Cast of blacks holes, sometimes they come back – Media Inaf

Slide with the third event, to which it refers Enzo Brocato in the interview, presented by Fulvio Ricci during the international press conference

on December 26, 2015, at 4:38 am Italian time, even for gravitational wave detectors came Santa Claus. Bringing the gift of the second clear signal produced by the ripples of the space-time fabric. Both detectors that make up the Laser Interferometer Gravitational-Wave Observatory (LIGO) have recorded the event, called GW151226. Scientific collaboration LIGO and Virgo have used data collected by the two interferometers and their results have been accepted for publication in the journal Physical Review Letters .

Gravitational waves allow us to get valuable information about their origins, and again physicists of LIGO and Virgo scientific team were able to conclude that, to produce the emission observed on 26 December, were the final moments of the merger of a binary system blacks holes . The historic LIGO detection of 14 September 2015 was the result of the merger of two blacks holes 36 and 29 times the mass of the sun. In this case, the holes blacks who gave birth to the second event were considerably lighter, “just” 14:08 times the mass of the Sun . Their merger has produced a single black hole with a mass equal to 21 times that of the Sun, transforming the additional solar mass in gravitational energy: that measured precisely by the LIGO detectors.

Enzo Brocato (left) during a team meeting GRAWITA. Credits: Media INAF

What are the consequences for research in astrophysics? Media INAF has asked Enzo Brocato , a researcher at the INAF Astronomical Observatory of Rome and head of GRAWITA project, “Gravitational Wave Astronomy with the first detections of adLIGO and adVIRGO experiments.”

what are the characteristics of this event?

“this second event was not as intense as the first. For this reason it has an area of ​​uncertainty in his major position: in fact surpass the 1,000 square degrees. The direction in this case is more centered toward the northern hemisphere. It is interesting to note that the mass of the two blacks holes is greatly reduced compared to those of the pair involved in the first event. The distance is the same order of magnitude of the event of September, about 1.4 billion light years, however, this does not mean that there is a sort of “skin” in the space around us full of blacks holes that blend. It is a distance that marks an optimum value for the efficiency of detection, and that the volume scanned at that distance begins to be significantly large, then the probability of observing actually a coalescence event is highest. “

what implications does this new detection of gravitational wave?

“to have captured this second event brings different effects: the first one to say that we are working in right direction, and so it is an injection of confidence for the whole scientific community that is working on this field. Then starts to give us directions, albeit crude, about what is the frequency with which we can identify these events in “run 2″, the second stage observational will initially involved the two LIGO interferometers and to which you will add VIRGO. The expected frequency for the next session of activity for these instruments, which will continue for about six months, ranging from 3 to 100 coalescence events between blacks holes. This will take a further leap to the science that can be done with this kind of study, because at this point you will understand how they are distributed in the distance, how many there are, how they are distributed in bulk and so on. A lowest bit are the expectations of identifying fusion events between neutron stars, which then are those for which we expect even more likely emission of electromagnetic radiation over the gravitational one. In this case we should identify a maximum of twenty episodes, or rather, more likely, one or two. “

What was the INAF participation in the study of possible events related to the event of waves gravitational?

“Even with this event, we in the INAF team named” Grawita “we have proven that it can react quickly with observations in the optical and infrared, not only in terms of research transient phenomena, but also in their characterization and study in the following days. We are touched to say goodbye to our Christmas holidays and New Year. And I began to observe, with the VST telescope, a portion of 90 square degrees of sky in the possible origin of the signal area, in an area a bit ‘at the limit of the instrument view, since it is placed in the hemisphere south in search of transient phenomena potentially related to the event. We then took it a step further, very important because he saw spectroscopic analysis of these transients, which is critical as it allows to analyze the energy distribution of its electromagnetic radiation and understand, ultimately, what is its nature: it is a supernova, if it is an active galactic nucleus, in short any particular celestial object that can be related to the event gravitational. In this direction, our team has been activated using data collected by various telescopes, largely INAF: the Telescopio Nazionale Galileo (TNG) to the Canary Islands, the telescope of the observing site of Asiago, and, for a transient, even the large binocular telescope LBT in Arizona. “

And did you notice something attributable gravitational wave?

” the very special characteristics of the event emerged from spectra collected with LBT which could be considered as a supernova “strange”, prompted us to investigate further, and so we were able to determine its distance, but unfortunately turned out to be incompatible with the one that has generated the ‘ gravitational wave on 26 December. The data collected, however, allow us to thoroughly study this supernova, which really has very special characteristics. Even with this event, we in the “Grawita” team have shown they can quickly react in the optical and infrared observations not only with regard to the search for transient phenomena, but also in their characterization and study in the following days. In short, we can say that we are ready for the second round of observations with the LIGO and Virgo interferometers. “

Here, you quote in the next round of observations also the Virgo interferometer. As it will be important to have another operating tool alongside those of the LIGO Collaboration?

‘We astrophysicists look forward to the entry into operation of the interferometer Virgo because, along with the pair LIGO, will determine more precisely the direction of gravitational waves coming. This means that also from the point of view of observation, for those who will make the ground observation with optical telescopes, there will be a smaller area to fathom. This does not mean having less work, but it means you can go and magnitudes weaker, and then look at a larger volume of space and somehow increase the chance to see the electromagnetic counterparts. “

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source: Media INAF | Written by Marco Galliani