Alert Notice 803: ASASSN-V J022007.17+610705.5 photometry campaign extended

Note: Please continue to observe this target until further notice.  -  Elizabeth O. Waagen, April 3, 2023

December 13, 2022

AAVSO Forum threads (scroll to the bottom of a thread for latest posts):
- Campaigns and Observation Reports:

Please subscribe to this thread if you are participating in the campaign so you can be updated by the astronomers and by HQ. Join in the discussion or ask questions there!

Further to AAVSO Alert Notice 794, Dr. Brandon Marshall (University of Nebraska - Kearney)  informs us that the campaign by him and Dr. Charles Kerton (Iowa State University) has been extended through March 2023. The target, for which photometric monitoring has been requested, is the unique variable  ASASSN-V J022007.17+610705.5 (Cas) = VES 735. Spectroscopy planned at the Dominion Astrophysical Observatory for October-December 2022 was not as successful as needed because of weather, and has been rescheduled for January-March 2023.

Dr. Marshall writes: "VES 735 is the exciting star of the compact Galactic HII region KR 140. Hα spectra of the star show double-peaked emission indicative of material in a circumstellar disk. The Hα emission was fairly consistent in observations from DDO and DAO in 1996 and 1997 as well as in spectra taken from WIRO in 2013 and 2014; the variability was minimal over timescales ranging from hours to years. This long-lived emission contrasts with well-studied emission from the Oe star ζ Oph where emission is more episodic. The most recent observations for VES 735 came in 2021 and 2022 from the DAO and Apache Point Observatory which showed the intensity of the Hα emission between 2 - 4 times the level of the stellar continuum. This is in strong contrast to the 1.1 - 1.5 times the continuum level that had been seen in the observations between 1996 and 2014.

"Our goal is to arrange photometric observations to complement a new spectroscopic campaign at DAO... The goal of the DAO campaign is to determine if the emission has returned to its pre-outburst state or if the strong emission is still ongoing. The AAVSO observing campaign observations will allow us to see if there is a relationship between the star’s Hα brightness and the star’s V-band magnitude."

V photometry is requested. The cadence requested per observer is a nightly snapshot (S/N > 20 (minimum S/N = 5)) from now through 2023 March 31. When the spectroscopy observations have been scheduled, they will be announced in the forum thread above. For those nights, hourly snapshots are requested. ASASSN-V J022007.17+610705.5 has a V range of 12.37 - 12.96 V and is spectral type O9.5V(e).

Coordinates (J2000): R.A. 02 20 07.17  Dec. +61 07 05.5 (from VSX page for the target)

Charts with comparison stars for ASASSN-V J022007.17+610705.5 may be created using the AAVSO Variable Star Plotter (VSP).

Please report observations to the AAVSO International Database using the name ASASSN-V J022007.17+610705.5.

This Alert Notice was compiled by Elizabeth O. Waagen using material supplied by Dr. Marshall.


Information on submitting observations to the AAVSO may be found at:
 - Photometry/visual observations:
 - Spectroscopy:


An Alert Notice archive is available at the following URL:

Subscribing and Unsubscribing may be done at the following URL:


Please support the AAVSO and its mission -- Join or donate today: