Alert Notice 853: Monitoring requested for AT 2000ch (LMi)

February 20, 2024

AAVSO Forum threads (scroll to the bottom of a thread for latest posts):
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Dr. Mojgan Aghakhanloo (University of Virginia) has requested AAVSO observers' assistance in monitoring the SDOR variable AT 2000ch (LMi) to document its next outburst. AT 2000ch, a supernova imposter, was originally thought to be a supernova (SN 2000ch) in NGC 3432.

Dr. Aghakhanloo writes: "AT 2000ch has experienced at least 23 eruptions from 2000 to 2022. We found that AT 2000ch’s eruptions occur approximately every 201 days. Based on this estimated period, we predict that its next eruption will occur around March 2024. As AT 2000ch’s light curve shows that eruptions sometimes begin months before, it is crucial to monitor it for about a month before and after the proposed timeline."

Beginning immediately and continuing for a month after the next outburst has concluded, R band (Cousins or Sloan) CCD photometry is requested. Unfiltered observations reduced to an R zero-point (CR) are also welcome. Nightly observations are requested, with a higher cadence (several observations per night) if the target is in outburst. DSLR and visual observations are not requested. AT 2000ch has a range of 17.4 - 22.0: r.

Dr. Aghakhanloo continues: "This target could be in a bright state, indicating an ongoing outburst, which should be observed. Alternatively, if it appears faint, this suggests it is in a dormant phase [but also needs to be monitored]. If the target is in eruption, we kindly request that the observer share the images with us. We will use one of the eruption images in the paper." If the target goes into outburst, instructions on how/where to send images will be posted in the forum threads given above.

Dr. Aghakhanloo provides the following image of NGC 3432 (North up, East left) with AT 2000ch indicated by the arrow.

Coordinates for AT 2000ch (2000.0):  R.A. 10 52 41.25  Dec. +36 40 09.0  (from VSX page for AT 2000ch)

Charts with comparison stars for AT 2000ch may be created using the AAVSO Variable Star Plotter (VSP).

Please submit observations to the AAVSO International Database using the name AT 2000CH.

This AAVSO Alert Notice was compiled by Elizabeth O. Waagen using information provided by Mojgan Aghakhanloo.


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