SiO maser astrometry of the red transient V838 Monocerotis

Simultaneous VLBI Astrometry of H2O and SiO Masers toward the Semiregular Variable R Crateris

We obtained, for the first time, astrometrically registered maps of the 22.2 GHz H2O and 42.8, 43.1, and 86.2 GHz SiO maser emission toward the semiregular b-type variable (SRb) R Crateris, at three epochs (2015 May 21, and 2016 January 7 and 26) using the Korean Very-long-baseline Interferometry Network. The SiO masers show a ring-like spatial structure, while the H2O maser shows a very asymmetric one-side outflow structure, which is located at the southern part of the ring-like SiO maser feature. We also found that the 86.2 GHz SiO maser spots are distributed in an inner region, compared to …

On the properties of dust and gas in the environs of V838 Monocerotis

Herschel FIR imaging and spectroscopy were taken at several epochs to probe the central point source and the extended environment of V838 Mon. PACS and SPIRE maps were used to obtain photometry of the near and far dust around V838 Mon. Fitting reveals 0.5-0.6 solar masses of ~19K dust in the environs (~2.7pc) surrounding the star. The surface-integrated infrared flux (signifying the thermal light echo) and derived dust properties do not vary significantly between the epochs. We also fit the SED of the point source. As the peak of the SED lies outside the Herschel spectral range, it is only by …

大犬座VY中SiO $v=0$, $J=1 \rightarrow 0$脉泽的首次VLBI成像

First VLBI Imaging of SiO $v=0$, $J=1 \rightarrow 0$ Masers in VY Canis Majoris

利用VERA望远镜首次对红超巨星VY CMa的SiO $v=0$和$v=3$态$J=1\rightarrow 0$脉泽进行VLBI探测，精确定位了致密且高亮度的$v=0$脉泽斑，揭示了其与星风强激波及剧烈质量抛射的关联。

High-resolution optical spectroscopy of V838 Monocerotis in 2009

V838 Mon erupted at the beginning of 2002. In the course of the outburst the object evolved to low effective temperatures and declined as a very late M-type supergiant. Among various scenarios proposed to explain the nature of the outburst, the most promising is a stellar merger event. We aim at studying the structure and evolution of the object in the decline from the 2002 eruption. We obtained spectroscopic observations of V838 Mon in January--March 2009 with UVES/VLT. The results are analysed and compared with similar observations obtained in October 2005 with HIRES/Keck. The most striking …

V838 Monocerotis as seen by ALMA: a remnant of a binary merger in a triple system

V838 Mon erupted in 2002 quickly becoming the prototype of a new type of stellar eruptions known today as (luminous) red novae. The red nova outbursts are thought to be caused by stellar mergers. The merger in V838 Mon took place in a triple or higher system involving two B-type stars. We mapped the merger site with ALMA at a resolution of 25 mas in continuum dust emission and in rotational lines of simple molecules, including CO, SiO, SO, SO$_2$, AlOH, and H$_2$S. We use radiative transfer calculations to reproduce the remnant's architecture at the epoch of the ALMA observations. For the firs…

Distance and Kinematics of the Red Hypergiant VY CMa: VLBA and VLA Astrometry

We report astrometric results of phase-referencing VLBI observations of 43 GHz SiO maser emission toward the red hypergiant VY Canis Majoris (\vycma) using the Very Long Baseline Array (VLBA). We measured a trigonometric parallax of 0.83 $\pm$ 0.08 mas, corresponding to a distance of 1.20$^{+0.13}_{-0.10}$ kpc. Compared to previous studies, the spatial distribution of SiO masers has changed dramatically, while its total extent remains similar. The internal motions of the maser spots are up to 1.4 \masy, corresponding to 8 \kms, and show a tendency for expansion. After modeling the expansion of…