J/ApJ/951/33 X-ray-Opt. flare monitoring obs. of AU MIC. I. (Tristan+, 2023)
A 7 day multiwavelength flare campaign on AU Mic.
I. High-time-resolution light curves and the thermal empirical Neupert effect.
Tristan I.I., Notsu Y., Kowalski A.F., Brown A., Wisniewski J.P.,
Osten R.A., Vrijmoet E.H., White G.L., Carter B.D., Grady C.A.,
Henry T.J., Hinojosa R.H., Lomax J.R., Neff J.E., Paredes L.A.,
Soutter J.
<Astrophys. J., 951, 33 (2023)>
=2023ApJ...951...33T 2023ApJ...951...33T
ADC_Keywords: Stars, variable; Stars, flare; X-ray sources; Photometry, H-alpha;
Photometry, UBV
Keywords: Red dwarf flare stars ; Stellar activity ; Stellar flares ;
Optical flares ; Stellar x-ray flares ; Planet hosting stars
Abstract:
We present light curves and flares from a 7 day, multiwavelength
observational campaign of AU Mic, a young and active dM1e star with
exoplanets and a debris disk. We report on 73 unique flares between
the X-ray to optical data. We use high-time-resolution near-UV (NUV)
photometry and soft X-ray (SXR) data from the X-ray Multi-Mirror
Mission to study the empirical Neupert effect, which correlates the
gradual and impulsive phase flaring emissions. We find that 65% (30 of
46) flares do not follow the Neupert effect, which is 3 times more
excursions than seen in solar flares, and propose a four-part Neupert
effect classification (Neupert, quasi-Neupert, non-Neupert types I and
II) to explain the multiwavelength responses. While the SXR emission
generally lags behind the NUV as expected from the chromospheric
evaporation flare models, the Neupert effect is more prevalent in
larger, more impulsive flares. Preliminary flaring rate analysis with
X-ray and U-band data suggests that previously estimated energy ratios
hold for a collection of flares observed over the same time period,
but not necessarily for an individual, multiwavelength flare. These
results imply that one model cannot explain all stellar flares and
care should be taken when extrapolating between wavelength regimes.
Future work will expand wavelength coverage using radio data to
constrain the nonthermal empirical and theoretical Neupert effects to
better refine models and bridge the gap between stellar and solar
flare physics.
Description:
The target of our flare-monitoring observations is the M1 star AU Mic,
a nearby pre-main-sequence star located at a distance of 9.72pc.
It is part of the β Pictoris moving group, with an age of
23±3Myr. AU Mic has been a frequent target of Hubble Space Telescope
(HST). AU Mic has been a source of energetic flares in the X-ray, UV,
optical, and radio wavelength regimes.
We observed AU Mic over 7 days spanning 2018 Oct 10--2018 Oct 17 with
the X-ray Multi-Mirror Mission (XMM-Newton), the Jansky Very Large
Array (JVLA), the Neil Gehrels Swift Observatory (Swift), the Las
Cumbres Observatory Global Telescope network (LCOGT), the
Astrophysical Research Consortiums 3.5m telescope at the Apache Point
Observatory (APO), the Australia Telescope Compact Array (ATCA), and
the Small and Moderate Aperture Research Telescope System (SMARTS)
0.9 and 1.5m telescopes at the Cerro Tololo Inter-American Observatory
(CTIO).
The XMM-Newton observations were conducted in four visits (Obs-IDs:
0822740301, 0822740401, 0822740501, and 0822740601), which spanned
2018 October 10 13:13:59.760 to 2018 October 12 01:42:19.177 UTC
(131.29ks), 2018 October 12 13:06:33.808 to 2018 October 14
01:36:22.232 UTC (131.40ks), 2018 October 14 12:21:18.787 to
2018 October 16 00:04:00.273 UTC (71.75ks), and 2018 October 16
23:39:21.362 to 2018 October 17 18:17:33.004 UTC (67.10ks). X-ray
photometry was obtained over a bandpass of E∼0.2-12keV using the
European Photon Imaging Camera (EPIC-pn) medium filter and 10s time
binning.
X-ray spectra over the energy range 0.33-2.5keV were obtained using
the Reflection Grating Spectrometer (RGS).
See Section 2.
Objects:
----------------------------------------------------------
RA (ICRS) DE Designation(s)
----------------------------------------------------------
20 45 09.53 -31 20 27.2 AU Mic = HD 197481
----------------------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table6.dat 129 173 Common flare properties
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See also:
B/xmm : XMM-Newton Observation Log (XMM-Newton Science Operation Center, 2012-)
V/137 : Extended Hipparcos Compilation (XHIP) (Anderson+, 2012)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
J/A+AS/121/369 : UBVRI observations of active stars (Cutispoto, 1997)
J/A+A/367/910 : UBV(RI)c photometry of active stars. IX (Cutispoto+, 2001)
J/A+A/400/659 : UBV(RI)c photometry of active stars. X. (Cutispoto+, 2003)
J/AJ/128/463 : A preliminary 20pc census from the NLTT catalog (Reid+, 2004)
J/A+A/474/495 : X-ray flares from Cygnus OB2 stars (Albacete Colombo+, 2007)
J/A+A/487/293 : Em. lines in a giant flare of CN Leo (Fuhrmeister+, 2008)
J/AJ/135/785 : SDSS-DR5 low-mass star spectroscopic sample (West+, 2008)
J/A+A/534/A133 : Proxima Cen chromospheric emission lines (Fuhrmeister+, 2011)
J/PASP/124/140 : UBVRI Hp BT and VT photonic responses (Bessell+, 2012)
J/AcA/62/67 : ASAS photometry of ROSAT sources (Kiraga, 2012)
J/ApJ/754/4 : HST monitoring of flaring stars in Gal. bulge (Osten+, 2012)
J/ApJS/207/15 : M dwarf flare spectra (Kowalski+, 2013)
J/AJ/149/5 : Solar neighborhood. XXXV. Dist. to M dwarfs (Winters+, 2015)
J/ApJ/829/23 : Stellar flares from Q0-Q17 Kepler LCs (Davenport, 2016)
J/ApJ/851/91 : Stat. studies of solar white-light flares (Namekata+, 2017)
J/AJ/155/265 : Solar neighborhood. XLIV. RECONS discoveries (Henry+, 2018)
J/AJ/160/215 : Solar neighborhood. XLVI. M dwarf binaries (Vrijmoet+, 2020)
J/AJ/164/110 : HST/COS far-UV sp. of AU Mic flares (Feinstein+, 2022)
J/MNRAS/512/L60 : Flare detections of TOI host stars (Howard+, 2022)
J/AJ/164/17 : GJ 1243 flares data with Kepler and TESS (Mendoza+, 2022)
Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- ID [1/73] Flare identifier
4- 10 A7 --- Obs Observation identifier (1)
12- 21 A10 --- Band Observation band used by Obs
23- 28 F6.2 min tTotal [0.5/482.4]? Flare duration
30- 35 F6.2 min tRise [0.17/331.5]? Rise time
37- 42 F6.2 --- PCRate [0.02/101.4]? Peak count rate (2)
44- 51 E8.1 10-7J Energy [1.8e+30/2.8e+33]? Observed Energy; ergs
52- 57 E6.1 10-7J e_Energy [0/6e+32]? Uncertainty in Energy
59- 62 I4 yr Start.Y ? Flare UTC start date (ISO)
63 A1 --- --- [-]
64- 65 I2 "month" Start.M ? Flare UTC start date (ISO)
66 A1 --- --- [-]
67- 68 I2 d Start.D ? Flare UTC start date (ISO)
69 A1 --- --- [T]
70- 71 I2 h Start.h ? Flare UTC start time (ISO)
72 A1 --- --- [:]
73- 74 I2 min Start.m ? Flare UTC start time (ISO)
75 A1 --- --- [:]
76- 81 F6.3 s Start.s ? Flare UTC start time (ISO)
83- 86 I4 yr End.Y Flare UTC end time (ISO)
87 A1 --- --- [-]
88- 89 I2 "month" End.M Flare UTC end time (ISO)
90 A1 --- --- [-]
91- 92 I2 d End.D Flare UTC end time (ISO)
93 A1 --- --- [T]
94- 95 I2 h End.h ? Flare UTC end time (ISO)
96 A1 --- --- [:]
97- 98 I2 min End.m ? Flare UTC end time (ISO)
99 A1 --- --- [:]
100- 105 F6.3 s End.s Flare UTC end time (ISO)
107- 110 I4 yr Peak.Y Flare UTC peak time (ISO)
111 A1 --- --- [-]
112- 113 I2 "month" Peak.M Flare UTC peak time (ISO)
114 A1 --- --- [-]
115- 116 I2 d Peak.D Flare UTC peak time (ISO)
117 A1 --- --- [T]
118- 119 I2 h Peak.h Flare UTC peak time (ISO)
120 A1 --- --- [:]
121- 122 I2 min Peak.m Flare UTC peak time (ISO)
123 A1 --- --- [:]
124- 129 F6.3 s Peak.s Flare UTC peak time (ISO)
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Note (1): Observation identifier as follows:
EPIC-pn = XMM-Newton observations (Obs-IDs: 0822740301, 0822740401,
0822740501, and 0822740601) using the European Photon Imaging
Camera (EPIC-pn); see Section 2.5.1
OM = the XMM-Newton Optical Monitor (OM) in FAST mode;
see Section 2.2.5
LCOGT = the Las Cumbres Observatory Global Telescope network;
see Section 2.2.6
CHIRON = the CTIO/SMARTS 1.5m using the cross-dispersed, fiber-fed echelle
CTIO High ResolutiON (CHIRON) spectrograph; see Section 2.2.8
RGS = XMM-Newton using the Reflection Grating Spectrometer;
see Section 2.2.3
2KCCD = the CTIO/Small and Moderate Aperture Telescope Research System
(SMARTS) 0.9m V band; see Sectin 2.2.7.
Note (2): The units of PCRate are counts/s for XMM-Newton OM, EPIC-pn, and
RGS data, Angstroms for CHIRON Hα data, and relative counts
for all other data.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 20-Aug-2025