Proposal #573

Good morning, I'm Sauro Gaudenzi, my observer code is GSAD, in support of AAVSO alert nr 874. I ask for the use of a telescope to observe the variable VES 735, I ask that at least 2 weekly observations be made, 60 shots of 60 seconds with V and B filters, with priority for the V filter, Drs. Brandon Marshall (University of Nebraska) 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 November and December. This is a followup to Alert Notice 794, which provided photometry that was included in a recent publication to MNRAS: Long-Term Monitoring of the Oe Star VES 735: Ope! Not So Quiet After All. 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 2022 and 2023 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. We are looking for photometric coverage from approximately November 5, 2024 until December 20, 2024. These dates are to ensure that observations can be made to book- end professional spectroscopic observations taken at the DAO on November 16/17 & 17/18, and December 14/15 & 15/16. Priority filter is Johnson V, then Johnson B. Unfiltered observations are not necessary. Nightly snapshots (with S/N > 20) are requested during the length of the entire campaign, with priority on and around the spectroscopic observation dates above, where hourly snapshots are requested. Minimum SNR: 5. Thank you very much for your cooperation and good day.