P.I.: Enzo Brocato

GRAWITA projects the INAF –OAR in the Multi-messenger Era.

The present research group is committed to taking part in the search and the study of photon-messengers (i.e. electromagnetic) counterparts of the gravitational messengers (i.e. gravitational wave) events by using different observational facilities.


INAF-OAR: E.Brocato (P.I.), L. Pulone, V.Testa, G. Iannicola, L. Stella, M. Lisi, S. Piranomonte, S. Ascenzi, G. Israel, P. Casella

ASI Science Data Center: L.A. Antonelli, G. Giuffrida, S. Marinoni, P. Marrese, V. D’Elia

Contact: Enzo Brocato – INAF-OA Roma – email:



Summary. In september 2015, the LIGO VIRGO Collaboration measured a gravitational wave (GW), this event opened a new windows in astrophysics: the Multi-messenger Era.

Several astrophysical sources are expected to be GW emitters (binary compact star mergers, core-collapse supernovae, GRBs, relativistic jets, magnetars). Candidates events can be identified and confirmed only through photon-messenger (electromagnetic) follow-up at all wavelengths. The present research group, organized in 5 INAF research units (OARoma, OaBrera, IASFBO, OACapodimonte, INAF-SNS), is committed, within an international consortium, to take part in the search for photon-messenger counterparts of the first reported GW events, by using different facilities, principally the VST. Moreover, follow-up of photon-messengers at all wavelengths is currently being organized at multi-wavelength facilities, including ground-based telescopes and satellites.

Our observational program will unfold over several years.

The context. Thanks to the Memorandum of Understanding (MoU) signed by INAF and Laser Interferometer Gravitational-Wave Observatory (LIGO) Collaboration and Virgo Collaboration (hereinafter LVC), we receive the results (in particular, time and position in the sky) of the first GW signals, immediately after its detection. These provide a unique opportunity to identify the first photon-messenger (electromagnetic EM) counterparts of GW emitters, leading a breakthrough of paramount importance to both physics and astrophysics.

The detection of GWs also open a new window in astrophysics to study gravitational collapse and explosion mechanisms, matter at supranuclear density and radiation processes in a way that is free from opacity, absorption and propagation problems that often affect observations in the EM domain. GWs probe the inner regions of many astrophysical phenomena that are otherwise inaccessible to investigation. Sources of GWs predicted by general relativity, e.g. NS-NS or NS-BH mergers, as possible GRBs’ progenitors, core-collapse SNe are expected to be identified thanks to their powerful EM signals. For example, a simultaneous and coincident detection of a short GRB and a GW signal would provide the final proof of models, which predict the merging of two compact objects as origin of short GRBs.

Thus, the identification of photon-messenger (EM) counterparts of gravitational-messenger (GW) Virgo/LIGO events will mark the birth of the Multi-Messenger Astronomy. Moreover, the availability of a new powerful messenger – together with the two other messengers, photons and high-energy particles (e.g. neutrinos) – will take us in unexplored domains of the physics of supranuclear density matter and very strong gravitational fields in the Universe.

An international networking activity has been carried out and we now are in close contact with a wide community of EU researchers for joint efforts in preparing observational proposals (most successful). A robust and collaborative relationship between this INAF group and the INFN and Virgo scientists has already been established. For example, we have jointly organized the first meeting between worldwide astronomers (MoU subscribers) and LVC researchers next April in Cascina (PI).

General perspectives and conclusions. This project intends to fully exploit at best the opportunity to reach a result of paramount importance: identifying and studying the first astrophysical counterparts of a GW event. The intrinsic high-risk character of this program is fully balanced by the extraordinary scientific outcome expected in case of positive identifications. We stress that the search for transients in wide field images will provide great benefits in the field of the Time Domain Astronomy.


Preliminary Results:

For the first measurement of a gravitational wave GW150914 by LIGO/VIRGO collaboration, Grawita was able to cover a sizeable part of the enormous error box due to the uncertainties in the sky localization area of the direction of origin of the gravitational wave obtained by LIGO/VIRGO measurements.