scholarly journals VLBI studies of SiO masers around VX Sagittarii

2007 ◽  
Vol 3 (S242) ◽  
pp. 312-313
Author(s):  
X. Chen ◽  
Z.-Q. Shen ◽  
D.-R. Jiang
Keyword(s):  
Variable Star ◽  
Circumstellar Envelope ◽  
Preliminary Results ◽  
Regular Variable

AbstractObservations of 43 GHz 28SiO (v = 1, J = 1-0) masers in the circumstellar envelope of the M-type semi-regular variable star VX Sgr were performed using the VLBA at 3 epochs during 1999 April-May. By tracing 42 matched maser features appearing in all the three epochs, we determined the contraction of an SiO maser shell toward VX Sgr at a velocity of about 4 km s−1 at a distance of 1.7 kpc to VX Sgr. We also report on some preliminary results from our first epoch of simultaneous VLBA observations of three 7 mm SiO masers toward VX Sgr.

scholarly journals The Carina Dwarf Galaxy Variable Star Population

2002 ◽  
Vol 185 ◽  
pp. 134-135
Author(s):  
V. Ripepi ◽  
M. Dall’Ora ◽  
L. Pulone ◽  
M. Castellani ◽  
C. Corsi ◽  
...  
Keyword(s):  
Variable Star ◽  
Dwarf Galaxy ◽  
Variable Stars ◽  
Photometric Data ◽  
Wide Field ◽  
Preliminary Results

AbstractWe present some preliminary results based on new observations of the variable stars belonging to the Carina Dwarf Galaxy (DG). Photometric data were collected with the two wide field imagers available at ESO ([email protected].) and CTIO (4m prime focus).

scholarly journals The Structure and Kinematics of Envelope around Red Supergiant AH Sco Traced by SiO Masers

2008 ◽  
Vol 4 (S252) ◽  
pp. 247-248 ◽  
Author(s):  
X. Chen ◽  
Z.-Q. Shen
Keyword(s):  
Model Fitting ◽  
Position Angle ◽  
Central Star ◽  
Circumstellar Envelope ◽  
Proper Motions ◽  
3 Dimensional ◽  
Long Baseline ◽  
Elliptical Ring ◽  
Regular Variable ◽  
Very Long Baseline Array

AbstractObservations of 43 GHz v = 1, J = 1−0 SiO masers in the circumstellar envelope of the M-type semi-regular variable star AH Sco were performed with the Very Long Baseline Array (VLBA) at 2 epochs in March 2004. These high-resolution VLBA images reveal that the distribution of SiO masers is roughly on a persistent elliptical ring with the lengths of the major and minor axes of about 18.5 and 15.8 mas, respectively, along a position angle of 150°. The 3-dimensional kinematics model-fitting for proper motions and spatial distributions of maser features clearly indicates that the SiO maser shell around AH Sco was undergoing an overall contraction to the star at a velocity of 15 km s−1 at a distance of 2.26 kpc to AH Sco due to the gravitation of the central star.

scholarly journals Annual parallax measurements of a semi-regular variable star, RW Leporis

2014 ◽  
Vol 66 (6) ◽  
pp. 107 ◽  
Author(s):  
Tatsuya Kamezaki ◽  
Tomoharu Kurayama ◽  
Akiharu Nakagawa ◽  
Toshihiro Handa ◽  
Toshihiro Omodaka ◽  
...  
Keyword(s):  
Variable Star ◽  
Regular Variable

scholarly journals The Circumstellar Envelope of the Semiregular Variable Star V CVn

2019 ◽  
Vol 45 (7) ◽  
pp. 453-461
Author(s):  
B. S. Safonov ◽  
A. V. Dodin ◽  
S. A. Lamzin ◽  
A. S. Rastorguev
Keyword(s):  
Variable Star ◽  
Circumstellar Envelope ◽  
Semiregular Variable

scholarly journals VLBI astrometry of the semi-regular variable star RX Bootis

2012 ◽  
Vol 8 (S289) ◽  
pp. 91-94
Author(s):  
Tatsuya Kamezaki ◽  
Akiharu Nakagawa ◽  
Toshihiro Omodaka ◽  
Toshihiro Handa ◽  
Hiroshi Imai ◽  
...  
Keyword(s):  
Variable Star ◽  
Absolute Magnitude ◽  
Distance Measurement ◽  
Reference Source ◽  
Maser Spot ◽  
Regular Variable ◽  
The Absolute ◽  
Stellar Properties ◽  
Water Maser ◽  
The Continuum

AbstractWe present a distance measurement to the semi-regular variable star RX Bootis (RX Boo). Using the VLBI Exploration of Radio Astrometry (VERA) telescope, we conducted astrometric observations of a water maser spot associated with RX Boo, as well as of the continuum reference source J1419+2706. Based on monitoring observations covering a full year, the annual parallax of RX Boo was measured at 7.31 ± 0.50 mas, corresponding to a distance of 136+10−9 pc. This distance uncertainty is smaller by a factor of two than those previously published, allowing us to determine the object's stellar properties more accurately. Using our distance, we can determine the absolute magnitude and discuss more precisely the locus of RX Boo on the period–luminosity (PL) relation. RX Boo exhibits two simultaneous pulsation periods and is located on the fundamental and first overtone Mira sequences of the PL relation. In addition, we calculated the radius and mass of the star.

scholarly journals Overall variation of the H2O masers around W Hydrae in 28 years

2019 ◽  
Author(s):  
Hiroshi Imai ◽  
Akiharu Nakagawa ◽  
Hiroshi Takaba
Keyword(s):  
Variable Star ◽  
Spherical Geometry ◽  
Spot Size ◽  
Radio Link ◽  
Very Large Array ◽  
Maser Spot ◽  
Spatially Resolved ◽  
Stellar Pulsation ◽  
Regular Variable ◽  
Physical Boundary

Abstract In this paper, we present the distribution of H$_2$O masers associated with the semi-regular variable star W Hydrae (W Hya). We have collected the radio interferometric data of the maser distribution taken with the Very Large Array (VLA), the Kashima–Nobeyama InterFErometer (KNIFE), the Multi-Element Radio Link Network (MERLIN), the VLBI Exploration of Radio Astrometry (VERA), and the combined array of the Korean VLBI Network (KVN) and VERA (KaVA) in order to trace the maser distribution variation in two decades. Even though differences in the sensitivities and angular resolutions of the interferometric observations should be taken into account, we attempt to find possible correlation of the maser distribution with the stellar light curve. Our failure in the measurement of the annual parallax of the masers with VERA is likely caused by the properties of the maser features, which have been spatially resolved by the synthesized beam and survived for only half a year or less. No dependence of the maser spot flux density on its size is found in the KNIFE data, suggesting that maser spot size is determined by the physical boundary, as is expected for a clump affected by outward propagation of a stellar pulsation shock wave, rather than the (spherical) geometry of maser beaming in the maser gas clump.

scholarly journals Variable Star Research by the PLANET Collaboration

2000 ◽  
Vol 176 ◽  
pp. 25-30
Author(s):  
Michael D. Albrow ◽  
K. R. Pollard ◽  
J.-P. Beaulieu ◽  
J. A. R. Caldwell ◽  
J. Menzies ◽  
...  
Keyword(s):  
High Precision ◽  
Variable Star ◽  
Current Status ◽  
Future Prospects ◽  
Preliminary Results ◽  
International Team ◽  
Star Studies ◽  
Photometric Monitoring

AbstractWe review the current status and future prospects of the PLANET collaboration, an international team of astronomers performing high-precision photometric monitoring of microlensing events. Our photometric precision and sampling is characterised and the suitability of the database for variable star studies is discussed. Preliminary results on K-giant stability are presented.

scholarly journals Preliminary Results of A World Wide Photoelectric Campaign on δ Scuti

1989 ◽  
Vol 111 ◽  
pp. 276-276
Author(s):  
B. McNamara ◽  
S. Baggett ◽  
J. Pena ◽  
K. Thompson ◽  
G. Moore ◽  
...  
Keyword(s):  
United States ◽  
South Africa ◽  
Frequency Spectrum ◽  
Preliminary Analysis ◽  
World Wide ◽  
Variable Star ◽  
Light Output ◽  
The United States ◽  
Preliminary Results

AbstractDuring June 17-27, 1987 observers in Mexico, Chile, Italy, South Africa, Australia and the United States monitored the light output of the prototype variable star, δ Scuti. The goal of the network was to obtain this star’s frequency spectrum. During the campaign, over 17,000 observations were obtained in the Stromgren b and y filters. A preliminary analysis has been performed and the frequencies listed in Table 1 have been tentatively identified.

scholarly journals VLBI Monitoring Observations of Water Masers around the Semi-Regular Variable Star R Crateris

2001 ◽  
Vol 53 (6) ◽  
pp. 1231-1238 ◽  
Author(s):  
José K. Ishitsuka ◽  
Hiroshi Imai ◽  
Toshihiro Omodaka ◽  
Munetaka Ueno ◽  
Osamu Kameya ◽  
...  
Keyword(s):  
Variable Star ◽  
Regular Variable ◽  
Water Masers

scholarly journals Shock waves - The trigger mechanism of SiO masers in circumstellar envelopes of cool giants and supergiants

1987 ◽  
Vol 122 ◽  
pp. 253-254
Author(s):  
Astrid Heske
Keyword(s):  
Shock Waves ◽  
Mass Loss ◽  
Upper Atmosphere ◽  
Circumstellar Envelope ◽  
Spectral Features ◽  
Circumstellar Envelopes ◽  
Trigger Mechanism ◽  
Regular Variable ◽  
Different Parts

Circumstellar envelopes of cool giants and supergiants are composed of different parts which can be observed through characteristic spectral features. One is SiO-maseremission which is typically found in Miras and some semi-regular variable supergiants. These masers are thought to originate in those parts of the upper atmosphere or lower circumstellar envelope where still no mass-loss takes place. Location and trigger mechanism was still not definitely clear.

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