J/A+A/691/A358 List of Variable objects in the Orion nebula (Noroozi+, 2024)
Variability of young stellar objects in the Orion nebula.
Noroozi S., Chen Z., Garcia-Diaz Ma.T., Gonzalez-Buitrago D.H.
<Astron. Astrophys. 691, A358 (2024)>
=2024A&A...691A.358N 2024A&A...691A.358N (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; YSOs ; Stars, variable ; Photometry ; Optical
Keywords: methods: observational - techniques: photometric -
stars: pre-main sequence - stars: rotation -
stars: variables: general - stars: variables: T Tauri, Herbig Ae/Be
Abstract:
The Orion Nebula is one of the best-studied star-forming regions in
our Galaxy and provides an ideal laboratory to study the early stages
of star formation. Understanding the variability of young stellar
objects (YSOs) can provide valuable insights into the underlying
physical processes that occur during this crucial phase of stellar
evolution. In this context, we have conducted a photometric survey
with high temporal resolution of a six-square-degree region centered
on NGC 1980. We used two filters (R and I) between 2012 and 2015 with
the 15cm twin telescope RoBoTT at the Universitaetssternwarte Bochum
in Chile.
Our goal is to identify and characterise the variable objects in this
sample using a unique observational setup that allows us to obtain
high quality light curves with time sampling on the order of minutes.
This is the first time such an intensive ground-based photometric
campaign has been conducted in the Orion Nebula.
After a careful quality control more than 13000 light curves were
produced in either R or I; the total number of matched light curves is
11889. The corresponding stars were subsequently matched with the
2MASS point source catalog, resulting in 8197 stars with I<16.5mag
and AAA quality flags. We employed three methods-amplitude, standard
deviation, and Stetson J-index - to identify variable objects in our
sample, successfully classifying 561 stars as variables (irregular,
periodic, and quasi-periodic). These stars serve as the foundation for
further analysis. We confirmed 456 of these as known pre-main sequence
stars through cross-referencing with existing young stellar object
catalogs, supported by spectroscopic and photometric data. The youth
of the remaining stars was established based on their optical and
infrared color signatures.
The period P could be determined for 147 sources and ranges from 0.2
days to several weeks. The frequency of very short periods (<1day) is
2 to 4 times higher than reported in previous studies. A significant
population (10%) comes primarily from Weak-line T Tauri stars, which
are characterized by rotation periods of less than 1 day. These
results emphasize the advantages of observations with an exceptional
time sampling strategy that allows the identification of variability
on scales from hours to years.
Description:
We provide a catalogue containing the results of our observations,
conducted between 2013 and 2015 using Johnson-Cousins R and I filters,
centered on Iota Orionis in the Orion Nebula. A total of 561 variable
objects were identified and analyzed, with their positions in the
color-color diagram supporting their classification. Among them, 147
exhibited periodicity. The dense time sampling of the data enabled us
to accurately detect short-period variables, offering new insights
into the evolution of young stellar objects in this star-forming
region.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablef1.dat 107 561 Catalogue of variable objects within the
Orion observation
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Byte-by-byte Description of file: tablef1.dat
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Bytes Format Units Label Explanations
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1- 8 F8.5 deg RAdeg Right Ascension (J2000.0)
10- 17 F8.5 deg DEdeg Declination (J2000.0)
19- 26 F8.5 mag Imag I magnitude
28- 34 F7.5 mag e_Imag I magnitude error
36- 42 F7.5 mag AmpI I amplitude
44- 51 F8.5 mag Rmag R magnitude
53- 59 F7.5 mag e_Rmag R magnitude error
61- 67 F7.5 mag AmpR R amplitude
69- 84 A16 --- 2MASS 2MASS-ID
86- 90 F5.2 --- alpha ?=- Lada SED slope classification
92- 96 F5.2 d Per ?=- Period
98-102 A5 --- TTS Bonafide T Tauri objects
103-107 I5 --- ID ID of objects in our variable list
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Acknowledgements:
Sadegh Noroozi, sdg.noroozi(at)gmail.com
(End) Patricia Vannier [CDS] 09-Oct-2024