We performed simultaneous observations of the H2O 6(1,6) - 5(2,3) (22.235080 GHz) and SiO v= 1, 2, J = 1 - 0, SiO v = 1, J = 2 - 1, 3 - 2 (43.122080, 42.820587, 86.243442, and 129.363359 GHz) masers towards the suspected D-type symbiotic star, V627 Cas, using the Korean VLBI Network. Here, we present astrometrically registered maps of the H2O and SiO v = 1, 2, J = 1 - 0, SiO v = 1, J = 2 - 1 masers for five epochs from January 2016 to June 2018. Distributions of the SiO maser spots do not show clear ring-like structures, and those of the H2O maser are biased towards the north-north-west to west with respect to the SiO maser features according to observational epochs. These asymmetric distributions of H2O and SiO masers are discussed based on two scenarios of a bipolar outflow and the presence of the hot companion, a white dwarf, in V627 Cas. We carried out ring fitting of SiO v = 1, and v = 2 masers and estimated the expected position of the cool red giant. The ring radii of the SiO v = 1 maser are slightly larger than those of the SiO v = 2 maser, as previously known. Our assumption for the physical size of the SiO maser ring of V627 Cas to be the typical size of a SiO maser ring radius (\sim4 au) of red giants yields the distance of V627 Cas to be \sim1 kpc.
We present results on a search for 86.243 GHz SiO (J = 2 -- 1, v = 1) maser emission toward 67 OH/IR stars located near the Galactic Centre. We detected 32 spectral peaks, of which 28 correspond to SiO maser lines arising from the envelopes of these OH/IR stars. In OH/IR stars, we obtained an SiO maser detection rate of about 40%. We serendipitously detected two other lines from OH/IR stars at 86.18 GHz, which could be due to a CCS-molecule transition at 86.181 GHz or probably to an highly excited OH molecular transition at 86.178 GHz. The detection rate of 86 GHz maser emission is found to be…
VLBI observations of SiO masers recover at most 40-50% of the total flux obtained by single dish observations at any spectral channel. Some previous studies seems to indicate that, at least, part of the lost flux is divided up into many weak components rather than in a large resolved emission area. Taking benefit of the high sensitivity and resolution of the HSA, we investigate the problem of the missing flux in VLBI observations of SiO maser emission at 7mm in the AGB stars and obtain a high dynamic range map of IRC+10011. We conclude that the missing flux is mostly contained in many very wea…
We report on the first 1,432 sources observed using the Atacama Large Millimeter/submillimeter Array (ALMA), from the Bulge Asymmetries and Dynamical Evolution (BAaDE) survey, which aims to obtain tens of thousands of line-of-sight velocities from SiO masers in Asymptotic Giant Branch (AGB) stars in the Milky Way. A 71% detection rate of 86 GHz SiO masers is obtained from the infrared color-selected sample, and increases to 80% when considering the likely oxygen-rich stars using Midcourse Space Experiment (MSX) colors isolated in a region where [D]-[E] <= 1.38. Based on Galactic distributions,…
We investigate the use of 183 GHz H2O masers for characterization of the physical conditions and mass loss process in the circumstellar envelopes of evolved stars. We used APEX SEPIA Band 5 to observe the 183 GHz H2O line towards 2 Red Supergiant and 3 Asymptotic Giant Branch stars. Simultaneously, we observed lines in 28SiO v0, 1, 2 and 3, and for 29SiO v0 and 1. We detected the 183 GHz H2O line towards all the stars with peak flux densities greater than 100 Jy, including a new detection from VY CMa. Towards all 5 targets, the water line had indications of being due to maser emission and had …
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 …
We present results of 3 mm observations of SiO maser sources in the Galactic Centre (GC) from observations with the Australia Telescope Compact Array between $2010-2014$, along the transitions of the SiO molecule at $v = 1, J = 2-1$ at 86.243 GHz and $v = 2, J = 2-1$ at 85.640 GHz. We also present the results of the 3 mm observations with Atacama Large Millimeter/Submillimeter Array (ALMA). We detected 5 maser sources from the ATCA data, IRS 7, IRS 9, IRS 10EE, IRS 12N, and IRS 28; and 20 sources from the ALMA data including 4 new sources. These sources are predominantly late-type giants or em…
This paper presents a component-level comparison of the polarized v=1 J =1-0, v=2 J=1-0 and v=1 J=2-1 SiO maser emission towards the supergiant star VY CMa at milliarcsecond-scale, as observed using the VLBA at $λ=7$mm and $λ=3$mm. An earlier paper considered overall maser morphology and constraints on SiO maser excitation and pumping derived from these data. The goal of the current paper is to use the measured polarization properties of individual co-spatial components detected across multiple transitions to provide constraints on several competing theories for the transport of polarized mase…
The SiO molecule is one of the candidates for the seed of silicate dust in the circumstellar envelope of evolved stars, but this opinion is challenged. In this work we investigate the relation of the SiO maser emis- sion power and the silicate dust emission power. With both our own observation by using the PMO/Delingha 13.7-m telescope and archive data, a sample is assembled of 21 SiO v=1,J=2-1 sources and 28 SiO v=1,J=1- 0 sources that exhibit silicate emission features in the ISO/SWS spectrum as well. The analysis of their SiO maser and silicate emission power indicates a clear correlation, …
The supergiant VX Sagittarii is a strong emitter of both H2O and SiO masers. However, previous VLBI observations have been performed separately, which makes it difficult to spatially trace the outward transfer of the material consecutively. Here we present the astrometrically registered, simultaneous maps of 22.2 GHz H2O and 43.1/42.8/86.2/129.3 GHz SiO masers toward VX Sagittarii. The H2O masers detected above the dust-forming layers have an asymmetric distribution. The multi-transition SiO masers are nearly circular ring, suggesting spherically symmetric wind within a few stellar radii. Thes…
We report on the astrometric registration of VLBI images of the SiO and water masers in OH231.8+4.2, the iconic Proto-Planetary Nebula also known as the Calabash nebula, using the KVN and Source/Frequency Phase Referencing. This, for the first time, robustly confirms the alignment of the SiO masers, close to the AGB star, driving the bi-lobe structure with the water masers in the out-flow. We are able to trace the bulk motions for the water masers over the last few decades to be 19 km/s and deduce that the age of this expansion stage is 38$\pm$2 years. The combination of this result with the d…
We present 3D velocity measurements and acceleration limits for stars within a few parsec of the Galactic Center (GC) black hole, Sgr A*, based on observations of 43 and 86 GHz circumstellar maser emission. Observations were taken with the Very Large Array (VLA) in 2013, 2014, and 2020 and with the Atacama Large Millimeter/submillimeter Array (ALMA) in 2015 and 2017. We detect 28 masers in total, of which four are new detections. Combining these data with extant maser astrometry, we calculate stellar proper motions and accelerations with uncertainties as low as ~10 $μ$as yr$^{-1}$ and 0.5 $μ$a…
H2O (22 GHz) and SiO masers (43, 86, 129 GHz) in the bipolar proto-planetary nebula OH231.8+4.2 were simultaneously monitored using the 21-m antennas of the Korean VLBI Network in 2009-2015. Both species exhibit periodic flux variations that correlate with the central star's optical light curve, with a phase delay of up to 0.15 for the maser flux variations with respect to the optical light curve. The flux densities of SiO v = 2, J = 1-0 and H2O masers decrease with time, implying that they may disappear in 10-20 years. However, there seems to have been a transient episode of intense H2O maser…
Simultaneous time monitoring observations of H$_{2}$O $6_{16}-5_{23}$, SiO $J$ = 1--0, 2--1, 3--2, and $^{29}$SiO $v$ = 0, $J$ = 1--0 lines were carried out in the direction of the Mira variable star TX Cam with the Korean VLBI Network single dish radio telescopes. For the first time, the H$_{2}$O maser emission from TX Cam was detected near the stellar velocity at five epochs from April 10, 2013 ($ϕ$ = 3.13) to June 4, 2014 ($ϕ$ = 3.89) including minimum optical phases. The intensities of H$_{2}$O masers are very weak compared to SiO masers. The variation of peak antenna temperature ratios am…
We present multi-epoch observations with the VLBA of SiO maser emission in the v=1, J=1-0 transition at 43 GHz from the remnant of the red nova V838 Mon. We model the positions of maser spots to derive a parallax of 0.166+/-0.060 mas. Combining this parallax with other distance information results in a distance of 5.6+/-0.5 kpc, which agrees with an independent geometric distance of 6.1+/-0.6 kpc from modeling polarimetry images of V838 Mon's light echo. Combining these results, and including a weakly constraining Gaia DR2 parallax, yields a best estimate of distance of 5.9+/-0.4 kpc. The mase…
Interactions between AGB stars and a secondary in a close orbit are one possible explanation of why some AGB stars develop into aspherical planetary nebulae. This study uses millimeter observations of the continuum and SiO maser emission in several symbiotic Miras looking for evidence of an interaction between the two stars. New JVLA observations at ~45 mas resolution are analyzed, imaging continuum and SiO masers. Two of the three targets were detected and accurately registered continuum and line images were derived. No clear evidence of an interaction was found between components B and A in …
OH231.8+4.2 is an archetypal pre-planetary nebulae (pPN). It is a binary system surrounded by bipolar nebula. Some years ago the authors extensively studied it and performed several VLBI observations from which they obtained mas-resolution maps of the SiO (7 mm) and H2O (1.3 cm) maser emissions. H2O masers were found to be distributed in two areas along the symmetry axis of the nebulae oriented nearly north-south delineating a bipolar outflow and their astrometric positions were accurately measured. SiO masers, indicating the position of the Mira component of the binary system, form a structur…
Context. Stars on the asymptotic giant branch (AGB) are long-period variables that present strong flux variations at almost all wavelengths, including the SiO maser lines. The periods of these variations are of 300-500 days in Mira-type stars and somewhat shorter in semi-regular variables. The variability of the SiO lines on short timescales has been investigated, but the data are inconclusive. Aims. We aim to study the time evolution of the SiO maser lines in Mira-type and semi-regular variables at short timescales. We also discuss the origin of the observed fast variations. Methods. We obser…
Simultaneous time monitoring observations of H$_{2}$O and SiO maser lines were performed toward the D-type symbiotic binary system V407 Cyg with the Korean VLBI Network single dish radio telescope. These monitoring observations were carried out from March 2, 2010 (optical phase $ϕ$ = 0.0), 8 days before the nova outburst on March 10, 2010 to June 5, 2014 ($ϕ$ = 2.13). Eight days before the nova outburst, we detected the SiO $v$ = 1, 2, $J$ = 1--0 maser lines which exhibited values of 0.51 K ($\sim$ 6.70 Jy) and 0.71 K ($\sim$ 9.30 Jy), respectively, while after the outburst we could not detect…
The full theory of polarized SiO maser emission from the near-circumstellar environment of Asymptotic Giant Branch stars has been the subject of debate, with theories ranging from classical Zeeman origins to predominantly non-Zeeman anisotropic excitation or propagation effects. Features with an internal electric vector position angle (EVPA) rotation of $\sim π/2$ offer unique constraints on theoretical models. In this work, results are presented for one such feature that persisted across five epochs of SiO $ν=1, J=1-0$ VLBA observations of TX Cam. We examine the fit to the predicted dependenc…
We use Atacama Large Millimeter/submillimeter Array Band 5 science verification observations of the red supergiant VY CMa to study the polarization of SiO thermal/masers lines and dust continuum at ~1.7 mm wavelength. We analyse both linear and circular polarization and derive the magnetic field strength and structure, assuming the polarization of the lines originates from the Zeeman effect, and that of the dust originates from aligned dust grains. We also discuss other effects that could give rise to the observed polarization. We detect, for the first time, significant polarization (~3%) of t…
The detailed polarization mechanisms of SiO masers originating from the near circum\-stellar environment of Asymptotic Giant Branch stars are not yet definitively known. Prevailing theories are broadly classified as either Zeeman or non-Zeeman in origin, the latter including effects such as anisotropic pumping or anisotropic resonant scattering. The predicted behavior of the linear and circular polarization fractions and electric vector position angle vary by theory. In particular, individual maser features that exhibit a rotation in linear polarization of $\sim π/2$ as a function of frequency…
There are indications that the third known eruption of the recurrent nova T CrB is imminent, and multi-wavelength observations prior to the eruption are important to characterise the system before it erupts. T CrB is known to display the SiO fundamental vibrational feature at 8$\,μ$m. When the anticipated eruption occurs, it is possible that the shock produced when the ejected material runs into the wind of the red giant in the system may be traced using SiO maser emission. We have used the 100m Effelsberg Radio Telescope to search for $^{28}$SiO emission in the $\upsilon=1$, $\upsilon=2$, $J=…
Circumstellar environments of oxygen-rich stars are among the strongest SiO maser emitters. Physical processes such as collisions, infrared pumping and overlaps favors the inversion of level population and produce maser emission at different vibrational states. Despite numerous observational and theoretical efforts, we still do not have an unified picture including all the physical processes involved in the SiO maser emission. The aim of this work is to provide homogeneous data in a large sample of oxygen-rich stars. We present a survey of 67 oxygen-rich stars from 7 to 1 mm, in their rotation…
We present the first images of the 28SiO v=1, J=2-1 maser emission around the closest known massive young stellar object Orion Source I observed at 86 GHz (3mm) with the VLBA. These images have high spatial (~0.3 mas) and spectral (~0.054 km/s) resolutions. We find that the 3mm masers lie in an X-shaped locus consisting of four arms, with blue-shifted emission in the south and east arms and red-shifted emission in the north and west arms. Comparisons with previous images of the 28SiO v=1,2, J=1-0 transitions at 7mm (observed in 2001-2002) show that the bulk of the J=2-1 transition emission fol…
We present the database of maser sources in H2O, OH and SiO lines that can be used to identify and study variable stars at evolved stages. Detecting the maser emission in H2O, OH and SiO molecules toward infrared-excess objects is one of the methods of identification long-period variables (LPVs, including Miras and Semi-Regular), because these stars exhibit maser activity in their circumstellar shells. Our sample contains 1803 known LPV objects. 46% of these stars (832 objects) manifest maser emission in the line of at least one molecule: H2O, OH or SiO. We use the database of circumstellar ma…
We observed the 43 GHz v=1, 2, and 3 and 86 GHz v=1 SiO maser transitions quasi-simultaneously for a Mira-variable-dominated sample of over 80 sources from the Bulge Asymmetries and Dynamical Evolution (BAaDE) project, using ATCA, and statistically compared the relative line strengths. On average, the 43 GHz v=1 line is brighter than the 86 GHz v=1 line by a factor of 1.36+/-0.15. As a result, an 86 GHz v=1 observed sample can be observed to 85.9% of the distance of a 43 GHz v=1 observed sample using the same sensitivity. We discuss what impact this may have on the BAaDE Galactic plane survey …
We present an observational study of the vibrationally excited H$_{2}$O line at 658 GHz ($ν_{2}$=1, 1$_{1, 0}$-1$_{0, 1}$) toward Orion KL using the Atacama Large Millimeter/Submillimeter Array (ALMA). This line is clearly detected at the position of the massive protostar candidate, the Source I. The spatial structure is compact with a size of about 100 AU and is elongated along the northeast-southwest low-velocity (18 km s$^{-1}$) bipolar outflow traced by 22 GHz H$_{2}$O masers, SiO masers, and thermal SiO lines. A velocity gradient can be seen perpendicular to the bipolar outflow. Overall s…
We present the first results from the MALT-45 (Millimetre Astronomer's Legacy Team - 45 GHz) Galactic Plane survey. We have observed 5 square-degrees ($l = 330 - 335$, $b = \pm0.5$) for spectral lines in the 7 mm band (42-44 and 48-49 GHz), including $\text{CS}$ $(1-0)$, class I $\text{CH}_3\text{OH}$ masers in the $7(0,7)-6(1,6)$ $\text{A}^{+}$ transition and $\text{SiO}$ $(1-0)$ $v=0,1,2,3$. MALT-45 is the first unbiased, large-scale, sensitive spectral line survey in this frequency range. In this paper, we present data from the survey as well as a few intriguing results; rigorous analyses o…
We observed polarization of the SiO rotational transitions from Orion Source I (SrcI) to probe the magnetic field in bipolar outflows from this high mass protostar. Both 43 GHz $J$=1-0 and 86 GHz $J$=2-1 lines were mapped with $\sim$20 AU resolution, using the Very Large Array (VLA) and Atacama Large Millimeter/Submillimeter Array (ALMA), respectively. The $^{28}$SiO transitions in the ground vibrational state are a mixture of thermal and maser emission. Comparison of the polarization position angles in the $J$=1-0 and $J$=2-1 transitions allows us to set an upper limit on possible Faraday rot…
SiO Maser Line-width Diagnostics of AGB Stars and Red Supergiants: The RSG-adjacent Region in the FWZI--Luminosity Plane
School of Physics and Astronomy, Sun Yat-sen University（中山大学物理学院）；CSST Science Center for the Guangdong-Hong Kong-Macau Greater Bay Area, Sun Yat-sen University（中山大学粤港澳大湾区宇宙线科学中心）；School of Physics and Astronomy, Beijing Normal University（北京师范大学物理学院）；Institute for Frontiers in Astronomy and Astrophysics, Beijing Normal University（北京师范大学天文与前沿物理研究所）
