J/ApJ/876/115 Optical follow-up of ASAS-SN M dwarf flares (Schmidt+, 2019)
The largest M dwarf flares from ASAS-SN.
Schmidt S.J., Shappee B.J., van Saders J.L., Stanek K.Z., Brown J.S.,
Kochanek C.S., Dong S., Drout M.R., Frank S., Holoien T.W.-S., Johnson S.,
Madore B.F., Prieto J.L., Seibert M., Seidel M.K., Simonian G.V.A.
<Astrophys. J., 876, 115 (2019)>
=2019ApJ...876..115S 2019ApJ...876..115S
ADC_Keywords: Spectra, optical; Stars, M-type; Stars, flare; Photometry, VRI;
Equivalent widths; Proper motions; Spectral types
Keywords: stars: chromospheres ; stars: late-type ; stars: low-mass
Abstract:
The All-sky Automated Survey for Supernovae (ASAS-SN) is the only
project in existence to scan the entire sky in optical light
approximately every day, reaching a depth of g∼18mag. Over the course
of its first 4yr of transient alerts (2013-2016), ASAS-SN observed 53
events classified as likely M dwarf flares. We present follow-up
photometry and spectroscopy of all 53 candidates, confirming flare
events on 47 M dwarfs, one K dwarf, and one L dwarf. The remaining
four objects include a previously identified T Tauri star, a young
star with outbursts, and two objects too faint to confirm. A detailed
examination of the 49 flare star light curves revealed an additional
six flares on five stars, resulting in a total of 55 flares on 49
objects ranging in V-band contrast from ΔV=-1 to -10.2mag. Using
an empirical flare model to estimate the unobserved portions of the
flare light curve, we obtain lower limits on the V-band energy emitted
during each flare, spanning log(EV/erg)=32-35, which are among the
most energetic flares detected on M dwarfs. The ASAS-SN M dwarf flare
stars show a higher fraction of Hα emission, as well as stronger
Hα emission, compared to M dwarfs selected without reference to
activity, consistent with belonging to a population of more
magnetically active stars. We also examined the distribution of
tangential velocities, finding that the ASAS-SN flaring M dwarfs are
likely to be members of the thin disk and are neither particularly
young nor old.
Description:
We obtained follow-up optical photometry and spectroscopy to
characterize the host stars of the 53 candidate M dwarfs and flare
events detected by the All-sky Automated Survey of Supernovae
(ASAS-SN; Shappee+ 2014, J/ApJ/788/48) at the original two sites at
Hawaii and Chile.
Low-resolution (R∼2000-4000) optical spectra for bright southern
sources were obtained on the Irenee du Pont 100-inch telescope at the
Las Campanas Observatory (LCO). We used the Wide Field Reimaging CCD
Camera (WFCCD) in long-slit grism mode yielding a wavelength range of
370-910nm and a resolution of 8Å.
Optical spectroscopy for faint southern sources was obtained using the
Inamori-Magellan Areal Camera and Spectrograph (IMACS) on the
Baade-Magellan 6.5m telescope.
Optical spectroscopy for bright northern sources was obtained using
the Ohio State Multi-Object Spectrograph (OSMOS) on the MDM
Observatory Hiltner 2.4m telescope. We observed candidates with
0.9"-1.2" slits and VPH grism, yielding a wavelength range of
390-680nm and R∼1600.
Finally, spectra for the faintest northern sources were obtained with
the Multi-Object Double Spectrograph 1 (MODS1) mounted on the dual
8.4m Large Binocular Telescope (LBT) on Mt. Graham.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 98 49 Properties of ASAS-SN flare dwarfs
table2.dat 70 57 Observation log for the 53 candidates
table3.dat 42 504 ASAS-SN photometry of flares
table5.dat 79 49 Kinematics
table6.dat 83 55 Flare properties for the 49 dwarfs
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See also:
B/vsx : AAVSO International Variable Star Index VSX (Watson+, 2006-2014)
III/198 : Palomar/MSU nearby star spectroscopic survey (Hawley+ 1997)
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
II/294 : The SDSS Photometric Catalog, Release 7 (Adelman- McCarthy+, 2009)
I/347 : Distances to 1.33 billion stars in Gaia DR2 (Bailer- Jones+, 2018)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
II/366 : ASAS-SN catalog of variable stars (Jayasinghe+, 2018-2020)
J/ApJ/300/779 : High-latitude H-alpha emission stars (Stephenson+, 1986)
J/AJ/133/439 : Luminosity function of M7-L8 ultracool dwarfs (Cruz+, 2007)
J/ApJ/657/884 : Spectroscopy of TTau & Herbig Ae/Be candidates (Lee+, 2007)
J/AJ/135/785 : SDSS-DR5 low-mass star spectroscopic sample (West+, 2008)
J/AJ/137/1 : PMs & astrometry of late-type dwarfs (Faherty+, 2009)
J/AJ/140/1402 : M dwarf flares from SDSS spectra (Hilton+, 2010)
J/AJ/141/50 : White-light flares on Kepler cool stars (Walkowicz+, 2011)
J/AJ/141/97 : SDSS DR7 M dwarfs (West+, 2011)
J/other/Nat/485.478 : Superflares on solar-type stars (Maehara+, 2012)
J/AJ/143/80 : Low-mass members of β Pic & AB DOR (Schlieder+, 2012)
J/ApJS/207/15 : M dwarf flare spectra (Kowalski+, 2013)
J/MNRAS/440/3430 : SDSS-2MASS-WISE stellar colour locus (Davenport+, 2014)
J/A+A/572/A89 : YSO candidates toward Orion (Sanchez+, 2014)
J/ApJ/788/48 : X-ray through NIR photometry of NGC 2617 (Shappee+, 2014)
J/AJ/149/158 : The BUD sample. I. L dwarf activity sample (Schmidt+, 2015)
J/ApJ/829/23 : Stellar flares from Q0-Q17 Kepler LCs (Davenport, 2016)
J/ApJ/831/133 : Follow-up of ASASSN-15qi (Herczeg+, 2016)
J/MNRAS/455/2918 : Photom. & line luminosities for ASASSN-14li (Holoien+, 2016)
J/MNRAS/463/3813 : ASASSN-15oi UBVI M2W1W2 light curves (Holoien+, 2016)
J/ApJ/826/144 : Follow-up observations of SNIa ASASSN-14lp (Shappee+, 2016)
J/A+A/590/A11 : BVRI light curves of V374 Peg (Vida+, 2016)
J/MNRAS/467/1098 : ASAS-SN bright supernova catalog 2015 (Holoien+, 2017)
J/MNRAS/471/4966 : ASAS-SN bright supernova catalog 2016 (Holoien+, 2017)
J/MNRAS/464/2672 : ASAS-SN bright supernova catalog 2013-2014 (Holoien+, 2017)
J/ApJ/843/31 : MUSCLES Treasury Survey. IV. M dwarfs (Youngblood+, 2017)
J/ApJ/856/23 : BANYAN. XI. The BANYAN Σ algorithm (Gagne+, 2018)
J/ApJ/870/13 : K2 LC alternative analysis of ASASSN-18bt (Shappee+, 2019)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 6 A6 --- ID ASAS-SN Identifier ( in Simbad)
8- 9 A2 --- SpT Sectral Type derived in this work
11- 11 A1 --- l_Halpha Limit flag for Hα
12- 16 F5.2 0.1nm Halpha [0.7/29.1] Hα Equivalent Width
18- 20 F3.1 0.1nm e_Halpha [0/7.3]? Uncertainty in Halpha
22- 26 F5.2 mag Vmag [12.66/24.2] V band magnitude
28- 31 F4.2 mag e_Vmag [0.01/0.5] Uncertainty in Vmag
33- 37 F5.2 mag Rmag [13.63/21.8]? R band magnitude
39- 42 F4.2 mag e_Rmag [0.01/0.08]? Uncertainty in Rmag
44- 48 F5.2 mag Imag [12.18/20.49]? I band magnitude
50- 53 F4.2 mag e_Imag [0.01/0.2]? Uncertainty in Imag
55- 59 F5.2 mag rmag [14.15/23.73]? SDSS r band (AB) magnitude
61- 64 F4.2 mag e_rmag [0.01/1.3]? Uncertainty in rmag
66- 70 F5.2 mag imag [13.85/24.36]? SDSS i band (AB) magnitude
72- 76 F5.2 mag e_imag [0.01/61.59]? Uncertainty in imag
78- 82 F5.2 mag zmag [12.14/21.84]? SDSS z band (AB) magnitude
84- 87 F4.2 mag e_zmag [0.01/3.4]? Uncertainty in zmag
89- 93 F5.2 mag Ksmag [9.69/15.47]? 2MASS Ks band magnitude
95- 98 F4.2 mag e_Ksmag [0.02/0.3]? Uncertainty in Ksmag
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 A6 --- ID ASAS-SN Identifier ( in Simbad)
8- 9 I2 h RAh Hour of right ascension (J2000)
11- 12 I2 min RAm Minute of right ascension (J2000)
14- 17 F4.1 s RAs Second of right ascension (J2000)
19 A1 --- DE- Sign of declination (J2000)
20- 21 I2 deg DEd Degree of declination (J2000)
23- 24 I2 arcmin DEm Arcminute of declination (J2000)
26- 29 F4.1 arcsec DEs Arcsecond of declination (J2000)
31- 44 A14 --- Tel Telescope/Instrument used for spectroscopy (1)
46- 64 A19 s Exp Exposure time(s) for spectroscopy
66- 68 A3 --- Band Observed photometric bands
70 A1 --- f_ID a: Objects published in stand-alone papers;
added in this table by CDS for completeness
(positions from SIMBAD)
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Note (1): Telescope as follows:
LBT = Multi-Object Double Spectrograph 1 (MODS1) mounted on the
dual 8.4m Large Binocular Telescope (LBT) on Mt. Graham
(8 occurrences)
MDM = the Ohio State Multi-Object Spectrograph (OSMOS) on the
MDM Observatory Hiltner 2.4m telescope (9 occurrences)
Magellan/Baade = the Inamori-Magellan Areal Camera and Spectrograph (IMACS)
on the Baade-Magellan 6.5m telescope (26 occurrences)
du Pont = the Wide Field CCD in long-slit grism mode of the Irenee
du Pont telescope at the Las Campanas Observatory (LCO)
(12 occurrences)
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 A6 --- ID ASAS-SN Identifier ( in Simbad)
8- 11 I4 yr obs.Y Year of observation
13- 14 I2 "month" obs.M Month of observation
16- 25 F10.7 d obs.D Day of observation in decimal days
27- 31 F5.2 mag B_Vmag [15.5/18.25] 3σ detection limit in V
33- 37 F5.2 mag Vmag [11.66/18.2]? V band magnitude, detection
39- 42 F4.2 mag e_Vmag [0.01/0.4]? Uncertainty in Vmag
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 A6 --- ID ASAS-SN Identifier ( in Simbad)
8- 24 A17 --- Src Source of kinematics (1)
26- 31 F6.1 pc Dist [10.6/1087] Distance
33- 37 F5.1 pc e_Dist [0.1/217] Uncertainty in Dist
39- 44 F6.1 pc Z [-749.1/237.4] Distance, vertically from
the plane of Galaxy
46- 51 F6.1 mas/yr pmRA [-421.1/248.4]? Proper motion,
corrected by cos(Dec)
53- 56 F4.1 mas/yr e_pmRA [0.1/15.3]? Uncertainty in pmRA,
corrected by cos(Dec)
58- 63 F6.1 mas/yr pmDE [-142.1/157.3]? Proper motion, in declination
65- 68 F4.1 mas/yr e_pmDE [0.1/26.3]? Uncertainty in pmDE
70- 74 F5.1 km/s Vtan [5.5/117.5]? Tangential velocity
76- 79 F4.1 km/s e_Vtan [0/26]? Uncertainty in Vtan
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Note (1): Source of kinematics as follows:
Gaia = Gaia DR2 (I/345);
Schmidt2016a/2M-W = Schmidt et al. (2016ApJ...828L..22S 2016ApJ...828L..22S) and 2M-W;
V-K/2M-W = V-K versus 2MASS-WISE color;
r-z/2M-W = r-z color versus 2MASS-WISE color.
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 A6 --- ID ASAS-SN Identifier
( in Simbad)
8- 12 F5.2 mag Vmag1 [12.66/24.2]? Quiescent V magnitude
14- 17 F4.2 mag e_Vmag1 [0.01/0.34]? Uncertainty in Vmag
19- 23 F5.2 mag Vmag2 [11.66/17.35] Flare peak V magnitude
25- 28 F4.2 mag e_Vmag2 [0.01/0.28] Uncertainty in Vmag
30- 35 F6.2 mag DVmag [-10.24/-1.0] ΔV magnitude,
Vmag1-Vmag2
37- 40 F4.2 mag e_DVmag [0.01/0.34] Uncertainty in DVmag
42- 47 A6 --- Type Flare Type
49- 49 I1 --- Nobs [1/7] Number of flare observations
51- 54 I4 s thalf1 [76/1533]? Flare half life
56- 60 F5.2 [10-7J] logEV-IQ1 [32.3/35]? Fit Flare Energy IQ1 in log(erg)
62- 66 F5.2 [10-7J] logEV-med [32.5/35]? Median fit Flare Energy
in log(erg)
68- 72 F5.2 [10-7J] logEV-IQ3 [32.6/35]? Fit Flare Energy IQ3 in log(erg)
74- 77 I4 s thalf2 [303/3493] Flare half life from thalf
relation
79- 83 F5.2 [10-7J] logEV-thalf [32/36.2] Flare Energy from thalf relation
in log(erg) units
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 19-Nov-2020