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Using gravitational wave early warning to pre-point neutron star mergers

Jacopo Tissino

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Collaborators:

B. Banerjee, M. Branchesi, A. Carosi, S. Macera, G. Oganesyan, A. Stamerra…

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GraceDB (gracedb.ligo.org)

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EMFollow userguide (emfollow.docs.ligo.org)

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Magee+2021

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EMFollow userguide (emfollow.docs.ligo.org)

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De Pietri, Vallero 2023

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We could detect VHE prompt emission from a short GRB if we manage to point it with an IACT before merger!

Banerjee+2023

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  • Mosaic for non well-localized events
    • Afterglow
  • One-shot for well-localized events
    • Prompt (cf. Samanta Macera’s talk)

Strategy

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GW instruments

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  • O5 LIGO-Virgo-KAGRA �(~2027, ~100 BNS)
  • Einstein Telescope, Cosmic Explorer �(~2035, ~100 000 BNS)

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Kiendrebeogo+2023, Branchesi+2023

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MAGIC started

observing GRB 160821B

within 24s of the GCN

arriving!

IACTs

Name

Field of View

Energy Band

Slew speed

MAGIC

~ 3.5 deg

⪆ 100 GeV

6 deg/s

ASTRI

~ 10 deg

⪆ 1 TeV

2 deg/s

CTA-LST

~ 4.5 deg

⪆ 100 GeV

6 deg/s

Aleksic+2016, Vercellone+2022, Abe+2023

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Pictured here:

ASTRI prototype,

Mount Etna, Italy

ASTRI

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Vercellone+2022

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PI: Biswajit Banerjee (GSSI), with Gor Oganesyan, Antonio Stamerra, JT…

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Injection study by Sachdev+2020, DOI: 10.3847/2041-8213/abc753

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  • An optimistic science case, but
  • Improving Early Warning and GW-IACT synergy will be helpful for observations generally

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Backup

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Is there detectable VHE prompt emission?

It’s plausible: the assumptions are

  • There is a HE component, with a spectrum that’s flat or harder
    • Specifically, the spectrum does not decay faster than dN/dE ~ E^-3
  • The prompt emission is at least as bright as the afterglow: see Nava+2014, �L_iso / E_iso > 0.03 Hz in the first 10 seconds
  • Then, for the first 10 seconds we expect a flux of