Alert Notice 538: Observations of V694 Mon (MWC 560) requested for Chandra campaign

February 26, 2016: Dr. Jeno Sokoloski (Columbia University) and Mx. Adrian Lucy (graduate student, Columbia University) have requested AAVSO observations of the jet-driving symbiotic star V694 Mon (MWC 560), which is in outburst, in support of upcoming Chandra observations to investigate the state of the inner accretion disk during this outburst.

The Chandra observations are scheduled (preliminary schedule) for 2016 March 8 (7:17-14:13 UTC) and March 9 (2:20-9:17 UTC).

Beginning now and continuing through April 2016, Dr. Sokoloski writes, "multi-band photometry (UBVRI, but especially UBV), spectroscopy, and minute-time-resolution light curves of the optical flickering are requested. Series of exposures in B or V will be very interesting.

"[A paper by Tomov et al. in Nature (1990, 346, 637)] describes optical spectroscopic evidence for jet acceleration during an outburst in early 1990. Perhaps this eruption will show the same sort of behavior. The current outburst is the first comparably bright outburst of MWC 560 since that 1990 event. In the related system CH Cyg, we saw changes in the amplitude and character of the flickering when a jet was produced (Sokoloski & Kenyon 2003, Ap.J., 584, 1021; e-print at, suggesting that the inner disk was disrupted and then rebuilt. We are hoping to use any changes in the flickering from MWC 560 during this outburst in a similar way to probe the structure of the inner disk."

Mx. Lucy adds that " is possible we could see the re-formation of the inner accretion disk following jet ejection over the next couple months, which could be traced by watching the degree of flickering change over time."

V694 Mon ranges between 8.8 and 12.7 V. Observations in the AAVSO International Database show it at 9.224 V (+/-0.001) on 2016 February 25.2627 UT (SGEA, G. Stone, Auberry, CA), down from its maximum brightness of about 8.8 V on 2016 February 10 (several observers).

Coordinates: R.A. 07 25 51.28  Dec. -07 44 08.2 (2000.0)

AAVSO finder charts for V694 Mon with comparison stars may be generated using the AAVSO Variable Star Plotter (VSP).

Please submit your observations to the AAVSO International Database using the name 'V694 MON'.

This campaign is being followed on the AAVSO Observing Campaigns page.


This AAVSO Alert Notice was compiled by Elizabeth O. Waagen.


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