Extragalactic Millimeter Transients in the Era of Next-generation CMB Surveys

Eftekhari, T.; Berger, E.; Metzger, Brian D.; Laskar, T.; Villar, V. Ashley; Alexander, K. D.; Holder, G. P.; Vieira, J. D.; Whitehorn, N.; Williams, Peter K. G.

doi:10.3847/1538-4357/ac7ce8

“…The millimeter-band emission from GRB 221009A is a factor of ≈5-10 less luminous than GRB 030329 (orange), but of comparable luminosity to that of other GRB afterglows. Adapted from Eftekhari et al (2022).…”

Section: Equipartition Analysis Of the Radio Componentmentioning

confidence: 99%

The Radio to GeV Afterglow of GRB 221009A

Laskar

¹

,

Alexander²,

Margutti

³

et al. 2023

ApJL

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GRB 221009A (z = 0.151) is one of the closest known long γ-ray bursts (GRBs). Its extreme brightness across all electromagnetic wavelengths provides an unprecedented opportunity to study a member of this still-mysterious class of transients in exquisite detail. We present multiwavelength observations of this extraordinary event, spanning 15 orders of magnitude in photon energy from radio to γ-rays. We find that the data can be partially explained by a forward shock (FS) from a highly collimated relativistic jet interacting with a low-density, wind-like medium. Under this model, the jet’s beaming-corrected kinetic energy (E K ∼ 4 × 1050 erg) is typical for the GRB population. The radio and millimeter data provide strong limiting constraints on the FS model, but require the presence of an additional emission component. From equipartition arguments, we find that the radio emission is likely produced by a small amount of mass (≲6 × 10−7 M ⊙) moving relativistically (Γ ≳ 9) with a large kinetic energy (≳1049 erg). However, the temporal evolution of this component does not follow prescriptions for synchrotron radiation from a single power-law distribution of electrons (e.g., in a reverse shock or two-component jet), or a thermal-electron population, perhaps suggesting that one of the standard assumptions of afterglow theory is violated. GRB 221009A will likely remain detectable with radio telescopes for years to come, providing a valuable opportunity to track the full lifecycle of a powerful relativistic jet.

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“…The mm-band emission from GRB 221009A is a factor of ≈ 5-10 less luminous than GRB 030329 (orange), but of comparable luminosity to that of other GRB afterglows. Adapted from Eftekhari et al (2022).…”

Section: Comparison To Other Grbsmentioning

confidence: 99%

The Radio to GeV Afterglow of GRB 221009A

Laskar¹,

Alexander²,

Margutti³

et al. 2023

Preprint

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GRB 221009A (z = 0.151) is one of the closest known long γ-ray bursts (GRBs). Its extreme brightness across all electromagnetic wavelengths provides an unprecedented opportunity to study a member of this still-mysterious class of transients in exquisite detail. We present multi-wavelength observations of this extraordinary event, spanning 15 orders of magnitude in photon energy from radio to γ-rays. We find that the data can be partially explained by a forward shock (FS) from a highlycollimated relativistic jet interacting with a low-density wind-like medium. Under this model, the jet's beaming-corrected kinetic energy (E K ∼ 4 × 10 50 erg) is typical for the GRB population. The radio and mm data provide strong limiting constraints on the FS model, but require the presence of

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“…However, there is a small chance this event is associated with an AGN. Eftekhari et al (2022) predict ACT will see on the order of 10 GRBs but this event is not associated with any known GRB flares listed in the Fermi All-sky Variability Analysis (Abdollahi et al 2017). The associations for events 9 and 13, are also unclear.…”

Section: Discussionmentioning

confidence: 88%

“…Millimeter wavelengths are also sensitive to reverse shock (RS) emission from GRBs. Largescale millimeter surveys will therefore be able to provide an unbiased estimate of the percentage of long GRBs with RS emission (Eftekhari et al 2022). Similarly, cosmic microwave background (CMB) surveys will allow us to constrain models of other types of transients such as TDEs.…”

Section: Introductionmentioning

confidence: 99%

“…Similarly, cosmic microwave background (CMB) surveys will allow us to constrain models of other types of transients such as TDEs. Since millimeter emission from TDEs indicated the presence of synchrotron emission, millimeter transient surveys can also constrain the fraction of TDEs that produce jets (Eftekhari et al 2022). Wide-field CMB surveys are uniquely poised to answer these science questions as, in contrast to current radio and infrared surveys, they survey large areas of the sky in short periods of time providing a key statistical window into synchrotron transients.…”

Section: Introductionmentioning

confidence: 99%

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The Atacama Cosmology Telescope: Systematic Transient Search of 3 Day Maps

Li,

Biermann,

Naess

et al. 2023

ApJ

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We conduct a systematic search for transients in 3 yr of data (2017–2019) from the Atacama Cosmology Telescope (ACT). ACT covers 40% of the sky at three bands spanning from 77–277 GHz. Analysis of 3 day mean-subtracted sky maps, which were match filtered for point sources, yielded 29 transient detections. Eight of these transients are due to known asteroids, and three others were previously published. Four of these events occur in areas with poor noise models and thus we cannot be confident they are real transients. We are left with 14 new transient events occurring at 11 unique locations. All of these events are associated with either rotationally variable stars or cool stars. Ten events have flat or falling spectra indicating radiation from synchrotron emission. One event has a rising spectrum indicating a different engine for the flare.

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Extragalactic Millimeter Transients in the Era of Next-generation CMB Surveys

Cited by 12 publications

References 141 publications

The Radio to GeV Afterglow of GRB 221009A

The Radio to GeV Afterglow of GRB 221009A

The Radio to GeV Afterglow of GRB 221009A

The Atacama Cosmology Telescope: Systematic Transient Search of 3 Day Maps

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