J/A+A/699/A337 Flaring stars and brown dwarfs radio emission (Perger+, 2025)
Radio emission from flaring stars and brown dwarfs.
Perger K., Seli B., Vida K.
<Astron. Astrophys. 699, A337 (2025)>
=2025A&A...699A.337P 2025A&A...699A.337P (SIMBAD/NED BibCode)
ADC_Keywords: Stars, brown dwarf ; Stars, flare ; X-ray sources ; Radio sources
Keywords: stars: activity - stars: flare - stars: statistics -
radio continuum: stars - X-rays: stars
Abstract:
The vicinities of intermediate-to-late type dwarf stars are considered
as an adequate terrain to host planets suitable for life to form.
However, they are oftentimes showing increased stellar activity, which
should be taken into consideration when seeking potential habitable
planetary systems.
With the aim to reveal the effects of the magnetic field to the
multi-band activity of dwarf stars, we search for associated radio
emission for an extensive list of 14915 brown dwarfs and 15124
flaring stars. Methods. We utilised the first and second epoch
catalogues and radio maps from all three epochs of the VLASS,
supplemented with X-ray catalogues based on observations by the ROSAT,
eROSITA, and XMM-Newton space telescopes, and 2-minute cadence optical
light curves from the TESS mission. The radio-detected sub-sample was
queried for concurrent TESS observations, and sources with coinciding
light-curves were studied individually.
We found no associated radio emission for brown dwarfs, and found 55
radio counterparts for the sample of flaring stars, out of which 7
have coincident TESS observations. The radio-detected sample follows
both the radio-X-ray and the period-activity relations. We found a
strong correlation between the radio powers and the stellar parameters
of surface gravity, radius, and mass. We found no connection between
the flare rate and the radio variability. For radio-detected stars
with available effective temperatures and rotational periods, we
estimated gyrochronological ages, which resulted in values of
Tgyro≲1Gyr, with the majority of the sample being younger than
150Myr. We found no strong connection between the occurrence of
optical flares and radio variability for the individually studied
stars.
We conclude that radio emission from intermediate-to-late type flaring
stars is of synchrotron nature, and shares a common origin with X-ray
processes. It is created by a predominantly young stellar population,
and is the collective contribution of stellar flares, accretion, and
coronal heating.
Description:
We collected two large samples to test the stellar activity in the
radio regime, searching for radio counterparts within sqrt(2')
separation in the VLA Sky Survey data. We found no associated radio
emission to any of the brown dwarf candidates from Reyle
(2018A&A...619L...8R 2018A&A...619L...8R, cat. J/A+A/619/L8), and 55 matches in the list
of intermediate-to-late spectral type flaring stars from Seli et al.
(2025A&A...694A.161S 2025A&A...694A.161S), out of which seven stars with coincident
short-cadence TESS light curves available were individually inspected
in detail.`
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 172 55 List of the 55 radio detected flaring stars
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See also:
IV/39 : TESS Input Catalog version 8.2 (TIC v8.2) (Paegert+, 2021)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 9 I9 --- ID TIC number
10 A1 --- n_ID [*] * for objects with coincident
TESS observations
12- 16 F5.3 --- rate Fraction of time the star spends in
flaring state
19- 23 F5.3 --- rate34 ?=- Flares above the threshold 1e34 erg
25- 31 F7.1 K Teff ?=- Effective temperature
33- 37 F5.1 K e_Teff ?=- Error of effective temperature
39- 43 F5.2 d Prot ?=- Rotation period
46- 49 F4.2 d e_Prot ?=- Error of rotation period
51- 56 F6.1 Myr Tgyro ?=- Gyrochronological age
58- 65 F8.1 Myr E_Tgyro ?=- Upper limit on gyrochronological age
67- 74 F8.1 Myr e_Tgyro ?=- Lower limit on gyrochronological age
76- 86 A11 --- Type spectral type
88- 91 F4.1 --- snr1 SNR of epoch 1 VLASS image
93- 96 F4.1 mJy/beam rms1 RMS of epoch 1 VLASS image
98-100 F3.1 mJy S1 Flux density of VLASS epoch 1
102-104 F3.1 mJy e_S1 Error of flux density of VLASS epoch 1
106-109 F4.1 --- snr2 SNR of epoch 2 VLASS image
111-114 F4.1 mJy/beam rms2 RMS of epoch 2 VLASS image
116-119 F4.1 mJy S2 Flux density of VLASS epoch 2
121-123 F3.1 mJy e_S2 Error of flux density of VLASS epoch
125-128 F4.1 --- snr3 SNR of epoch 3 VLASS image
130-133 F4.1 mJy/beam rms3 RMS of epoch 3 VLASS image
135-137 F3.1 mJy S3 Flux density of VLASS epoch 3
139-141 F3.1 mJy e_S3 Error of flux density of VLASS epoch 3
143-146 F4.1 10-7W L1RX ?=- 1st ROSAT survey luminosity 0.1-2.4keV
149-152 F4.1 10-7W L2RXpl ?=- 2nd ROSAT survey luminosity 0.1-2.4keV
156-159 F4.1 10-7W LeRASS1 ?=- SRG/eROSITA luminosity 0.2-2.3keV
164-167 F4.1 10-7W LeRASSP3 ?=- SRG/eROSITA luminosity 1-2keV
169-172 F4.1 10-7W LXMM3 ?=- XMM-Newton luminosity 1-2keV
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Acknowledgements:
Krisztina Perger, perger.krisztina(at)csfk.org
(End) Patricia Vannier [CDS] 25-Jun-2025