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Special Notice #429: V694 Mon (MWC 560) spectroscopy requested

May 2, 2017: Further to AAVSO Alert Notice 538, the campaign from 2016 on V694 Mon (MWC 560) has been continued, but with different requirements. Photometry is no longer specifically requested on a regular basis (although ongoing observations that do not interfere with other obligations are welcome). Spectroscopy on a cadence of a week or two is requested to monitor changes in the disk outflow. V694 Mon is presently nearing opposition, but the request for spectroscopy continues until further notice.

Investigator Adrian Lucy writes: "Adrian Lucy and Dr. Jeno Sokoloski (Columbia University) have requested spectroscopic monitoring of the broad-absorption-line symbiotic star V694 Mon (MWC 560), as a follow-up to coordinated multi-wavelength observations obtained during its recent outburst (ATel #8653, #8832, #8957; #10281). This system is a perfect place in which to study the relationship between an accretion disk and disk winds/jets, and a high-value target for which even low-resolution spectra can be extraordinarily useful.

"Broad, blue-shifted Balmer absorption lines in MWC 560 have signified a variable high-velocity outflow for decades, sometimes extending up to 6000 km/s (e.g., Tomov et al. 1990, Nature, 346, 637). Optical brightening in MWC 560 tends to predict higher-velocity absorption, but sometimes jumps in absorption velocity also appear during optical quiescence (e.g., Iijima 2001, ASPCS, 242, 187). If such a velocity jump occurs during photometric quiescence, it may prompt radio observations to confirm and test the proposed outflow origin for recently-discovered flat-spectrum radio emission (Lucy et al. ATel #10281). We cannot know whether interesting changes in velocity will happen, but we can hope!

"Furthermore, volunteer spectroscopic monitoring of this system has proved useful in unpredictable ways. For example, 'amateur' spectra obtained by Somogyi Péter in 2015 December demonstrated that the velocity of absorption was very low only a month before an optical outburst peak prompted absorption troughs up to 3000 km/s, which constrains very well the timing of the changes to the outflow to a degree that would not have been otherwise possible.

"Spectroscopy may be uploaded to the ARAS database (, or sent to Adrian and Jeno directly at <>. Any resolution can be useful. A wavelength range that can accommodate a blueshift of at least 140 angstroms (6000 km/s) from the rest wavelengths of H-alpha at 6562 angstroms and/or H-beta at 4861 angstroms is ideal, though spectra with a smaller range can still be useful. Photometry could potentially still be useful, but will be supplementary to medium-cadence photometry being collected by the ANS collaboration."

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 variable star observations to the AAVSO International Database using the name V694 MON.

This campaign is being followed on the AAVSO Observing Campaigns page. The thread that was created on the Campaigns forum for this campaign in 2016 ( should be used to continue the discussion for the current phase of the campaign.

This AAVSO Alert Notice was prepared by Elizabeth O. Waagen with text provided by Adrian Lucy.


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