J/A+A/634/A41 G107.298+5.639 multi-frequency maser light curves (Olech+, 2020)
Long-term multi-frequency maser observations of the intermediate-mass young
stellar object G107.298+5.639.
Olech M., Szymczak M., Wolak P., Gerard E., Bartkiewic A.
<Astron. Astrophys. 634, A41 (2020)>
=2020A&A...634A..41O 2020A&A...634A..41O (SIMBAD/NED BibCode)
ADC_Keywords: Molecular clouds ; Masers ; Radio lines
Keywords: masers - stars: formation - ISM: clouds - radio lines: ISM -
individual: G107.298+5.639
Abstract:
Periodic flares of maser emission are thought to be induced either by
variations of the seed photon flux in young binary systems or the pump
rate regulated by stellar and accretion luminosities.
We seek to study the variability of four maser transitions of three
different species in G107.298+5.639 to constrain the dominant
mechanism of periodic flares.
Light curves of the 6.7GHz methanol and 22.2GHz water vapour maser
were obtained with the Torun 32m radio telescope over 39 and 34
cycles, respectively. The target was also monitored at the 1.6GHz
hydroxyl transitions with the Nancay radio telescope over 13 cycles.
All these maser lines were imaged using VLBI arrays.
The study confirms alternating flares of the methanol and water masers
with a period of 34.4d and reveals the synchronised behaviour of the
methanol and hydroxyl masers in this source. The observed spatial
distribution of the methanol maser cloudlets and the measured time
delays of the flares of individual features imply a ring-like
structure of radius 240au and thickness 30au. Internal proper
motions indicate that the velocity of methanol cloudlets is dominated
by a disc-wind component of about 5km/s. The methanol emission
detected during only one VLBI observation is located in a region about
550 au from a central star, which also exhibits OH maser flares. The
erratic appearance of methanol features can be related to a powering
object of relatively low luminosity which, during some variability
cycles, can excite molecules only in the nearest part of the disc. A
careful analysis of the maser and infrared light curves reveal a
strong correlation between the 6.7GHz line and the infrared flux
densities supporting a radiative pumping of the maser.
The synchronised behaviour of the hydroxyl 1665/1667MHz and 6.7GHz
methanol transitions indicates a common pumping mechanism for the
periodic flares of G107.298+5.639.
Description:
Light curves of the periodic 6.7GHz methanol and 22.2GHz water vapour
maser were obtained with the Torun 32m radio telescope over 39 and 34
cycles, respectively. The target was also monitored at the 1.6GHz
hydroxyl transitions with the Nancay radio telescope over 13 cycles.
Synchronised flares of OH and CH3OH have been documented and
anticorelation of water maser was confirmed.
Objects:
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RA (2000) DE Designation(s)
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22 21 22.5 +63 51 13 G107.298+5.639 = LDN 1204A
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
ch3oh.dat 36 1843 Light curve of 6.7GHz methanol maser
oh-1665.dat 36 144 Light curve of 1.665GHz hydroxyl maser
oh-1667.dat 36 144 Light curve of 1.667GHz hydroxyl maser
h2o.dat 32 1128 Light curve of 22GHz water maser
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Byte-by-byte Description of file: *.dat
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Bytes Format Units Label Explanations
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1- 10 F10.4 d MJD Date of measurement in MJD
12- 20 F9.4 yr Year Date of measurement in years
22- 36 F15.9 Jy.km/s Flux Measured integrated flux density
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Acknowledgements:
Mateusz Olech, olech(at)astro.umk.pl
(End) Patricia Vannier [CDS] 10-Jan-2020