"The Gravitational Wave Astronomy has begun!


On September 14 a gravitational wave produced by the merger of two massive black holes stretched and squashed the Earth, making themselves “audible” from the two LIGO Interferometers. After that date, several tests have been performed to confirm the detection, until on February 11 we were finally ready to announce to the world such a revolutionary discovery. Since then, our lives have been spiced by outreach and dissemination activities, aimed in getting people involved in this historical observation. In particular, in Birmingham we prepared a special event for the advertised LIGO press release. We projected the conference, which took place at the National Press Club in Washington on a big screen and in this way assisted and intensively participated to the famous “We did it!”. It was really a unique moment that I will remember in my whole life, it was really incredibly exciting.

A contextualisation of the historical importance of such discovery and of the involvement the University of Birmingham were then emphasised with some talks adequately prepared. We finally celebrated all together the extraordinary achievement, always remaining available for further clarifications and, in some cases, for reviews.

The following week we also organised a special edition of "Astronomy in the City", dedicated to the first direct gravitational wave detection. "Astronomy in the City" is a serie of free public events which takes place during the autumn-spring seasons and it is managed by some researchers, PhD and undergrads students involved in astronomical studies. Talks, videos and demonstrations were set up and shown to an enthusiastic public of about 400 people.

I feel particularly grateful to have had the opportunity of holding a conference about the discovery in a public event. For this chance I have to thank the association “Unione Astrofili Tesino e Valsugana”, which invited me to talk about the gravitational waves and the important implications of their direct observations, while telling my own story and involvement. I already had the pleasure to collaborate with such an association: I used the Celado Observatory to collect data and study temperature and chemical composition of the three stars Altair, Deneb and Vega. Thanks to that event, I could also write an advertising article for one of the most important local journal of the region I come from. I was really enthusiastic: for the first time I had the chance of getting people involved in the fascinating field I’m working on. I did that with an animated presentation, which lasted about an hour, and with a prototype of the fabric of space-time, as the one we usually show in Birmingham for outreach events, but built with more common/casual objects.


In the meanwhile, a relatively-small group of us, which I belong to, keeps also to be involved in preparing the material for an exhibition at the Science Museum ThinkThank, concerning gravitational waves in general and the discovery. This active and exciting atmosphere has been pushing me in focusing with a renewed passion on my own research projects. In particular I performed further checks on the Phase-Interpolation procedure: the approach implemented to speed up the estimation of the parameters which describe the coalescence of compact binaries. The results obtained with these last tests have been particularly interesting and thus will probably become the key point on the related paper, which we are working on. With these last checks we measured the effectiveness of our approach on the a second class of waveforms, called IMRPhenomPv2. The model behind such class of waveforms is much more complex than the one supporting TaylorF2 waveforms, which we used for the previous investigations. The complexity of the models translates in an increase of the time required for the waveform generation. This is the reason why it took so much time to actually measure the gain due to the introduction of our Phase-Interpolation procedure. This also explains the great results obtained by the implementation of our approach. Indeed the Phase-Interpolation algorithm allows to decrease the number of waveform computation, therefore the more the waveform is computationally expanse the higher is the gain. This means we are indeed mitigating the timing issue for the most problematic or slowest analyses, which are usually the most accurate. This enlighten the effectiveness of our approach.

The key achievement is a gain in the template generation up to a factor of ~ 150 for lower frequency limit < 20Hz. Since the performances generally increase with the decrease of the lower frequency cut off this approach is particularly suitable for advanced and future generation on interferometers, such as ET. I presented the previous results with a poster at the LVC meeting in Pasadena, where I could personally see the great interest of the LIGO-Virgo community in this kind of studies.

With the beginning of April I have also started my secondment in Urbino (INFN Firenze) under the supervision of Marica Branchesi. I was immediately overwhelmed by the enthusiasm of researchers and people in general about the discovery, so that only two evening after my arrival I was invited to take part to an outreach event focused on the gravitational wave detection which took place in the main square of Urbino. Here I also started to deepen my knowledge about the models concerning the physics and the electromagnetic emissions related to the mergers of two compact objects, focusing my attention in binaries containing at least one neutron star. In particular, we are collecting models which derive and describe strong emissions in the X band originating from such energetic phenomena. In the following couple of months we are thus going to compare the expectations of such models with archived data. The data we are going to use are the ones collected by the EPIC instrument onboard the ESA XMM-Newton. Two different types of data are available: the “pointing” ones and the “slews”, which consist in the information recorded when the instrument passes from one pointing to another. The former has a much higher sensitivity and which the hole observations covers ~800 square degrees of the sky. The latter covers ~80% of the sky for an equivalent duration of about a quarter of hour. In this case each point of the sky has been followed for 10 seconds and can be randomly chosen again with an interval of time which is larger than an hour.

The actual plan consists in two different checks. The first is to derive the expected rates of the most luminous models and compare them with the actual observations in the “slew” data. The second part instead consists in a more detailed comparison of light curves and spectra to check if some of the unclassified sources are consistent to these models, and in that case put constrain on them. If no correlation between observations and models will be found, it is always possible to put constrain on the expected rates and check if they are still consistent with the one expected for neutron star binary coalescences. It is possible that the available data will include also the observations of the BebboSAX satellite. These work will be hopefully useful also to prove the sensitivity of future X ray observatories to these kind of phenomena.

To conclude I’m really enthusiastic about GraWIToN project and, for sure, this wonderful location, where incredibly beautiful views keep appearing, doesn’t hurt."

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