J/MNRAS/496/3257 The ASAS-SN catalogue of variable stars - VIII (Bredall+, 2020)
The ASAS-SN catalogue of variable stars - VIII.
'Dipper' stars in the Lupus star-forming region.
Bredall J.W., Shappee B.J., Gaidos E., Jayasinghe T., Vallely P.,
Stanek K.Z., Kochanek C.S., Gagne J., Hart K., Holoien T.W.-S.,
Prieto J.L., Van Saders J.
<Mon. Not. R. Astron. Soc., 496, 3257-3269 (2020)>
=2020MNRAS.496.3257B 2020MNRAS.496.3257B (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; YSOs ; Milky Way ; Spectral types ;
Photometry ; Optical
Keywords: stars: variables: T Tauri, Herbig Ae/Be
Abstract:
Some young stellar objects such as T Tauri-like 'dipper' stars vary
due to transient partial occultation by circumstellar dust, and
observations of this phenomenon inform us of conditions in the
planet-forming zones close to these stars. Although many dipper stars
have been identified with space missions such as Kepler/K2,
ground-based telescopes offer longer term and multiwavelength
perspectives. We identified 11 dipper stars in the Lupus star-forming
region in data from the All-Sky Automated Survey for SuperNovae
(ASAS-SN), and further characterized these using observations by the
Las Cumbres Global Observatory Telescope (LCOGT) and the Transiting
Exoplanet Survey Satellite (TESS), as well as archival data from other
missions. Dipper stars were identified from a catalogue of nearby
young stars and selected based on the statistical significance,
asymmetry, and quasi-periodicity or aperiodicity of variability in
their ASAS-SN light curves. All 11 stars lie above or redwards of the
zero-age main sequence and have infrared (IR) excesses indicating the
presence of full circumstellar discs. We obtain reddening-extinction
relations for the variability of seven stars using our combined
ASAS-SN-TESS and LCOGT photometry. In all cases, the slopes are below
the ISM value, suggesting larger grains, and we find a tentative
relation between the slope (grain size) and the Ks-[22µm] IR
colour regarded as a proxy for disc evolutionary state.
Description:
As the starting point of this investigation, we compiled a catalogue
of all known candidate members of young associations, open clusters,
and moving groups within 150pc based on the member lists in
literature. Of these sources, 307 are members of the Lupus
star-forming region.
The ASAS-SN network consists of 20 telescopes mounted on five fully
robotic mounts located at the Haleakala Observatory, the Cerro Tololo
International Observatory, McDonald Observatory, and the South African
Astrophysical Observatory. Observations span from late 2012 to
mid-2018 in the V band, and from late 2017 in the g band, providing
∼800 epochs per source on average. Each science image consists of
three dithered 90-s exposures taken using 14-cm aperture Nikon
telephoto lenses and thinned back-illuminated CCDs with 8.0-arcsec
pixels.
Obscuration by dust produces reddening as well as extinction, and the
relation between these depends on the grain size distribution and
composition. Simultaneous multiband observations of dipping events
allow this to be investigated and compared between dipper stars and
with the ISM. To perform a higher precision examination of individual
dimming events and compare with contemporaneous ASAS-SN measurements,
we utilize the observations made by TESS during Sector 12 and the
LCOGT (Brown et al. 2013PASP..125.1031B 2013PASP..125.1031B) 0.4-m telescopes in the g and
i bands.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 99 91 Average ASAS-SN V magnitudes, peak-to-peak
variability, quasi-periodicity, flux asymmetry,
and variability classification for all Lupus
YSO members present in our catalogue, as well as
additional information for quasi-periodic
dippers
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See also:
II/366 : ASAS-SN catalog of variable stars (Jayasinghe+, 2018-2020)
IV/39 : TESS Input Catalog version 8.2 (TIC v8.2) (Paegert+, 2021)
J/AJ/147/82 : Monitoring of disk-bearing stars in NGC 2264 (Cody+, 2014)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- Name Star name
21- 27 F7.3 deg RAdeg Right ascension (J2000)
29- 36 F8.4 deg DEdeg Declination (J2000)
38- 42 A5 --- SpType Spectral type
44 A1 --- r_SpType Reference for SpType (1)
46- 51 F6.3 mag Vmag Mean Johnson V-band magnitude
53- 57 F5.3 --- p2p Peak-to-peak variability metric (2)
59- 64 F6.3 --- Q Quasi-periodicity (3)
66- 71 F6.3 --- M Flux asymmetry (4)
73- 75 A3 --- Desig Variability classification (5)
77- 81 F5.3 --- Ag/AT ? Extinction in the Sloan g-band to extinction
in the TESS band ratio
83- 87 F5.3 --- e_Ag/AT ? Error on Ag/AT
89- 93 F5.3 --- Ag/Ai ? Extinction in the Sloan g-band to extinction
in the Sloan i-band ratio
95- 99 F5.3 --- e_Ag/Ai ? Error on Ag/Ai
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Note (1): Reference as follows:
a = Hughes et al. (1994AJ....108.1071H 1994AJ....108.1071H)
b = Gahm et al. (1989A&A...211..115G 1989A&A...211..115G)
c = Alcala et al. (2017A&A...600A..20A 2017A&A...600A..20A, Cat. J/A+A/600/A20)
d = Herczeg & Hillenbrand (2014ApJ...786...97H 2014ApJ...786...97H, Cat. J/ApJ/786/97)
e = Romero et al. (2012ApJ...749...79R 2012ApJ...749...79R, Cat. J/ApJ/749/79)
Note (2): In order to quantify variability, we use the peak-to-peak variability
metric, v=[(mi-σi)max-(mi+σi)min]/
[(mi-σi)max+(mi+σi)min] from Sokolovsky et al.
(2017MNRAS.464..274S 2017MNRAS.464..274S), where mi is a measured magnitude and
σi is its associated uncertainty
Note (3): The quasi-periodicity is defined in Cody et al. (2014AJ....147...82C 2014AJ....147...82C,
Cat. J/AJ/147/82) as Q=(σ2resid-{sigms}2phot)/
(σ2m-σ2phot) and quantifies the degree to which
variability is periodic or stochastic. Here σphot is the
estimated photometric uncertainty, σ2m is the variance of
the original light curve, and σ2resid is the variance of the
residual light curve after subtracting the dominant periodic signal.
For a perfectly periodic signal, the variance of the residual is
equivalent to photometric noise, yielding Q∼0.
Note (4): The second metric to classify variability is flux asymmetry,
M=<m_10 per cent>-mmed/σm_, where <m_10 per cent_> is the
mean of the top and bottom 10 per cent of magnitude measurements,
mmed is the median of all measurements, and σm is the
standard deviation of the light curve. M determines whether the
variability is predominantly brightening (M<0) or predominantly
dimming (M>0).
Note (5): The classifications are P, QP, and AP for periodic, quasi-periodic,
and aperiodic, respectively, and D, S, and B for dipper, symmetric,
and burster, respectively
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History:
From electronic version of the journal
References:
Jayasinghe et al., Paper I 2018MNRAS.477.3145J 2018MNRAS.477.3145J, Cat. II/366
Jayasinghe et al., Paper II 2019MNRAS.486.1907J 2019MNRAS.486.1907J, Cat. II/366
Jayasinghe et al., Paper III 2019MNRAS.485..961J 2019MNRAS.485..961J, Cat. II/366
Pawlak et al., Paper IV 2019MNRAS.487.5932P 2019MNRAS.487.5932P, Cat. II/366
Jayasinghe et al., Paper V 2020MNRAS.491...13J 2020MNRAS.491...13J, Cat. II/366
Jayasinghe et al., Paper VI 2020MNRAS.493.4186J 2020MNRAS.493.4186J, Cat. II/366
Jayasinghe et al., Paper VII 2020MNRAS.493.4045J 2020MNRAS.493.4045J, Cat. II/366
Jayasinghe et al., Paper IX 2021MNRAS.503..200J 2021MNRAS.503..200J
Christy et al., Paper X 2023MNRAS.519.5271C 2023MNRAS.519.5271C
(End) Ana Fiallos [CDS] 05-Jul-2023