Identifying the mechanisms of water maser variability during the accretion burst in NGC6334I
文献类型：期刊论文
| 作者 | Vorster, J. M.8,9; Chibueze, J. O.1,9,10; Hirota, T.2,11; Macleod, G. C.3,4; van der Walt, D. J.9; Vorobyov, E. I.5,6; Sobolev, A. M.5,7; Juvela, M.8 |
| 刊名 | ASTRONOMY & ASTROPHYSICS
 |
| 出版日期 | 2024-11-08 |
| 卷号 | 691页码:A157 |
| 关键词 | masers techniques: high angular resolution stars: formation ISM: jets and outflows ISM: individual objects: NGC6334I |
| ISSN号 | 0004-6361 |
| DOI | 10.1051/0004-6361/202450751 |
| 产权排序 | 11 |
| 英文摘要 | Context. High-mass young stellar objects gain most of their mass in short intense bursts of accretion. Maser emission is an invaluable tool in discovering and probing these accretion bursts. Aims. Our aim was to observe the 22 GHz water maser response induced by the accretion burst in NGC6334I-MM1B and to identify the underlying maser variability mechanisms. Methods. We report seven epochs of very long baseline interferometry (VLBI) observations of 22 GHz water masers in NGC6334I with the VLBI Exploration of Radio Astrometry (VERA) array, from 2014 to 2016, spanning the onset of the accretion burst in 2015.1. We also report 2019 Atacama Large Millimeter/submillimeter Array (ALMA) observations of 321 GHz water masers and 22 GHz single-dish maser monitoring by the Hartebeesthoek Radio Astronomical Observatory (HartRAO). We analysed long-term variability patterns and used proper motions with the 22 GHz to 321 GHz line ratio to distinguish between masers in non-dissociative C-shocks and dissociative J-shocks. We also calculated the burst-to-quiescent variance ratio of the single-dish time series. Results. We detected a water maser distribution resembling a bipolar outflow morphology. The constant mean proper motion before and after the burst indicates that maser variability is due to excitation effects from variable radiation rather than jet ejecta. For the whole region, we find that the flux density variance ratio in the single-dish time series can identify maser efficiency variations in 22 GHz masers. The northern region, CM2-W2, is excited in C-shocks and showed long-term flaring with velocity-dependent excitation of new maser features after the onset of the burst. We propose that radiative heating of H2 due to high-energy radiation from the accretion burst be the main mechanism for the flaring in CM2-W2. The southern regions are excited by J-shocks, which have shown short-term flaring and dampening of water masers. We attribute the diverse variability patterns in the southern regions to the radiative transfer of the burst energy in the complex source geometry. Conclusions. Our results indicate that the effects of source geometry, shock type, and incident radiation spectrum are fundamental factors affecting 22 GHz maser variability. Investigating water masers in irradiated shocks will improve their use as a diagnostic in time-variable radiation environments, such as accretion bursting sources. |
| WOS关键词 | EXTRAORDINARY OUTBURST ; H2O MASERS ; MASSIVE PROTOSTARS ; ALMA OBSERVATIONS ; MAGNETIC-FIELDS ; METHANOL ; DISCOVERY ; EMISSION ; VELOCITY ; STARS |
| 资助项目 | Research Council of Finlandhttp://dx.doi.org/10.13039/501100002341[UID: 134192] ; National Research Foundation[348342] ; Research Council of Finland[17K05398] ; Research Council of Finland[18H05222] ; Research Council of Finland[20H05845] ; MEXT/JSPS KAKENHI[23-12-00258] ; Russian Science Foundation[150551] ; South African Department of Science and Innovation's National Research Foundation[2018.1.00024] ; ALMA ; National Research Foundation (NRF), South Africa |
| WOS研究方向 | Astronomy & Astrophysics |
| 语种 | 英语 |
| WOS记录号 | WOS:001351092800004 |
| 出版者 | EDP SCIENCES S A |
| 资助机构 | Research Council of Finlandhttp://dx.doi.org/10.13039/501100002341 ; National Research Foundation ; Research Council of Finland ; MEXT/JSPS KAKENHI ; Russian Science Foundation ; South African Department of Science and Innovation's National Research Foundation ; ALMA ; National Research Foundation (NRF), South Africa |
| 源URL | [http://ir.xao.ac.cn/handle/45760611-7/7294]  |
| 专题 | 研究单元未命名 |
| 通讯作者 | Vorster, J. M. |
| 作者单位 | 1.Univ Nigeria, Fac Phys Sci, Dept Phys & Astron, Carver Bldg,1 Univ Rd, Nsukka 410001, Nigeria 2.Grad Univ Adv Studies SOKENDAI, 2-21-1 Osawa, Mitaka, Tokyo 1818588, Japan 3.Open Univ Tanzania, Dept Phys Sci, POB 23409, Dar Es Salaam, Tanzania 4.SARAO, Hartebeesthoek Radio Astron Observ, POB 443, ZA-1740 Krugersdorp, South Africa 5.Ural Fed Univ, 19 Mira Str, Ekaterinburg 620002, Russia 6.Southern Fed Univ, Res Inst Phys, Rostov Na Donu 344090, Russia 7.Chinese Acad Sci, Xinjiang Astron Observ, Urumqi 830011, Peoples R China 8.Univ Helsinki, Dept Phys, POB 64, FI-00014 Helsinki, Finland 9.Northwest Univ, Ctr Human Metabol, Potchefstroom Campus, ZA-2531 Potchefstroom, South Africa 10.Univ South Africa, Dept Math Sci, Cnr Christian Wet Rd & Pioneer Ave Florida Pk, ZA-1709 Florida Pk, Roodepoort, South Africa |
| 推荐引用方式 GB/T 7714 | Vorster, J. M.,Chibueze, J. O.,Hirota, T.,et al. Identifying the mechanisms of water maser variability during the accretion burst in NGC6334I[J]. ASTRONOMY & ASTROPHYSICS,2024,691:A157. |
| APA | Vorster, J. M..,Chibueze, J. O..,Hirota, T..,Macleod, G. C..,van der Walt, D. J..,...&Juvela, M..(2024).Identifying the mechanisms of water maser variability during the accretion burst in NGC6334I.ASTRONOMY & ASTROPHYSICS,691,A157. |
| MLA | Vorster, J. M.,et al."Identifying the mechanisms of water maser variability during the accretion burst in NGC6334I".ASTRONOMY & ASTROPHYSICS 691(2024):A157. |
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