J/AJ/168/234 Flares & flaring stars from TESS & machine learning (Lin+, 2024)
Scalable, advanced machine learning based approaches for stellar flare
identification: application to TESS short-cadence data and analysis of a
new flare catalog.
Lin C.-L., Apai D., Giampapa M.S., Ip W.-H.
<Astron. J. 168, 234 (2024)>
=2024AJ....168..234L 2024AJ....168..234L (SIMBAD/NED BibCode)
ADC_Keywords: Stars, flare ; Optical ; Photometry ; Models
Keywords: Stellar flares; Optical flares; Random Forests; Classification
Neural networks
Abstract:
We apply multialgorithm machine learning models to TESS 2min survey
data from Sectors 1-72 to identify stellar flares. Models trained with
deep neural network, random forest, and XGBoost algorithms utilize
four flare light-curve characteristics as input features. Model
performance is evaluated using the accuracy, precision, recall, and
F1 score metrics, all exceeding 94%. Validation against previously
reported TESS M dwarf flare identifications shows that our models
successfully recover over 92% of the flares while detecting ∼2000 more
small events, thus extending the detection sensitivity of previous
work. After processing 1.3 million light curves, our models identify
nearly 18,000 flare stars and 250,000 flares. We present an extensive
catalog documenting both flare and stellar properties. We find strong
correlations of total flare energy and flare amplitude with color, in
agreement with previous studies. Flare frequency distributions are
analyzed, refining power-law slopes for flare behavior with frequency
uncertainties due to the detection incompleteness of low-amplitude
events. We determine rotation periods for ∼120,000 stars thus yielding
the relationship between rotation period and flare activity. We find
that the transition in rotation period between the saturated and
unsaturated regimes in flare energy coincides with the same transition
in rotation period separating the saturated and unsaturated levels in
coronal X-ray emission. We find that X-ray emission increases more
rapidly with flare luminosity in earlier-type and unsaturated stars,
indicating more efficient coronal heating in these objects.
Additionally, we detect flares in white dwarfs and hot subdwarfs,
which likely arise from unresolved low-mass companions.
Description:
The Transiting Exoplanet Survey Satellite (TESS), launched on
2018 April 18, utilizes 2min short-cadence time-series data with high
photometric precision and a wavelength coverage of approximately
600-1000nm. The four cameras of TESS cover the sky in two hemispheres
divided into 13 sectors each. Each sector is being observed for
approximately 27 days. By 2024 January, TESS has observed 72 sectors
covering about 85% of the sky and accumulating approximately
1.3 million short-cadence light curves from over 490,000 sources.
For the purposes of this study, we have utilized the Pre-search Data
Conditioning Simple Aperture Photometry (PDCSAP) flux, specifically
selecting data points with a "good-quality" flag (flag bits
QUALITY = 0) for our analysis.
Our models identified 18,032 Quadrant IV flare stars with a total of
249,562 flares in the entire TESS 2min light curves from Sector 1 to
Sector 72.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 .
table9.dat 111 249562 Catalog of flares detected by machine
learning models
table10.dat 131 18032 Catalog of flaring stars identified by
machine learning models
--------------------------------------------------------------------------------
See also:
I/347 : Dist. to 1.33 billion stars in Gaia DR2 (Bailer-Jones+, 2018)
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
IV/38 : TESS Input Catalog - v8.0 (TIC-8) (Stassun+, 2019)
IV/39 : TESS Input Catalog version 8.2 (TIC v8.2) (Paegert+, 2021)
J/A+AS/139/555 : Catalogue and Bibliography of UV Cet stars (Gershberg+ 1999)
J/A+A/397/147 : Activity-rotation relationship in stars (Pizzolato+ 2003)
J/ApJ/743/48 : Stars rotation periods & X-ray luminosities (Wright+, 2011)
J/other/Nat/485.478 : Superflares on solar-type stars (Maehara+, 2012)
J/ApJS/209/5 : Superflares of Kepler stars. I. (Shibayama+, 2013)
J/MNRAS/445/2268 : Bayesian method for detecting stellar flares (Pitkin+, 2014)
J/ApJ/814/35 : Flare events in M dwarf of M37 (Chang+, 2015)
J/A+A/581/A28 : Stellar X-ray flares from the 2XMM catalog (Pye+, 2015)
J/ApJ/809/77 : Transiting Exoplanet Survey Satellite (TESS) (Sullivan+, 2015)
J/ApJ/829/23 : Stellar flares from Q0-Q17 Kepler LCs (Davenport, 2016)
J/AJ/156/178 : NIR transmission spectra of TRAPPIST-1 planets (Zhang+, 2018)
J/A+A/628/A41 : KIC stars in Kepler/XMM-Newton (Pizzocaro+, 2019)
J/ApJS/241/29 : Flare catalog through LC data of Kepler DR25 (Yang+, 2019)
J/AJ/159/60 : 8695 flares from 1228 stars: TESS sect. 1 & 2 (Gunther+, 2020)
J/ApJ/905/107 : Spectroscopic activity indicators of TIC stars (Medina+, 2020)
J/A+A/637/A22 : M dwarfs rotation-activity relations and flares (Raetz+, 2020)
J/AJ/162/11 : EDEN proj.: Flare act. of nearby M-dwarf Wolf 359 (Lin+, 2021)
J/A+A/664/A105 : Stellar content of the ROSAT all-sky survey (Freund+, 2022)
J/ApJ/926/204 : TESS monitoring campaign: low-mass flare stars (Howard+, 2022)
J/ApJS/258/16 : TESS Eclipsing Binary stars. I. Sectors 1-26 (Prsa+, 2022)
J/ApJ/935/90 : Superflare candidates in ∼72000 G-stars (Tu+, 2022)
J/A+A/669/A15 : TESS flare events and physical parameters (Yang+, 2023)
J/ApJS/271/57 : Flares in hot subdwarf & WDs from TESS phot. (Xing+, 2024)
Byte-by-byte Description of file: table9.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 I10 --- TIC [33905/2055217415] TESS Input Catalog
identifier
12- 19 F8.5 --- FAmp [1e-4/32] Observed flare amplitude
21- 28 F8.5 --- FAmp-cal [2e-4/31] Calibrated flare amplitude
30- 36 F7.2 min FDur [6.9/3712] Observed flare duration
38- 45 F8.2 min FDur-cal [6.9/13050] Calibrated flare duration
47- 56 E10.3 10-7J FEner ? Observed flare energy in ergs
58- 67 E10.3 10-7J FEner-cal ? Calibrated flare energy in ergs
69- 74 F6.4 --- ED1/ED2 [0.02/1] Upper-to-lower equivalent durations
ratio (1)
76- 81 F6.4 --- t1/t2 [3e-3/1] Impulsive-decay time ratio
83- 91 F9.4 d tStart Flare Start Time, Barycentric TESS Julian
Date (2)
93- 101 F9.4 d tPeak Flare Peak Time, Barycentric TESS Julian
Date (2)
103- 111 F9.4 d tEnd Flare End Time, Barycentric TESS Julian
Date (2)
--------------------------------------------------------------------------------
Note (1): ED1 is the equivalent duration above the half-peak amplitude of
the light-curve profile, ED2 is the one below half-peak
Note (2): Flare times given in Barycentric TESS Julian Date (BTJD),
which is the time corrected for light travel time to solar system
barycenter, based on TNS coordinates. TESS Julian date is JD-2457000.
--------------------------------------------------------------------------------
Byte-by-byte Description of file:table10.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 I10 --- TIC [33905/2055217415] TESS Input Catalog identifier
12- 20 F9.5 deg RAdeg Right Ascension from TIC v8.2 (IV/39) (J2000)
22- 30 F9.5 deg DEdeg Declination from TIC v8.2 (IV/39) (J2000)
32- 39 F8.5 mag BP-RP [-1.9/11.4]? Gaia DR3 (I/355) BP-RP color
41- 48 F8.5 mag Gmag [2.6/19.4]? Gaia DR3 (I/355) G-band magnitude
50- 55 F6.3 mag Tmag [1.3/18.6] TESS magnitude from TIC v8.2 (IV/39)
57- 63 F7.1 K Teff [2722/58450]? Effective temperature from
TIC v8.2 (IV/39)
65- 71 F7.3 Rsun Rad [0.1/202]? Radius from TIC v8.2 (IV/39)
73- 82 F10.5 pc Dist [1/9401]? Distance from TIC v8.2 (IV/39) and
Bailer-Jones+ 2018 (I/327)
84- 91 F8.5 d Prot [0.03/26.5]? Mean Rotation period
93- 102 F10.5 d e_Prot [0/5e3]? Uncertainty in Prot
104- 110 F7.5 --- Vamp [3e-4/2]? Mean light curve variation index
112- 118 F7.5 --- e_Vamp [0/3.1]? Uncertainty in Vamp
120- 127 F8.5 --- Rcont [0/61.4]? Contamination ratio from TIC-8 (IV/38),
see Section 2.1
129- 131 I3 --- Nf [1/857] Number of flares detected
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Prepared by [AAS], Robin Leichtnam [CDS] 01-Jul-2025