Can we identify lensed gamma-ray bursts?

Nowak, M. A.; Grossman, Scott A.

doi:10.1086/174837

Cited by 13 publications

(8 citation statements)

References 9 publications

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“…We conclude that the best cases to unambiguously study microarcsec structure in GRB afterglows will probably be those GRBs that are multiply imaged (about per cent expected, see, e.g. Paczyński 1987; Mao 1992, 1993; Narayan & Wallington 1992; McBreen, Plunkett & Metcalfe 1993; Wambsganss 1993; Nowak & Grossman 1994; Williams & Wijers 1997; Holz et al 1999; Komberg, Kurt & Kuznetsov 1999; Marani et al 1999). Those (soon to be discovered!)…”

Section: Discussionmentioning

confidence: 88%

On the probability of microlensing in gamma-ray burst afterglows

Koopmans

Wambsganß

2001

Monthly Notices of the Royal Astronomical Society

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The declining light curve of the optical afterglow of gamma‐ray burst (GRB) GRB000301C showed rapid variability with one particularly bright feature at about t−t0=3.8 d. This event was interpreted as gravitational microlensing by Garnavich, Loeb & Stanek and subsequently used to derive constraints on the structure of the GRB optical afterglow. In this paper, we use these structural parameters to calculate the probability of such a microlensing event in a realistic scenario, where all compact objects in the universe are associated with observable galaxies. For GRB000301C at a redshift of z=2.04, the a posteriori probability for a microlensing event with an amplitude of Δm0.95 mag (as observed) is 0.7 per cent (2.7 per cent) for the most plausible scenario of a flat Λ‐dominated Friedmann–Robertson–Walker (FRW) universe with Ωm=0.3 and a fraction f∗=0.2 (1.0) of dark matter in the form of compact objects. If we lower the magnification threshold to Δm0.10 mag, the probabilities for microlensing events of GRB afterglows increase to 17 per cent (57 per cent). We emphasize that this low probability for a microlensing signature of almost 1 mag does not exclude that the observed event in the afterglow light curve of GRB000301C was caused by microlensing, especially in light of the fact that a galaxy was found within 2 arcsec from the GRB. In that case, however, a more robust upper limit on the a posteriori probability of ≈5 per cent is found. It does show, however, that it will not be easy to create a large sample of strong GRB afterglow microlensing events for statistical studies of their physical conditions on microarcsec scales.

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Section: Discussionmentioning

confidence: 88%

On the probability of microlensing in gamma-ray burst afterglows

Koopmans

Wambsganß

2001

Monthly Notices of the Royal Astronomical Society

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“…It is expected that gravitational lensing by galaxies should yield echoes of roughly 0.1% of bursts (Paczyński 1986b;Mao 1992), but this effect has never been clearly detected. The null results to date (Nemiroff et al 1994;Marani et al 1999) are not highly statistically significant, nor is it trivial to recognise echoes even if they are simply scaled copies of the "orig-inal" -see Wambsganss (1993), and Nowak and Grossman (1994). This means that the lack of any identified echoes, while consistent with the present model, is not a decisive argument in its favour.…”

Section: Discussionmentioning

confidence: 46%

Nanolensing of Gamma‐Ray Bursts

Walker

Lewis

2003

ApJ

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All quasars vary in their optical flux on a time-scale of years, and it has been proposed that these variations are principally due to gravitational lensing by a cosmologically distributed population of planetary mass objects. This interpretation has implications for the observable properties of gamma-ray bursts (GRBs) -as a source expands across the nano-arcsecond caustic network, variability is expected -and data on GRBs can be used to test the proposed model of quasar variability. Here we employ an ultra-relativistic blast-wave model of the source, with no intrinsic variations, to study the effects of nanolensing on GRBs. Taken in isolation the lightcurves of the caustic crossings are predictable, and we find that a subset of the predicted lightcurves (the image-annihilating fold crossings) resemble the "pulses" which are commonly seen in long GRBs. Furthermore, for sources at high redshift the expected time between caustic crossings is of order seconds, comparable to the observed time between pulses. These points suggest that it might be possible to model some of the observed variations of GRBs in terms of nanolensing; however, our simulated light-curves exhibit a small depth of modulation compared to what is observed. This means that the GRB data do not significantly constrain the quasar nanolensing model; it also means that the simplest nanolensing model cannot explain the observed GRB "pulses". Viable nanolensing models for pulses probably require a large external beam shear. If a viable model can be constructed it would effect a considerable simplification in source modelling and, ironically, it would explain why no macro-lensed GRBs have been identified to date.Independent of the particular theoretical model, we can test for the presence of nanolensing in GRB data because any variability due to nanolensing should manifest parallax: the timing of caustic crossings, and hence the temporal substructure of bursts should be different as seen by separated observers. Parallax therefore shifts triangulated burst locations away from their true positions; this displacement is typically expected to be at the few arcminute level, and existing astrometry is not good enough to reveal the predicted effects. Useful constraints can, however, be obtained by comparing the relative timing of individual peaks in the light-curves recorded by spacecraft in the Inter-Planetary Network; published data show hints of the predicted temporal shifts, but the photon counting statistics are not good enough to categorically decide the matter. There is no plausible alternative interpretation for this phenomenon, and if it is confirmed as a real effect then it compels acceptance of a cosmology that is very different from the currently popular model.

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“…The rate at which we observe the in‐spiral events that originate in the redshift interval is given by Nowak & Grossman (1994)…”

Section: Redshift Distribution Of Observed Eventsmentioning

confidence: 99%

“…The rate d Ṅ (> ρ 0 ) dz at which we observe the inspiral events that originate in the redshift interval [z, z + dz] is given by [30]:…”

Section: Redshift Distribution Of Observed Eventsmentioning

confidence: 99%

Cosmic equation of state and advanced LIGO-type gravitational wave experiments

Biesiada

2001

Monthly Notices of the Royal Astronomical Society

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It is hoped that the future generation of interferometric gravitational wave detectors will provide accurate measurements of the final stages of binary in-spirals. The sources probed by such experiments are of extragalactic origin and the observed chirp mass is the intrinsic chirp mass multiplied by ð1 1 zÞ where z is the redshift of the source. Moreover the luminosity distance is a direct observable in such experiments. This creates the possibility to establish a new kind of cosmological test, supplementary to more standard ones.Recent observations of distant type Ia supernovae light curves suggest that the expansion of the Universe has recently begun to accelerate. A popular explanation of the present accelerating expansion of the Universe is to assume that some part V Q of the matter -energy density is in the form of a dark component called 'the quintessence' with the equation of state p Q ¼ wr Q with w $ 21. In this paper we consider the predictions concerning observations of binary in-spirals in future LIGO-type interferometric experiments assuming a 'quintessence cosmology'. In particular we compute the expected redshift distributions of observed events in the a priori admissible range of parameters describing the equation of state for the quintessence. We find that this distribution has a robust dependence on the cosmic equation of state.

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Can we identify lensed gamma-ray bursts?

Cited by 13 publications

References 9 publications

On the probability of microlensing in gamma-ray burst afterglows

On the probability of microlensing in gamma-ray burst afterglows

Nanolensing of Gamma‐Ray Bursts

Cosmic equation of state and advanced LIGO-type gravitational wave experiments

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