
In 2017, the Nobel Prize in Physics was awarded for the direct detection of gravitational waves – ripples in spacetime produced by the merger of compact astronomical objects like black holes or neutron stars. This major breakthrough has opened up new opportunities for fundamental physics that go far beyond the study of compact objects. In particular, present and upcoming gravitational wave interferometers offer unprecedented possibilities for unraveling the nature of the mysterious dark matter that appears to permeate the universe on all scales. Dark matter is known to exist in one form or another – we see its gravitational effects everywhere in the universe on the scale of galaxies and beyond – but its fundamental nature remains unknown.

In their proposal, __Gianfranco Bertone__ and __Samaya Nissanke__ – leading experts on dark matter and gravitational waves – propose new methods to robustly discriminate gravitational wave signatures of dark matter from other astrophysical signals. With the team of two additional scientific researchers that the ENW-M grant allows them to set up, the grant makes it possible to infer dark matter models and parameters from upcoming gravitational wave interferometers, paving the way for searches that will be performed with the [LISA space interferometer](https://www.grappa.amsterdam/news/green-light-for-dutch-lisa-contribution) over the next decade. This will allow the team to get closer to solve one of the biggest mysteries of the Universe: ‘What is dark matter?’
For more information, see: [ENW-M grants](https://www.nwo.nl/en/news/nineteen-innovative-research-projects-launched-through-open-competition-domain-science-m-programme)

SOURCE: Press release NWO

GRAPPA physicists Gianfranco Bertone and Samaya Nissanke receive NWO ENW-M2 grant for their research project "Searching for dark matter with gravitational waves"

DM spike

GRAPPA physicists Gianfranco Bertone and Samaya Nissanke have received an NWO ENW-M2 grant for their research project ‘Searching for dark matter with gravitational waves’ to develop new methods to distinguish different possible forms of dark matter.

## LISA
The Laser Interferometer Space Antenna (LISA) consists of three spacecraft that, starting in 2035, will follow the Earth in its orbit around the Sun. By continuously measuring their relative distances, the detectors will detect gravitational waves coming from elsewhere in the universe. In this way, LISA’s arms cover a distance of 2.5 million kilometres, allowing the detector to measure gravitational waves of longer wavelengths than its terrestrial counterparts.

__Samaya Nissanke__, one of the UvA (GRAPPA) astrophysicists involved in the project, says: ‘LISA will allow us to ‘listen’ to what happens in space. We can hear echoes of the big bang and the first black holes that populated the universe, and follow the chaotic trajectories of stars that are devoured by black holes. These will be marvelous tests of Einstein’s general theory of relativity.’

## Dutch Contribution
The consortium, led by space research institute SRON, consists of many partners. Besides UvA and Nikhef, the universities of Nijmegen, Leiden, Utrecht, Maastricht and Groningen are involved, as is TNO. Together, they will build photo diodes (LISA’s ‘eyes’), software, the pointing mechanism and the electronics to read out its data.

Michael Wise, SRON director, professor by special appointment of Observational High-Energy Astrophysics at UvA and one of the driving forces behind the proposal, explains: ‘Pointing LISA is not straightforward. The directions have to be extremely precise, since every laser needs to hit a lens about 2.5 million kilometres away. Moreover, the light takes 8 seconds to reach that point, and in the mean time the detectors move. It is like pointing a laser from Amsterdam to hit a small coin dropping from the Eiffel tower in Paris, at the precise moment it hits the ground.’

The photo diodes must also be extremely sensitive. They have to detect the laser light, emitted with 1 Watt of power – comparable to a table lamp – but arriving with over a billion times less, around 250 picoWatts.

Finally, developing the software is a challenge in itself. The software has to be able to distinguish all different types of gravitational waves, coming from all possible directions, that continuously make the spacecraft vibrate with different frequencies and amplitudes.

## Dutch Interest
‘The Dutch contribution to LISA is very important,’ Gijs Nelemans, one of the leaders of the LISA-NL consortium, says. ‘Dutch scientists will gather unique expertise, and the access to all data will help us build a lead in the only existing way into a completely new field of research.’

The institutes that are involved will collect knowledge and insight into how to develop such extremely precise techniques. In this way, they will support and strengthen their candidacy to build, together with German and Belgian partners, the Einstein Telescope – another gravitational wave detector that is projected to be built in the region where the Netherlands, Germany and Belgium meet.

SOURCE: Press release NWO / SRON / Nikhef

Green light for Dutch LISA-contribution

LISA

A Dutch consortium in which UvA researchers Samaya Nissanke and Michael Wise are involved, received a €12 million Road Map grant that allows the consortium to become an important partner in the LISA mission of ESA and NASA.

The European Research Council (ERC) has awarded a Synergy Grant, named “BlackHolistic”, of 14 million Euro to a team of Dutch, British, Finnish, and Namibian astronomers to make colour movies of black holes. The team, among whom Professor Sera Markoff of the University of Amsterdam, will build the first ever African millimetre-wave radio telescope in Namibia to achieve their goal. The telescope will take part in the global Event Horizon Telescope network that became famous for making the first image of a black hole. The new grant will help to transform this network from making still images towards making movies and to understand black holes across the entire Universe.
Over the course of six years, astronomers Heino Falcke (Radboud University), __Sera Markoff__ (API, GRAPPA, University of Amsterdam) and Rob Fender (Oxford University) will conduct research on black holes from different perspectives. Black holes are icons of the fundamental nature of gravity, the mysterious force shaping the Universe. They are also the Universe’s most efficient power houses, turning infalling gas into energy and outflows that, together with gravity, help mould galaxies and ultimately stars and planets. The Principal Investigators (PIs) bring together complementary expertise over the entire black hole mass scale in combining radio imaging with monitoring across the entire electromagnetic spectrum, astroparticle physics, and theoretical modelling to bear on the problem.
*‘Via the ‘BlackHolistic’ Synergy Grant, we will try to understand what goes on just outside the event horizon of black holes. We need a better grasp of how the complicated physics of plasmas leads to the radiation and high-energy particles we observe, before we can do things like further test theories of gravity. At the same time understanding all of that will help us develop a complete picture of how black holes affect their environments on the largest scales,’* says __Sera Markoff__.
The challenge in understanding the astrophysics of black holes and their impact on the cosmos is that they span >8 orders of magnitude in mass, size, and timescales, and emit light over 15 orders of magnitude in frequency. The new approach overcomes this scale separation by simultaneously addressing the dynamics of large and small black holes, in colour, i.e. across the entire electromagnetic spectrum.  
Rob Fender: *‘With this funding we will take existing and future EHT observations and compare them with multi-frequency observations of black holes across the electromagnetic and mass spectrum. These data sets will allow us, for the first time, to understand the entire process of black hole accretion and jet formation from launch to termination. We will truly bring about a new paradigm for black hole research.’*

__Africa Millimetre Telescope__

The Synergy Grant centres around the construction of the Africa Millimetre Telescope (AMT) in Namibia. The first millimetre-wave telescope in Africa will be located at or near the Gamsberg Mountain in the Khomas Highlands. This will give it a unique vantage point with which the telescope will join the Event Horizon Telescope (EHT) network. The EHT collaboration published the first images of two supermassive black holes in 2019 and 2022, respectively. 
*‘We played a leading role in making the first image of a black hole and captured the imagination of scientists and the public alike. Since then, the Event Horizon Telescope has made a major expansion effort, but Africa has been missing in this global network.  Now we can fill this glaring gap and bring these black hole pictures to life, in full colour,’* says Heino Falcke. 
Located in the southern hemisphere, the AMT will have a particularly good view of the black hole in the centre of our Milky Way and will be a crucial link between telescopes in Europe, South and Latin America, as well as the South Pole. The team will also look for flashes of mm-wave emission from cosmic explosions, providing a new window to transient phenomena in the Universe. Construction and operation of the telescopes is also supported by a 12 million Euro guarantee from Radboud University over 10 years.  

__Partners__

The lead investigators will work together with partners in Namibia and Finland. Researchers at the University of Namibia (UNAM) will support the construction and operation of, and science with, the AMT. They will also support the implementation of a social impact plan which focuses on skills and knowledge development in science and engineering in Namibia. The project will support several Master level and doctoral students via fellowships. *‘With the AMT, we will continue our investigation of supermassive black holes and their multi-wavelength emission properties. It will complement and build-upon the world-leading astrophysics research that has been conducted from Namibia with the H.E.S.S. telescopes during the past 20 years,’* comments Michael Backes, head of the Namibian H.E.S.S. group and of astrophysics research at UNAM.
With the AMT, researchers at the University of Turku, Finland, will collaborate with the leading team to obtain high cadence observations of supermassive black holes, particularly during flaring phases that produce gamma rays and possibly neutrinos, allowing a unique new multi-messenger approach. *‘We are excited by the chance to collaborate, and to provide our expertise on long-term, high-cadence monitoring of supermassive black holes, and connections to gamma rays via the upcoming Cherenkov Telescope Array (CTA) project,’* says Elina Lindfors from University of Turku, who has served also as Science Coordinator for CTA.

__Source__

[(News) Anton Pannekoek Institute - University of Amsterdam](https://api.uva.nl/content/news/2022/12/erc-synergy.html?origin=r67NetATRQ2YmqT5f7LpUQ "API-News")

Astronomers receive ERC Synergy Grant to make colour movies of black holes and build new telescope in Africa

ERC synergy grant awardees including GRAPPA faculty Sera markoff.

ERC synergy awardees

ERC synergy grant of 14 million euros awarded to astronomers including GRAPPA faculty Sera Markoff for building mm radio telescope in Africa.

  The center of our galaxy is blowing a pair of colossal bubbles of gamma
radiation (magenta structures in the image above) that span a whopping
50,000 light-years across. Discovered with the Fermi Gamma-ray Space Telescope about a decade ago, the source of this hourglass-shaped phenomenon remains unclear.
![sgr oscar new](//images.ctfassets.net/g94voriuozkd/AEWdZnjydLcqqFXO38xxp/4542f783f7f3ac2ec50e285529874cfe/sgr_oscar_2.png)

> Fig. Gamma-ray image of the Fermi bubbles (blue) overlaid on a map of RR Lyrae stars (red) observed by the GAIA telescope. The shape and orientation of the Sagittarius (Sgr) dwarf match perfectly well those of the Fermi cocoon – a bright substructure of gamma-ray radiation in the southern part of the Fermi bubbles. This is strong evidence that the Fermi cocoon is due to energetic processes occurring in Sagittarius, which from our perspective, is located behind the Fermi bubbles.  [Image: Crocker, **Macias**, Mackey, Krumholz, **Ando**, Horiuchi et al. (2022)].

These Fermi bubbles are patched with a few enigmatic substructures of
very bright gamma-ray emission. One of the brightest spots, the so-called
Fermi cocoon, is found in the southern lobe and was originally thought to be due to past outbursts from the galaxy’s supermassive black hole. 
**Shin’ichiro Ando** and **Oscar Macias** at the Gravitation Astroparticle Physics Amsterdam (GRAPPA) institute, (and colleagues) analyzed data from GAIA and  Fermi space telescopes to reveal that the Fermi cocoon is actually
due to emission from the Sagittarius dwarf galaxy. This satellite galaxy of the Milky Way is seen through the Fermi Bubbles from our position on Earth (see figure). Due to its tight orbit around our galaxy and previous passages through the galactic disk, it has lost most of its interstellar gas and many of its stars have been ripped from its core into elongated streams. Given that Sagittarius is completely quiescent — it has no gas, and no stellar nurseries —  there are only a few possibilities for its gamma-ray emission, including: 
- a population of unknown millisecond pulsars or 
- dark matter annihilations. 

Millisecond pulsars are the remnants of certain types of stars, significantly more massive than the Sun, that are in close binary systems, but now blast out cosmic particles as a result of their extreme rotational energies. The electrons fired by millisecond pulsars collide with low-energy photons of the Cosmic Microwave Background propelling them to high-energy gamma radiation. 
Crocker, **Macias**, and collaborators have convincingly demonstrated that the
gamma-ray cocoon is explained by millisecond pulsars in the Sagittarius
dwarf and that the dark matter hypothesis is strongly disfavored.
This discovery sheds light on millisecond pulsars as efficient accelerators of highly-energetic  electrons   and  positrons.   It  also   suggests   that  similar physical processes could be ongoing in other dwarf satellite galaxies of the Milky Way. This is highly significant because dark matter researchers have long believed that an observation of gamma rays from a dwarf satellite would be a smoking gun signature for dark matter annihilation.
This study compels a reassessment of the high energy emission capabilities
of quiescent stellar objects, such as dwarf spheroidal galaxies, and their role as prime targets for dark matter annihilation searches.

Gamma-ray emission from the Sagittarius dwarf spheroidal galaxy due to millisecond pulsars

Small satellite galaxy of the Milky Way – called Sagittarius – has been observed from Earth through giant lobes of gamma radiation (aka the Fermi bubbles).

Crocker, Macias, and collaborators have convincingly demonstrated that the gamma-ray cocoon in the Fermi bubbles is explained by millisecond pulsars in the Sagittarius dwarf and that the dark matter hypothesis is strongly disfavored.

Astronomers have unveiled the first image of the supermassive black hole at the centre of our own Milky Way galaxy. This result provides overwhelming evidence that the object is indeed a black hole and yields valuable clues about the workings of such giants, which are thought to reside at the centre of most galaxies. The image was produced by a global research team called the Event Horizon Telescope (EHT) Collaboration, using observations from a worldwide network of radio telescopes.

The image is a long-anticipated look at the massive object that sits at the very centre of our galaxy. Scientists had previously seen stars orbiting around something invisible, compact, and very massive at the centre of the Milky Way. This strongly suggested that this object — known as Sagittarius A* (Sgr A*, pronounced "sadge-ay-star") — is a black hole, and today’s image provides the first direct visual evidence of it.

Further details can be found in the official [press release](https://eventhorizontelescope.org/blog/astronomers-reveal-first-image-black-hole-heart-our-galaxy).

Astronomers Reveal First Image of the Black Hole at the Heart of Our Galaxy

First image of the black hole at the centre of the Milky Way

MW BH image

Astronomers have unveiled the first image of the supermassive black hole at the centre of our own Milky Way galaxy.

"Millisecond Pulsars from Accretion Induced Collapse naturally explain the Galactic Center Gamma-ray Excess", reports a team of astrophysicists including GRAPPA fellow *Oscar Macias*. The paper published in Nature Astronomy can be found [here](https://www.nature.com/articles/s41550-022-01658-3).  

Gamma-ray data from the Fermi-Large Area Telescope reveal an unexplained, apparently diffuse, signal from the center of the Milky Way. The origin of this “Galactic Center Excess” has been debated with proposed sources prominently including self-annihilating dark matter.  However, recent studies have put forward evidence supporting the claim that this excess could have an astrophysical source. It was pointed out that old and fast spinning neutron stars called millisecond pulsars could also be responsible for the signal.  If the Millisecond Pulsar interpretation holds, the Galactic Center Excess would be evidence of a new population of astrophysical sources in the center of the Galaxy which would help shed light on the star formation history of the Milky Way.  

Hitherto, much of the discussion regarding the plausibility of the millisecond pulsar interpretation has been based on the ‘recycling’ scenario where an old neutron star, formed originally via a core-collapse supernova, accretes material from a binary companion, in an X-ray binary phase, and is spun up to millisecond periods. In our study we focus on a millisecond pulsar formation channel which produces more than half of all millisecond pulsars: accretion induced collapse. The birthrate of accretion induced collapse pulsars has been previously shown to be comparable or even larger than the traditional core-collapse supernovae by various studies.

We investigated the accretion-induced-collapse scenario where an oxygen-neon white dwarf  acquires mass from its binary companion (typically low mass) through accretion up to the Chandrasekhar limit (∼ 1.4 solar masses) and subsequently collapses to form a neutron star. During the collapse, the rotational angular momentum of the collapsing white dwarf is conserved, resulting in the formation of a neutron star spinning with, or close to, millisecond periods. Magnetic flux conservation during the white dwarf collapse leads to extremely high final neutron star magnetic field strength. However, just as in the conventional recycling scenario involving core-collapse, neutron stars created via accretion-induced-collapse may also undergo further accretion from a binary companion star in a low-mass X-ray binary  phase. Millisecond pulsars formed through this process do not receive any significant natal kick on birth as compared to natal kicks imparted to neutron stars resulting from core-collapse supernovae (because of an asymmetrical explosion mechanism). It is important to note that half of the approximately 300 known millisecond pulsars are detected in globular clusters which have shallow gravitational potentials. Pulsars retained in globular clusters cannot have formed with large natal kicks since these clusters have small escape velocities. Thus, millisecond pulsars born via accretion-induced-collapse are likely to remain trapped in the bulge gravitational potential, allowing for a large population to build up over its history and proffering an explanation of the detailed match between bulge stellar and Galactic center excess morphologies. 

In this paper we used the Binary Stellar Evolution ([BSE](https://ui.adsabs.harvard.edu/abs/2013ascl.soft03014H/abstract)) algorithm to evolve binary star systems as our model population. The code considers a very complete list of physical processes including accretion torques and angular momentum loss due to gravitational wave radiation, to predict the spin evolution of the pulsars throughout the history of the Galaxy. The model created in the framework of our new study shows that the integrated gamma-ray emission of a population of millisecond pulsars can explain both the spectrum and total luminosity of the Galactic center excess. Interestingly, millisecond pulsars could also explain other outstanding puzzles in high-energy astrophysics: the gamma-ray signal from our closest neighbor galaxy, Andromeda, [could also be produced by a population of millisecond pulsars](https://arxiv.org/pdf/2204.00636.pdf). At the same time, we believe that emissions from a population of millisecond pulsars could also contribute to the mysterious Microwave Haze detected in the interior of our galaxy. In 2012, this strange Haze was detected using the European Space Agency's (ESA) Planck space observatory. It appears as a non-thermal diffuse emission from the region surrounding the galactic center. A definitive explanation for this phenomenon has not yet been found, but our study sheds light on its origin. 


Millisecond Pulsars from Accretion Induced Collapse naturally explain the Galactic Center Gamma-ray Excess 

Artist's rendition of accretion on to a highly magnetized neutron star

Accretion on to a highly magnetized neutron star

Cassiopeia A is the remnant of an exploded star in the Cassiopeia constellation, about 11,000 light years away from us. Light from the explosion should have reached Earth for the first time around 1670. However, there was too much gas and dust around the star for the explosion to be seen with the naked eye or with the then very basic telescopes. The Cassiopeia A explosion nebula is expanding at an average rate of 4000 to 6000 kilometres per second and has a temperature of about 30 million degrees Celsius. The expansion is most likely occurring in gas that was blown out by the star long before the explosion. Cassiopeia A is now about 16 light years across.

## 19 years of data

The researchers, led by GRAPPA member Jacco Vink analysed 19 years of data from the Chandra X-ray Observatory. This is an American X-ray satellite with Dutch spectrometers that orbits the Earth in a high elliptical orbit. The scientists observed that on the western side of Cassiopeia A, the inner regions of the explosion nebula are not expanding, but moving inwards. The researchers also took measurements of the acceleration or deceleration of the outer shock wave. This outer shock wave turned out to accelerate in the west instead of decelerating as was expected.

“The backward movement in the west can mean two things,” says Jacco Vink. “Either there is a hole somewhere, a kind of vacuum, in the supernova material, causing the hot shell to suddenly move inwards locally. Or the nebula has collided with something.” From the models of Vink and his colleagues, a collision appears most likely. The computer models predict that after a collision, the shock first decreases in speed but then accelerates. “Exactly as we have measured,” says Vink.

## Italian group

The collision scenario was also investigated recently by an Italian group with whom Vink collaborates. They suspect that the shock wave collided with a shell of gas particles. This shell would have been created when the unexploded star blew away an irregular wind of gas particles at the end of its life.

The cooperation between Vink and the Italians did not happen out of the blue. The Italian group got to work on preliminary results that Vink showed at a conference in 2019. “When we recently found an acceleration and they predicted just that in their models, the puzzle pieces fell into place,” says Vink.

Cassiopeia A has attracted a lot of attention lately. For example, NASA’s new X-ray satellite IXPE published its first image of the exploded star on Valentine’s Day. And the James Webb Space Telescope will turn its infrared gaze to the supernova remnants later this year.

[Read the prepint](https://arxiv.org/abs/2201.08911).

Ejection nebula of supernova Cassiopeia A does not expand evenly

Ejection nebula


Astrophysicists and GRAPPA member Jacco Vink has received an NWO Large Investment grant in the amount of 1.5 million euros from the Netherlands Organisation for Scientific Research (NWO). The grant money will enable the Netherlands to develop and manufacture highly specialised cameras for the future southern Cherenkov Telescope Array (CTA), which is scheduled for construction in northern Chile. Jacco Vink will implement this project together with astronomers and physicists from the University of Amsterdam (GRAPPA members Sera Markoff and Christoph Weniger), the University of Groningen (Manuela Vecchi and Andrey Baryshev) and the NOVA lab located at the latter.

The array of 50 telescopes will indirectly measure the gamma-ray photons (particles of light) that enter our atmosphere and then generate a cloud composed mainly of electrons that are moving at close to the speed of light. This causes the electrons to emit a bluish light known as Cherenkov radiation. CTA’s telescopes register this nanosecond-long flashes of blue light and identify the direction in which the electron cloud is moving. In doing so, the CTA actually uses the atmosphere as a detector: the larger the portion of the atmosphere that is being looked at, the more sensitive the CTA is. And when the same flash is detected using multiple telescopes, it is possible to much more accurately determine the direction in which the electron cloud is moving. This, in turn, enables the scientists to more precisely identify the direction of the original gamma-ray photon as well. That is why they use so many telescopes.

Measuring the flash from multiple angles enables them to reconstruct the direction from which the gamma rays came and how much energy the gamma ray photon had. In this way, the location of a gamma ray source can be pinpointed to a precision of 0.1% of the lunar diameter, while images can be made with a pixel size of 10% of the lunar diameter. Known sources of gamma rays include jets created by black holes, the remnants of supernovas and neutron stars, though it might also be emitted when neutron stars merge and set off gravitational waves. Massive particles of dark matter can emit gamma rays as well. CTA hopes to shed new light on the composition of this mysterious and dark component of the universe.

CTA is a European project with international partners including the United States, Japan and Australia. While Dutch astronomers have been involved in the scientific plans for CTA for some time, countries are required to contribute to the array’s construction before they can participate in the CTA observation project. Thanks to the NWO Large grant, the Netherlands will now be able to make such a contribution. The Dutch project will be led from within the UvA, in close cooperation with the University of Groningen and the NOVA lab it hosts, which specialises in the development and construction of astronomical detectors via serial production. This NOVA team will build the detectors for the 50 telescopes that are meant to enable CTA to measure extremely high-energy gamma rays between 10 and 100 tera-electronvolts (TeV). 

More information can be found at [IoP](https://iop.uva.nl/shared/uva/en/news/news/2021/05/jacco-vink-to-use-large-grant-to-seek-out-the-sources-of-gamma-rays.html?origin=LiCYSg5eS82AR0H56Byw2A) and [NOVA](https://www.astronomie.nl/nieuws/jacco-vink-gaat-met-grote-subsidie-op-jacht-naar-de-bronnen-van-gammastraling-2820).

Jacco Vink to use large grant to seek out the sources of gamma rays

Gamma-rays as measured by the HESS array on the night sky over Namibia, with one of the small HESS telescopes in the foreground.

facero-hess-space

GRAPPA member Jacco Vink received an NWO Large Investment grant for €1.5M that will enable the Netherlands to develop and manufacture highly specialised cameras for the future southern Cherenkov Telescope Array (CTA).

Physicist Dr Samaya Nissanke of GRAPPA, the University of Amsterdam and Nikhef will receive the prestigious Suffrage Award for outstanding science, science communication and support of women in STEM. Dr Nissanke and eleven other awardees will be honored at an online celebration on Monday 8 March 2021, the tenth anniversary of the scheme. This will be the fifth Suffrage Science awards for the Engineering and Physical Sciences.

Professor Amina Helmi, University of Groningen, who nominated Dr Samaya Nissanke, University of Amsterdam and Nikhef, said: “Samaya is an excellent researcher focusing on a very hot topic in modern Astrophysics, namely on gravitational waves (Nobel Prize 2017) and how they tell us about the merger of pairs of neutron stars and black holes. She was part of the discovery of the first ever binary neutron star merger that was seen by gravitational waves by the international LIGO and Virgo collaboration in 2017. She was in fact part of the writing team for the discovery paper and was responsible for coordinating the follow-up from many different observatories. Not only is she an outstanding scientist, but she is also a fervent and devoted advocate of diversity and inclusion in science, and beyond. She is the chair of Netherlands Astronomy Equity and Inclusion Committee, which she helped set up.”

On International Woman’s Day in 2011, the inaugural cohort of eleven ‘Suffrage Scientists’ from the life sciences were recognised in a ceremony at the Institute of Contemporary Arts, London. Their awards were hand-crafted items of jewellery created by art students from Central Saint Martins-UAL, who worked with scientists to design pieces inspired by research and by the Suffragette movement. But rather than produce a new set of pieces for the next awards, each holder chose who they would like to pass their award onto, thus generating an extensive ‘family tree’ of incredible scientists and communicators.

Suffrage Science pioneer Professor Fisher said: “We dreamed up the awards scheme to celebrate the contribution that women have made to science, which often gets overlooked. This is as important now as it was ten years ago. This year’s awardees join a community of over 148 women scientists. I’m thrilled that since 2011, the awards have travelled from the UK, across Europe to the USA, Hong Kong, Iran and to Ghana, illustrating the international nature of science and engineering, and the global effort to improve the representation of women in STEM.”

Samaya Nissanke receives Suffrage Science Award

Samaya Nissanke speaking at Breakthrough Prize Symposium

Physicist Dr Samaya Nissanke of GRAPPA, the University of Amsterdam and Nikhef will receive the prestigious Suffrage Award for outstanding science, science communication and support of women in STEM. 

We are pleased to announce two GRAPPA Postdoctoral Fellows who will be starting from fall 2021. They are Lionel London (postdoc at MIT) and Oscar Macias (postdoc at Kavli IPMU). We are very excited and look forward to welcoming and working with them in the very near future!

## Lionel London
![Lionel London](//images.ctfassets.net/g94voriuozkd/sQUP3aamPLSD92Ix6N5mR/e69d594f3b79897566e662405c7b8f3c/LionelLondon-768x769.png)

Lionel London earned his PhD in Physics at the Georgia Institute of Technology under the supervision of Deirdre Shoemaker. There he specialized in using simulations of binary black hole collisions to model gravitational waves from binary black hole mergers. He has since gone on to work as a postdoc at Cardiff University, and at MIT. His research to date has been impactful in tests of gravity as well as the detection and parameter estimation of astrophysical black hole mergers. His work combines General Relativity theory and numerics with insights from computer science and pure maths. 

As a member of the LIGO-Virgo-KAGRA collaboration, London is involved in efforts at the intersection of signal modelling, parameter estimation, and tests of General Relativity.

London says, “I am excited about solving puzzles related to black holes, general relativity, and the fundamental structure and story of the universe. My research aims to tackle some of the big questions in these topics. I want to know if it is possible to understand the nonlinear structure of black hole merger, and whether we use this understanding to learn more about the Universe from exotic theories of gravity to cosmology. During my time at GRAPPA I hope to make progress on these topics and thereby contribute to what we can learn from current Earth based experiments like LIGO, Virgo and KAGRA, as well as future detectors such as the Einstein Telescope and LISA.”

## Oscar Macias
![Oscar Macias](//images.ctfassets.net/g94voriuozkd/I3sBsHVRrbRkR2fS7d8NG/067482c1d927d40055e0fbbffc851e23/OscarMacias-300x200.png)

Oscar Macias currently holds a postdoctoral position at Kavli IPMU. He was previously a postdoctoral researcher in the Center for Neutrino Physics at Virginia Tech for 2015-2018. Before that, he completed his PhD in Physics from University of Canterbury, where he worked with Chris Gordon on dark matter searches with gamma rays.

Macias says, “I study energetic astrophysical phenomena, with a focus on potential signals from dark matter emission. I apply my expertise in analyzing cosmic rays and multiwavelength electromagnetic signals, my experience with numerical simulations, and my rigorous statistical background to probe the inner workings of the Universe. My work informs the current limitations of dark matter models to explain the observations, improves the sensitivity to dark matter searches by producing better background models, and provides precise probes of the high-energy Universe.”

Macias received his undergraduate degree in Civil Engineering from the National University of Colombia, Medellin in 2008, where he also completed his master degree in Physics in 2011. Before moving to Medellin for his undergraduate studies, he lived in a small village — far away from Colombian cities — which was badly affected by the Colombian internal conflict.

Macias adds, “The challenges I faced in the early stages of my educational path have galvanized my passion for equity, diversity and justice in academia. I plan to design and run workshops aimed at increasing the representation of minorities in Physics and Astronomy.”

GRAPPA Postdoctoral Fellows: Lionel London and Oscar Macias

GRAPPA Fellows

We are pleased to announce two GRAPPA Postdoctoral Fellows who will be starting from fall 2021. They are Lionel London (postdoc at MIT) and Oscar Macias (postdoc at Kavli IPMU).

Astronomers may have found our galaxy’s first example of an unusual 
kind of stellar explosion. This discovery, made with NASA’s Chandra 
X-ray Observatory, adds to the understanding of how some stars shatter 
and seed the universe with elements critical for life on Earth.
This intriguing object, located near the center of the Milky Way, is a
 supernova remnant called Sagittarius A East, or Sgr A East for short. 
Based on Chandra data, astronomers previously classified the object as 
the remains of a massive star that exploded as a supernova, one of many 
kinds of exploded stars that scientists have catalogued. Using longer 
Chandra observations, a team of astronomers has now instead concluded 
that the object is left over from a different type of supernova. It is 
the explosion of a white dwarf, a shrunken stellar ember from a 
fuel-depleted star like our Sun. When a white dwarf pulls too much 
material from a companion star or merges with another white dwarf, the 
white dwarf is destroyed, accompanied by a stunning flash of light.
Astronomers use these “Type Ia supernovae” because most of them mete 
out almost the same amount of light every time no matter where they are 
located. This allows scientists to use them to accurately measure 
distances across space and study the expansion of the universe. Data 
from Chandra have revealed that Sgr A East, however, did not come from 
an ordinary Type Ia. Instead, it appears that it belongs to a special 
group of supernovae that produce different relative amounts of elements 
than traditional Type Ias do, and less powerful explosions. This subset 
is referred to as “Type Iax,” a potentially important member of the 
supernova family.
“While we’ve found Type Iax supernovae in other galaxies, we haven’t 
identified evidence for one in the Milky Way until now,” said Ping Zhou 
of Nanjing University in China, who led the new study while at the 
University of Amsterdam. “This discovery is important for getting a 
handle of the myriad ways white dwarfs explode.”
The explosions of white dwarfs is one of the most important sources 
in the universe of elements like iron, nickel, and chromium. The only 
place that scientists know these elements can be created is inside the 
nuclear furnace of stars or when they explode.

Astronomers are still debating the cause of Type Iax supernova 
explosions, but the leading theory is that they involve thermonuclear 
reactions that travel much more slowly through the star than in Type Ia 
supernovae. This relatively slow walk of the blast leads to weaker 
explosions and, hence, different amounts of elements produced in the 
explosion. It is also possible that part of the white dwarf is left 
behind.
UvA researcher Ping Zhou and GRAPPA member Jacco Vink are co-authors of the [paper](https://arxiv.org/abs/2006.15049), and more details can be found on [Harvard's Chandra website](https://chandra.harvard.edu/photo/2021/sgrae/ "Harvard Chandra website") and [NASA's website](https://www.nasa.gov/mission_pages/chandra/images/rare-blast-s-remains-discovered-in-milky-way-center.html "NASA's Chandra website").

Rare Blast’s Remains Discovered in Milky Way Center

X-ray & radio image of Sagittarius A East

Rare Blast

This discovery, made with NASA’s Chandra  X-ray Observatory, adds to the understanding of how some stars shatter  and seed the universe with elements critical for life on Earth.

We are happy to announce a new GRAPPA postdoctoral fellowship position. We invite applications for a GRAPPA Postdoctoral Fellowship position in the areas of Astroparticle Physics, Cosmology, and Gravitation. Established in 2012, GRAPPA Institute strives for revealing fundamental aspects of the universe and laws of physics. The GRAPPA Fellowship has been our flagship postdoctoral program, which fully ensures academic freedom to pursue any theoretical and experimental research subjects that are of relevance to the GRAPPA’s scientific focus.

Deadline for application is 20 December and we encourage applications from people of diverse backgrounds and underrepresented groups.

All details can be [found on the UvA website](https://www.uva.nl/en/content/vacancies/2020/12/20-756-grappa-postdoctoral-fellowship.html).


Opening of GRAPPA Postdoctoral Fellowship!

We are happy to announce a new GRAPPA postdoctoral fellowship position. We invite applications for a GRAPPA Postdoctoral Fellowship position in the areas of Astroparticle Physics, Cosmology, and Gravitation.

The Dutch Black Hole Consortium (DBHC), which includes several GRAPPA members, has been awarded a grant of € 4.9 million by the Dutch Research Council (NWO) as part of the National Science Agenda. This new interdisciplinary consortium aims to further unravel the mysteries surrounding black holes and the wider universe.

Astronomers and physicists are joining forces to make new discoveries about black holes, using the Event Horizon Telescope, the international project that took the first direct image of a black hole last year, and via gravitational waves, where geologists are also ‘delving into the ground’ for the potential underground construction of the planned gravitational wave detector Einstein Telescope. The consortium will work with universities of applied sciences to develop new educational materials aimed at sparking interest in science among people of all backgrounds and especially children. Lead applicant Stefan Vandoren from Utrecht University: ‘This is an excellent project in which we are combining research, technology and the interests of society.’

The Dutch Black Hole Consortium is made up of researchers from the fields of theoretical physics, astronomy and geology, technicians working on the next generation of gravitational wave detectors and researchers of science communication and science history, combined with teacher training courses and museums. The UvA researchers who are part of the consortium are Sera Markoff, Jan de Boer, Franke Linde, Ralph Wijers, Alejandra Castro, Jeroen van Dongen, Erik Verlinde, Alessandro Bertollini, Sarah Caudill and Samaya Nissanke from the Anton Pannekoek Institute (API), Institute of Physics (IOP) and GRAPPA.

Sera Markoff, who sits on the Consortium Board: ‘We are excited to launch this interdisciplinary project in order to enhance our understanding of the nature of black holes, while also conveying our enthusiasm about our discoveries to the public through museums and outreach projects.’

The consortium is made up of 31 applicants from universities and universities of applied sciences and six partners from industry, museums and government. More information can be found on the [UvA news page](https://www.uva.nl/en/shared-content/subsites/anton-pannekoek-instituut-voor-sterrenkunde/en/news/2020/11/black-hole-consortium-granted-49-million-euros-from-nwa.html).


The Dutch Black Hole Consortium receives €4.9 million in funding

blackhole small

The Dutch Black Hole Consortium (DBHC), which includes several GRAPPA members, has been awarded a grant of € 4.9 million by the Dutch Research Council (NWO) as part of the National Science Agenda.


Altair, a project launched by GRAPPA member astronomer Sera Markoff, has been awarded the NWO Diversity Initiative Award. The project introduces primary school children to astronomy and physics. The Diversity Initiative Award is awarded to initiatives that improve diversity in the field. Initiator Prof. Sera Markoff (University of Amsterdam) will receive € 50,000 to help further develop the project.

Markoff wants to use the award to launch Altair+. ‘The idea is to work together with a team of students and volunteers to develop new activities for secondary school pupils, also at the Science Park in Amsterdam. We want to keep in touch with the Altair “graduates”from the primary school by organising annual activities, which also involve other pupils from nearby schools and their parents. This is a step towards a “pre-academic” programme. This will hopefully result in more students with a non-Western background studying at the Science Park!’

The jury was impressed with how the project successfully promotes the sciences to a wide range of communities. Children from various ethnic backgrounds are taught by UvA academics, and their parents are also involved with a range of activities on the university campus. This project reaches 140 children a year. The jury noted that it is remarkable that Markoff launched the initiative alongside her regular work as Professor of Theoretical Astrophysics.

More information can be found on [Sera's personal site](https://www.seramarkoff.com/2020/12/nwo-domain-science-diversity-initiative-award/?fbclid=IwAR26S5LZLLWCudHzsXwSJ0yFvCaliwSmOzFlFjMcPdMUi1LsmulAK_2ptbY) and on the [IOP news](https://www.uva.nl/en/shared-content/subsites/anton-pannekoek-instituut-voor-sterrenkunde/en/news/2020/12/nwo-diversity-initiative.html?origin=cnUSYqO%2BT4OvERocBmGxmw).

Sera Markoff receives Diversity Initiative Award

iftar

Altair, a project launched by GRAPPA member astronomer Sera Markoff, has been awarded the NWO Diversity Initiative Award. The project introduces primary school children to astronomy and physics.


Dark matter is even more elusive than thought before. This is the main message of a new study by a group of scientists that includes GRAPPA member Shin’ichiro Ando. The results of the new study were published in Physical Review D Rapid Communications this week.

Revealing the nature of dark matter might be achieved by looking for faint signatures coming from pairs of dark matter particles. These pairs may annihilate each other and turn into gamma-ray light that could be observed. Some of the best targets for such a search strategy, using gamma-ray telescopes such as the Fermi satellite, are dwarf spheroidal galaxies – small satellite galaxies that are trapped in the gravitational pull of our own Milky Way. Dwarf galaxies are full of dark matter but little else, meaning they are nearly pristine laboratories to look for the tell-tale signatures of dark matter annihilation without the pesky complications of other astronomical phenomena.

In order to perform the search, the scientists combined theoretical and observational methods to put together the first ‘end to end’ analysis that models the dwarf galaxies in their cosmic context. Shin’ichiro Ando said: “Our method starts at the big bang, follows the evolution of dark matter and the growth of galaxies across cosmic time, and uses this as the basis to understand how dark matter might be distributed within the individual dwarf galaxies we see in the sky today. This understanding is then used as the basis to search for the gamma-ray signal which reveals information about the microscopic properties of dark matter particles.”

In particular, the team concluded that the expected signal of the dark matter annihilation is much weaker than earlier estimates. Simply put: dark matter is harder to detect using dwarf galaxies than previously expected. Adopting the more holistic analysis therefore implies, counter-intuitively, that the gamma-ray data actually tells scientists less about dark matter than they thought it did previously. One immediate consequence is that there is still a possibility that dark matter annihilation explains one of the great current astronomical mysteries — the anomalous and unexplained gamma-ray glow that we see emerging from the center of our own galaxy. Until now, it was difficult to see how dark matter annihilation could power the galactic center anomaly but avoid generating a similar signal from the dwarf galaxies.

The results strongly call for revising one of the key search strategies towards discovery of dark matter particles and the quest for physics beyond the Standard Model. More information can be found at the [IOP news](https://iop.uva.nl/content/news/2020/09/dark-matter-even-more-elusive-than-previously-thought.html?cb), and the paper can be found at [APS journals](https://journals.aps.org/prd/abstract/10.1103/PhysRevD.102.061302).

Dark matter even more elusive than previously thought

sculptor

A consortium of knowledge institutions and public stakeholders, led by UvA physicist Auke Pieter Colijn, was awarded a 1.1 million euro NWA-ORC grant to study so-called ‘relic neutrinos’ that came into existence in the very first second after the Big Bang.

Every second Earth is bombarded with an enormous number of neutrinos from the cosmos. These neutrinos were created in the primordial soup one second after the Big Bang, but they have never been observed. In the proposed research, the consortium will develop an experiment to observe these relic neutrinos by investigating the decay of heavy-hydrogen tritium. The proposed project is called PTOLEMY, and is a new method to measure such low-energy particles. This is particularly difficult because neutrinos hardly interact with ordinary matter, such as a detector. If this is possible with the proposed detector, it will be a groundbreaking result.

Besides the University of Amsterdam, the consortium, for which Auke Pieter Colijn is the coordinator and which also involves UvA physicist Shin’ichiro Ando, consists of the Radboud Universiteit, De Haagse Hogeschool (The Hague University of Applied Sciences), TNO, the Princeton Physics Department, the Laboratorio Nazionale di Gran Sasso (LNGS), the Netherlands’ Physical Society (NNV), Ampulz, and the Karlsruhe Institute of Technology (KIT).

More information can be found at the [IOP news](https://iop.uva.nl/content/news/2020/11/nwa-orc-for-neutrino-observations.html?origin=LiCYSg5eS82AR0H56Byw2A) as well as at the [Nikhef press release](https://www.nikhef.nl/en/news/black-holes-and-the-big-bang-under-scrutiny-in-the-dutch-research-agenda-nwa/).

NWA-ORC for neutrino observations

The Gran Sasso laboratory in Italy, one of the places where the search for relic neutrinos will be performed. Drone image made by Auke Pieter Colijn.

lngs

Pareidolia is a tendency that pushes humans to see shapes in clouds or faces in inanimate objects. The picture shown here is a composition of four cosmic radio sources that can in fact look like a scary monster. To obtain this effect, the sources have been rearranged compared to their original position in the sky but their apparent sizes were preserved.

However, in some sense, these sources are real monsters. Their names are: Cassiopeia A (top left), Taurus A (top right), Cygnus A (center), and Virgo A (bottom). These are the four most powerful radio sources in the northern hemisphere. Historically, the brightest radio sources in the sky were named after the constellation in which they were found followed by a letter starting with an “A”. They were then grouped in the so-called A-team, like the famous TV series from the 80s.

The nature of these four monsters is very diverse. The eyes of the monster (Cassiopeia A and Taurus A) are two supernova remnants: the leftovers of the explosions of two stars in our own Galaxy. The evil pupil that stares at you in Taurus A is the Crab pulsar. The nose of the monster, Cygnus A, is an extremely powerful radio galaxy 600 million light years away, whose two lobes are powered by jets of energetic particles formed near a supermassive black hole. The mouth of the monster (Virgo A) is the extended structure (larger than an entire galaxy) that surrounds the famous supermassive black hole at the centre of the galaxy M87, the same black hole recently imaged by the Event Horizon Telescope.

These four sources are well known to radio astronomers, but this is the first time that they were able to see them in such great detail at the extremely long wavelengths of 5 meters, close to the longest wavelength we can observe with ground instruments. The images used to make the radio monster were obtained with the Low Frequency Array (LOFAR), a pan-European radio telescope made by 52 stations spread across 8 different countries (The Netherlands, Germany, France, UK, Poland, Sweden, Latvia, Ireland, and soon Italy) and coordinated by a supercomputer in Groningen (NL).

GRAPPA member Jacco Vink is one of the co-authors on the paper. [Read the full paper here](https://arxiv.org/pdf/2002.10431.pdf).

LOFAR images cosmic radio monsters

Lofar

The top prize in high-energy astrophysics, the Bruno Rossi Prize 2020, has been awarded to the Event Horizon Telescope team for the landmark image and analysis of the first shadow of a black hole. The UvA-researchers Sera Markoff, Oliver Porth, Doosoon Yoon and Koushik Chatterjee are part of this team.

The American Astronomical Society awards the Rossi Prize in recognition of significant contributions as well as recent and original work in high-energy astrophysics.

The Event Horizon Telescope, is a planet-scale array of eight ground-based radio telescopes that was designed to capture images of black holes. In April 2019, the EHT collaboration announced that it had successfully taken the first picture of the black hole at the center of the Messier 87 galaxy, with the results published in a series of six papers in the Astrophysical Journal Letters. The image, a bright ring formed by light bending around the black hole, quickly circled the globe, appearing across the front pages of newspapers and throughout social media. The 2020 Rossi Prize recognizes this historic scientific achievement.

The prize is in honor of Professor Bruno Rossi, an authority on cosmic ray physics and a pioneer in the field of X-ray astronomy. The Rossi Prize includes an engraved certificate and a 1,500 dollar award. Dr. Doeleman will give a lecture at the 237th AAS meeting in Phoenix, Arizona, in January 2021.

More information can be found on the [AAS website](https://head.aas.org/PR/2020_Rossi_prize).

Top prize in high-energy awarded to Event Horizon Telescope

Samaya Nissanke has been elected as the new spokesperson for the Gravitation and AstroParticle Physics Amsterdam (GRAPPA) centre of excellence at the University of Amsterdam. Nissanke is the successor of Gianfranco Bertone, who was recently appointed director of EuCAPT.

Nissanke is currently an assistant professor at the University of Amsterdam. She is a joint faculty member at the Anton Pannekoek Institute for Astronomy and the Institute for High Energy Physics, and is already a member of GRAPPA.

Nissanke’s predecessor, Gianfranco Bertone, said: ‘I am sure that thanks to her scientific excellence, enthusiasm and leadership, Samaya will shine in this role. I look forward to seeing GRAPPA further strengthening its scientific impact and establishing its presence at the local, national and international level under her leadership.’

Samaya Nissanke elected GRAPPA spokesperson

On July 10, 2019, a group of leading theoretical physicists active in fields of astroparticle physics and cosmology met with representatives of APPEC and CERN to kick-off EuCAPT (European Consortium for AstroParticle Theory), a new initiative that aims to coordinate and favour theoretical astroparticle and cosmology activities in European centres and institutions.

The steering committee of EuCAPT includes internationally renowned scientists affiliated to leading European institutions: Gianfranco Bertone (U. of Amsterdam), Philippe Brax (CEA Saclay), Vitor Cardoso (IST Lisbon), Gian Giudice (CERN), David Langlois (APC Paris), Silvia Pascoli (U. of Durham), Hiranya Peiris (UCL London & OKC Stockholm) Antonio Riotto (U. of Geneva), Subir Sarkar (U. of Oxford), Piero Ullio (SISSA Trieste), Andrew Taylor (DESY Hamburg), Licia Verde (U. of Barcelona). CERN has agreed to act as central hub for EuCAPT, and committed to provide financial and administrative support to its activities.

GRAPPA Spokesperson Gianfranco Bertone, who has been appointed EuCAPT director, said: “EuCAPT is a bottom-up initiative that aims to be open and inclusive. We will soon reach out to to the scientific community and to the broader society, with an invitation to participate in our exciting programme of scientific and outreach activities. Stay tuned!”.

The first EuCAPT activities will include one annual meeting of the entire theoretical astroparticle community that will take place at CERN starting in 2020, and two topical workshops at other participating institutions. More information on EuCAPT activities will be released in September, when the website of the initiative will be be launched.![eucapt-team](//images.ctfassets.net/g94voriuozkd/UxY3D5kr8fCYpglYxO21s/82787f4e50e9ceb2f92aeaed2289dcdf/201906-190_10-960x540.jpg)

Gianfranco Bertone appointed founding director of EuCAPT

We will welcome Kenny Ng to GRAPPA later this year, who has been awarded, together with ten talented researchers, a Marie Skłodowska-Curie Individual Fellowship to conduct research at the University of Amsterdam (UvA). The awarded projects include research on public support for different interpretations of ‘Social Europe’, the transmission of pathogens from animals to humans and metaphorical narratives in discourses on dementia. The awarded fellowships range from 175,000 to 280,000 euros. The grants are awarded as part of the Marie Skłodowska-Curie Actions, which forms part of the European Union’s Horizon 2020 research and innovation programme. The aim of the fellowship is to equip researchers with the necessary skills and international experience to pursue a successful career.

__Kenny Ng’s research will be on understanding the peculiar gamma-ray emission of the sun.__
With space telescopes, we only recently gained the sensitivity to precisely study the gamma rays from the Sun, presumably caused by energetic cosmic particles (cosmic rays) bombarding the Sun. Surprisingly, many properties of these gamma rays are not yet explained. Kenny Chun Yu Ng plans to understand them through new observational and theoretical investigations, which will ultimately help us better understand the Sun itself and the solar system space environment.

Kenny Ng will collaborate with Dr Shin’ichiro Ando here at GRAPPA.

Kenny Ng to join GRAPPA on a Marie Curie Individual Fellowship

*If upcoming direct searches discover the elusive dark matter in the universe, they may be able to measure the mass of the particle or the way it interacts with ordinary matter, but can only do both if we’re lucky, researchers from the UvA Institute of Physics argue.*

It is one of the great open questions of modern-day physics and astronomy: what is the mysterious dark matter in the universe? Astronomers suspect that the universe contains much more matter than they can see through there telescopes – simply because there is much more gravity than visible matter can account for. So far, however, nobody has been able to find particles that this dark matter can be made of.

## Rare interactions

Yet, many astronomers and particle physicists are optimistic that a dark matter candidate particle can be found soon, in the next generation of experiments and observations. While this may be true, Amsterdam researchers now point out that even if such a new dark matter particle is found, this does not automatically mean that we will immediately know all of its properties.

In their investigation, the researchers looked at planned underground detectors which aim to detect dark matter by looking for its rare interactions with ordinary atomic nuclei. The as yet undiscovered dark matter particle has an unknown mass (how heavy it is) and an unknown cross section (how strongly it interacts with nuclei).

Using new statistical tools, inspired by a concept known as ‘information geometry’ that the same researchers developed earlier this year, the physicists mapped out what a discovery would look like, without assuming a particular dark matter particle mass or cross section – allowing to explore a wide range of these dark matter properties.

## New materials and techniques

It was found that a discovery using multiple different target materials that the dark matter particle can interact with, will substantially improve the measurement of the dark matter properties. However, even with multiple detectors, it will be hard to measure the mass of heavy dark matter particles and at the same time understand their precise interactions. Only over a narrow range of properties can both of these things be measured simultaneously.

This result, which was accepted for publication in Physical Review Letters last week, should spur the dark matter community to explore new detector materials and techniques which will improve the prospects for pinning down the properties of the dark matter particle in the event of a future discovery.

## Reference

[Assessing near-future direct dark matter searches with benchmark-free forecasting](https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.121.181101), Thomas D. P. Edwards, Bradley J. Kavanagh, and Christoph Weniger, Physical Review Letters 2018. ([arXiv preprint](https://arxiv.org/abs/1805.04117)


Mass or interaction, but not both

In a Nature review article published this week, physicists Gianfranco Bertone (GRAPPA, UvA) and Tim Tait (UvA and UC Irvine) discuss the past accomplishments and the current status of dark matter search experiments and how they will shape the future efforts for dark matter searches.

More information can be found at the [IOP news](http://iop.uva.nl/content/news/2018/10/a-new-era-in-the-quest-for-dark-matter.html), [Nature article](https://www.nature.com/articles/s41586-018-0542-z), and
[pre-print version](https://arxiv.org/abs/1810.01668).![Dark Matter cloud](//images.ctfassets.net/g94voriuozkd/6ojL747fXb0a6QJrfrQpNX/f10a98f6a8fa47c4dd54ac5985b9fe35/DM_visual.png)

A new era in the quest for dark matter

Observations of the gamma-ray radiation from the Galactic center region with the Fermi Large Area Telescope have revealed a mysterious diffuse and extended emission. Discovered almost 10 years ago, this emission generated a lot of excitement in the particle physics community, since it had all the characteristics of a long-sought-after signal from the self-annihilation of dark matter particles in the inner Galaxy. Finding such a signal would confirm that dark matter, a substance that so far has only been observed through its gravitational effects on other objects, is made out of new fundamental particles. Moreover, it would help to determine the mass and other properties of these elusive dark matter particles. However, recent studies show that arguably the best astrophysical interpretation of the excess emission is a new population in the Galactic bulge of thousands of rapidly spinning neutron stars called millisecond pulsars, which have escaped observations at other frequencies up to now.

![Dark matter annihilation](//images.ctfassets.net/g94voriuozkd/4XLWlHy1djlVcVKNd9YHcp/f97292f38ac197294854c9a588ea9092/grappa_news1.png)
__Figure 1.__ Observed gamma-ray emission from the Galactic disk, with the bulge region indicated. The insets show the expected profiles of excess radiation coming from dark matter and stars respectively. The researchers were able to show that the stars profile matches the measurements much better than the dark matter profile.

## Where there are stars, there is radiation
‘Understanding in detail the morphology [the location and shape] and spectrum [the combined frequencies] of the excess emission is of vital importance for discriminating between the dark matter and astrophysical interpretations of the Galactic Center excess radiation.’, says Christoph Weniger, one of the researchers that conducted the study. A new study by researchers at the University of Amsterdam and the Laboratoire d’Annecy-le-Vieux de Physique Théorique, a research unit of the French Centre National de la Recherche Scientifique, found strong evidence that the emission actually seems to come from regions where there is also a large amount of stellar mass in the Galactic bulge (the ‘boxy bulge’) and center (the ‘nuclear bulge’). Furthermore, the researchers found that the light-to-mass ratio in the Galactic bulge and center are mutually consistent, so that the gamma-ray GeV emission is a surprisingly accurate tracer of stellar mass in the inner Galaxy – see figure 2. This study was based on a new analysis tool, SkyFACT (Sky Factorization with Adaptive Constrained Templates), developed by the researchers themselves, which combines physical modeling with image analysis.

![Stellar mass and gamma-ray luminosity comparison](//images.ctfassets.net/g94voriuozkd/4mtzHNAsmNbya01E4lChbH/4cafc910b6e75738fd851889350beb63/grappa_news2.png)
__Figure 2.__ Comparison of the stellar mass (horizontal axis) and gamma-ray luminosity (vertical axis) for the “boxy bulge” (in blue) and for the “nuclear bulge” (in green). The prediction for a population of millisecond pulsars in the Galactic disk (in red) and the bulge of the nearby Andromeda galaxy (M31, in pink) are also shown. Stellar mass and luminosity are proportional to each other in the inner Galaxy (dashed line), which shows that the mysterious excess radiation very likely has a stellar origin and is not coming from dark matter.

The findings support the millisecond pulsar interpretation of the excess emission, since neither a dark matter signal nor other astrophysical interpretations are expected to show such a correlation. ‘The results will help guide upcoming radio searches for this hidden population of millisecond pulsars in the Galactic bulge with MeerKAT and the future Square Kilometre Array’, said Francesca Calore, another of the paper’s authors. ‘This makes these upcoming searches even more promising.’

### Reference

R. Bartels, E. Storm, C. Weniger and F. Calore, The Fermi-LAT GeV excess traces stellar mass in the Galactic bulge, Nature Astronomy 2018.


Another blow for the dark matter interpretation of the Galactic Center Excess

In January 2018, UvA-IoP/GRAPPA researchers Shin’ichiro Ando and Bradley Kavanagh led a team of 9 bachelors students to investigate radiative neutrino decay and its impact on the cosmic microwave background. They set precise constraints on the neutrino lifetime, which was found to be orders of magnitude longer than the age of the universe. More information can be found at the [IOP news][1].

[1]: http://iop.uva.nl/content/news/2018/07/bachelor-workshop-results-in-publication-on-neutrino-decay.html?origin=%2BmF538O4Qz6cnSjy3y%2FYlA

Bachelor workshop results in publication on neutrino decay

Bachelors students with key staff

UvA-IoP/GRAPPA researchers Shin’ichiro Ando and Bradley Kavanagh led a team of 9 bachelors students to investigate radiative neutrino decay and its impact on the cosmic microwave background.

We are delighted to welcome [Samaya Nissanke](https://samayanissanke.wordpress.com/) as a faculty member at GRAPPA, shared between [IHEF](http://iop.uva.nl/ihef/ihef.html) and [API](http://api.uva.nl/). Samaya’s current research focuses on the detection, measurement and interpretation of gravitational waves, the astrophysics of compact object (black holes, neutron stars and white dwarfs) binaries, and general relativity.
Samaya expressed her excitement by stating, “I am very excited to be joining the GRAPPA department and building a new dynamic gravitational wave and multi-messenger astrophysics group here. It is an incredible time to be working in strong-field gravity astrophysics thanks to the recent gravitational wave detections, time-domain electromagnetic surveys and astroparticle experiments, and recent advances in cosmology and computational astrophysics. I am greatly looking forward to the many scientific adventures here, and working with the excellent students, postdocs and staff members in both the physics and astronomy departments at UvA, as well as the nearby Nikhef institute.”
Samaya will start her first day at GRAPPA on June 15. We look forward to her contributions to our intellectual community for many years to come.

Welcome, Samaya Nissanke!

We are delighted to welcome Samaya Nissanke as a faculty member at GRAPPA, shared between IHEF and API.

This year’s TeVPA will be hosted in Berlin, Germany from 27 – 31 August, 2018. TeVPA is a five day conference which aims to bring together leading scientists in the field to discuss recent advances in Astroparticle Physics. Early bird registration closes on July 7, 2018.

TeVPA 2018

This year’s TeVPA, a five-day conference, will be hosted in Berlin, Germany from 27 – 31 August, 2018.

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