Bursting Activity in a High-Mass Star-Forming Region G33.640.21 Observed with the 6.7 GHz Methanol Maser

We report on the detection of bursts of 6.7 GHz methanol maser emission in a high-mass star-forming region, G33.64� 0.21. One of the spectral components of the maser in this source changed its flux density by 7 times that of the previous day, and it decayed with a timescale of 5 days. The burst occurred repeatedly in the spectral component, and no other components showed such variability. A VLBI observation with the Japanese VLBI Network (JVN) showed that the burst location was at the southwest edge of a spatial distribution, and the bursting phenomenon occurred in a region much smaller than 70 AU. We suggest an impulsive energy release, like a stellar flare, as a possible mechanism for the burst. These results imply that 6.7 GHz methanol masers could be a useful new probe for studying bursting activity in the process of the star formation of high-mass YSOs with a high-resolution of AU scale.

[1]  A. Bartkiewicz,et al.  Periodic variability of 6.7 GHz methanol masers in G22.357 + 0.066 , 2011, 1105.4089.

[2]  H. Langevelde,et al.  VLA observations of water masers towards 6.7 GHz methanol maser sources , 2010, 1009.2334.

[3]  W. Goss,et al.  QUASI-PERIODIC FORMALDEHYDE MASER FLARES IN THE MASSIVE PROTOSTELLAR OBJECT IRAS 18566+0408 , 2010, 1006.2164.

[4]  D. A. Rafferty,et al.  Proceedings of the 10th European VLBI Network Symposium and EVN Users Meeting , 2010 .

[5]  Periodic class II methanol masers in G9.62+0.20E , 2009, 0906.0876.

[6]  D. Walt,et al.  Short-period variability in the Class II methanol maser source G12.89+0.49 (IRAS 18089-1732) , 2009, 0906.0295.

[7]  Astronomy,et al.  The diversity of methanol maser morphologies from VLBI observations , 2009, 0905.3469.

[8]  H. Kobayashi,et al.  A Synchronized Variation of the 6.7GHz Methanol Maser in Cepheus A , 2008, 0804.4623.

[9]  W. Vlemmings.  A new probe of magnetic fields during high-mass star formation Zeeman splitting of 6.7 GHz methanol masers , 2008, 0804.1141.

[10]  K. Menten,et al.  A high-sensitivity 6.7 GHz methanol maser survey toward H2O sources , 2008, 0803.2232.

[11]  H. Kobayashi,et al.  Mapping Observations of 6.7GHz Methanol Masers with the Japanese VLBI Network , 2007, 0710.4872.

[12]  R. Cesaroni,et al.  Massive star-formation in G24.78+0.08 explored through VLBI maser observations , 2007 .

[13]  F. Bertoldi,et al.  Synchrotron emission from the T Tauri binary system V773 Tauri A , 2006, astro-ph/0604124.

[14]  L. I. Matveyenko,et al.  VLBA Observations of a Bursting Water Maser in Orion KL , 2005 .

[15]  E. Feigelson,et al.  X-Ray Emission from Early-Type Stars in the Orion Nebula Cluster , 2005, astro-ph/0505503.

[16]  P. Godfrey,et al.  Models of class II methanol masers based on improved molecular data , 2005, astro-ph/0504194.

[17]  K. Hamaguchi,et al.  X-Ray Study of Herbig Ae/Be Stars , 2005 .

[18]  D. Walt,et al.  Long-term monitoring of 6.7-GHz methanol masers , 2004 .

[19]  R. Dodson,et al.  High-resolution observations of 6.7-GHz methanol masers with the Long Baseline Array , 2004, astro-ph/0403430.

[20]  K. Nakanishi,et al.  A Giant Flare on a T Tauri Star Observed at Millimeter Wavelengths , 2003, astro-ph/0310727.

[21]  Michael C. Liu,et al.  A Giant Outburst at Millimeter Wavelengths in the Orion Nebula , 2003, astro-ph/0308277.

[22]  R. Norris,et al.  The protostellar mass limit for 6.7 GHz methanol masers. I. A low-mass YSO survey , 2003 .

[23]  D. Walt,et al.  Periodic flares in the methanol maser source G9.62+0.20E , 2003 .

[24]  J. Conway,et al.  VLBI observations of 6.7 and 12.2 GHz methanol masers toward high mass star-forming regions - III. The milliarcsecond structures of masing regions , 2002 .

[25]  A. Kus,et al.  A survey of the 6.7 GHz methanol maser emission from IRAS sources - I. Data , 2000 .

[26]  K. Koyama,et al.  Magnetic activities in young stellar objects , 1999 .

[27]  H. Murakami,et al.  ASCA Detection of a Superhot 100 Million K X-Ray Flare on the Weak-lined T Tauri Star V773 Tauri , 1998 .

[28]  K. Koyama,et al.  ASCA Observations of the Barnard 209 Dark Cloud and an Intense X-Ray Flare on V773 Tauri , 1997 .

[29]  E. Feigelson,et al.  Polarized Radio Emission From the Multiple T Tauri System HD 283447 , 1996 .

[30]  J. Cordes,et al.  Variability of interstellar hydroxyl masers , 1991 .