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Spectral and VLBI-structure monitoring of OH-maser flare in W75N: preliminary results

Spectral and VLBI-structure monitoring of OH-maser flare in W75N: preliminary results. Alexey Alakoz & Vyacheslav Slysh Astro Space Center Moscow, Russia. 8th EVN Symposium 2006 Exploring the Universe with the real-time VLBI.

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Spectral and VLBI-structure monitoring of OH-maser flare in W75N: preliminary results

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  1. Spectral and VLBI-structure monitoring of OH-maser flare in W75N: preliminary results Alexey Alakoz & Vyacheslav Slysh Astro Space Center Moscow, Russia 8th EVN Symposium 2006Exploring the Universe with the real-time VLBI

  2. 8th EVN Symposium 2006Exploring the Universe with the real-time VLBI A. Alakoz V. Slysh Outline • Background • Star-forming region W75N • Nancey (single dish) observations • VLBA archive data • Kalyazin 64-m (single dish) observations • EVN observations • Summary

  3. To understand physical conditions in high-mass star-forming regions. To observe strong , long-term burst of OH maser emission at 1665 MHz Regular single-dish monitoring (Kalyazin 64m, Russia ) EVN observations at several epochs (fine-scale structure, proper motions etc.) 8th EVN Symposium 2006Exploring the Universe with the real-time VLBI A. Alakoz & V. Slysh Scientific background

  4. 8th EVN Symposium 2006Exploring the Universe with the real-time VLBI A. Alakoz & V. Slysh W75N • W75N – high mass star forming region at a distance of 2 kpc (Dickel et al. 1979) in Cyg X containing various UC H II regions and OH, H2O and CH3OH maser emission. • The region of strong OH maser emission coincides with two continuum sources, identified as VLA 1 and VLA 2 by Torrelles et al. (1997) • Since 2003 has become one of the strongest 1665 MHz OH masers ever observed (flux ~ 1 kJy).

  5. 8th EVN Symposium 2006Exploring the Universe with the real-time VLBI A. Alakoz V. Slysh

  6. 8th EVN Symposium 2006Exploring the Universe with the real-time VLBI A. Alakoz & V. Slysh NRAO VLBA data archive search (BF064 V. Fish11/22/2000 01/06/2001 )

  7. 8th EVN Symposium 2006Exploring the Universe with the real-time VLBI A. Alakoz & V. Slysh Reference position α=20h38m36.414sδ=42o37'’35.44’’ W75N Dec. offset (mas) R.A. offset (mas)

  8. 8th EVN Symposium 2006Exploring the Universe with the real-time VLBI A. Alakoz & V. Slysh Observations: Kalyazin 64-m ant., 1665 GHz W75N jul 2004 RCP W75N oct 2004 RCP W75N jul 2005 RCP W75N may 2005 RCP

  9. 8th EVN Symposium 2006Exploring the Universe with the real-time VLBI A. Alakoz & V. Slysh Observations: Kalyazin 64-m ant., 1665 GHz W75N mar 2006 RCP W75N nov 2005 RCP

  10. 8th EVN Symposium 2006Exploring the Universe with the real-time VLBI A. Alakoz & V. Slysh Observations: Kalyazin 64-m ant., 1665 GHz W75N may 2005 W75N jul 2005 W75N nov 2005 W75N mar 2006

  11. 8th EVN Symposium 2006Exploring the Universe with the real-time VLBI A. Alakoz & V. Slysh EVN • EA035A 12h 5 Nov. 2005 Jb Wb Ef Mc Ur On Tr • EA035B 12h 2 Mar. 2006 Jb Wb Ef Mc Ur On Tr Nt • EA035C 12h 7 Jun. 2006 Jb Wb Ef Mc Ur On Tr Nt 1667+1665 MHz nchan = 4 samprate = 4 bits= 2 bbfilter = 0.5 pol= dual, cross + data from BF079 V. Fish VLBA 09/16/2004

  12. 8th EVN Symposium 2006Exploring the Universe with the real-time VLBI A. Alakoz & V. Slysh Reference position α=20h38m36.414sδ=42o37'’35.44’’ W75N VLA1 Dec. offset (mas) VLA2 R.A. offset (mas)

  13. 8th EVN Symposium 2006Exploring the Universe with the real-time VLBI A. Alakoz & V. Slysh VLA1 VLA2

  14. 8th EVN Symposium 2006Exploring the Universe with the real-time VLBI A. Alakoz & V. Slysh

  15. 8th EVN Symposium 2006Exploring the Universe with the real-time VLBI A. Alakoz & V. Slysh

  16. 8th EVN Symposium 2006Exploring the Universe with the real-time VLBI A. Alakoz & V. Slysh Summary • A new flare of the OH maser emission source W75N has appeared in 2003, after the100-Jy flare of 2000. Three major spectralfeatures N1, N2, and N3 were present at all epochs, with N1 declining and N2 increasing in fluxdensity during the period of observations 2003-2006. • All three features have strong linearpolarization approaching 90 per cent. VLBI maps show thatalong with the strong features N1-3, many weaker features have appeared within 100 mas of theultra compact HII region VLA 2. • All the maser spots are aligned along two almost orthogonal straight lines centred on VLA 1and VLA 2, respectively. A possible model involves two edge-on discs surrounding the twoultra compact regions.

  17. 8th EVN Symposium 2006Exploring the Universe with the real-time VLBI A. Alakoz & V. Slysh Summary • Preliminary analysis of the proper motion for the flare feature N1 gives: • Delta alpha=1.36+/-0.3; Delta delta= -0.31+/-0.3 mas in 1.75 years. This corresponds to the tangentialvelocity of about 8 km/s relative to the rest of the features, and is comparable to the radialvelocity range in the VLA 2 disk. • The OH maser flare can be explained as a result of a MHDshockwhich is travelling from the young star and energizes maser emission in clumpsencountered on its way out.

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