J/ApJ/905/107 Spectroscopic activity indicators of TIC stars (Medina+, 2020)
Flare rates, rotation periods, and spectroscopic activity indicators of a
volume-complete sample of mid- to late-M dwarfs within 15pc.
Medina A.A., Winters J.G., Irwin J.M., Charbonneau D.
<Astrophys. J., 905, 107 (2020)>
=2020ApJ...905..107M 2020ApJ...905..107M
ADC_Keywords: Stars, flare; Stars, distances; Equivalent widths;
Spectra, optical; Stars, masses
Keywords: Stellar activity ; Stellar rotation ; Stellar flares
Abstract:
We present a study of flare rates, rotation periods, and spectroscopic
activity indicators of 125 single stars within 15 parsecs and with
masses between 0.1 and 0.3M☉ observed during the first year of
the TESS mission, with the goal of elucidating the relationship
between these various magnetically connected phenomena. We gathered
multiepoch high-resolution spectra of each target, and we measured
equivalent widths of the activity indicators helium I D3, Hα,
and the calcium infrared triplet line at 8542.09Å. We present 18
new rotation periods from MEarth photometry and 19 new rotation
periods from TESS photometry. We present a catalog of 1392 flares.
After correcting for sensitivity, we find the slope of the flare
frequency distribution for all stars to have a standard value of
α=1.98±0.02. We determine R31.5, the rate of flares per day
with energies above E=3.16x1031ergs in the TESS bandpass. We find
that below a critical value of HαEW=-0.71Å, logR31.5
increases linearly with increasing Hα emission; above this
value, logR31.5 declines rapidly. The stars divide into two groups:
26% have Hα in emission, high flare rates with typical values of
logR31.5=-1.30±0.08, and have Rossby numbers <0.50. The remaining
74% show little to no Hα in emission and exhibit
logR31.5<-3.86, with the majority of these stars not showing a
single flare during the TESS observations.
Description:
We begin with the volume-complete sample of 419 main-sequence stars
with masses between 0.1 and 0.3M☉ and distances shorter than
15pc from Winters+ (2020, J/AJ/161/63). For this study we only use a
subset of these stars, namely those that are single. See Section 2.
We obtained two or more high-resolution spectra for each of the 125
star in our final sample.
For stars with declinations below -15deg, we use the cross-dispersed,
fiber-fed echelle CTIO HIgh ResolutiON (CHIRON) spectrogragh located
on the CTIO/SMARTS 1.5m telescope at CTIO (4100-8700Å with
R∼80,000).
We gathered spectra for all stars with declinations greater than 15
degrees with the high-throughput, fiber-fed, Tillinghast Reflector
Echelle Spectrograph (TRES) located on the 1.5m Tillinghast Reflector
at the Fred Lawrence Whipple Observatory on Mount Hopkins, Arizona
(3900-9100Å with R∼44,000). See Section 3.
The MEarth-North and MEarth-South arrays each comprise eight 40cm
telescopes and are located on Mt. Hopkins in Arizona and at Cerro
Tololo Inter-American Observatory (CTIO), Chile, respectively.
We follow the same method used in Newton+ (2016, J/ApJ/821/93 and
2018, J/AJ/156/217) to estimate the rotation periods of one additional
star with MEarth-North and 17 additional stars with MEarth-South.
See Section 4.
As part of its survey of the southern ecliptic hemisphere in year 1,
TESS obtained two-minute cadence data of the 125 stars in our sample
through a guest investigator program (PI Winters; G011231).
See Section 5.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 156 125 Stellar properties, equivalent widths, and flare rate
table3.dat 86 1392 Catalog of stellar flares
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
IV/38 : TESS Input Catalog - v8.0 (TIC-8) (Stassun+, 2019)
J/AJ/123/3356 : Palomar/MSU nearby star sp. survey. III. (Gizis+, 2002)
J/A+A/397/147 : Activity-rotation relationship in stars (Pizzolato+ 2003)
J/AJ/128/426 : Subdwarfs in the SDSS (West+, 2004)
J/AJ/135/785 : SDSS-DR5 low-mass star spectroscopic sample (West+, 2008)
J/ApJ/720/1118 : i-band photometry of HAT-P-16 (Buchhave+, 2010)
J/AJ/140/1402 : M dwarf flares from SDSS spectra (Hilton+, 2010)
J/ApJ/733/L9 : Stellar rotation for 71 NGC 6811 members (Meibom+, 2011)
J/ApJ/743/48 : Stars with rot. periods and X-ray luminosities (Wright+, 2011)
J/ApJS/207/15 : M dwarf flare spectra (Kowalski+, 2013)
J/ApJ/795/161 : Activity & rotation in Praesepe & the Hyades (Douglas+, 2014)
J/ApJ/814/35 : Flare events in M dwarf of M37 (Chang+, 2015)
J/ApJ/809/77 : Transiting Exoplanet Survey Satellite (TESS) (Sullivan+, 2015)
J/ApJ/812/3 : MEarth mid-to-late M dwarfs rot. & kinematics (West+, 2015)
J/AJ/152/141 : Solar neighborhood. XXXVII. RVs for M dwarfs (Benedict+, 2016)
J/ApJ/829/23 : Stellar flares from Q0-Q17 Kepler LCs (Davenport, 2016)
J/ApJ/822/47 : K2 rotation periods for 65 Hyades members (Douglas+, 2016)
J/ApJ/821/93 : Rotation & Galactic kinematics of mid M dwarfs (Newton+, 2016)
J/AJ/152/113 : Pleiades members with K2 LCs. I. Periods (Rebull+, 2016)
J/ApJ/834/85 : Hα emission in nearby M dwarfs (Newton+, 2017)
J/ApJ/839/92 : Praesepe members with K2 light curve data (Rebull+, 2017)
J/A+A/618/A142 : Radial velocity for GJ 1132 (Bonfils+, 2018)
J/AJ/156/217 : Stellar data for M dwarfs in MEarth-South (Newton+, 2018)
J/ApJ/881/9 : EvryFlare. I. Stars's flares in southern sky (Howard+, 2019)
J/A+A/622/A133 : M45, M44 and M67 flare stars (Ilin+, 2019)
J/AJ/159/60 : 8695 flares from 1228 stars in TESS (Gunther+, 2020)
J/AJ/161/63 : M dwarfs with 0.1≲M☉≲0.3 within 15pc (Winters+, 2021)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 23 A23 --- Name Star name
25- 33 I9 --- TIC [3127674/471012790] TIC identifier
35- 36 I2 h RAh Hour of Right Ascension (J2000)
38- 39 I2 min RAm Minute of Right Ascension (J2000)
41- 45 F5.2 s RAs Second of Right Ascension (J2000)
47- 47 A1 --- DE- Sign of the Declination (J2000)
48- 49 I2 deg DEd Degree of Declination (J2000)
51- 52 I2 arcmin DEm Arcminute of Declination (J2000)
54- 57 F4.1 arcsec DEs Arcsecond of Declination (J2000)
59- 63 F5.3 Msun Mstar [0.1/0.31] Stellar mass
65- 69 F5.2 pc Dist [1.3/15] Distance
71- 77 F7.3 d Prot [0.17/180.11]? Rotation period
79- 86 F8.6 mag Amp [0.00098/0.042]? Semi-amplitude of variability
88- 94 F7.5 mag e_Amp [0.00012/0.0095]? Uncertainty in Amp
96- 96 I1 --- r_Prot [1/6]? Reference for Prot (1)
98-103 F6.4 --- Ro [0.0009/1.58]? Rossby Number (Prot/τ)
105-109 F5.2 mag Tmag [7.49/13.34] TESS Magnitude
111-116 F6.2 0.1nm EWHa [-11.1/0.7] Equivalent width, Hα
118-121 F4.2 0.1nm e_EWHa [0/1.4] Uncertainty in EWHa
123-127 F5.2 0.1nm EWCaII [-0.2/0.8] Equivalent width, Calcium II triplet,
8542.1Å
129-132 F4.2 0.1nm e_EWCaII [0.01/0.2] Uncertainty in EWCaII
134-138 F5.2 0.1nm EWHeI [-0.86/0.65] Equivalent width, HeI D3
140-143 F4.2 0.1nm e_EWHeI [0/0.6] Uncertainty in EWHeI
145-150 F6.2 --- Rate [-14.21/0.5] Natural log rate of flares per day,
ln(flares/day) (2)
152-156 F5.2 --- e_Rate [-2.8/1.4] Uncertainty in Rate
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Note (1): References for rotation period as follows:
1 = Newton et al. (2016, J/ApJ/821/93);
2 = Newton et al. (2018, J/AJ/156/217);
3 = Suarez et al. (2016A&A...595A..12S 2016A&A...595A..12S);
4 = Vanderspeck et al. (2019ApJ...871L..24V 2019ApJ...871L..24V);
5 = This work using TESS photometry;
6 = This work using MEarth photometry.
Note (2): Natural log rate of flares per day at energies greater
than 3.16*1031ergs
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 23 A23 --- Name Star name
25- 33 I9 --- TIC [3127674/471012790] TIC identifier
35- 39 F5.2 mag Tmag [7.49/13.34] Tess magnitude
41- 52 F12.4 d Time [2458325.9/2458681.6] Time of peak flux,
Barycentric Julian Date
54- 61 F8.2 ct/s Amp [18.17/58391] Flare amplitude
63- 69 F7.1 s dt [360/20280] Flare duration
71- 77 F7.2 s ED [0.36/3773] Equivalent duration
79- 86 E8.2 10-7J Energy [2.9e+29/6.3e+33] Flare energy in
the TESS bandpass, in erg units
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 27-Jul-2022