From U Wisconsin IceCube Collaboration: “Looking for dark matter in the center of the Milky Way”

U Wisconsin ICECUBE neutrino detector at the South Pole

From U Wisconsin IceCube Collaboration

17 Mar 2020
Madeleine O’Keefe

We know very few things about dark matter: it makes up more than a quarter of all matter and energy in the universe; it clumps in specific pockets of space, like the centers of galaxies, including the Milky Way; and it has gravitational effects on the visible matter that surrounds it. Still, there are many things we want to learn, and since it has yet to be directly detected, scientists must find ways to study dark matter indirectly.

That’s where neutrinos might be able to help. These weakly interacting, nearly massless fundamental particles might be produced (according to some theories) when particles of dark matter annihilate with each other. If these theories are true, neutrino detectors—like the IceCube Neutrino Observatory at the South Pole and ANTARES in the Mediterranean Sea—can look for excess neutrinos coming from known dark matter hotspots. And if these sources produce more neutrinos than expected, it would support the theory that dark matter is connected to Standard Model particles.

So, the IceCube and ANTARES Collaborations recently probed one of these sources—the center of the Milky Way—by combining data from their respective neutrino telescopes. They did not find any unusual excesses of neutrinos, but they put stronger constraints on the dark matter annihilation cross-section averaged over the dark matter velocity. The results of the analysis are outlined in a paper submitted recently to Physical Review D.

This plot shows the upper limit on the thermally averaged self-annihilation cross section obtained by this combined analysis as a function of the dark matter mass for a specific annihilation channel and halo profile assumption. The limits from IceCube, ANTARES, VERITAS, Fermi-MAGIC, and HESS are also presented. Credit: IceCube and ANTARES Collaborations

Anteres Neutrino Telescope Underwater, a neutrino detector residing 2.5 km under the Mediterranean Sea off the coast of Toulon, France

CfA/VERITAS, a major ground-based gamma-ray observatory with an array of four Čerenkov Telescopes for gamma-ray astronomy in the GeV – TeV energy range. Located at Fred Lawrence Whipple Observatory,Mount Hopkins, Arizona, US in AZ, USA, Altitude 2,606 m (8,550 ft)

MAGIC Čerenkov telescopes at the Observatorio del Roque de los Muchachos (Garfia, La Palma, Spain)), Altitude 2,396 m (7,861 ft)

H.E.S.S. Čerenkov Telescope Array, located on the Cranz family farm, Göllschau, in Namibia, near the Gamsberg searches for cosmic rays, altitude, 1,800 m (5,900 ft)

The IceCube Neutrino Observatory is an array of 5,160 optical sensors buried in a cubic kilometer of ice beneath the South Pole. ANTARES (the Astronomy with a Neutrino Telescope and Abyss environmental RESearch project) is made up of 885 similar sensors installed underwater in the Mediterranean Sea off the coast of France. Both experiments detect light that is produced when neutrinos interact with a nucleus in the surrounding medium.

According to Nadège Iovine, an IceCube collaborator from Université Libre de Bruxelles and one of the leads on this analysis, the main motivation for this work was to improve the potential of detecting dark matter–produced neutrinos by combining datasets from the ANTARES and IceCube neutrino experiments. They specifically chose dark matter masses between 50 to 1000 GeV/c^2, a range for which each experiment had already independently obtained limits. The researchers also wanted to confirm that both experiments were operating under the same model assumptions and analysis methods.

So Iovine and her collaborators combined nine years of ANTARES data with three years of IceCube data. These datasets were from previous analyses carried out separately by each collaboration that were optimized for the search for dark matter in the Galactic Center. They then looked for neutrinos that could be produced by the annihilation of dark matter particles through various specific channels and under the assumptions of two different dark matter halo profiles.

They did not find evidence for dark matter; there were no excess neutrinos coming from the Galactic Center. Therefore, the researchers put limits on the dark matter annihilation cross section averaged over the speed of the particle—the thermally averaged dark matter self-annihilation cross section. The combined limits were improvements on the limits previously obtained by each experiment.

Ultimately, the analysis demonstrated the promising potential of combined analyses using datasets from both the ANTARES and IceCube neutrino telescopes. “This work brought to light the differences that can occur between two similar analyses and provides a benchmark for future combined analyses,” says Iovine.

Still, the hunt for dark matter is not over yet. Sebastian Baur, another IceCube scientist from Brussels, says, “With more years of data to come, a better understanding of the detector, and new statistical methods under development, we expect to further improve our results in the near future.”

See the full article here .

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IceCube is a particle detector at the South Pole that records the interactions of a nearly massless sub-atomic particle called the neutrino. IceCube searches for neutrinos from the most violent astrophysical sources: events like exploding stars, gamma ray bursts, and cataclysmic phenomena involving black holes and neutron stars. The IceCube telescope is a powerful tool to search for dark matter, and could reveal the new physical processes associated with the enigmatic origin of the highest energy particles in nature. In addition, exploring the background of neutrinos produced in the atmosphere, IceCube studies the neutrinos themselves; their energies far exceed those produced by accelerator beams. IceCube is the world’s largest neutrino detector, encompassing a cubic kilometer of ice.

IceCube employs more than 5000 detectors lowered on 86 strings into almost 100 holes in the Antarctic ice NSF B. Gudbjartsson, IceCube Collaboration

Lunar Icecube

IceCube DeepCore annotated

IceCube PINGU annotated

DM-Ice II at IceCube annotated

From Harvard-Smithsonian Center for Astrophysics: “Astrophysicists Once Again Seek Public’s Help to Unmask Muons Disguised as Gamma Rays”

From Harvard-Smithsonian Center for Astrophysics

March 14, 2019

Amy Oliver
Public Affairs
Fred Lawrence Whipple Observatory
Center for Astrophysics | Harvard & Smithsonian
amy.oliver@cfa.harvard.edu

Tyler Jump
Public Affairs
Center for Astrophysics | Harvard & Smithsonian
+1 617-495-7462

Minneapolis, MN & Amado, AZ –
Muon Hunters 2: Return of the Ring, launches new Zooniverse citizen science project on March 14th, 2019.

After achieving highly successful results with their citizen science project, Muon Hunters, in 2017, scientists from the VERITAS (Very Energetic Radiation Imaging Telescope Array System) gamma-ray observatory—a part of the Center for Astrophysics | Harvard & Smithsonian at the Fred Lawrence Whipple Observatory in Amado, Arizona, USA—collaboration are once again asking the public for help in identifying hundreds of thousands of ring patterns produced in the cameras at VERITAS.

Scientists use VERITAS to study gamma rays—the most energetic radiation in the universe—in order to explore the most exotic and extreme processes and physical conditions in space, like black holes, supernovae, and pulsars.

Like the original project, Muon Hunters 2: Return of the Ring, will engage citizen scientists to identify patterns from muons—elementary particles like electrons, but heavier—and distinguish them from those produced by gamma rays, which the telescopes are designed to detect.

“At VERITAS, we’re searching for gamma rays, which have the shortest wavelengths and the highest energy of any portion of the electromagnetic spectrum,” said Dr. Michael Daniel, Operations Manager, VERITAS. Muons are background that we have to get rid of so that we can more easily identify gamma rays, but they’re also useful to help us calibrate our telescopes. That’s where Muon Hunters, and the citizen scientists behind it, come in.”

New to Muon Hunters 2 is the manner in which data will be presented to citizen scientists. Muon Hunters 2 will present images in a grid pattern, rather than individually, to bring additional efficiency to the project.

“This time around, we’re trying to make both the project and the telescopes more efficient,” said Dr. Lucy Fortson, University of Minnesota Physics and Astronomy Professor and VERITAS researcher. “We use a machine to help the people work more efficiently and the classifications we get from citizen scientists help the machine to work more efficiently, so it’s a virtuous loop. Scientists will use the images that citizen scientists have identified to better train their computer programs to automatically tell the difference between muons and gamma rays.”

Muon Hunters 2: The Return of the Ring, is run by Zooniverse, the largest online platform for collaborative volunteer research, in conjunction with VERITAS. Citizen science projects at Zooniverse allow researchers to efficiently and effectively comb through large amounts of complex data utilizing the enthusiastic efforts of millions of volunteers from around the world. Other current Zooniverse projects include Snapshot Safari, in which volunteers identify wildlife to help scientists understand the diversity and dynamics of wildlife populations across the African continent.

The original Muon Hunters project welcomed 6,107 citizen scientists who made 2,161,338 classifications of 135,000 objects. “We are hoping to have as many, if not more, classifications than we had in the original project,” said Fortson. “The more data we get, the more efficient we can be, and that’s great for both the scientists and the machines.”

Citizen scientists can become Muon Hunters here.

About VERITAS

VERITAS (Very Energetic Radiation Imaging Telescope Array System) is a ground-based array of four, 12-m optical reflectors for gamma-ray astronomy located at the Center for Astrophysics | Harvard & Smithsonian, Fred Lawrence Whipple Observatory in Amado, Arizona. VERITAS detects gamma rays via the extremely brief flashes of blue “Cherenkov” light they create when they are absorbed in the Earth’s atmosphere.

VERITAS is supported by grants from the U.S. Department of Energy Office of Science, the U.S. National Science Foundation, and the Smithsonian Institution, and by NSERC in Canada.

The VERITAS Collaboration consists of about 80 scientists from 20 institutions in the United States, Canada, Germany and Ireland.

For more information about VERITAS visit http://veritas.sao.arizona.edu

About Muon Hunters

Muon Hunters is a citizen science-based data collection and identification project led by the University of Minnesota and Zooniverse. The project receives data from VERITAS telescopes and direct support from specific VERITAS collaborating institutions including the University of California-Los Angeles; University of California-Santa Cruz; McGill University, Canada; Deutsches Electron-Synchrotron Laboratory, Berlin, Germany; Barnard College/Columbia University; Cal State University – East Bay; University College Dublin, Ireland; and the Center for Astrophysics | Harvard & Smithsonian. In addition, Muon Hunters is supported by the ASTERICS program of the European Union.

For more information about Muon Hunters, visit http://www.muonhunters.org

For more information, contact:
Dr. Lucy Fortson
Zooniverse
lffortson@gmail.com

See the full article here .

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Please help promote STEM in your local schools.

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The Center for Astrophysics combines the resources and research facilities of the Harvard College Observatory and the Smithsonian Astrophysical Observatory under a single director to pursue studies of those basic physical processes that determine the nature and evolution of the universe. The Smithsonian Astrophysical Observatory (SAO) is a bureau of the Smithsonian Institution, founded in 1890. The Harvard College Observatory (HCO), founded in 1839, is a research institution of the Faculty of Arts and Sciences, Harvard University, and provides facilities and substantial other support for teaching activities of the Department of Astronomy.

From Harvard-Smithsonian Center for Astrophysics: “Once-In-A-Lifetime Observations by Veritas Astronomers Reveal High Energy Gamma-Rays from a Binary Star System”

From Harvard-Smithsonian Center for Astrophysics

November 13, 2018
Tyler Jump
Public Affairs
Harvard-Smithsonian Center for Astrophysics
+1 617-495-7462
tyler.jump@cfa.harvard.edu

CfA/VERITAS, a major ground-based gamma-ray observatory with an array of four 12m optical reflectors for gamma-ray astronomy in the GeV – TeV energy range. Located at Fred Lawrence Whipple Observatory, Mount Hopkins, Arizona, US in AZ, USA, Altitude 2,606 m (8,550 ft)

A new discovery reported in The Astrophysical Journal Letters might lay claim to title of the most unusual extreme class of astronomical object: very high energy (VHE) gamma-ray emitting, neutron star-massive star binary pairs. Of the one-hundred billion stars in our galaxy, fewer than ten are in known to be in gamma-ray binary systems, with this discovery being only the second with an identified neutron star. The gamma-ray emission was discovered during an event that will not happen again until 2067.

A neutron star is the dense remains of a type of supernova, the explosive death of a star that started its life more massive than about eight solar-masses. Containing as much material as the sun but in an object only the diameter of a city, neutron stars are so dense that most of their matter is in the form of neutrons, the uncharged atomic particles found in atomic nuclei. Neutron stars spin rapidly and generate powerful magnetic fields, fast winds and narrow beams that sweep like a lighthouse across the sky as the star rotates. If the Earth happens to lie in the path of one of these beams as it passes, astronomers can detect the radiation as regular pulses at radio and other wavelengths. There are a few thousand of these “pulsars” known, beating at a variety of rates from more than a thousand times a second to less than about once a second.

It is common for massive stars to form in binary pairs, and so it is not surprising that some pulsars have an orbiting companion that has survived its partner’s explosive death. Both the pulsar and its companion are likely to have disks of material around them. The rapidly spinning pulsar and its wind can in some cases slam into the disk and wind of the companion star as the two periodically approach in their orbital dance. The energetic collision can produce intense shocks that accelerate charged particles to energies high enough to produce very high energy (VHE) gamma ray radiation by accelerating the particles to nearly the speed of light. When light scatters off such energetic particles it too becomes energized and becomes VHE gamma ray photons each one of which can pack a billion times more energy than a photon of optical light. The precise timing of the radio pulses allows astronomers to use the radio signals to deduce some parameters of the stars and their orbit. Although there are plenty of pulsars, until now most of the explanation was speculation, with only one known case of a binary pulsar system exhibiting VHE gamma-ray emission.

An international team of astronomers began intensively tracking a second, possible VHE gamma-ray pulsar system in 2016. Located about five thousand light-years away in a massive stellar nursery in the direction of the constellation Cygnus, the pulsar was identified as having a massive stellar companion that orbited it every 50 years in an extreme elliptical orbit. At their closest approach the two were expected to come within a mere one astronomical unit of each other (one AU is the average distance of the Earth from the sun), and the scientists had calculated that this would happen on November 13, 2017 – exactly one year ago.

CfA astronomers Wystan Benbow, Gareth Hughes, and Michael Daniel direct VERITAS operations and enabled the VERITAS collaboration’s participation in the program to monitor the behavior of this bizarre object before, after and during its expected closest approach. VERITAS is an array of four 12 m diameter optical telescopes located at the SAO’s Fred Lawrence Whipple Observatory near Tucson, Arizona. VERITAS detects gamma rays via the extremely brief flashes of blue “Cherenkov” light created when gamma rays are absorbed in the Earth’s atmosphere. The VERITAS Collaboration consists of about 80 scientists from 20 institutions in the United States, Canada, Germany and Ireland. VERITAS scientists were joined by a team using the two 17 m MAGIC Cherenkov telescopes located at El Roque de Los Muchachos on the island of La Palma, Spain.

As the binary system is embedded in a larger, diffuse region of VHE gamma-ray emission, the international team of astronomers anxiously awaited the event to see whether the VHE gamma-rays emission brightened near the pulsar. According to Alicia López Oramas, a researcher with MAGIC at the Instituto de Astrofísica de Canarias (IAC), and one of the corresponding authors of the study, “such a unique system was expected to emit very-high-energy gamma rays during this approach, and this opportunity could not be missed.” Graduate student Tyler Williamson and his advisor Professor Jamie Holder, both from University of Delaware’s Department of Physics and Astronomy, played leading roles in the VERITAS campaign, together with Ralph Bird, a post-doctoral researcher at the University of California, Los Angeles.

Initial observations, in 2016, revealed weak gamma-ray emission, consistent with earlier results. “This low-level, steady emission is most likely from a nebula which is being continuously powered by the pulsar,” explains Dr. Bird. Starting in September 2017, the results became much more exciting. “The gamma-ray flux we observed in September was twice the previous value,” says Williamson. But the fireworks were just beginning. “During the closest approach between the star and the pulsar, in November 2017, the flux increased 10 times in just a single night.”

In an attempt to explain not only the strength of the gamma rays, but also their gradual variability and then sudden flaring, the team tried to match a recent theoretical model to their observations. The model contains the latest ideas about pulsars, the binary disk and wind environment, the nature of the ionized nebulosity around the object, the spectrum of emission and tries to refine the orbital parameters of the binary. It was unsuccessful and so the scientists conclude that significant revision is needed to the models in order to fit the observations, including better information about the geometry of the encounter. Since information about the structure of disks and winds around pulsars depends on many diverse yet key parameters like magnetic field strength and environmental history, this object – if it can be successfully modeled – offers to be a potential Rosetta Stone about the birth and evolution of compact objects, and so includes all compact objects produced in supernovae, pulsars without companions, and even many black hole binary systems. In the coming years the scientists plan to continue to monitor this and other pulsars to monitor the exotic behavior of these most unusual and extreme cosmic characters. Wystan Benbow from the CfA states that “continued investment in the operation of unique, leading edge facilities like VERITAS is critical and will ensure further opportunities to achieve transformative science.”

See the full article here .

five-ways-keep-your-child-safe-school-shootings
Please help promote STEM in your local schools.

Stem Education Coalition

The Center for Astrophysics combines the resources and research facilities of the Harvard College Observatory and the Smithsonian Astrophysical Observatory under a single director to pursue studies of those basic physical processes that determine the nature and evolution of the universe. The Smithsonian Astrophysical Observatory (SAO) is a bureau of the Smithsonian Institution, founded in 1890. The Harvard College Observatory (HCO), founded in 1839, is a research institution of the Faculty of Arts and Sciences, Harvard University, and provides facilities and substantial other support for teaching activities of the Department of Astronomy.