J/ApJ/957/113 Multi-color light curves of Ex Lup (Wang+, 2023)
The accretion history of EX Lup: a century of bursts, outbursts, and quiescence.
Wang M.-T., Herczeg G.J., Liu H.-G., Fang M., Johnstone D., Lee H.-G.,
Walter F.M., Hambsch F.-J., Contreras Pena C., Lee J.-E., Millward M.,
Pearce A., Monard B., Zhou L.
<Astrophys. J., 957, 113 (2023)>
=2023ApJ...957..113W 2023ApJ...957..113W
ADC_Keywords: Stars, variable; Photometry, UBVRI; YSOs
Keywords: Eruptive variable stars ; Stellar accretion ;
Classical T Tauri stars ; Light curves
Abstract:
EX Lup is the archetype for the class of young stars that undergoes
repeated accretion outbursts of ∼5mag at optical wavelengths that last
for months. Despite extensive monitoring that dates back 130yr, the
accretion history of EX Lup remains mostly qualitative and has large
uncertainties. We assess historical accretion rates of EX Lup by
applying correlations between optical brightness and accretion,
developed on multi-band magnitude photometry of the ∼2mag optical
burst in 2022. Two distinct classes of bursts occur: major outbursts
(ΔV∼5mag) have year-long durations, are rare, reach accretion
rates of dM/dtacc∼10-7M☉/yr at peak, and have a total
accreted mass of around 0.1 Earth mass. The characteristic bursts
(ΔV∼2mag) have durations of ∼2-3 months, are more common, reach
accretion rates of dM/dtacc∼10-8M☉/yr at peak, and have a
total accreted mass of around 10-3 Earth masses. The distribution of
total accreted mass in the full set of bursts is poorly described by a
power law, which suggests different driving causes behind the major
outburst and characteristic bursts. The total mass accreted during two
classes of bursts is around 2 times the masses accreted during
quiescence. Our analysis of the light curves reveals a color-dependent
time lag in the 2022 post-burst light curve, attributed to the
presence of both hot and cool spots on the stellar surface.
Description:
The photometry data covered in this paper come from the Digital Access
to a Sky Century@Harvard (DASCH) database, the American Association of
Variable Star Observers (AAVSO) database, the All-Sky Automated Survey
for Supernovae (ASAS-SN) catalog, NEOWISE, TESS, and SMARTS/1.3m
telescope.
We obtain the EX Lup B-band light curves available between 1893 and
1954 from DASCH. See Section 2.1.
The American Association of Variable Star Observers (AAVSO) database
has a wealth of photometry of EX Lup from 1955-2022. We obtained the
full collection of EX Lup photometry from the AAVSO website on
2022-Nov-10. See Section 2.2.
The All-Sky Automated Survey for Supernovae (ASAS-SN) catalog
(Shappee+ 2014, J/ApJ/788/48; Kochanek+ 2017PASP..129j4502K 2017PASP..129j4502K) provides
V-band photometry from 2016 March 10 to 2018 September 17 and g-band
photometry from 2018 June 13 to the present, downloaded on 2023-Jul-17
from the ASAS-SN website. see Section 2.3.
EX Lup was observed by TESS in Sectors 12 (2019-May-21 to Jun-18) and
39 (2021-May-27 to Jun-24) with a 20s cadence. See Section 2.4.
The mid-IR data presented were obtained between 2010 and 2022 and
downloaded from the single-epoch catalogs stored at the NASA/IPAC
Infrared Science Archive (IRSA) catalogs (NEOWISE), using a 3" radius
from the coordinates of the YSO. See Section 2.5.
EX Lup was observed in the Johnson B and V bands by SMARTS/Andicam on
the 1.3m telescope from 2004 January 27 to 2005 June 29 in quiescence
on a weekly cadence, and from 2008 January 22 to 2009 July 30 during
outburst on nightly cadence. In total, SMARTS/Andicam obtained
297 B-band observations on 292 nights and 286 V-band observations on
286 nights.
EX Lup was observed by VLT/X-Shooter on UTC 2010 May 04 03:44:51.779
as part of program 085.C-0764 (PI: H.M. Gunther) and was initially
published by Alcala+ (2017, J/A+A/600/A20). The X-Shooter spectrum is
flux-calibrated and covers a range of 3000-25000Å. See Section 2.7.
We obtained a flux-calibrated high-resolution spectrum of EX Lup with
Keck I/HIRES on MJD 54609.416 (2008 May 23), during the large burst in
2008, originally published in Aspin+ (2010ApJ...719L..50A 2010ApJ...719L..50A).
See Section 2.8.
Finally, We obtained a high-resolution (R∼45000) spectrum of EX Lup
from 1.4-2.5um using Immersion Grating Infrared Spectrograph (IGRINS)
at Gemini South on 2022 March 14 (MJD 59652.36), obtained in
GS-2022A-Q-109 (PI: H-G Lee) through the Korean partnership in Gemini
Observatory. See Section 2.9.
Objects:
----------------------------------------------------------
RA (ICRS) DE Designation(s)
----------------------------------------------------------
16 03 05.49 -40 18 25.4 EX Lup = TIC 69094113
----------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
fig1.dat 42 43425 The full light curve collections of EX Lup;
version updated by the author
fig7.dat 29 3164 The multi-color light curves of burst of EX Lup in 2022
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See also:
B/vsx : AAVSO International Variable Star Index VSX (Watson+, 2006-)
II/179 : Southern Spectrophotometric Standards. I + II (Hamuy+ 1992,94)
I/322 : UCAC4 Catalogue (Zacharias+, 2012)
II/328 : AllWISE Data Release (Cutri+ 2013)
I/350 : Gaia EDR3 (Gaia Collaboration, 2020)
II/366 : ASAS-SN catalog of variable stars (Jayasinghe+, 2018-2020)
IV/39 : TESS Input Catalog version 8.2 (TIC v8.2) (Paegert+, 2021)
I/357 : Gaia DR3 Part 3. Non-single stars (Gaia Collaboration, 2022)
J/A+A/507/881 : Emission lines in EX Lup optical spectrum (Sipos+, 2009)
J/ApJ/743/156 : NEOWISE obs. of NEOs: preliminary results (Mainzer+, 2011)
J/A+A/551/A107 : X-shooter spectra of 24 young stellar objects (Manara+, 2013)
J/ApJS/208/9 : Intrinsic colors and temperatures of PMS stars (Pecaut+, 2013)
J/A+A/561/A2 : 36 accreting YSOs emission lines (Alcala+, 2014)
J/ApJ/786/97 : Photospheric properties of T Tauri stars (Herczeg+, 2014)
J/ApJ/792/30 : NEOWISE magnitudes for near-Earth objects (Mainzer+, 2014)
J/ApJ/788/48 : X-ray through NIR photometry of NGC 2617 (Shappee+, 2014)
J/A+A/570/A82 : Mapping accretion variability in NGC 2264 (Venuti+, 2014)
J/AJ/150/175 : YSOVAR: infrared photometry in NGC 1333 (Rebull+, 2015)
J/A+A/600/A20 : Lupus YSOs X-shooter spectroscopy (Alcala+, 2017)
J/MNRAS/465/3011 : VVV high amplitude NIR var. stars (Contreras Pena+, 2017)
J/MNRAS/495/3614 : IR and sub-mm variability in protostars (Contreras+, 2020)
J/ApJ/920/132 : NEOWISE 6.5yr variability in YSOs (Park+, 2021)
J/AJ/162/101 : K2 ugri & Hα phot. in the Lagoon Nebula (Venuti+, 2021)
J/AJ/164/201 : Accretion in 9 Orion OB1b T-Tauri stars (Pittman+, 2022)
J/ApJ/935/54 : LDT UBVRI photometry of 14 T-Tauri (Robinson+, 2022)
J/ApJ/945/L7 : MIRI MRS sp. of EX Lup taken in quiescence (Kospal+, 2023)
http://dasch.cfa.harvard.edu/ : DASCH homepage
http://www.aavso.org/ : AAVSO homepage
http://asas-sn.osu.edu/ : ASAS-SN homepage
http://heasarc.gsfc.nasa.gov/docs/tess/ : NASA TESS Science Support Center
Byte-by-byte Description of file: fig1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 18 F18.10 d JD Julian Date of Observation Epoch
20- 26 F7.4 mag omag [6.84/15.17] Magnitude in Filter
28- 33 F6.3 mag e_omag [0.001/99]? Error of omag
35- 42 A8 --- Filter Filter name (1)
--------------------------------------------------------------------------------
Note (1): Filter list as follows:
B_dasch = Digital Access to a Sky Century@Harvard (DASCH,
Laycock+ 2010AJ....140.1062L 2010AJ....140.1062L; Tang+ 2013PASP..125..857T 2013PASP..125..857T)
Johnson B (1276 occurrences)
B_smarts = SMARTS/Andicam on the 1.3-m telescope B band (297 occurrences)
TESS = TESS in Sector 12 and 39 with a 20-second cadence
(doi:10.17909/T9-NMC8-F686; 30920 occurrences)
V_JA = American Association of Variable Star Observers
(AAVSO) database [accessed on: 2022-11-10], originally
Visual magnitudes made by Albert Jones, transformed into
Johnson V band via Equation 1: V=0.895xVis.+0.63
(1800 occurrences)
V_asassn = All-Sky Automated Survey for Supernovae (ASAS-SN)
catalog (Shappee+ 2014, J/ApJ/788/48;
Kochanek+ 2017PASP..129j4502K 2017PASP..129j4502K) V band [accessed on: 2023-07-29]
(691 occurrences)
V_smarts = SMARTS/Andicam on the 1.3-m telescope V band (286 occurrences)
Vis. = American Association of Variable Star Observers (AAVSO)
database [accessed on: 2022-11-10], originally
Visual magnitudes, transformed into Johnson V band via
Equation 1: V=0.895xVis.+0.63 (5083 occurrences)
W1 = NEOWISE-R W1 (doi:10.26131/IRSA144; 261 occurrences)
W2 = NEOWISE-R W2 (doi:10.26131/IRSA144; 261 occurrences)
g = All-Sky Automated Survey for Supernovae (ASAS-SN)
catalog (Shappee+ 2014, J/ApJ/788/48;
Kochanek+ 2017PASP..129j4502K 2017PASP..129j4502K) g band [accessed on: 2023-07-29]
(2672 occurrences)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: fig7.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 14 F14.6 d JD Julian Date of Observation Epoch
16- 21 F6.3 mag omag [9.26/14.3] Magnitude in Filter
23- 27 F5.3 mag e_omag [0.001/0.7] Error of omag
29 A1 --- Filt [UBVRI] Filter name (1)
--------------------------------------------------------------------------------
Note (1): Johnson UBVRI photometry from American Association of
Variable Star Observers (AAVSO) database [accessed on: 2022-11-10].
--------------------------------------------------------------------------------
Acknowledgements:
Mutian Wang [mutianwang at smail.nju.edu.cn]
History:
From electronic version of the journal
04-Feb-2026: Insert into VizieR
05-Feb-2026: In Figure 1, W1- and W2-band magnitudes corrected;
file sent by the author.
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 20-Jan-2026