Determine whether reported short-timescale LRD variability is genuine

Determine whether tentative variability signals reported on timescales shorter than 10 rest-frame years in a small number of Little Red Dots persist after accounting for position-dependent slit variations and related observational systematics.

Background

The paper uses the general lack of optical variability in Little Red Dots over approximately 10-year baselines to constrain the dynamical time of their extended pseudo-photospheres and thereby obtain an upper bound on the central-engine mass. However, several studies have reported tentative variability on shorter rest-frame timescales, often from slit-based spectroscopy.

Because Little Red Dots exhibit strong radial color gradients and the relevant observations may use slightly different slit positions, position-dependent slit losses could mimic temporal changes. Resolving whether the signals are intrinsic is therefore important for validating the variability-based mass constraint.

References

While some studies report tentative variability on $< 10$ rest-frame yr timescales in a handful of LRDs often using slit-based spectroscopy \citep[e.g.,][]{Ji25BT, Furtak25, Naidu26BHstar, Lambrides26, Brooks26, DEugenio26z5lrd}, it remains to be seen whether these signals survive after accounting for position-dependent slit variations, which are hard to quantify for LRDs that show strong radial color gradients.

— Overmassive No More: The Case for Little Red Dots Hosting Black Hole Seeds as Massive as Single Supermassive Stars  (2609.09274 - Sun et al., 8 Sep 2026) in Section 3.4, “Variability”

Given the sharp difference between the point source and extended source \citep[e.g.,][]{Ishikawa26}, each subtly different slit position might produce different spectra mimicking variability.

— Overmassive No More: The Case for Little Red Dots Hosting Black Hole Seeds as Massive as Single Supermassive Stars  (2609.09274 - Sun et al., 8 Sep 2026) in Section 3.4, “Variability”