J/A+A/682/A59 WISE Be phenomena (Jian+, 2024)
Exploring Be phenomena in OBA stars: a mid-infrared search.
Jian M., Matsunaga N., Jiang B., Yuan H., Zhang R.
<Astron. Astrophys. 682, A59 (2024)>
=2024A&A...682A..59J 2024A&A...682A..59J (SIMBAD/NED BibCode)
ADC_Keywords: Stars, emission ; Stars, Be ; Stars, OB
Keywords: stars: emission-line, Be - stars: massive - circumstellar matter -
stars: rotation
Abstract:
As early-type stars with a rotation speed close to their critical
velocity, Be stars experience a kind of event called Be phenomenon.
The material in their equator, during the Be phenomenon, is ejected to
the outside space and forms a circumstellar disk. The mechanism
triggering these events remains poorly understood, and observations of
these events are limited since the duration of such events ranges from
months to years. Long-term epoch photometry in the infrared bands is
expected to be ideal for detecting Be phenomena since the brightness
variation is larger than that in the optical, and the effect of
interstellar extinction is also smaller.
In this work, we conducted a systematic search for Be phenomena among
Milky Way OBA stars in the mid-infrared. We examined the brightness
and colour variations of known classical Be stars using the WISE W1
and W2 photometry bands to quantify their characteristics.
Subsequently, we established a set of criteria to identify similar
photometric variations in a large sample of OBA stars. 916 OBA stars
have been found to show Be phenomena in the past 13 years, with 736
newly discovered. The peak-to-peak variations in magnitude and colour
were found to be correlated, indicating the common presence of a
decretion disk. The increase in colour was observed to be strongly
correlated with the emission of the Hα line, providing further
evidence of the association with circumstellar disks. The brightness
variation of a star with Be phenomena can be up to 1.5mag, and colour
variations up to 0.4mag. The median durations for the disk build-up
and decay phases are 474 and 524 days, respectively (while those less
than 180 days are not sampled).
The search for Be phenomena in the WISE bands greatly enlarge the
number of stars showing disk variation, and makes multi-band
photometry analysis of these events possible, with the help of current
and future optical photometry surveys.
Description:
Outbursts caused by Be phenomena were detected in 916 early-type stars
in the mid-infrared bands. These BeT stars exhibit an increased
brightness in the W1 and W2 bands and reddening in (W1-W2), or vice
versa.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 116 916 Catalogue of BeT stars found in this study
table3.dat 84 574 The BeT LAMOST spectra and measurement of
Hα line emission
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See also:
I/328 : AllWISE Data Release (Cutri+ 2013)
J/AJ/155/50 : WISE photometry of Be stars in young open clusters
(Granada+, 2018)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 10 F10.6 deg RAdeg Right ascension (J2000)
12- 21 F10.6 deg DEdeg Declination (J2000)
23- 38 A16 --- Name Name of the BeT star (HHMMSSss+DDMMSSs)
40- 43 F4.2 mag (W1-W2)-ptp Peak-to-peak range of (W1-W2)
45- 48 F4.2 mag W1-ptp Peak-to-peak range of W1
50- 54 F5.2 --- r-value Pearson correlation coefficient
56- 59 I4 d TimeSpanO ? Mean timespan of the outburst phase
61- 64 I4 d TimeSpanD ? Mean timespan of the decay phase
66- 73 A8 --- Sample Sample source: golden / extended sample
75- 87 A13 --- Cluster The open cluster if belongs to
89-102 A14 --- TypeL Variable type in Labadie-Bartz et al.
(2017AJ....153..252L 2017AJ....153..252L, Cat. J/AH/153/252)
104-116 A13 --- TypeS Variable type in Simbad
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 16 A16 --- Name Name of the BeT star (HHMMSSss+DDMMSSs)
18- 22 I5 --- LMJD Observation date, Local Modified Julian Day
24- 42 A19 --- PlanId Plan id
44- 45 I2 --- spId [1-16] Spectrograph id
47- 49 I3 --- FiberId Fiber id
51- 69 F19.16 mag W1-W2 ? Closest-match of (W1-W2)
71- 84 F14.9 0.1nm EWHa ? Closest-match of EW(Hα)
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Acknowledgements:
Mingjie Jian, mingjie.jian(at)astro.su.se
(End) Patricia Vannier [CDS] 14-Nov-2023