When the most massive stars die, they collapse under their own gravity and leave behind black holes; when stars that are a bit less massive die, they explode in supernovas and leave behind dense, dead remnants of stars called neutron stars. For decades, astronomers have been puzzled by a gap that lies between neutron stars and black holes: the heaviest known neutron star is no more than 2.5 times the mass of our sun, or 2.5 solar masses, and the lightest known black hole is about 5 solar masses. The question remained: does anything lie in this so-called mass gap?

Now, in a new study from the National Science Foundation's Laser Interferometer Gravitational-Wave Observatory (LIGO) and the Virgo detector in Europe, scientists have announced the discovery of an object of 2.6 solar masses, placing it firmly in the mass gap. The object was found on August 14, 2019, as it merged with a black hole of 23 solar masses, generating a splash of gravitational waves detected back on Earth by LIGO and Virgo. A paper about the detection has been accepted for publication in The Astrophysical Journal Letters.

Figure 1.This graphic shows the masses for black holes detected through electromagnetic observations purple), the black holes measured by gravitational-wave observations (blue), the neutron stars measured with electromagnetic observations (yellow), and the neutron stars detected through gravitational waves (orange). GW190814 is highlighted in the middle of the graphic as the merger of a black hole and a mystery object around 2.6 times the mass of the sun. Image credit: LIGO-Virgo/ Frank Elavsky & Aaron Geller (Northwestern)

"We've been waiting decades to solve this mystery" says Vicky Kalogera, a professor at Northwestern University. "We don't know if this object is the heaviest known neutron star, or the lightest known black hole, but either way it breaks a record."

"This is going to change how scientists talk about neutron stars and black holes," says co-author Patrick Brady, a professor at the University of Wisconsin, Milwaukee, and the LIGO Scientific Collaboration spokesperson. "The mass gap may in fact not exist at all but may have been due to limitations in observational capabilities. Time and more observations will tell."

The cosmic merger described in the study, an event dubbed GW190814, resulted in a final black hole about 25 times the mass of the sun (some of the merged mass was converted to a blast of energy in the form of gravitational waves). The newly formed black hole lies about 800 million light-years away from Earth.

Before the two objects merged, their masses differed by a factor of 9, making this the most extreme mass ratio known for a gravitational-wave event. Another recently reported LIGO-Virgo event, called GW190412, occurred between two black holes with a mass ratio of about 4:1.

"It's a challenge for current theoretical models to form merging pairs of compact objects with such a large mass ratio in which the low-mass partner resides in the mass gap. This discovery implies these events occur much more often than we predicted, making this a really intriguing low-mass object," explains Kalogera. "The mystery object may be a neutron star merging with a black hole, an exciting possibility expected theoretically but not yet confirmed observationally.

However, at 2.6 times the mass of our sun, it exceeds modern predictions for the maximum mass of neutron stars, and may instead be the lightest black hole ever detected."

When the LIGO and Virgo scientists spotted this merger, they immediately sent out an alert to the astronomical community. Dozens of ground- and space-based telescopes followed up in search of light waves generated in the event, but none picked up any signals. So far, such light counterparts to gravitational-wave signals have been seen only once, in an event called GW170817. The event, discovered by the LIGO-Virgo network in August of 2017, involved a fiery collision between two neutron stars that was subsequently witnessed by dozens of telescopes on Earth and in space. Neutron star collisions are messy affairs with matter flung outward in all directions and are thus expected to shine with light. Conversely, black hole mergers, in most circumstances, are thought not to produce light.

According to the LIGO and Virgo scientists, the August 2019 event was not seen by light-based telescopes for a few possible reasons. First, this event was six times farther away than the merger observed in 2017, making it harder to pick up any light signals. Secondly, if the collision involved two black holes, it likely would have not shone with any light. Thirdly, if the object was in fact a neutron star, its 9-fold more massive black-hole partner might have swallowed it whole; a neutron star consumed whole by a black hole would not give off any light.

"I think of Pac-Man eating a little dot," says Kalogera. "When the masses are highly asymmetric, the smaller neutron star can be eaten in one bite."

How will researchers ever know if the mystery object was a neutron star or a black hole? Future observations with LIGO and possibly other telescopes may catch similar events that would help reveal whether additional objects exist in the mass gap.

"This is the first glimpse of what could be a whole new population of compact binary objects," says Charlie Hoy, a member of the LIGO Scientific Collaboration and a graduate student at Cardiff University. "What is really exciting is that this is just the start. As the detectors get more and more sensitive, we will observe even more of these signals, and we will be able to pinpoint the populations of neutron stars and black holes in the universe."

"The mass gap has been an interesting puzzle for decades, and now we've detected an object that fits just inside it," says Pedro Marronetti, program director for gravitational physics at the National Science Foundation (NSF). "That cannot be explained without defying our understanding of extremely dense matter or what we know about the evolution of stars. This observation is yet another example of the transformative potential of the field of gravitational- wave astronomy, which brings novel insights with every new detection."

“Thanks to improvements in the Virgo / EGO observatory, in data analysis techniques and in dynamic astrophysical models, areas where the Institut de Ciències del Cosmos de la Universitat de Barcelona (ICCUB) has a relevant role, we hope to be able to detect more events like GW190814 that allow us to understand the exact nature of these intriguing astrophysical objects ”, explains Jordi Portell, coordinator of the Virgo group at ICCUB.

Additional information about the gravitational-wave observatories:

LIGO is funded by the NSF and operated by Caltech and MIT, which conceived of LIGO and lead the project. Financial support for the Advanced LIGO project was led by the NSF with Germany (Max Planck Society), the U.K. (Science and Technology Facilities Council) and Australia (Australian Research Council-OzGrav) making significant commitments and contributions to the project. Approximately 1,300 scientists from around the world participate in the effort through the LIGO Scientific Collaboration, which includes the GEO Collaboration. A list of additional partners is available at https://my.ligo.org/census.php.

The Virgo Collaboration is currently composed of approximately 550 members from 106 institutes in 12 different countries including Belgium, France, Germany, Hungary, Italy, the Netherlands, Poland, and Spain. The European Gravitational Observatory (EGO) hosts the Virgo detector near Pisa in Italy, and is funded by Centre National de la Recherche Scientifique (CNRS) in France, the Istituto Nazionale di Fisica Nucleare (INFN) in Italy, and Nikhef in the

Netherlands. A list of the Virgo Collaboration groups can be found at http://public.virgo-gw.eu/the-virgo-collaboration/. More information is available on the Virgo website at http://www.virgo-gw.eu.

On April the 25th, 2019, the network of gravitational-wave (GW) detectors formed by the European Advanced Virgo, in Italy, and the two Advanced LIGO, in the US, detected a signal, named GW190425. This is the second observation of a gravitational-wave signal consistent with the merger of a binary-neutron-star system after GW170817. GW190425 was detected at 08:18:05 UTC; about 40 minutes later the LIGO Scientific Collaboration and the Virgo Collaboration sent an alert to trigger follow-up telescope observations.

The source of GW190425 is estimated to be at a distance of 500 million light years from the Earth. It is localized in the sky within an area about 300 times broader than was the case for the BNS observed by LIGO and Virgo in 2017, the famous GW170817, which gave birth to multi-messenger astrophysics. However, unlike GW170817, no counterpart (electromagnetic signals, neutrinos or charged particles) has been found to date.

There are a few explanations for the origin of GW190425. The most likely is the merger of a BNS system. Alternatively, it might have been produced by the merger of a system with a black hole (BH) as one or both components, even if light BHs in the mass-range consistent with GW190425 have not been observed. Yet, on the basis solely of GW data, these exotic scenarios cannot be ruled out. The estimated total mass of the compact binary is 3.4 times the mass of the Sun. Under the hypothesis that GW190425 originated from the merger of a BNS system, the latter would have been considerably different to all known BNS in our galaxy, the total mass range of which is between 2.5 and 2.9 times the mass of the Sun. This indicates that the NS system that originated GW190425 may have formed differently than known galactic BNSs.

"After the surprise of the initial results", says Alessandro Nagar of the Istituto Nazionale di Fisica Nucleare (INFN) of Turin, Italy, "we have finally reached a reliable understanding of this event. Although predicted theoretically, heavy binary systems like those that might have originated GW190425 may be invisible through electromagnetic observations."

"While we did not observe the object formed by the coalescence, our computer simulations based on general relativity predict that the probability that a BH is formed promptly after the merger is high, about 96%", says Sebastiano Bernuzzi of the University of Jena, Germany.

Gamma-ray bursts (GRBs) are brief and extremely powerful cosmic explosions, suddenly appearing in the sky, about once per day. They are thought to result from the collapse of massive stars or the merging of neutron stars in distant galaxies. They commence with an initial, very bright flash, called the prompt emission, with a duration ranging from a fraction of a second to hundreds of seconds. The prompt emission is accompanied by the so-called afterglow, a less brighter but longer-lasting emission over a broad range of wavelengths that fades with time. The first GRB detected by the MAGIC telescopes, known as GRB 190114C, reveals for the first time the highest energy photons measured from these objects.

This ground-breaking achievement by MAGIC provides critical new insight for understanding the physical processes at work in GRBs, which are still mysterious. The photons detected by MAGIC must originate from a process hitherto unseen in the afterglows of GRBs, clearly distinct from the physical process that is known to be responsible for their emission at lower energies.

MAGIC detection and multi-wavelength observations of GRB 190114C

On January 14th, 2019, a GRB was discovered independently by two space satellites: the Neil Gehrels Swift Observatory and the Fermi Gamma-ray Space Telescope. The event was named GRB 190114C, and within 22 seconds, its coordinates in the sky were distributed as an electronic alert to astronomers worldwide, including the MAGIC Collaboration, which operates two 17m diameter Cherenkov telescopes located in La Palma, Spain. Since GRBs appear at unpredictable locations in the sky and then rapidly fade, their observation by telescopes such as MAGIC requires a dedicated follow-up strategy.

An automatic system processes in real time the GRB alerts from satellite instruments and makes the MAGIC telescopes point rapidly to the sky position of the GRB. The telescopes were designed to be very light and capable of fast repointing: despite the weight of 64 tons each, they can reach and start observing any given position in the sky in just about 25 seconds. MAGIC was able to start the observation of GRB 190114C just 50 seconds after the beginning of the GRB.

The analysis of the resulting data for the first tens of seconds reveals emission of photons in the afterglow reaching teraelectronvolt (TeV) energies, that is, a trillion times more energetic than visible light. During this time, the emission of TeV photons from GRB 190114C was 100 times more intense than the brightest known steady source at TeV energies, the Crab Nebula. In this way, GRB 190114C became the record setter as the brightest known source of TeV photons. As expected for GRB afterglows, the emission faded quickly with time, similar to the afterglow emission that had been known at lower energies. The last glimpses were seen by MAGIC half an hour later.

For the very first time, the unambiguous detection of TeV photons from a GRB was announced by the MAGIC Collaboration to the international community of astronomers just a few hours after the satellite alerts, after a careful check of the preliminary data. This facilitated an extensive campaign of multi-wavelength (MWL) follow-up observations of GRB 190114C by over two dozens of observatories and instruments, providing a full observational picture of this GRB from the radio band to TeV energies. In particular, optical observations allowed a measurement of the distance to GRB 190114C. It was found that this GRB is located in a galaxy from which it took 4.5 billion years for the light to reach the Earth.

Highest energy photons from a newly revealed emission process

Although TeV emission in GRB afterglows had been predicted in some theoretical studies, it had remained observationally elusive for a long time, despite numerous searches at TeV energies over the past decades with various instruments, including MAGIC. What physical mechanism is behind the production of the TeV photons finally detected by MAGIC? Antonio Stamerra, the Deputy Spokesperson of the MAGIC collaboration, points out: "These energies are much higher than what can be expected from synchrotron radiation, caused by high-energy electrons spiraling in magnetic fields. This process is understood to be responsible for the emission that had been previously observed at lower energies in GRB afterglows. These new results, together with the very comprehensive MWL data, provide the first unequivocal evidence for an additional, distinct emission process in the afterglow”. Lara Nava, scientist associated with the MAGIC collaboration, adds: “ From our study, the most likely origin of the TeV emission is the so-called inverse Compton process, where a population of photons are significantly kicked up in energy by colliding with high energy electrons”.

“After more than 50 years since GRBs were first discovered, many of their fundamental aspects still remain mysterious”, says Razmik Mirzoyan, the Spokesperson of the MAGIC Collaboration. “The discovery of gamma-ray emission from GRB 190114C in the new, TeV window of the electromagnetic spectrum shows that the GRB explosions are even more powerful than thought before. The wealth of new data on GRB 190114C acquired by MAGIC and the extensive MWL follow-up observations now offer important clues to unravel some of the mysteries concerning the physical processes at work in GRBs”.

A comparative study of all previous GRB observations by MAGIC suggests that GRB 190114C was not a particularly unique event except for its relative proximity (light took 4.5 billion years to reach the Earth), and that the successful detection owes to the excellent performance of the instrument. "MAGIC has opened a new window to study GRBs", says Susumu Inoue, the coordinator of the MAGIC Transients working group most involved in the project. "Our results indicate we may be able to detect many more GRBs at TeV energies. This will pave the way for a much deeper understanding of these fascinating cosmic explosions."

Advanced Virgo and the two Advanced LIGO detectors have been taking science data continuously since the 1st of April, 2019, when they began their third observation period, named O3. Together, they form the most sensitive global gravitational-wave observatory to date.

During the past six months, the network has operated with all three of the interferometers active concurrently for 44% of the time. Candidate signals have been identified from as far as 17 billion light years away, as was the case with the candidate event of the 6th of July, 2019 (more information is available here).

O3 has proven very rich in terms of alerts. A total of 31 candidate events have been recorded so far, and the LIGO-Virgo Collaboration has issued several public alerts, which are freely accessible at the Gravitational Wave Candidate Event Database. The alerts facilitate follow-up observations by other telescopes (e.g. electromagnetic and neutrino) and enhance the extraordinary potential of multi-messenger observations, pioneered with the GW170817 event.

During the first and second observation runs - O1 and O2 - ten mergers of binary black holes and one merger of a binary neutron star were identified by the LIGO-Virgo Collaboration (more information here). Since the beginning of O3, the LIGO-Virgo Collaboration has identified approximately one binary merger candidate a week. Preliminary results suggest that the majority are mergers of binary black holes. Detailed analysis is ongoing to understand the properties of all the candidates.

"There have been so many triggers!", says Giuseppe Greco - post-doctoral researcher at the University of Urbino and collaborator at the Istituto Nazionale di Fisica Nucleare (INFN) in Italy - enthusiastically. "It was really exciting to issue so many candidate events. They triggered an extraordinary effort by scientists from all over the world".

"After the alerts are sent, work continues to fully assess whether they are true gravitational-wave detections and to extract all available physics information from the data. The quest for the discovery of a new type of source is extremely motivating", says Marie-Anne Bizouard, CNRS researcher at the Observatoire Côte d’Azur, in France, and Burst Source Group co-chair. "Compact binary system mergers are not the only gravitational-wave source the data analysis groups are working on, day and night, either."

Nicolas Arnaud, a CNRS researcher, currently seconded to the European Gravitational Observatory (EGO), also points out that, "Candidate gravitational-wave events keep the Detector Characterization Group permanently on the look-out. Alerts can pop up at any time, including nights and weekends. Each time Virgo is part of such a trigger, we need to quickly assess the quality of our data. This is one of the inputs required to decide whether the alert will go public or should be retracted. Shifters on duty for a week use tailored automated software and growing expertise to vet the events."

During O3, the interferometers have been left almost undisturbed, in order to maximise the amount of data collected. For Advanced Virgo, the only interruptions have been to allow for weekly maintenance and calibration and sum to an average of around 20 hours per week.

The Virgo and LIGO Scientific Collaborations have, however, agreed to pause O3 for a month, as of the 1st of October. For Advanced Virgo, the break will be used to improve the performance achieved during the O3 run, both in terms of sensitivity to gravitational-waves and duty cycle - the extent to which the interferometers are taking useful science data. O3 will then restart on the 1st of November and will run until the 30th of April, 2020.

"After six months of continuous data-taking, the interferometer needs a check-up", says Matteo Tacca, researcher at Nikhef in The Netherlands and the Virgo Commissioning Coordinator. "Acquiring data for such a long period is not only exciting for gravitational-wave searches, but it is also helpful from the instrumental point of view.

"We can analyse the data that have been produced by the instrument while it was undisturbed, in order to better understand its behaviour. We already have some useful indications for further studies, which may help to improve the instrument. During this break, we will make some hardware upgrades to fix a few issues we have found relating to the stability of the machine. We will also have the opportunity to hunt for some technical noise sources that impact upon the detector sensitivity."

When the O3 pause concludes at the start of November, Advanced Virgo and LIGO should be even better placed to continuously acquire useful science data for another 6 months.

The Virgo and LIGO detectors are ready to start the new Observing run called O3.The hunt for gravitational waves is set to start on April 1st.

3rd Observations Run

The European Virgo detector, based in Italy at the European Gravitational Observatory (EGO), and the NSF-funded LIGO twin detectors, located in the states of Washington and Louisiana (USA), will start to take data next week. This one-year collaboration will register science data continuously, and the three detectors will operate as a global observatory. Since August 2017, the end of the second observation run O2, the two collaborations have intensively worked on their interferometers to improve the sensitivity and reliability.

In 2015, after LIGO began observing for the first time in an upgraded program called Advanced LIGO, it soon made history by making the first direct detection of gravitational waves. The ripples traveled to Earth from a pair of colliding black holes located 1.3billion light-years away - a discovery which led to the award of the 2017 Nobel Prize in Physics. Since then, the LIGO-Virgo detector network has uncovered nine additional blackhole mergers and one explosive smashup of two neutron stars.

“With our three detectors now operational at a significantly improved sensitivity, the global LIGO-Virgo detector network is expected to make several new detections. Moreover it will allow precise triangulation of the sources of gravitational waves. This will be an important step towards our quest of multi-messenger astronomy”, says Jo van den Brand of Nikhef (the Dutch National Institute for Subatomic Physics) and VU University Amsterdam, who is the spokesperson for the Virgo collaboration.

The detector sensitivity is commonly given in terms of the distance at which it can observe the merger of a binary neutron star system. “During O2 Advanced Virgo could observe neutron star events up to a distance of 88 million light years, and Virgo sensitivity has now improved by a factor of 2 over O2”, says Alessio Rocchi, researcher at INFN and Virgo’s commissioning coordinator.

The scientific outcome of O3 is expected to be tremendous, and it will potentially reveal new exciting signals coming from new sources, such as the merger of mixed binaries made by a black hole and a neutron star. O3 will also target long lasting gravitational waves produced for instance by spinning neutron stars which are not symmetric with respect to their axis. However, thedetection of such signals, as well as those from core collapse supernova and other sources, is still an enormous challenge. Nevertheless, thanks to the upgrades of Virgo and LIGO, signals for the merger of binary black holes -such as for GW150914, the first gravitational-wave event ever detected- are expected to become quite common, up to one per week. Scientists also expect to observe perhaps up to tens of binary neutron star mergers, such as GW170817 which opened the era of multi-messenger astronomy as well as providing insights into binary evolution, nuclear physics, cosmology and fundamental physics.

Updating and testing

Since August 2017 both LIGO and Virgo have been updated and tested. Scientists have improved their offline and online data analysis and developed further the procedures for releasing Open Public Alerts: these will within minutes notify the physics and astronomy community when a potentia lgravitational-wave event is observed.

Virgo has fully replaced the steel wires which were used in O2 to suspend the four main mirrors of the 3 km long interferometer: the mirrors are now suspended with thin fused-silica (‘glass’) fibers, a procedure which has allowed toincrease the sensitivity in the low-medium frequency region, and has a dramatic impact in the capabilities to detect mergers of compact binary systems.

A second major upgrade was the installation of a more powerful laser source, which improves the sensitivity at high frequencies. Last but not least, squeezed vacuum states are now injected into Advanced Virgo thanks also to a collaboration with the Albert Einstein Institute in Hannover. This technique takes advantage of the quantum nature of light and improves the sensitivity at high frequencies.

Squeezing is a major upgrade also implemented in the two LIGO interferometers in the US for this next observation run. Moreover, the laser power has been doubled tomore precisely measure the effect of passing gravitational waves. Other upgrades were made to LIGO’s mirrors at both locations, with a total of five of eight mirrors being swapped out for better-performing versions.

Network of international contributions

During O3 the LIGO-Virgo Collaboration will continue to communicate new findings to the scientific community as well as to the general public. Furthermore, scientists will keep on extracting all possible physics results from the data. The global LIGO-Virgo network will provide prompt localizations of gravitational-wave signals and will release confident events publicly through the Open Public Alert system. This will maximize the science that the entire scientific community can do with the gravitational-wave detections and to minimize the chance of missing any electromagnetic or neutrino counterparts.

The Japanese detector KAGRA is expected to join the global LIGO-Virgo network in the last part of O3, extending the detection and pointing capabilities of the global network.

Five groups in Spain are contributing to LIGO-Virgo gravitational wave astronomy, in areas that range from theoretical modelling of the astrophysical sources to improving the detector’s sensitivity for current and future runs. Two groups, in UIB and IGFAE-USC, are within the LIGO Scientific Collaboration; the University of Valencia (UV), ICCUB and IFAE are Virgo members. After the wonderful discoveries brought by the first two observing runs, the Spanish LIGO-Virgo Groups are eagerly looking forward to the imminent O3 run.

A research team from the Institute (ICCUB) will help processing and analyzing vast amounts of data from O3 more efficiently and reliably. Massive data handling and cutting-edge instrumentation and electronics expertise is being transferred to Virgo, knowledge emerging from the successful ICCUB participation in high-energy physics LHCb and large astronomical surveys as Gaia. In this way, multidisciplinary ICCUB experts will contribute to the detection and analysis of gravitational waves, providing both instrumentation and software. Furthermore, they will contribute with data analysis and their large scientific know-how especially in the field of cosmology.

The gravitational physics group at UIB will follow a broad scientific program to study gravitational waves emitted from black holes and neutron stars. The team will continue leading searches for continuous wave signals from unknown neutron stars, as well as for the transient signals emitted after the merger of two neutron stars. Models of the gravitational wave signal from merging black holes are an essential part of the data analysis process, and the UIB is involved in the development of one of the two key models used so far, the value of which will be tested in making new discoveries.

The IGFAE Gravitational Wave group at the University of Santiago de Compostela is currently significantly upgrading the PyCBC detection pipeline to maximize the reach of binary searches in the new O3 network. The group will also be involved in deducing information about the populations of gravitational-wave sources as a whole, including hints that the dozens of likely new binary black hole detections will give on the formation and evolution of these so far mysterious systems.

The Valencia Virgo Group is anticipating the promise of O3 to increase the number of detections of binary neutron star systems and, perhaps, yield the first observations ever of systems yet undetected such as mixed black hole - neutron star mergers and (however unlikely due to the low gravitational-wave amplitude and event rate) core-collapse supernova explosions. Astrophysical sources like neutron stars and supernova progenitors are the main focus of the Valencia Virgo Group, regarding wave form modelling through numerical relativity simulations, parameter estimation, and data analysis.

The High Energy Physics Institute IFAE was already playing an important role in the commissioning of the interferometer prior to O3 started. This energetic involvement will continue in aspects related to operations and the upgrade of the interferometer. IFAE is working on the construction of new baffles instrumented with photo sensors around the testmasses in the suspended areas, allowing for a much more efficient alignment andfine-tune of the parameters of the interferometer during operations.

LIGO is funded by NSF and operated by Caltech and MIT, which conceived of LIGO and led the Initial and Advanced LIGO projects. Financial support for the Advanced LIGO project was led by the NSF with Germany (Max Planck Society), the U.K. (Scienceand Technology Facilities Council) and Australia (Australian Research Council-OzGrav) making significant commitments and contributions to the project. Nearly 1300 scientists from around the world participate in the effort through the LIGO Scientific Collaboration, which includes the GEO Collaboration. A list of additional partners is available at https://my.ligo.org/census.php.

EGO-Virgo Media Contacts:

INFN Press Office

Antonella Varaschin, Eleonora Cossi

+39 06 6868162

antonella.varaschin@presid.infn.it ; eleonora.cossi@presid.infn.it

CNRS Press Office

Clémence EPITALON

Clemence.EPITALON@cnrs.fr + 33 1 44 96 40 35

Nikhef Press Office

Martijn Van Calmthout

martijn.van.calmthout@nikhef.nl

Livia Conti

Virgo Outreach Coordinator

livia.conti@pd.infn.it , +39 049 8068 826

Valerio Boschi

EGO Outreach Coordinator

valerio.boschi@ego-gw.it; +39 050 752 463

Isabel Cordero-Carrión

University of Valencia

Valencia Virgo Group Outreach Coordinator

isabel.cordero@uv.es; +34 963543233

Sebastian Grinschpun

IFAE Outreach Officer

sgrinschpun@ifae.es; +34 93 170 2723

Esther Pallarés Guimerà

Institute of Cosmos Sciences (University of Barcelona) Communication Office

estpallgui@icc.ub.edu; 934020146

LIGO Media Contacts:

Kimberly Allen

Director of Media Relations and

Deputy Director, MIT News Office

allenkc@mit.edu; +1 617-253-2702

Whitney Clavin

Senior Content and Media Strategist

Caltech Communications

wclavin@caltech.edu; +1 626-395-1856

John Toon

Institute Research and Economic Development Communications

Georgia Institute of Technology

john.toon@comm.gatech.edu; +1 404-894-6986

Amanda Hallberg Greenwell

Head, Office of Legislative and Public Affairs

National Science Foundation

agreenwe@nsf.gov; +1 703-292-8070

Andreu Perelló Ferrando

Servei de Comunicació, Promoció i Imatge

Universitat de les Illes Balears

andreu.perello@uib.cat

Tel. +34 971 17 34 74 / 971 17 25 51/ 620 881 284

Ricardo Rodriguez

Chief Operating Officer

IGFAE, University of Santiago de Compostela

ricardojulio.rodriguez@usc.es

+34 881 81 40 68

IGFAE Outreach team

outreach@igfae.usc.es

On Wednesday, 10 October 2018, more than 200 guests from around the world gathered on the northern array site of the Cherenkov Telescope Array (CTA) to celebrate the inauguration of the first prototype Large-Sized Telescope (LST). The telescope, named LST-1, is intended to become the first of four LSTs on the north site of the CTA Observatory, which is located on the existing site of the Instituto de Astrofisica de Canarias’ (IAC’s) Observatorio del Roque de los Muchachos located in the municipality of Villa de Garafia on the island of La Palma. The plan for the site also includes 15 Medium-Sized Telescopes (MSTs). .

It was on 9 October 2015 that the first stone-laying ceremony took place for the LST-1. After the telescope foundation was completed in January 2017, the team moved swiftly and steadily toward its next major milestones: installation of the center pin and rails (September 2017), mounting of the dish (December 2017). In 2018, the LST-1 structure was completed in February and the camera support structure was installed in June. The final step, the camera installation, was completed on 25 September 2018.

The LST team consists of more than 200 scientists from ten countries: Brazil, Croatia, France, Germany, India, Italy, Japan, Poland, Spain and Sweden. In this truly international effort, the design and management leadership was shared among LAPP, Annecy, France; Max Planck Institute for Physics, Munich, Germany; INFN, Italy; ICRR, University of Tokyo, Japan; and IFAE, Barcelona and CIEMAT, Madrid, Spain. Among the participating centers in the construction there is also the Institute of Cosmos Sciences of the University of Barcelona (ICCUB) and the Institute of Sciences of the Space ICE (IEEC-CSIC).

Figure 2.Pedro Duque, Minister of Science, Innovation and Universities; Xavier Luri, director of the ICCUB; Josep Maria Paredes, Director of the FQA department and Domènec Espriu, Vice-Rector for Research of the University of Barcelona .

Three Catalan research centers have had an important participation in the technological development of the LST-1. The Institute of High Energy Physics (IFAE) has been responsible for coordinating, controlling and assembling the camera of the LST-1 as well of the design and assembling of the mechanical system that allows the telescope to rotate and anchoring it to the ground. The Institute of Cosmos Sciences of the University of Barcelona (ICCUB) has contributed to the design of one of the signal amplification devices. The Institute of Space Sciences, ICE (IEEC-CSIC), has participated in the development of control software and scheduler. All three institutions have contributed to the definition of the scientific objectives of the project.

In addition to the LST, two other classes of telescope are required to cover CTA’s full energy range from 20 gigaelectronvolt (GeV) to 300 teraelectronvolt (TeV): Medium-Sized Telescopes and Small-Sized Telescopes. Because gamma rays with low energies produce a small amount of Cherenkov light, telescopes with large mirrors are required to capture the images. Four LSTs will be arranged at the centre of both the northern and the southern hemisphere arrays of the Observatory to cover the low-energy sensitivity of CTA between 20 and 150 GeV.

The LST has a 23-metre diameter parabolic reflective surface, which is supported by a tubular structure made of reinforced carbon fibre and steel tubes. A reflective surface of 400 m2 collects and focuses the Cherenkov light into the camera, where photomultiplier tubes convert the light in electrical signals that can be processed by dedicated electronics. Although the LST-1 stands 45 metres tall and weighs around 100 tonnes, it is extremely nimble, with the ability to re-position within 20 seconds to capture brief, low-energy gamma-ray signals.

CREDIT: Iván Jiménez (IAC)

Figure 2.LST Prototype, the LST-1

The LSTs will expand the science reach to cosmological distances and fainter sources with soft energy spectra. Both the re-positioning speed and the low energy threshold provided by the LSTs are critical for CTA studies of transient gamma-ray sources in our own Galaxy and for the study of active galactic nuclei and gamma-ray bursts at high redshift.

The prototype is foreseen to become the first LST telescope of CTA, and, in fact, the first telescope on a CTA site, to be operated by the CTA Observatory (CTAO). As any other technical delivery in the large, multinational CTA project, the LST-1 will need to undergo a critical design review to verify that the design complies with CTA science goals, operational needs, safety standards, etc. before it is formally accepted by CTAO.

The second Sonar transmission to be sent into Luyten Star b will take place on May 14, 15 and 16. This potentially inhabitable exoplanet is 12,4 light years far from Earth, about 120 billion kilometres. This action is part of the project Sonar Calling, which counts on the participation of the researchers from the Institute of Space Studies of Catalonia (IEEC). Among those are Jordi Portell, researcher at the Institute of Cosmos Sciences of the UB (ICCUB-IEEC), who was in charge of the message design, coding and coordination of the consignment.

Sonar Calling is the first series of radio transmissions sent to a near potentially inhabitable exoplanet. There has been a total of thirty-eight 10-second musical pieces by artists related to the festival that summarize the exploring essence of Sonar over its twenty-five years of existence. The response could arrive in about twenty-five years more, with the 50th anniversary of Sonar. In this case, Luyten Star b was chosen as its target because it is the closest one having a potentially inhabitable, which is known and is visible from the north hemisphere. All transmissions are sent from the European Incoherent Scatter Scientific Association antenna (EISCAT), in Tromsø (Norway). This transmission has been carried out in collaboration with the Canadian astrophysicist Yvan Dutil.

How to communicate with potential extra-terrestrials?

Transmissions have a series of tutorials for the potential extra-terrestrials, which intend to explain things about humans without having to understand a whole new language. These tutorials are based on self-decodable messages, which display a progressive introduction of concepts and information on mathematics, physics, humanity and cosmos. In 1999, Professor Dutil, together with Stéphane Dumas (1970-2016), created a small dictionary of symbols and concepts, each described with an image of a few pixels. The tutorial section in the sent message in Sonar Calling shows the different concepts little by little, as if we were teaching a baby how to speak. The last part of the tutorials, in which Jordi Portell (ICCUB-IEEC) participated, is necessary to understand the digital music –created by our artists, and has an illustration and practical demonstration of the concepts of digital music and simple sounds.

In order to discover the artistic and scientific aspects of this initiative, Sonar 2018 will be included in the “Sonar Calling GJ273b Control Room by Absolut”, which will be available in the space Sonar by Day. Also, framed within the international conference Sonar+D, there will be a conference given by the researchers who took part in the project, and ICCUB researcher Xavier Luri will carry out a workshop on the analysis of astronomical data for creative applications.

La Universitat de Barcelona i el Banc Santander, a través de Santander Universitats, han renovat avui el seu conveni de col·laboració i han signat un acord específic sobre les activitats que volen desenvolupar en el marc de la Unió Iberoamericana d'Universitats.

El rector de la Universitat de Barcelona, Joan Elias, i el president de Santander Universitats, Matías Rodríguez, han signat els acords en un acte a l'Edifici Històric de la UB en el qual també s'han presentat alguns dels èxits aconseguits fins ara amb la col·laboració entre les dues institucions. Així, hi han intervingut el vicerector Àlex Aguilar, per parlar dels projectes vinculats a la projecció i internacionalització de la Universitat; Jaume Valls, director del Barcelona Institut d'Emprenedoria (BIE), i Jordi Portell, coordinador de la Unitat Tecnològica de l'Institut de Ciències del Cosmos (ICCUB).

L'acord recull els programes de suport i impuls a la recerca i la transferència, de manera que es promogui la captació de talent i alhora es doni suport a la millora d'equipaments. També hi ha programes orientats a la conservació del patrimoni, al desenvolupament de les tecnologies de la informació i les comunicacions i a l'impuls de la transformació digital. Així mateix, es destaca un programa de potenciació i consolidació de la internacionalització, inclosa la projecció internacional de la Universitat així com la mobilitat i formació internacional dels estudiants, professorat, investigadors i el personal administratiu i tècnic de la Universitat. L’acord també preveu un projecte dedicat a la dimensió emprenedora de la Universitat i el suport a les activitats de les càtedres de la UB. A més, segons aquest conveni, el Santander facilitarà a la UB la col·laboració tecnològica, operativa i de gestió amb l'objectiu de contribuir a l'eficiència de la gestió acadèmica i administrativa de la UB, així com enriquir l'oferta de serveis a la comunitat universitària.

El president de Santander Universitats, Matías Rodríguez, ha destacat: «El Santander s'honora de donar suport a projectes com els que ens han presentat avui: la missió Gaia, les activitats de la Unió Iberoamericana d'Universitats o el Barcelona Institut d'Emprenedoria». Així mateix, ha felicitat el rector i el seu equip pel mèrit que té que «la Universitat de Barcelona, amb un pressupost tan limitat com el que té, ocupi posicions tan bones en els rànquings i se situï entre les 200 millors universitats del món».

Per la seva banda, el rector de la UB ha afirmat que «la visió d'Emilio Botín va ser determinant a l'hora d'impulsar la relació entre el Banc Santander i la Universitat de Barcelona, perquè des del primer moment va considerar que la UB era estratègica», i ha remarcat «l'esforç mutu de les dues institucions durant aquests anys, generant sinergies, per aconseguir l'excel·lència». Finalment, Elias ha mostrat el seu desig que el Santander segueixi donant suport a la Universitat de Barcelona com ho ha fet fins ara».

Les dues parts també han signat un acord relatiu a la Unió Iberoamericana d'Universitats (UIU), xarxa que integren les universitats de Barcelona, Buenos Aires, Complutense de Madrid, Nacional Autònoma de Mèxic i São Paulo. La UIU va néixer el 2016 amb l'objectiu de tenir una veu coordinada en els temes que afecten les universitats signants d'aquesta aliança i que són primordials per a Iberoamèrica en l'àmbit del coneixement. La UIU, que té el patrocini de Santander Universitats, s'implica en activitats que promoguin la recerca, prioritzin la seva qualitat i l'avenç del coneixement, i el progrés i benestar de la societat, en particular del desenvolupament de les societats iberoamericanes. En l'acord bilateral que ara signa amb la UB, Santander Universitats dona suport econòmic a activitats acadèmiques conjuntes amb els altres integrants de la UIU.

Banco Santander, empresa que més inverteix en suport a l'educació en el món (Informe Varkey/UNESCO–Fortune 500), manté més de 1.200 acords de col·laboració amb universitats i institucions acadèmiques de 21 països a través de Santander Universitats i, a través de la xarxa Universia, agrupa a més de 1.300 institucions acadèmiques iberoamericanes.