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 2006 Exploring the Universe with the real-time VLBI

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

3. 8th EVN Symposium 2006 Exploring the Universe with the real-time VLBI A. Alakoz & V. Slysh Scientific background To understand physical conditions in high- mass star-forming regions. To understand physical conditions in high- mass star-forming regions. To observe strong, long-term burst of OH maser emission at 1665 MHz 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.)

4. 8th EVN Symposium 2006 Exploring the Universe with the real-time VLBI A. Alakoz & V. SlyshW75N W75N – high mass star forming region at a distance of 2 kpc (Dickel et al. 1979) in Cyg X 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, H 2 O and CH 3 OH 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 2006 Exploring the Universe with the real-time VLBI A. Alakoz V. Slysh

6. 8th EVN Symposium 2006 Exploring the Universe with the real-time VLBI A. Alakoz & V. Slysh NRAO VLBA data archive search (BF064 V. Fish 11/22/2000 01/06/2001 )

7. 8th EVN Symposium 2006 Exploring the Universe with the real-time VLBI A. Alakoz & V. Slysh W75N R.A. offset (mas) Dec. offset (mas) Reference position α=20 h 38 m 36.414 s δ=42 o 37 ' ’35.44 ’’

8. 8th EVN Symposium 2006 Exploring the Universe with the real-time VLBI A. Alakoz & V. Slysh Observations: Kalyazin 64-m ant., 1665 GHz W75N jul 2004 RCPW75N oct 2004 RCP W75N may 2005 RCP W75N jul 2005 RCP

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

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

11. 8th EVN Symposium 2006 Exploring the Universe with the real-time VLBI A. Alakoz & V. SlyshEVN EA035A 12h 5 Nov. 2005 Jb Wb Ef Mc Ur On Tr 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 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 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 2006 Exploring the Universe with the real-time VLBI A. Alakoz & V. Slysh W75N R.A. offset (mas) Dec. offset (mas) Reference position α=20 h 38 m 36.414 s δ=42 o 37 ' ’35.44 ’’ VLA1 VLA2

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

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

15. 09/2004- 06/2006 N1N1N1N1 N2N2N2N2Δα +1.36 mas -0.41 mas +/- 0.3 mas Δδ -0.31 mas +1.29 mas

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

17. 8th EVN Symposium 2006 Exploring the Universe with the real-time VLBI A. Alakoz & V. Slysh 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 tangential velocity of about 8 km/s relative to the rest of the features, and is comparable to the radial velocity range in the VLA 2 disk. The OH maser flare can be explained as a result of a MHDshock which is travelling from the young star and energizes maser emission in clumps encountered on its way out. Summary