RadioAstron reveals super-compact structures in the bursting H 2 O maser source G25.65+1.05
Por:
Bayandin, O. S., Shakhvorostova, N. N., Alakoz, A. V., Burns, R. A., Kurtz, S. E., Val'tts, I. E.
Publicada:
1 ene 2019
Resumen:
Water masers are well-known to be variable on a variety of time scales, but only three Galactic H 2 O masers are known to flare to the level of 10 5 –10 6 Jy (T B ~10 17 K): Orion KL, W49N, and the recently discovered G25.65+1.05. Recently detected flaring activity of H 2 O maser in the massive star-forming region G25.65+1.05 gave us a unique opportunity to study the fine structure of H 2 O maser emission in the bursting state with extremely high space VLBI angular resolution. Observation of the source was carried out with ~9 Earth diameter space-ground baseline within the framework of the RadioAstron project. H 2 O maser emission from two spectral features, including the bursting one, was detected in the experiment. Only ~1% of the bursting H 2 O maser emission was detected on the space-ground baselines: it indicates the presence of a very compact spatial structure with a size of ~25 µas, which corresponds to 0.05 AU or ~5 solar diameters at the distance to the source of 2.08 kpc, and the brightness temperature of ~3 × 10 16 K. Analysis of the flux density as a function of the baseline length for the bursting H 2 O maser feature in the source shows that most of the emission comes from an extended “halo” structure, while the core of emission is very compact and has an extreme brightness temperature. These results are in agreement with the model of interacting maser clouds considered as the likely explanation of the nature of the burst in the source. Under the assumption of such a model, the beam size of maser emission is reduced while the brightness temperatures similar to the highest observed values are produced. © 2019
Filiaciones:
Bayandin, O. S.:
Astro Space Center, Lebedev Physical Institute, Russian Academy of Sciences, 84/32 Profsoyuznaya st., Moscow, GSP-7117997, Russian Federation
Russian Acad Sci, Lebedev Phys Inst, Astro Space Ctr, 84-32 Profsoyuznaya St,GSP-7, Moscow 117997, Russia
Shakhvorostova, N. N.:
Astro Space Center, Lebedev Physical Institute, Russian Academy of Sciences, 84/32 Profsoyuznaya st., Moscow, GSP-7117997, Russian Federation
Astronomical Observatory, Institute for Natural Sciences and Mathematics, Ural Federal University, 19 Mira Street, Ekaterinburg, 620002, Russian Federation
Russian Acad Sci, Lebedev Phys Inst, Astro Space Ctr, 84-32 Profsoyuznaya St,GSP-7, Moscow 117997, Russia
Ural Fed Univ, Inst Nat Sci & Math, Astron Observ, 19 Mira St, Ekaterinburg 620002, Russia
Alakoz, A. V.:
Astro Space Center, Lebedev Physical Institute, Russian Academy of Sciences, 84/32 Profsoyuznaya st., Moscow, GSP-7117997, Russian Federation
Russian Acad Sci, Lebedev Phys Inst, Astro Space Ctr, 84-32 Profsoyuznaya St,GSP-7, Moscow 117997, Russia
Burns, R. A.:
Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
Natl Astron Observ Japan, Mizusawa VLBI Observ, 2-21-1 Osawa, Mitaka, Tokyo 1818588, Japan
Kurtz, S. E.:
Instituto de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, Morelia, 58090, Mexico
Univ Nacl Autonoma Mexico, Inst Radioastron & Astrofis, Morelia 58090, Michoacan, Mexico
Val'tts, I. E.:
Astro Space Center, Lebedev Physical Institute, Russian Academy of Sciences, 84/32 Profsoyuznaya st., Moscow, GSP-7117997, Russian Federation
Russian Acad Sci, Lebedev Phys Inst, Astro Space Ctr, 84-32 Profsoyuznaya St,GSP-7, Moscow 117997, Russia
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