A network of pulsars to "listen" to the cosmic buzz of gravitational waves: the international study
Among the authors also Delphine Perrodin, Andrea Possenti and Marta Burgay of the INAF of Cagliari
There are also Delphine Perrodin, Andrea Possenti and Marta Burgay, from INAF of Cagliari, among the authors of the International Pulsar Timing Array (IPTA) project, who, using the work and skills of various collaborations of astrophysicists from all over the world, analyzed the most complete archive available today of data on the arrival times of pulses of 65 pulsars, the remnants of large-mass stars that exploded as supernovae.
The careful experimental investigation reinforces the theoretical indications that would suggest the presence of a real cosmic "buzz", produced by gravitational waves of ultra-low frequencies (from billionths to millionths of Hertz) emitted by a multitude of pairs of black holes super-massive.
The pulsars studied by the team are called "millisecond" because they rotate around their axis hundreds of times per second, emitting narrow beams of radio waves that appear as pulses due to their rotational motion. The arrival times of these pulses were then combined into a single set of data, combining the independent observations of three international collaborations: the European Pulsar Timing Array (EPTA, to which researchers from INAF and the University of Milan belong Bicocca involved in the project), the North American Nanohertz Observatory for Gravitational Waves (NANOGrav), and the Parkes Pulsar Timing Array in Australia (PPTA). These three collaborations are also the founders of the IPTA.
The IPTA team's investigation of these combined data revealed the presence of a very low frequency signal.
“This result - explains Delphine Perrodin - confirms and greatly strengthens the gradual emergence of similar signals that have been found in recent years in the individual data sets, regardless of the various collaborations participating in IPTA. In particular, in the framework of the EPTA experiment, we have been used for over two decades to combine data from five different European radio telescopes, including the Sardinia Radio Telescope (SRT, located in Sardinia), and often to observe the same pulsar simultaneously. This experience was very helpful in creating the current version of the data. Furthermore, a large part of the methodology used to understand the characteristics of the possible signal during the many years of monitoring has been developed within EPTA ”.
The next step for the IPTA team will be measuring the so-called 'spatial correlation' between pulsars. “The correlation of the signal between the pairs of pulsars - specifies Andrea Possenti - is the key to clarifying the source of the signal. For this to be the gravitational wave background, each pair of pulsars must behave in a very specific way, depending on their angular separation in the sky. At the moment nothing can be concluded in this regard: in fact we need a stronger signal to measure this correlation ”.
"This is a real international teamwork - concludes Delphine Perrodin - in which the Italian contribution, between INAF and the University of Milan Bicocca, becomes increasingly important, with the observations at SRT, the combination with the data of the other radio stations. telescopes, their astrophysical analysis and interpretation. One can only be optimistic about the ability to soon arrive at a discovery that would be epochal ".
(Unioneonline / vl)
