Observational Establishment of the Period-Luminosity Relation in the Evolution of High-mass Protostars

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K03921
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 16010:Astronomy-related
• Research Institution: National Astronomical Observatory of Japan
• Principal Investigator: SUGIYAMA Koichiro 国立天文台, 水沢VLBI観測所, 特別客員研究員 (50624954)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 電波天文学 / 大質量星形成 / 強度変動 / メーザー / 周期変動 / 周期光度関係 / 突発増光 / 降着バースト

Outline of Final Research Achievements

To understand the evolutionary track of high-mass protostars, we aimed to observationally establish Period-Luminosity relation that could be an exclusively way for measurement of accretion rates onto the stellar surface, via completing 1) new detections of periodic methanol masers in beyond 30 sources via high-cadence & long-term intense flux monitoring with Ibaraki 32-m radio telescope since the end of 2012, & 2) parallax measurements to determine accurate distances (within 20% uncertainties) for two periodic targets: G35.79 & G37.47 with very-long-baseline-interferometry VERA. In addition, as by-product of the intense monitoring with Ibaraki 32-m, we achieved a new detection of drastic flux bursting activities of methanol masers at the high-mass protostar G358.93-00.03MM1, and via follow-up observations with M2O that is the world-wide maser monitoring organization this phenomenon was verified to be caused by an accretion burst and its accreting structure on a disk was unveiled.

Free Research Field

大質量星形成

Academic Significance and Societal Importance of the Research Achievements

大質量星の進化に最も大きな影響を及ぼす物理現象でありながら、1天文単位未満と微小な星表面において生じるガス降着率の、ほぼ唯一と言っても良いほど希少な導出法と期待される周期-光度関係の観測的確立へ向けて、周期変動サンプルの大幅な増加と、光度を高精度に決定する上で不可欠な距離計測を複数天体で達成出来たことは、本確立へ向けた大きな前進と言える。また、G358における降着バーストの新検出と、そのガス降着構造を詳細に明らかに出来たことは、大質量星の進化に不可欠なガス降着現象の直接的な観測研究の達成、および進化トラックにおける降着バースト現象の普遍性を高めた、という点で高い学術的意義を持つ結果と言える。