The Sardinia Radio Telescope, which was inaugurated in 2013, is getting ready to participate in the Search for ExtraTerrestrial Intelligence (SETI) observations. This involves, in collaboration with the SETI collaboration and the ``Breakthrough Listen initiative", the onsite installation of the SERENDIP VI setup for SETI observations. In parallel, a scientific team at the Cagliari Astronomical Observatory is becoming acquainted with SETI search algorithms: both standard algorithms using the Fast Fourier Transform; and more versatile algorithms using the Kahrunen-Loève Transform (KLT) as well as Wavelets. The team is also investigating the possibility to pursue, with the SERENDIP VI setup, the simultaneous search for Extraterrestrial Intelligence, pulsars and Fast Radio Bursts

Antonietti, N.

Aresu, G.

BURGAY, MARTA

CASU, Silvia

CONCU, Raimondo

EGRON, ELISE MARIE JEANNE

Loi, F.

LORU, SARA

Lunesu, M. I.

Maccone, C.

MELIS, Andrea

MIGONI, CARLO

MILIA, Sabrina

Montebugnoli, S.

MURGIA, MATTEO

NAVARRINI, Alessandro

Pari, P.

PELLIZZONI, ALBERTO PAOLO

PERRODIN, DELPHINE

PILIA, Maura

PISANU, Tonino

POSSENTI, ANDREA

TROIS, ALESSIO

VACCA, VALENTINA

Valente, G.

OA@INAF - Istituto Nazionale di Astrofisica

2018Publication Year2021-02-12T10:34:57ZAcceptance in OA@INAFSETI scientific activities in Sardinia: Search for ET, pulsars and Fast Radio BurstsTitlePERRODIN, DELPHINE; MELIS, Andrea; CONCU, Raimondo; POSSENTI, ANDREA; BURGAY, MARTA; et al.Authorshttp://hdl.handle.net/20.500.12386/30348HandleMEMORIE DELLA SOCIETA ASTRONOMICA ITALIANAJournal89NumberMem. S.A.It. Vol. 89, 421c© SAIt 2018 Memorie dellaSETI scientic activities in Sardinia:Search for ET, pulsars and Fast Radio BurstsD. Perrodin1, A. Melis1, R. Concu1, A. Possenti1, M. Burgay1, M. Pilia1, A. Trois1,N. Antonietti, G. Aresu1, S. Casu1, E. Egron1, F. Loi1, S. Loru1, M.I. Lunesu4,C. Maccone2, S. Milia1, C. Migoni1, S. Montebugnoli3, M. Murgia1, A. Navarrini1,P. Pari3, A. Pellizzoni1, T. Pisanu1, V. Vacca1, and G. Valente51 INAF Osservatorio Astronomico di Cagliari, Via della Scienza 5, Selargius (CA), Italye-mail: delphine.perrodin@inaf.it2 INAF IASF Milano, Via Alfonso Corti 12, Milano (MI), Italy3 INAF IRA Bologna, Via Gobetti 101, Bologna (BO), Italy4 DIEE Universita’ di Cagliari, Via Marengo 2, Cagliari (CA), Italy5 Agenzia Spaziale Italiana, Via del Politecnico sn, 00133 Roma (RM), ItalyAbstract. The Sardinia Radio Telescope, which was inaugurated in 2013, is getting ready toparticipate in the Search for ExtraTerrestrial Intelligence (SETI) observations. This involves, incollaboration with the SETI collaboration and the “Breakthrough Listen initiative”, the onsiteinstallation of the SERENDIP VI setup for SETI observations. In parallel, a scientific team atthe Cagliari Astronomical Observatory is becoming acquainted with SETI search algorithms:both standard algorithms using the Fast Fourier Transform; and more versatile algorithms usingthe Kahrunen-Loève Transform (KLT) as well as Wavelets. The team is also investigating thepossibility to pursue, with the SERENDIP VI setup, the simultaneous search for ExtraterrestrialIntelligence, pulsars and Fast Radio Bursts.Key words. Sardinia Radio Telescope, SERENDIP VI, pulsars, FRB1. IntroductionSince 2013, a number of technological andscientific staff of the Cagliari AstronomicalObservatory 1 (OAC) are involved in devel-oping SETI activities at the Sardinia RadioTelescope (SRT) 2. A thorough description ofOAC’s efforts in SETI are described in Meliset al. (these proceedings): this includes a de-scription of SRT as a SETI facility, both in1 http://www.oa-cagliari.inaf.it/2 http://www.srt.inaf.it/piggy-back mode and for targeted searches; theSERENDIP VI setup at SRT which is currentlyunder development; as well as a descriptionof the KLT and Wavelets algorithms. In thispaper, we discuss the efforts to combine thesearch for ExtraTerrestrial Intelligence, pulsarsand Fast Radio Bursts (FRBs) at SRT.2. SETI data analysisWhile the technological team works on theinstallation of the SERENDIP VI setup for422 Perrodin: SETI scientific activities in Sardiniafuture SETI data acquisition, the scientificteam is learning how to perform the analy-sis of SETI data, through a collaboration withthe Breakthrough Listen (BL) program at UCBerkeley. This involves the testing of SETI de-tection software such as BL’s GPU acceleratedsoftware spectroscopy suite on BL basebanddata from the Green Bank Telescope and theParkes telescopes. In parallel, the team, also incollaboration with UC Berkeley, is developingKLT algorithms which are being tested on BLdata (Melis et al. 2016).3. PulsarsThe data collected for SETI at radio telescopesare versatile and can also be used to search forexotic objects such as pulsars. Discovered in1967 by Jocelyn Bell, the original radio sig-nals (received as pulses) were so regular thatthey were thought to be emitted by intelligentlife; these “pulsars” were thus dubbed LGMfor “Little Green Men”. It was later found outthat the radio pulses were not emitted by in-telligent life but rather by fast-rotating neu-tron stars. Their rotation periods range fromroughly 1 ms to 10 seconds. They are highlymagnetized and emit radio waves in the formof radio beams emanating from the star’s mag-netic poles. Those beams reach the Earth’s lineof sight only once per rotation of the pulsar:pulsars thus act as “cosmic lighthouses” whereradio telescopes on Earth observe a series ofpulses. Millisecond pulsars (with periods in theorder of 1 -2 30 milliseconds) are particularlyinteresting since they are extremely stable. Theconcept of “pulsar timing” was born: by mon-itoring the arrival times of the radio pulses atEarth’s radio telescopes (we can predict thepulse arrival times to about 10 nanosecondsover one year!), we can determine pulsar prop-erties with very high accuracy. In fact, after afew years of collected data, the rotation periodcan be known to 15 significant figures. One canalso determine the dispersion measure, or theamount of interstellar dispersion between thepulsar and Earth; as well as orbital parametersif the pulsar is in a binary. In particular, the es-timation of orbital parameters in binary pulsarsallows the testing of general relativity and al-ternative theories of gravity in the strong-fieldenvironment of the neutron star. In addition,the monitoring of a large sample of precise mil-lisecond pulsars, a so-called “pulsar timing ar-ray”, allows the detection of deformations inthe spacetime between Earth and the pulsar,which would be caused by gravitational wavesemitted by, for example, pairs of supermassiveblack holes in distant galaxy mergers (Perrodin& Sesana 2017).3.1. Pulsar science at SRT: pulsartimingSRT takes part in the monitoring of an ar-ray of precise millisecond pulsars as part ofthe European Pulsar Timing Array (EPTA).Five large European radio telescopes ob-serve pulsars and later combine their datasets,involving: the 100-m Effelsberg Telescope(Germany), the 94-m equivalent NancayRadio Telescope (France), the 94-m equivalentWesterbork Synthesis Radio Telescope (TheNetherlands), the 76-m Lovell Telescope (UK),and the 64-m Sardinia Radio Telescope (Italy).At SRT, EPTA observations generally involvethe monitoring of pulsars at L-band, P-bandand S-band. We show in Fig. 1 the observa-tion of the millisecond pulsar J1713+0747 atL-band with SRT.In addition, the Large European Array forPulsars (LEAP) project, which is part of theEPTA and was supported by an ERC ad-vanced grant (2M euro, PI: M. Kramer), offi-cially ran from 2009-2014 and was later con-tinued thanks to local funding at each insti-tution. The LEAP project involves the simul-taneous monitoring of millisecond pulsars atall five EPTA radio telescopes (Bassa et al.2016) (Perrodin et al. 2016). The simultaneityof the observations allows us to find the pre-cise offsets between the telescopes and to addthe data coherently. The resulting signal-to-noise of pulsar signals increases linearly withthe number of telescopes, as opposed to thesquare root of the number of telescopes in thecase of non-simultaneous observations. Withthe added signal-to-noise, the LEAP experi-ment is essentially equivalent to a 196-m ra-dio telescope. This high sensitivity allows us toPerrodin: SETI scientific activities in Sardinia 423search for gravitational wave signatures in pul-sar data over several years or decades. Whiledetecting gravitational waves in the nanohertzfrequency range would be groundbreaking, wecan, in the meantime, find stringent limits ona background of supermassive black hole bina-ries.At SRT, we also monitor pulsars with aneutron star companion, i.e. double neutronstar binaries, which allow us to test general rel-ativity in the strong gravity limit. Eclipsing bi-naries are also a focus of SRT research.3.2. Pulsar science at SRT: pulsarsearchingIn order to search for gravitational wave signa-tures and test the strong gravity regime aroundpulsars, we need to find more pulsars. Pulsarsearching can be done at L-band, P-band withSRT’s dual-band LP receiver. A new, 7-beamS-band receiver was funded by the Sardinia re-gion in 2013, was built and saw its first pulsarsin 2016 (Valente et al. 2014). The S-band fre-quencies are particularly well-suited to searchfor millisecond pulsars in the Galactic Center.The pulsar search software capabilities at OACand SRT are currently being upgraded to in-volve GPUs. OAC is also involved in FRBsearches and their follow-ups thanks to theSUPERB collaboration.3.3. Pulsar instrumentation at SRTThe currently-used pulsar backend instrumentsat SRT include a Parkes Digital Filberbank(PDFB) backend as well as a ROACH back-end. The instruments have been used to ob-serve mostly at L-band (1300-1800 MHz) andP-band (305-410 MHz). A second ROACHboard is being installed and will allow the useof two ROACH boards to observe in L-bandand P-band simultaneously; the use of a GPUcluster will enable the observation of the fullL-band bandwidth (500 MHz). Further ahead,we plan to install pulsar timing and search-ing capabilities with the ROACH2 backends(7 ROACH2 and GPUs), in other words SRT’s“SARDARA” setup (Melis et al. 2018), whichin turn is an integral part of the SERENDIPVI setup. Therefore the instruments used forpulsar timing and searching will be fully inte-grated within the SERENDIP VI setup.4. Fast Radio BurstsDiscovered by Duncan Lorimer in 2007, FRBsare astrophysical transients that emit shortbursts of radio waves with a duration of just afew milliseconds. They appear as single pulsesignals in radio waves, and can sometimes berepeating or periodic. The signals are highlydispersed because of the effects of the inter-stellar medium, which need to be taken intoaccount. The origin of FRBs is still unknown:could they be stellar phenomena or artificialsignals?4.1. Pulsar and FRB searches with BLdataOur scientific team is collaborating with theBL project for the development of pulsar andFRB search pipelines. The next step will be totest these pipelines on BL data. The goal thatonce SERENDIP VI is fully set up at SRT, wewill have pipelines ready for SETI, pulsars, andFRB searches.4.2. FRB searches with the KLTA. Trois & M. Pilia have proposed to searchfor FRBs using GPU technology and the KLTmethod. Their project was funded by theSardinia region. This is an extension of AlessioMagro’s work (Magro 2013) on real-time GPUbackends, adding on the KLT method (Melis etal. 2016). The project is about the developmentof software tools for the study of transientssuch as FRBs using the KLT method; asidefrom FRBs, it is also applicable to the searchfor transients such as SETI. It will involve aGPU implementation and machine learning;the implementation of KLT on GPUs; an op-timized de-dedispersion algorithm for GPUs;candidate searching via machine learning. TheKLT will allow the team to detect weaker sig-nals (both FRBs and SETI), while the reduc-424 Perrodin: SETI scientific activities in SardiniaFig. 1. SRT timing observation of the millisecond pulsar B1937+21tion in computing time (thanks to GPUs) willallow for real-time searches.5. ConclusionThe OAC scientific team is involved in a num-ber of SETI-related activities. The main goalfor SETI at SRT is to install the SERENDIP VIsetup and search simultaneously for ET, pul-sars and Fast Radio Bursts (whether with tar-geted searches or in piggy-back mode). Thisinvolves a technological setup as well as,from the perspective of the scientific team, thepreparation and testing of search pipelines. Thepipelines can in particular be diversified andoptimized using the KLT method (as an al-ternative to the standard Fast Fourier trans-form) to allow the detection of weak sources;and GPUs to reduce the computing time. Morespecifically, the team is currently involved intesting standard SETI detection software onBL data; testing the KLT method on BL data;developing pulsar and FRB search pipelines;testing pulsar and FRB search pipelines on BLdata; and software tool development for com-bined FRB searches and SETI with the KLTmethod.ReferencesBassa, C., et al. 2016, MNRAS, 456, 2196Magro, A. 2013, PhD dissert., Univ. of MaltaMelis, A., et al. 2016, Proc. SPIE, 9914,99143DMelis, A., et al. 2018, J. Astron. Instrum., 7,1850004Perrodin, D., et al. 2016, arXiv:1608.01839Perrodin, D. & A. Sesana 2017, arXiv:1709.02816Valente, G., et al. 2014, Proc. SPIE, 9153,91530Q

SETI scientific activities in Sardinia:  Search for ET, pulsars and Fast Radio Bursts

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SETI scientific activities in Sardinia: Search for ET, pulsars and Fast Radio Bursts

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