Request for photometric follow-up of a candidate planetary collision afterglow Gaia20ehk

[Andy Tzanidakis]

Hi everyone,

My name is Andy Tzanidakis, and I'm a Ph.D. candidate at the University of Washington working with Professor James Davenport. 

I'm writing to request photometric follow-up observations on our newly reported giant impact afterglow candidate stellar system, Gaia20ehk/Gaia-GIC-1/AT2020tdg (please see Tzanidakis & Davenport 2026; for more details). Since 2020-03-05, the system has been undergoing irregular photometric dips of ~1-2 mag in Gaia-G, while IR detections from NEOWISE/WISE and SPHEREx have revealed an IR outburst, suggesting newly formed hot circumstellar material. 

Based on recent photometric follow-up from CTIO/SALT a few months ago, it's unclear if the source is still undergoing this irregular variability. The source is currently peaking at maximum airmass and will be visible for the coming months in the Southern hemisphere. 

We are hoping to obtain observations in red wavelengths (r/i filters), where this source should be the brightest, around 20 mag. Based on archival variability levels from Gaia, the source ranges from ~20 mag to 18.9 mag in Gaia-G. Attempts at blue-wavelength filters (i.e., V or g band) are also welcomed, though we suspect the source can be very faint, >21 mag. 

Nightly monitoring over the next few days and weeks will be extremely helpful. We're currently looking to allocate more spectroscopic time and would need to better understand the current variability levels. Thus, deep, nightly photometric monitoring will be very beneficial to our follow-up campaign. 

Thank you so much in advance, and please reach out if you have any follow-up questions. 

Kind regards,
Andy Tzanidakis
Email: atza...@uw.edu

[Lukasz Wyrzykowski]

Dear All,

Just to add to Andy's email. The BHTOM target is here: https://bh-tom2.astrouw.edu.pl/targets/8504

I also encourage you to observe this one, but keep in mind the challenge of this being quite faint.

Also, please note we just switched to a new server, so all the urls should now have bh-tom2.astrouw.edu.pl.

Clear skies!

Lukasz

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