A Search for Gravitationally Lensed Gamma-Ray Bursts in the Data of the Interplanetary Network and Konus-Wind

Abstract

We examine a sample of 2301 gamma-ray bursts, detected by Konus-Wind in the triggered mode between 1994 and 2017 and localized by the interplanetary network (IPN), for evidence of gravitational lensing. We utilize all the available gamma-ray burst (GRB) data: time histories, localizations, and energy spectra. We employ common IPN techniques to find and quantify similarities in the light curves of 2,646,150 burst pairs, and for the pairs with significant similarities, we examine their IPN localizations to determine whether they are consistent with a common origin. For pairs that are consistent, we derive and compare energy spectra, and compute a figure of merit that allows us to compare and rank burst pairs. We conduct both a blind search, between all possible burst pairs, and a targeted search, between pairs in which one burst has both a spectroscopic redshift and an identification of an intervening system, as measured by one or more lower spectroscopic redshifts. We identify six pairs in the blind search that could be taken as evidence for lensing, but none are compelling enough to claim a detection with good confidence. No candidates were detected in the targeted search. For our GRB sample, we set an upper limit to the optical depth to lensing of 0.0033, which is comparable to that of optical sources. We conclude that proposed scenarios in which a large fraction of the GRB population is lensed are extremely unlikely.

Strong gravitational lensing of explosive transients

“…Despite some explicit attempts to search for lensed image pairs in the gamma-ray burst catalogs for a wide range of time delays [370][371][372][373], no secure candidate of multiply imaged gamma-ray bursts has been identified so far. The latest search by Hurley et al [373] makes use of the gamma-ray burst sample detected by Konus-Wind [374], which has the high duty cycle and large sky coverage, to search for lensed image pairs. Based on the absence of any candidate of strongly lensed gammaray burst, an upper limit of the lensing probability of 0.0033 is placed.…”

Imprints of Gravitational Millilensing on the Light Curve of GRBs

“…Previous works on searching for gravitationally lensed GRBs focused mostly on strong lensing where the time delay between the images is greater than the duration of the burst. Similarities among pairs of GRBs light curves with identical spectra and close locations in the sky as the primary search criteria were uti-lized in multiple searches (Li and Li [2014], Davidson et al [2011], Ahlgren and Larsson [2020], Hurley et al [2019], Marani et al [1996]). Null results of these investigations did not rule out the presence of strong gravitationally lensed GRBs but reduced its likelihood and set upper limits to the lensing optical depth (Hurley et al [2019]).…”

nazgul: A statistical approach to gamma-ray burst localization

“…Even in cases of an existing a priori model, our methods might be advantageous if observing times are too short to beat the (timing) noise, such as X-ray millisecond pulsar navigation (Becker et al 2018). Finally, these methods could be used in the search for gravitationally lensed GRBs (Grossman & Nowak 1994;Hurley et al 2019) as they do not require the search for any a priori defined pulse shape or the use of cross-correlations.…”

“…Estimating the precise location on the celestial sphere from which a detected gamma-ray burst (GRB) has been received -a process known as "localization" -has become a critical component of a multi national, multi mission campaign to alert astronomers to observational follow-up opportunities regarding associated transients (e.g., Hurley et al 2019Hurley et al , 2000Kozlova et al 2016), gravitational waves (Hurley et al 2016), and neutrinos (Aartsen et al 2017). All-sky survey missions optimized for temporal and spectral signal resolution, such as the Fermi Gamma-Ray Burst monitor (GBM; Meegan et al 2009), Konus (Aptekar et al 1995) or INTEGRAL SPI-ACS (Vedrenne et al 2003), have a high sensitivity for detection of an incoming GRB, but they either offer no spatial information or struggle to achieve precise localizations.…”