Periodic variability of 6.7 GHz methanol masers in G22.357 + 0.066

Szymczak, M.; Wolak, P.; Bartkiewicz, A.; Langevelde, H. J. van

doi:10.1051/0004-6361/201117145

Cited by 46 publications

(47 citation statements)

References 23 publications

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“…The discovery of periodic variability in the 6.7-and 12.2-GHz methanol masers reported by Goedhart et al (2003Goedhart et al ( , 2004Goedhart et al ( , 2009Goedhart et al ( , 2013) was unexpected as it had not been previously reported in any maser transitions associated with high-mass star formation regions. Further monitoring programmes have been conducted independently and confirmed the existence of periodic variations in eight more methanol masers (Araya et al 2010;Szymczak et al 2011Szymczak et al , 2015Fujiswa et al 2014;Maswanganye et al 2015), bringing the total number of periodic masers to 15.…”

Section: Introductionmentioning

confidence: 85%

Discovery of periodic class II methanol masers associated with G339.986−0.425 region

Maswanganye

Walt

Goedhart

et al. 2016

Mon. Not. R. Astron. Soc.

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Ten new class II methanol masers from the 6.7-GHz Methanol Multibeam survey catalogues III and IV were selected for a monitoring programme at both 6.7 and 12.2 GHz with the 26m Hartebeesthoek Radio Astronomy Observatory (HartRAO) radio telescope for two years and nine months, from August 2012 to May 2015. In the sample, only masers associated with G339.986-0.425 were found to show periodic variability at both 6.7 and 12.2 GHz. The existence of periodic variation was tested with four independent methods. The analytical method gave the best estimation of the period, which was 246 ± 1 days. The time series of G339.986-0.425 show strong correlations across velocity channels and between the 6.7 and 12.2 GHz masers. The time delay was also measured across channels and shows structure across the spectrum which is continuous between different maser components.

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Section: Introductionmentioning

confidence: 85%

Discovery of periodic class II methanol masers associated with G339.986−0.425 region

Maswanganye

Walt

Goedhart

et al. 2016

Mon. Not. R. Astron. Soc.

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“…This actually matches the rarity expected from observations. The number of 6.7 GHz methanol masers observed ever is ∼900 (e.g., Pestalozzi et al 2005;Caswell et al 2011;Green et al 2012), and of those, 56 masers have been monitored for more than a year at intervals shorter than a week or a month (Goedhart et al 2007(Goedhart et al , 2009Araya et al 2010;Szymczak et al 2011). About 20% of such sources show the characteristic periodic variabilities (Table 1).…”

Section: Period-luminosity Relationmentioning

confidence: 99%

Direct Diagnostics of Forming Massive Stars: Stellar Pulsation and Periodic Variability of Maser Sources

Inayoshi

Sugiyama

Hosokawa

et al. 2013

ApJ

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The 6.7 GHz methanol maser emission, a tracer of forming massive stars, sometimes shows enigmatic periodic flux variations over several 10-100 days. In this Letter, we propose that these periodic variations could be explained by the pulsation of massive protostars growing under rapid mass accretion with rates ofṀ * 10 −3 M yr −1 . Our stellar evolution calculations predict that the massive protostars have very large radii exceeding 100 R at maximum, and here we study the pulsational stability of such bloated protostars by way of the linear stability analysis. We show that the protostar becomes pulsationally unstable with various periods of several 10-100 days depending on different accretion rates. With the fact that the stellar luminosity when the star is pulsationally unstable also depends on the accretion rate, we derive the period-luminosity relation log(L/ L ) = 4.62 + 0.98 log(P /100 days), which is testable with future observations. Our models further show that the radius and mass of the pulsating massive protostar should also depend on the period. It would be possible to infer such protostellar properties and the accretion rate with the observed period. Measuring the maser periods enables a direct diagnosis of the structure of accreting massive protostars, which are deeply embedded in dense gas and are inaccessible with other observations.

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“…Periodic or regular flaring behaviour of 6.7, 12.2, and 107 GHz CH 3 OH masers have been reported and discussed by Goedhart et al (2003, Araya et al (2010) and Szymczak et al (2011). Currently nine confirmed periodic maser sources are known.…”

Section: Introductionmentioning

confidence: 98%

Pumping of the 4.8 GHz H₂CO masers and its implications for the periodic masers in G37.55+0.20

Walt¹

2014

A&A

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Context. Periodic or regular flaring of class II CH 3 OH masers in nine high mass star forming regions is now a well established phenomenon. Amongst the nine star forming regions, G37.55+0.20 is the only case at present where apart from the presence of a periodic class II CH 3 OH maser, correlated flaring of another masing species, H 2 CO in this case, has been detected. Aims. We perform numerical calculations to investigate under which conditions the 1 10 −1 11 transition (4.8 GHz) of ortho-H 2 CO is inverted in order to address the question of the correlated flaring of the 6.7 GHz CH 3 OH and 4.8 GHz H 2 CO masers in G37.55+0.20. Methods. We developed a numerical code to study the population inversion of o-H 2 CO. Equilibrium solutions for the level populations are found by integrating the rate equations using Heun's method. Results. It is found that collisional excitation with H 2 as well as radiative excitation by the free-free radio continuum radiation from a nearby ultra-or hyper-compact H  region can invert the 1 10 −1 11 transition. It is also found that radiative excitation by the dust infrared radiation field does not lead to an inversion of the 1 10 −1 11 transition. The 2 11 −2 12 (14.5 GHz) and 3 12 −3 13 (28.9 GHz) transitions are inverted only in the presence of the free-free continuum radiation field of a very compact H  region. Conclusions. Due to the different pumping mechanisms of the H 2 CO and CH 3 OH masers it is unlikely that the near simultaneous flaring of the CH 3 OH and H 2 CO masers in G37.55+0.20 is due to changes in the pumping of the masers.

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Periodic variability of 6.7 GHz methanol masers in G22.357 + 0.066

Cited by 46 publications

References 23 publications

Discovery of periodic class II methanol masers associated with G339.986−0.425 region

Discovery of periodic class II methanol masers associated with G339.986−0.425 region

Direct Diagnostics of Forming Massive Stars: Stellar Pulsation and Periodic Variability of Maser Sources

Pumping of the 4.8 GHz H₂CO masers and its implications for the periodic masers in G37.55+0.20

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Periodic variability of 6.7 GHz methanol masers in G22.357 + 0.066

Cited by 46 publications

References 23 publications

Discovery of periodic class II methanol masers associated with G339.986−0.425 region

Discovery of periodic class II methanol masers associated with G339.986−0.425 region

Direct Diagnostics of Forming Massive Stars: Stellar Pulsation and Periodic Variability of Maser Sources

Pumping of the 4.8 GHz H2CO masers and its implications for the periodic masers in G37.55+0.20

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Pumping of the 4.8 GHz H₂CO masers and its implications for the periodic masers in G37.55+0.20