The low frequency radio follow-up of gravitational wave merger - - PowerPoint PPT Presentation

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Sep 10, 2022 43 likes •254 views

The low frequency radio follow-up of gravitational wave merger events with LOFAR Kelly Gourdji PhD student, University of Amsterdam. On behalf of the LOFAR GW follow-up team. Outline EM follow-ups of GW events LOFAR: What, why and how

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The low frequency radio follow-up of gravitational wave merger events with LOFAR

Kelly Gourdji

PhD student, University of Amsterdam. On behalf of the LOFAR GW follow-up team.

SLIDE 2

Outline

EM follow-ups of GW events LOFAR: What, why and how Our GW follow-up strategy Results for GW170817 Byproduct: extremely deep transient searches

Kelly Gourdji 2

SLIDE 3

Kelly Gourdji 3

Compact mergers involving at least one neutron star: possible evolutionary scenarios and accompanying emission

Chu et al. 2016 Coherent Incoherent

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Multimessenger observations of GW170817

Kelly Gourdji 4 Abbott et al. 2017

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Kelly Gourdji 5

Chu et al. 2016 (adapted)

bserved for GW170817
Coherent

Incoherent

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Some of the proposed emission mechanisms have been confirmed, while there have been additional surprises…

Kelly Gourdji 6

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Some of the proposed emission mechanisms have been confirmed, while there have been additional surprises…

Kelly Gourdji 7

1.7 s time delay between GW and GRB
delay in observation of X-rays
dimmest, yet closest sGRB ever observed
Radio emission at unexpected late timescale

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Some of the proposed emission mechanisms have been confirmed, while there have been additional surprises…

Kelly Gourdji 8

More events & EM follow-ups needed!

1.7 s time delay between GW and GRB
delay in observation of X-rays
dimmest, yet closest sGRB ever observed
Radio emission at unexpected late timescale
cocoon vs off-axis jet? High velocity tail of the kilonova

merger ejecta?

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Low-frequency radio follow-up with the LOw Frequency ARray (LOFAR)

Kelly Gourdji 9

We collect data from 110-190 MHz

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Large instantaneous field of view

Kelly Gourdji 10

Why LOFAR?

~60 deg2

Contours: cWB probability map LOFAR follow-up of GW 150914

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Low frequency

Kelly Gourdji 11

Why LOFAR?

Lorimer et al. 2007

Dispersion delay scales inversely with frequency. Lower frequencies arrive later. Gives us a chance to catch coherent emission related to mergers!

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LOFAR rapid response

Kelly Gourdji 12

On source within <5 mins of trigger!

Searching for coherent emission from e.g. FRB related to merger. Check out www.asterics2020.eu (ASTERICS) for more info.

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Late time follow-up

Kelly Gourdji 13

Example for GW170817 Searching for incoherent emission from e.g. reverse shock and/or afterglow.

K. Hotokezaka

LOFAR observations

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Sensitivity

Kelly Gourdji 14

Why LOFAR?

GW170817

T. Shimwell

~2 mJy/beam upper limit

Best limit at these frequencies (2 mJy/beam) MWA: 17 mJy/beam Deeper image to come following more calibration/cleaning The deepest image ever made at very southerly declinations with LOFAR. Max elevation of observation: ~13.7 deg

2017-12-25 to 2018-01-2

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Late time follow-up

1 week, 1 month, 3 months, 6 months, 1 year timescales

Kelly Gourdji 15

Our preliminary images are reaching 0.8 mJy/beam noise.

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Byproduct: deep transient searches

Kelly Gourdji 16

40-840 MHz

Our data

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Looking ahead

We have 10 triggers for the next 2 years + ~300 hours of

follow-up time

we rely on NS system probability
Larger GW detector network
Smaller localization thus deeper images
Lower latencies for GW alerts and LOFAR triggering

Kelly Gourdji 17

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Thank you

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Additional slides

Kelly Gourdji 19

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Turnover in light curve supports structured jet model

Kelly Gourdji 20

Alexander et al 2018

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Kelly Gourdji 21

Mooley et al 2018

Recent light curves disagree somewhat. Somewhere between these two models?