[Paper Review] On the rate and on the gravitational wave emission of short and long GRBs

R. Ruffini, Juan Rodríguez+14 more|arXiv (Cornell University)|Feb 10, 2016

Gamma-ray bursts and supernovae152 references20 citations

TL;DR

This paper proposes a unified binary progenitor framework for short and long gamma-ray bursts (GRBs), classifying them into seven subclasses based on compact object combinations (e.g., COcore-NS, NS-BH). It models gravitational wave (GW) emission from these systems and estimates detectability by Advanced LIGO, Virgo, eLISA, and resonant bars, showing that long GRBs—previously thought non-GW-emitting—can produce detectable GWs via induced gravitational collapse in tight binaries, with BdHNe and XRFs contributing significantly to the GW and GRB rate budget.

ABSTRACT

On the ground of the large number of gamma-ray bursts (GRBs) detected with cosmological redshift, we classified GRBs in seven subclasses, all with binary progenitors originating gravitational waves (GWs). Each binary is composed by combinations of carbon-oxygen cores (CO$_{ m core}$), neutron stars (NSs), black holes (BHs) and white dwarfs (WDs). The long bursts, traditionally assumed to originate from a BH with an ultra-relativistic jetted emission, not emitting GWs, have been subclassified as (I) X-ray flashes (XRFs), (II) binary-driven hypernovae (BdHNe), and (III) BH-supernovae (BH-SNe). They are framed within the induced gravitational collapse (IGC) paradigm with progenitor a CO$_{ m core}$-NS/BH binary. The supernova (SN) explosion of the CO$_{ m core}$ triggers an accretion process onto the NS/BH. If the accretion does not lead the NS to its critical mass, an XRF occurs, while when the BH is present or formed by accretion, a BdHN occurs. When the binaries are not disrupted, XRFs lead to NS-NS and BdHNe lead to NS-BH. The short bursts, originating in NS-NS, are subclassified as (IV) short gamma-ray flashes (S-GRFs) and (V) short GRBs (S-GRBs), the latter when a BH is formed. There are (VI) ultra-short GRBs (U-GRBs) and (VII) gamma-ray flashes (GRFs), respectively formed in NS-BH and NS-WD. We use the occurrence rate and GW emission of these subclasses to assess their detectability by Advanced LIGO-Virgo, eLISA, and resonant bars. We discuss the consequences of our results in view of the announcement of the LIGO-Virgo Collaboration of the source GW 170817 as being originated by a NS-NS.

Motivation & Objective

• To reclassify long and short GRBs into a unified binary progenitor framework based on compact object combinations (COcore, NS, BH, WD).
• To re-evaluate the gravitational wave (GW) emission potential of long GRBs, traditionally assumed to be non-GW-emitting.
• To estimate the detectability of GRB-associated GWs by current and future detectors (Advanced LIGO, Virgo, eLISA, resonant bars).
• To reconcile observed GRB rates with theoretical models by linking them to binary evolution and hypercritical accretion processes.
• To interpret the GW170817 NS-NS merger as a validation of the binary progenitor model for short GRBs and U-GRBs.

Proposed method

• Classifies GRBs into seven subclasses based on progenitor binaries: (I) XRFs, (II) BdHNe, (III) BH-SNe, (IV) S-GRFs, (V) S-GRBs, (VI) U-GRBs, (VII) GRFs.
• Applies the induced gravitational collapse (IGC) paradigm to long GRBs, modeling hypercritical accretion from SN ejecta onto a compact companion (NS or BH).
• Uses the luminosity function and cosmic GRB rate to compute local observed event rate densities via convolution, with redshift-independent f(z) = 1.
• Applies the distance-limited detection method (Schaefer 2007) to compute zmax(L) from peak flux thresholds, using detector-specific fields of view and operational times.
• Evaluates GW detectability using estimated rates and GW emission models, including merger timescales and baryonic environment cleanliness.
• Incorporates orbital dynamics and non-instantaneous mass loss effects (e.g., SN shock crossing times) to assess binary survival post-SN.

Experimental results

Research questions

• RQ1 Can long GRBs, traditionally considered non-GW-emitting, be reinterpreted as sources of detectable gravitational waves via binary progenitor models?
• RQ2 What are the detectable gravitational wave emission rates for the seven proposed GRB subclasses across LIGO, Virgo, eLISA, and resonant bar detectors?
• RQ3 How do the estimated rates of XRFs, BdHNe, and BH-SNe compare with observed long GRB rates, and what does this imply for progenitor models?
• RQ4 What is the role of non-instantaneous mass loss and SN shock crossing in determining whether COcore-NS binaries survive to form NS-BH or NS-NS binaries?
• RQ5 How does the recent GW170817 NS-NS merger support the proposed binary progenitor framework for short and ultra-short GRBs?

Key findings

• The XRF subclass has a local observed rate of ρXRF = 100+45−34 Gpc−3 yr−1, consistent with low-luminosity long GRBs.
• The BdHNe subclass has a local observed rate of ρBdHN = 0.77+0.09−0.08 Gpc−3 yr−1, matching high-luminosity long GRB rates.
• The BH-SN subclass is bounded by the BdHNe rate, with ρBH−SN ≲ 0.77+0.09−0.08 Gpc−3 yr−1, suggesting it arises from a small fraction (0.5–5%) of ultra-stripped binaries.
• Tight COcore-NS binaries (Porb ≲30 min) can survive SN explosions and form νNS-BH binaries if the SN shock crossing time is comparable to the orbital period, enabling GW-driven merger on timescales of ∼10^4 yr.
• The U-GRB subclass (NS-BH mergers) is predicted to form from BdHNe survivors, with clean merger sites and potential for ultrashort GRB emission.
• The model explains the GW170817 NS-NS merger as a progenitor of S-GRBs and S-GRFs, validating the binary origin of short GRBs and extending the framework to U-GRBs and GRFs.