Proposal to observe spectra of events detected by the gravit

Proposal to observe spectra of events detected by the gravit

Postby Franck Boubault » Sun Jan 20, 2019 8:14 pm


Please find below the description of a very interesting and challenging proposal, whose aim is to

observe spectra of events that will be detected by the gravitational wave (GW) detectors Ligo and

Virgo during the next run starting in March-April 2019 for a year.
This proposal is from Olivier Godet, Lecturer at the University Toulouse III - Paul Sabatier (FRANCE).

Franck Boubault

In August 2017, the gravitational wave (GW) detectors Ligo and Virgo
detected the first GW signal coming from the merger of 2 neutron stars.
This GW event was also detected in a coincident manner in Gamma-rays as
a short Gamma-ray burst (GRB) by NASA & ESA satellites (Fermi &
Integral). This was followed by an intensive multi-wavelength campaign
from ground and space facilities.

This event is a milestone for astrophysics and fundamental physics!
Since it confirms that the progenitors of short Gamma-ray bursts are
indeed due to the merger of 2 neutron stars (NS). It also enabled to
perform some tests of the General Relativity. Such events also offer
very interesting prospects to probe the equation of state of matter
(i.e. the type of matter) at supra-nuclear densities in the NS core.

The GRB was followed by a kilonova powered by the decay of radioactive
heavy elements produced from the ejected material following the merger.
The kilonova emission peaked at an AB magnitude around 17.5 one day
after the event detection. The source is located at 40 Mpc from Earth.

The GW instruments Virgo & Ligo will perform an observation run called
O3 starting in March-April 2019 for a year. During this run, estimates
show that the detectors may be able to catch few NS-NS mergers. The
electromagnetic follow-up of these events will be of great importance to
better understand the physics of such extreme events and any help to do
so will be highly regarded.

From the O3 run, the GW sky maps showing the event position and the
associated error contours on the sky will be released rapidly after a
detection to the community to organize the EM follow-up activities.
Typical GW positioning errors cover a few square degrees and even more
sometimes. Therefore, it is very challenging to cover such large
fractions of the sky with current facilities with a prompt reaction time
as required by the transient nature of such events. As astronomers we
developed various observing strategies to enhance the probability to
detect an EM counterpart to the GW detections. Such strategies still
have to be fully tested on forthcoming GW observing runs to assess their

Luckily the detected GW sources will be located in the local Universe
given the current sensitivity of the GW detectors (< 120 Mpc for Ligo
and < 60 Mpc for Virgo). But we do not really know the distance
distribution of the GW sources in that volume of the Universe yet. The
EM counterparts associated to GW sources (in particular NS-NS / NS-BH
mergers) are expected to be fairly bright over the EM spectrum and
therefore offer some promises to catch them even if there are some
uncertainties on how bright could be a kilonova for instance.

For all the above reasons, photometric and/or spectroscopic
observations of some events may be accessible to non professional
telescopes. In addition to the EM counterpart , the study of the host
galaxy also offers interesting prospects to understand in which
environment such mergers could happen.

In any case, it may be worth a try! I would like to know what you think
about this idea and how many of you as non professional astronomers will
be willing to give it a try to start with. I also would like to have a
clearer view of your observing capabilities as well as some of your main
observing constraints. From then, we could discuss some practical ways
to implement such a project.

If you have any questions, do not hesitate to contact me.

Best regards,
Dr. Olivier Godet

Lecturer at the University Toulouse III - Paul Sabatier (FRANCE)
Institut de Recherche en Astrophysique & Planetologie (IRAP)
9 avenue du colonel Roche
31028 Toulouse Cedex 04, France
Email: ogodet at
Franck Boubault
Posts: 9
Joined: Fri Jun 01, 2012 8:04 am

Re: Proposal to observe spectra of events detected by the gr

Postby Robin Leadbeater » Sun Mar 31, 2019 4:34 pm

I have tried to contact Dr Godet several times but I have not had a reply. Is this going ahead?

LHIRES III #29 ATIK314 ALPY 600/200 ATIK428 Star Analyser 100/200 C11 EQ6
Robin Leadbeater
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Joined: Mon Sep 26, 2011 4:41 pm

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