J/MNRAS/521/1700 NGTS clusters survey. IV. (Moulton+, 2023)
NGTS clusters survey. IV. Search for Dipper stars in the Orion Nebular Cluster.
Moulton T., Hodgkin S.T., Smith G.D., Briegal J.T., Gillen E., Acton J.S.,
Battley M.P., Burleigh M.R., Casewell S.L., Gill S., Goad M.R.,
Henderson B.A., Kendall A., Ramsay G., Tilbrook R.H., Wheatley P.J.
<Mon. Not. R. Astron. Soc. 521, 1700-1726 (2023)>
=2023MNRAS.521.1700M 2023MNRAS.521.1700M (SIMBAD/NED BibCode)
ADC_Keywords: Molecular clouds ; Stars, pre-main sequence ; Stars, variable ;
Photometry, infrared ; Optical
Keywords: methods: data analysis - techniques: photometric - stars: low-mass -
stars: pre-main sequence - stars: variable: T Tauri/Herbig Ae/Be
Abstract:
The dipper is a novel class of young stellar object associated with
large drops in flux on the order of 10-50 per cent lasting for hours
to days. Too significant to arise from intrinsic stellar variability,
these flux drops are currently attributed to disk warps, accretion
streams, and/or transiting circumstellar dust. Dippers have been
previously studied in young star forming regions including the Orion
Complex. Using Next Generation Transit Survey (NGTS) data, we
identified variable stars from their lightcurves. We then applied a
machine learning random forest classifier for the identification of
new dipper stars in Orion using previous variable classifications as a
training set. We discover 120 new dippers, of which 83 are known
members of the Complex. We also investigated the occurrence rate of
disks in our targets, again using a machine learning approach. We find
that all dippers have disks, and most of these are full disks. We use
dipper periodicity and model-derived stellar masses to identify the
orbital distance to the inner disk edge for dipper objects, confirming
that dipper stars exhibit strongly extended sublimation radii, adding
weight to arguments that the inner disk edge is further out than
predicted by simple models. Finally, we determine a dipper fraction
(the fraction of stars with disks which are dippers) for known members
of 27.8±2.9 per cent. Our findings represent the largest population
of dippers identified in a single cluster to date.
Description:
All variable NGTS sources analyzed in this paper, including photometry
from NGTS, Gaia, 2MASS and WISE. The table also includes metrics
derived from the NGTS lightcurves which are additional features used
by the machine learning algorithm for dipper classification. Members
of the classification training set are identifiable when there is a
value for the 'Original Classification' column, otherwise
probabilities derived by Random Forest for classification as Periodic,
Dipper, or Eclipsing Binary are given. The 'Class' column is filled
following the methods outlined in the paper, except for the Periodic
class, which is assigned when (P-Prob)>0.9
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
ngtsvar.dat 741 2100 All variable NGTS sources analyzed in the paper
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Byte-by-byte Description of file: ngtsvar.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- Index [0/2099] Running number
6- 10 I5 --- NGTS [34/35795] NGTS identification number
12- 28 F17.14 deg RAdeg Right Ascension from NGTS (J2000)
30- 48 F19.16 deg DEdeg Declination from NGTS (J2000)
50- 68 F19.16 mag magmean Mean NGTS magnitude (MEAN-MAG)
70- 89 F20.18 mag magrms NGTS magnitude RMS (MAG-RMS)
91-113 F23.20 --- FluxAsymM Flux asymmetry of the lightcurve
(M statistic) (Flux-Asymmetry-M)
115-134 F20.17 d LSperiod Lomb-Scargle period (LS-period)
136-155 E20.15 --- LSpdgmstddev Standard deviation of the Lomb-Scargle
periodogram (LS-pdgm-std-dev)
157-176 F20.18 --- LSmaxPower Maximum power of the Lomb-Scargle
periodogram (LS-MAX-Power)
178-198 F21.19 --- AperQ Aperiodicity of the lightcurve
(Q statistic) (Aperiodicity-Q)
200-219 F20.18 --- amp9010 Difference between the 90th and 10th
percentile of the lightcurve (amp9010)
221-240 F20.18 --- stddev Standard deviation of the lightcurve
(std-dev)
242-262 F21.19 --- MAD Median absolute deviation of the
lightcurve (MAD)
264-287 E24.17 --- dtav Difference between the mean and the median
of the lightcurve (dtav)
289-318 F30.16 d BLSPer Box least squares period (BLS-Period)
320-341 E22.17 --- BLSmaxPower Maximum power of the BLS periodogram
(BLS-Max-power)
343-362 F20.17 d BLSdur BLS duration of the transit (BLS-duration)
364-383 F20.18 mag BLSdepth BLS depth of the transit (BLS-depth)
385-407 F23.19 mag K-W2 K-W2 colour index
409-428 F20.16 mag Gmag ? Gaia G magnitude
430-449 F20.16 mag BPmag ? Gaia BP magnitude
451-470 F20.16 mag RPmag ? Gaia RP magnitude
472-491 F20.16 mag Jmag ? 2MASS J magnitude
493-512 F20.16 mag Hmag ? 2MASS H magnitude
514-533 F20.16 mag Kmag ? 2MASS K magnitude
535-554 F20.16 mag W1mag ? WISE W1 magnitude
556-575 F20.16 mag W2mag ? WISE W2 magnitude
577-596 F20.16 mag W3mag ? WISE W3 magnitude
598-617 F20.17 mag W4mag ? WISE W4 magnitude
619-640 F22.19 --- P-Prob ? Periodic probability (P-Probability)
642-663 E22.16 --- D-Prob ? Dipper Probability (D-Probability)
665-686 E22.16 --- EB-Prob ? Eclipsing Binary probability
(EB-Probability)
688-689 A2 --- Class Assigned Class (D, P or EB) (1)
691-700 I10 --- TIC ? TIC identification number
704-741 A38 --- r_Class ? Source of training set classification
from the literature
(Original-Classification-Source)
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Note (1): Assigned Class as follows:
P = Periodic
D = Dipper
EB = Eclipsing Binary
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Acknowledgements:
Simon Hodgkin, sth(at)ast.cam.ac.uk
References:
Gillen et al., Paper I 2020MNRAS.492.1008G 2020MNRAS.492.1008G
Jackman et al., Paper II 2020MNRAS.497..809J 2020MNRAS.497..809J
Smith et al., Paper III 2021MNRAS.507.5991S 2021MNRAS.507.5991S
(End) Patricia Vannier [CDS] 14-Feb-2023