Alert Notice 794: ASASSN-V J022007.17+610705.5 photometry requested in support of spectroscopy observations

October 3, 2022

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Drs. Brandon Marshall (University of Nebraska - Kearney) and Charles Kerton (Iowa State University) request AAVSO observers' assistance in monitoring the unique variable  ASASSN-V J022007.17+610705.5 (Cas) = VES 735 in support of spectroscopy observations being obtained at the Dominion Astrophysical Observatory in October, November, and December.

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 this fall. 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 2022 October 13 through December 10, with the following exceptions: hourly snapshots on the nights of October 16/17, November 10/11, and December 7/8, the nights when spectra will be obtained. 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). Comparison stars are presently being selected by the AAVSO Sequence Team; if they are not available when a chart is created, please hold on to your images and reduce them when comp stars have been added.

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.


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