Weighing Little Red Dots with Transient Events
Abstract
Recent JWST observations have revealed a large population of compact red sources at z ≳ 4, known as Little Red Dots (LRDs), many of which show signatures of accreting massive black holes (BHs). The physical nature of these sources and their connection to host galaxies are under debate. We propose an independent avenue for constraining their nature through transient phenomena, such as tidal disruption events (TDEs) and quasi-periodic eruptions (QPEs), arising from interactions between a star and the gas envelope surrounding the BH. These event rates depend sensitively on BH mass and provide a way to "weigh" LRDs. We calculate the expected TDE and QPE rates in LRDs under three distinct scenarios: (1) LRDs are truly overmassive BHs, (2) LRDs have BH masses following the classical local scaling relations (and the reported BH masses in observations are overestimated), and (3) the currently observed LRDs are only the tip of the iceberg of a larger population of low-mass BHs. We find that the predicted TDE and QPE rates differ dramatically across scenarios, especially in the presence of steep stellar cusps. The expected TDE rates per degree-square, assuming a Hernquist stellar distribution with a Bahcall-Wolf cusp embedded, are 2.78 × 10−3, 1.96 × 10−3, and 3.37 × 10−2 yr−1 deg−2 for the three scenarios, respectively, while the QPE rates are 1.64 × 10−2, 4.72 × 10−2, and 4.96 × 10−1 yr−1 deg−2. Upcoming wide-field surveys with Euclid, Roman, and LSST may be capable of detecting these high-redshift transient events and obtaining light curves, which encode additional information about the BH mass and the gas structure of LRDs. Stellar transient events will provide valuable insight into the early assembly of massive BHs.
Related
- A Spectral Framework for Testing the Quasi-Star Hypothesis in Little Red Dots I: Weighing LRDs by Their Super-Eddington Luminosity Ratios---No Signs of Overmassive Black Holes
- Little Red Dots as a Transient Phase of Self-Interacting Dark Matter Assisted Black Hole Growth
- A critical evaluation of the physical nature of the little red dots
- Massive black holes seeded by dark matter: Implications for little red dots and gravitational wave signatures
- Paschen jumps in little red dots: Evidence of nebular continua
BibTeX
@misc{tran2026weighing,
title = {{Weighing Little Red Dots with Transient Events}},
author = {Vinh Tran and Xuejian Shen and Oliver Zier and Anna de Graaff and Rohan P. Naidu and Mark Vogelsberger},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.00113},
eprint = {2609.00113},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.00113},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Weighing Little Red Dots with Transient Events
AU - Vinh Tran
AU - Xuejian Shen
AU - Oliver Zier
AU - Anna de Graaff
AU - Rohan P. Naidu
AU - Mark Vogelsberger
PY - 2026
DA - 2026/09/01
PB - arXiv
DO - 10.48550/arxiv.2609.00113
UR - https://arxiv.org/abs/2609.00113
AB - Recent JWST observations have revealed a large population of compact red sources at z ≳ 4, known as Little Red Dots (LRDs), many of which show signatures of accreting massive black holes (BHs). The physical nature of these sources and their connection to host galaxies are under debate. We propose an independent avenue for constraining their nature through transient phenomena, such as tidal disruption events (TDEs) and quasi-periodic eruptions (QPEs), arising from interactions between a star and the gas envelope surrounding the BH. These event rates depend sensitively on BH mass and provide a way to "weigh" LRDs. We calculate the expected TDE and QPE rates in LRDs under three distinct scenarios: (1) LRDs are truly overmassive BHs, (2) LRDs have BH masses following the classical local scaling relations (and the reported BH masses in observations are overestimated), and (3) the currently observed LRDs are only the tip of the iceberg of a larger population of low-mass BHs. We find that the predicted TDE and QPE rates differ dramatically across scenarios, especially in the presence of steep stellar cusps. The expected TDE rates per degree-square, assuming a Hernquist stellar distribution with a Bahcall-Wolf cusp embedded, are 2.78 × 10^−3, 1.96 × 10^−3, and 3.37 × 10^−2 yr^−1 deg^−2 for the three scenarios, respectively, while the QPE rates are 1.64 × 10^−2, 4.72 × 10^−2, and 4.96 × 10^−1 yr^−1 deg^−2. Upcoming wide-field surveys with Euclid, Roman, and LSST may be capable of detecting these high-redshift transient events and obtaining light curves, which encode additional information about the BH mass and the gas structure of LRDs. Stellar transient events will provide valuable insight into the early assembly of massive BHs.
ER -