Welcome on board !

GRANDMA is an international scientific collaboration of astrophysicists that work on the gravitational wave (GW) astronomy. This web site, developped by us, is based on the idea of crowdsourcing that aims any volunteered astronomer to join us in our research efforts and to share with us a common passion for the gravitational wave science and astronomy.

The GRANDMA team

Kilonova Catcher will allow you to contribute to tremendous discoveries in the GW science. With this app you will be able to participate to the optical follow-up of any GW event that will be detected by the current three GW interferometers during the upcoming 2019-2020 GW scientific run (so-called O3 run). Our holy grail is to catch the kilonova emission emerging from the coalescence of two neutron stars bounded in a compact binary system (BNS).

How to join us ?

Join the O3 GW run with GRANDMA

If you have any telescope in your hands or a temporary access to any telescope you are very welcome to help us on this project !
First, create an account and fill the form to tell us which instrument you have and where it is located. It will help us to send to you the best sky position to observe knowing your location and your telescope capabilities.

Once your account is created we will communicate to you how to receive the GW alerts, how to observe portions of the sky related to the localization area of the GW events and how to share your observations with the GRANDMA database system to make science with us.
You will be alerted by us if your observations lead to the detection of the optical counterparts associated to the gravitational wave sources !

Basics of the GW astronomy

The gravitational wave sources

For our purpose, GW will be mainly produced in galaxies from the merger of compact objects in binary systems involving either two black holes (BBH), two neutron stars (BNS) or a mix of them (NSBH). From the GW data we have a direct access to the distance (so the number of the galaxy candidates) of the event and the masses (so the nature) of the two compact objects involved in the merger.
The BNS mergers are the most promising source of electromagnetic counterparts as a fraction of the neutron stars matter can be expulsed and radiate through several mechanisms right after the coalescence.

The O3 run

Alert rate and localization error boxes

Three GW interferometers will participate to O3. The two LIGO (Handford and Livigston) detectors in the US and the european Virgo detector in Italy. The GW detection rate is uncertain depending on the sensitivity of the GW interferometers of such events. For O3, we expect the detection of few BBH mergers per month/week while for BNS we expect 1 BNS per month at maximum. As illustrated on the right (for O2 GW events), the sky localization area and shapes of GW sources is poorly constrained. it depends on the number and the repartition of the GW detectors on Earth.
We need a collaborative effort to observe the full error boxes !

A kilonova ?

It is a relatively fast (day/week timescale) and faint visible/infrared (Mv = -16 at maximum luminosity) transient phenomenon. It is radiated by a fairly isotropic ejecta expulsed at few fractions of the light speed. The kilonova emissions are powered by the radioactive decay of heavy nuclei within the ejecta from the intense bombardment of nuclei lighter than iron by energetic neutrons. Called r-process, this physics requires an energetic and extremely neutron-rich environment to be effective. The violent matter ejections resulting from the coalescences of two neutron stars can produce such environment and has been proposed, two decades ago, as being the main candidates of kilonova and the production sites of the heaviest elements in the Universe.

GW170817 / AT2017gfo

The first kilonova ever observed

On 2017, August 17th a GW signal triggers the two LIGO interferometers. Albeit no detection with Virgo, it helps to strongly the sky localization of GW170817. The analysis of the signal revealed that this event originated from the coalescence of two neutron stars located at a distance of about 40 Mpc. About 11h after the GW signal, an optical emission at magnitude of about 17 was detected in the galaxy NGC4993 and unambiguously associated with the merger of the two neutron stars. Additional optical and infrared data taken days after the merger event later confirmed that this optical emission was a kilonova powered by r-process channels. The first ever discovered so far!

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