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Long-term and highly frequent monitor of 6.7 GHz methanol masers to statistically research periodic flux variations around high-mass protostars using the Hitachi 32-m

Published online by Cambridge University Press:  16 July 2018

Koichiro Sugiyama
Affiliation:
Mizusawa VLBI Observatory, National Astronomical Observatory of Japan (NAOJ), 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan email: koichiro.sugiyama@nao.ac.jp Center for Astronomy, Ibaraki University, 2-1-1 Bunkyo, Mito, Ibaraki 310-8512, Japan
Y. Yonekura
Affiliation:
Center for Astronomy, Ibaraki University, 2-1-1 Bunkyo, Mito, Ibaraki 310-8512, Japan
K. Motogi
Affiliation:
Graduate School of Sciences and Technology for Innovation, Yamaguchi University, 1677-1 Yoshida, Yamaguchi, Yamaguchi 753-8512, Japan
Y. Saito
Affiliation:
Center for Astronomy, Ibaraki University, 2-1-1 Bunkyo, Mito, Ibaraki 310-8512, Japan
T. Yamaguchi
Affiliation:
College of Science, Ibaraki University, 2-1-1 Bunkyo, Mito, Ibaraki 310-8512, Japan
M. Momose
Affiliation:
Center for Astronomy, Ibaraki University, 2-1-1 Bunkyo, Mito, Ibaraki 310-8512, Japan College of Science, Ibaraki University, 2-1-1 Bunkyo, Mito, Ibaraki 310-8512, Japan
M. Honma
Affiliation:
Mizusawa VLBI Observatory, NAOJ, 2-12 Hoshigaoka-cho, Mizusawa-ku, Oshu, Iwate 023-0861, Japan
T. Hirota
Affiliation:
Mizusawa VLBI Observatory, National Astronomical Observatory of Japan (NAOJ), 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan email: koichiro.sugiyama@nao.ac.jp
M. Uchiyama
Affiliation:
Advanced Technology Center, NAOJ, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
N. Matsumoto
Affiliation:
Mizusawa VLBI Observatory, National Astronomical Observatory of Japan (NAOJ), 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan email: koichiro.sugiyama@nao.ac.jp
K. Hachisuka
Affiliation:
Mizusawa VLBI Observatory, NAOJ, 2-12 Hoshigaoka-cho, Mizusawa-ku, Oshu, Iwate 023-0861, Japan
K. Inayoshi
Affiliation:
Department of Astronomy, Columbia University, 550 W. 120th Street, New York, NY 10027, USA
K. E. I. Tanaka
Affiliation:
Department of Astronomy, University of Florida, Gainesville, FL 32611, USA
T. Hosokawa
Affiliation:
Department of Physics, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
K. Fujisawa
Affiliation:
The Research Institute for Time Studies, Yamaguchi University, 1677-1 Yoshida, Yamaguchi, Yamaguchi 753-8511, Japan
Corresponding
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Abstract

We initiated a long-term and highly frequent monitoring project toward 442 methanol masers at 6.7 GHz (Dec >−30 deg) using the Hitachi 32-m radio telescope in December 2012. The observations have been carried out daily, monitoring a spectrum of each source with intervals of 9–10 days. In September 2015, the number of the target sources and intervals were redesigned into 143 and 4–5 days, respectively. This monitoring provides us complete information on how many sources show periodic flux variations in high-mass star-forming regions, which have been detected in 20 sources with periods of 29.5–668 days so far (e.g., Goedhart et al. 2004). We have already obtained new detections of periodic flux variations in 31 methanol sources with periods of 22–409 days. These periodic flux variations must be a unique tool to investigate high-mass protostars themselves and their circumstellar structure on a very tiny spatial scale of 0.1–1 au.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2018 

References

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Long-term and highly frequent monitor of 6.7 GHz methanol masers to statistically research periodic flux variations around high-mass protostars using the Hitachi 32-m
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Long-term and highly frequent monitor of 6.7 GHz methanol masers to statistically research periodic flux variations around high-mass protostars using the Hitachi 32-m
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Long-term and highly frequent monitor of 6.7 GHz methanol masers to statistically research periodic flux variations around high-mass protostars using the Hitachi 32-m
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