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Session 1 Poster 72

U Ori



Radio Spectroscopy of Circumstellar Molecular Masers

Georgij M. Rudnitskij*, Pierre Colom**, Evguenij E. Lekht*, Mikhail I. Pashchenko*, Vladimir A. Samodurov***, Il'nur A. Subaev***, Alexander M. Tolmachev*** *Sternberg Astronomical Institute, Russia **Observatoire de Paris-Meudon, France ***Pushchino Radio Astronomy Observatory, Russia H2O, = 1.35 cm
Results of observations of circumstellar maser sources in long-period variable stars are reported. We have monitored a sample of Mira-type and semiregular variables in the H2O (wavelength 1.35 cm) and OH (wavelength 18 cm) radio lines. A comparison with data of optical photometry and spectroscopy has been done. WATER VAPOUR The observations in the H2O line at 1.35 cm were carried out on the RT-22 radio telescope of the Pushchino Radio Astronomy Observatory in 1980-2011. Sensitivity is ~10-15 Jy, velocity resolution 0.082 km/s. The sample included sixty late-type variable stars with circumstellar envelopes and sixty-five star-forming regions. For most stars twenty to thirty variability cycles (lasting about a year) were covered. There is a correlation of the H2O line flux density with the light variations: in general, the maser intensity follows the optical variability with a certain phase lag. A model, in which the maser variability is caused by the joint influence of a shock wave propagating in the circumstellar envelope and of the variable radio continuum of the stellar photosphere, is considered. There are indications to a quasiperiodic character of the variations of the integrated H2O line flux and mean radial velocity of the maser emission at a timescale of 14-15 years. HYDROXYL Polarimetry of the OH maser emission has allowed us to draw conclusions about circumstellar magnetic field. The observations of OH masers were carried out at a wavelength of 18 cm on the radio telescope of the Nancay Radio Astronomy Observatory (France). , The recent upgrade of the telescope allows us to measure simultaneously all four Stokes parameters of the OH maser emission. In 2007-2011 seventy late-type stars (including Mira-type and semiregular variables) were observed as well as some OH masers in star-forming regions. The sample largely overlaps with that of the sources observed in the H2O line. For 53 of the late-type stars the emission in at least one of three OH lines (1612, 1665, or 1667 MHz) was detected and all four Stokes parameters were measured. The emission of T Lep in the 1665 and 1667 MHz OH lines was observed for the first time. In the Stokes profiles of several stars (including T Lep) features probably due to Zeeman splitting were detected. Estimates of the magnetic intensity in the maser sources (0.46-2.32 mG) were obtained. This work was supported by the Russian Foundation for Basic Research (project code 09-02-00963-a).
References 1. Rudnitskij, G. M.; Pashchenko, M. I.; Colom, P. Polarization observations of circumstellar OH masers Astronomy Reports, 2010, 54, 400. 2. Slysh, V. I.; Pashchenko, M. I.; Rudnitski, G. M.; Vitrishchak, V. M.; Colom, P. Polarization observations of the OH maser W75N on the NanГay radio telescope Astronomy Reports, 2010, 54, 599. 3. Pashchenko, M. I.; Rudnitski, G. M.; Colom, P. The fast variable maser source IRAS 05338-0624 Astronomy Reports, 2009, 53, 541. 4. Rudnitskij, G. M.; Pashchenko, M. I.; Esipov, V. F.; Samodurov, V. A.; Subaev, I. A.; Tolmachev, A. M.; Lekht, E. E. Twenty-six-year monitoring of water masers 2007, IAUS, 242, 32. 5. Rudnitskij, G. M.; Lekht, E. E.; Mendoza-Torres, J. E.; Pashchenko, M. I.; Berulis, I. I. Variability of the H2O maser associated with U Orionis Astronomy and Astrophysics Supplement Series, 2000, 146, 385.

OH,

= 18 cm

Nancay Radio Telescope, OH 18-cm line observations , since 1969
F, Jy
6 4 2 0 0 -1 -2 0 -1 -2 0 -2 -4 -6 30 40 50

1612 MHz
I

HU Pup August 5, 2009
1665 MHz
4 2 0 0.5 0.0 -0.5 -1.0 -1.5 1.0 0.5 0.0 -0.5 4 3 2 1 0 -1

1667 MHz
I

I

1.0 0.5 0.0 0.5 0.0

22-meter telescope, Pushchino Radio Astronomy Observatory H2O line observations since 1980
4 6 8 10 3 2 1 0 -19 -20 -21

Q

Q

Q U

-0.5 0.5 0.0 -0.5

U

R Leo

U

V

0.5 0.0 -0.5

V

V
60

30

40

50

60

30

40

50

60

VLSR, km/s

49500 1994.0 1995.0

50000 1996.0

50500 1997.0

51000 JD-2400000 1998.0 1999.0

Profiles of the Stokes parameters in the 18-cm OH lines for the semiregular variable HU Pup.
F, Jy
1.0 0.5 0.0 0.4 0.2 0.0 -0.2 -0.4 0.4 0.2 0.0 -0.2 -0.4 -0.6 0.6 0.4 0.2 0.0 -0.2 -0.4 -70 -60 -50 -40 -30 -20 -10 0

Mira-type star R Leo. H2O line variations versus visual light curve and H line intensity.
U Her, P = 406d
6 8 10 12 60 40 20 0 30 20 10 0 44000 1980.0 46000 1985.0 48000 1990.0 50000 1995.0 52000 2000.0 54000 JD-2400000 2005.0 (c) (a)

1665 MHz

T Lep Jan 4, 2009
I
1.0 0.5 0.0

1667 MHz
I

Q

0.4 0.2 0.0 -0.2 -0.4

Q

U

0.4 0.2 0.0 -0.2 -0.4

U

(b)

V

0.4 0.2 0.0 -0.2 -0.4

V

10

-70 -60 -50 -40 -30 -20 -10

0

10

. Mira-type star U Her. H2O line variations versus visual light curve.
F, Jy
200 100 0 200 100 0 200 100 0 25 30 35 40 45 50
2010.01.26 2004.07.22

Profiles of the Stokes parameters in the 18-cm OH lines for the Mira-type variable T Lep (new detection).
F, Jy
4 2 0 1 0 -1 10 20 30 40 50 60 70 80 -1 2 1 0 1 -1

VLSR, km/s

IRC-10414
2003.08.05

1612 MHz
I

IRC­10414
4 2 0

1665MHz

Feb 25 2010 ,
I
10 5 0 2 1

1667MHz
I

Q

0

Q

Q U

0 1 0

U

VLSR, km/s

Sample H2O line spectra for the (optically nonvariable) M-type supergiant IRC-10414.

-1 8 1 V V V 6 4 0 0 2 0 -1 -2 -1 -4 10 20 30 40 50 60 70 80 10 20 30 40 50 60 70 80 10 20 30 40 50 60 70 80

VLSR, km/s

Stokes parameters in the 18-cm OH lines for the M-type supergiant IRC-10414.
F, Jy
2 0 -2 -4 -6 -8 1 0 -1 1 0 -1 4 2 0 -2 30 40 50

W33C January 7, 2011 1667 MHz 1665 MHz
0 -5

I Q

-10 1 0 -1

I Q

U

1 0 -1

U

V

1 0 -1 30 40

V

50

VLSR, km/s

3D presentation of the H2O line variations for the Mira-type star U Ori. A strong flare in early 1980s is prominent.

Stokes parameters in the 18-cm OH lines for the star-forming region W33C.

Contact: Georgij M. Rudnitskij gmr@sai.msu.ru