rotation and/or orbital period, and
single or binary star system labels (Bin) and evolutionary stages
(Evo). File table2 compiled the specific flare parameters of the flare
radio stars (for both Sample 1 and Sample 2), it includes TESS ID,
SECTOR, the start and end time of flare, the time of flare peak,
duration, amplitude and bolometric flare energy. In both tables, we
provide Sample ID (1 and/or 2) to indicate from which sample the
corresponding row's data originates.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 181 1635 Parameters of TESS radio stars
table2.dat 90 16147 Parameters of flare events from radio stars
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See also:
VIII/99 : Catalogue of Radio Stars (Wendker, 2001)
IV/38 : TESS Input Catalog - v8.0 (TIC-8) (Stassun+, 2019)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 15 A15 --- TIC TESS ID, TIC NNNNNNNNN
17 I1 --- Sample [1/2] Sample id
19- 31 F13.9 degree RAdeg Right ascension (J2000)
33- 45 F13.9 degree DEdeg Declination (J2000)
47- 58 F12.8 mag TESSMAG TESS magnitude
60- 72 F13.7 K Teff ?=- Effective temperature
73- 83 F11.8 [cm/s2] logg ?=- Surface gravity
85- 97 F13.8 Rsun Radius ?=- Radius
99-103 F5.3 Msun Mass ?=- Mass
105-115 F11.8 [-] [Fe/H] ?=- Metallicity [Fe/H]
117-122 F6.3 Gyr Age ?=- Age
124-138 F15.9 d Per ?=- Rotation and/or orbital period
140-153 F14.8 pc Dist ?=- Gaia distance
155-160 F6.2 km/s RV ?=- Radial velocity
162-167 A6 --- Bin Single or binary star flag, single or binary
169-181 A13 --- Evol Evolutionary stage
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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- 15 A15 --- TIC TESS ID, TIC NNNNNNNNN
17- 18 I2 --- Sector [1/72] TESS SECTOR
20- 30 F11.6 d BeginTime Flare begin time
32- 42 F11.6 d PeakTime Flare peak time
44- 54 F11.6 d EndTime Flare end time
56- 66 F11.9 d Duration Flare duration
68- 79 F12.9 --- Amplitude Flare amplitude
81- 88 A8 10-7J Ebol ?=- Bolometric flare energy
90 I1 --- Sample [1/2] Sample id
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Acknowledgements:
Wang Yinpeng, liy_zhang(at)hotmail.com
(End) Wang Yinpeng [GZU, P.R. China], Patricia Vannier [CDS] 11-Mar-2024