astronomers discover 18 new pulsars arecibo

Astronomers Discover 18 New Pulsars Using Arecibo Telescope Data

Discovery of 18 New Pulsars

Astronomers from West Virginia University, in collaboration with other institutions, have identified 18 new pulsars through the Arecibo Observatory, as a part of the AO 327-MHz Drift Survey. These discoveries were outlined in a paper published on February 6.

What Are Pulsars?

Pulsars are rapidly rotating neutron stars with strong magnetic fields that emit beams of electromagnetic radiation. Typically identified through brief radio bursts, some pulsars are also observed in optical, X-ray and gamma-ray wavelengths.

The AO327 Survey: Purpose and Scope

The AO327 survey, conducted with the Arecibo telescope at 327 MHz, operated from 2010 to December 2020. Its objective was to systematically search the entire Arecibo-visible sky (declinations between-1° and 38°) for pulsars and radio transients.

Key Findings from the AO327 Survey

By examining data from the AO327 survey, astronomers under the leadership of Timothy E.E. Olszański have uncovered 18 additional pulsars, raising the survey's overall pulsar count to 95.

Final Discoveries from the Arecibo Observatory

"With a total of 95 pulsars identified through the AO327 survey, these represent the final discoveries that can be further examined using the Arecibo Observatory," the researchers stated in their paper.

Analysis and Classification of Discovered Pulsars

Olszański and his team analyzed AO327 data, leading to the identification of 49 pulsars, 18 of which were newly discovered. They then obtained phase-connected timing solutions for all of them.

Characteristics of the Identified Pulsars

The analysis revealed that all identified pulsars, except for the partially recycled PSR J0916+0658, are non-recycled. Their spin periods vary from 40 milliseconds to 5.05 seconds and their dispersion measures fall within the range of 17.8 to 133.2 pc/cm³.

Unique Emission Phenomena in the Discovered Pulsars

The study reports that 29 pulsars in the sample exhibit only amplitude modulation, while one source displays subpulse drift exclusively and 13 show characteristics of both phenomena.

Rare Pulsar Phenomena

Researchers discovered that PSR J1942+0147 demonstrates the rare bi-drifting effect, whereas PSR J0225+1727 displays an interpulse offset by 164 degrees relative to the main pulse. Bi-drifting is a unique subpulse drift phenomenon characterized by opposing drift slopes in different components.

Future Prospects and Additional Discoveries

According to the astronomers, future investigations of the pulsars identified in this study will delve deeper into their emission characteristics and polarization properties. The AO327 survey is expected to yield additional pulsar discoveries.

Potential for Further Discoveries

The authors conclude that with less than 2% of survey observations yet to be processed and over 60% of search candidates still requiring inspection, at least 100 more pulsars are anticipated to be discovered.

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Exciting Discovery Alert in the World of Pulsars! Dive into the latest findings from the Arecibo Observatory, where astronomers have identified 18 new pulsars! Stay updated on space research and get insights into the universe's mysteries by reading more.

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supernova dark matter axion gamma ray detection

Could a Nearby Supernova Hold the Key to Solving the Dark Matter Mystery?

The Mystery of Dark Matter

The quest to uncover the universe's dark matter could reach its conclusion as early as tomorrow—if a nearby supernova offers the right conditions. For 90 years, astronomers have been puzzled by the elusive nature of dark matter, which constitutes 85% of the universe's mass yet remains invisible to telescopes. Current research focuses on the axion, a lightweight particle widely regarded as the leading candidate.

The Role of Axions in Dark Matter Research

Identifying Axions Through Supernova Gamma Rays

Researchers at the University of California, Berkeley, propose that axions could be identified almost instantly following the detection of gamma rays from a nearby supernova. If axions exist, they would be generated in vast numbers during the first 10 seconds of a massive star's collapse into a neutron star. These particles would then escape and convert into high-energy gamma rays within the star's powerful magnetic field.

The Challenge of Detecting Gamma Rays

At present, such a detection can occur only if the Fermi Gamma-ray Space Telescope, the only operational gamma-ray telescope in orbit, is oriented toward the supernova at the moment of its explosion. With the telescope's restricted field of view, the probability of this alignment is approximately 10%.

Implications of Gamma-Ray Detection

Determining the Mass of the QCD Axion

A single gamma-ray detection could precisely determine the mass of the axion, specifically the QCD axion, across a vast range of theoretical possibilities, including those under investigation in Earth-based experiments. Conversely, the absence of such a detection would rule out a significant portion of potential mass ranges, rendering many current dark matter searches obsolete.

The Need for a Nearby Supernova

The challenge lies in the fact that gamma rays must be sufficiently bright to detect, which requires the supernova to occur nearby—within the Milky Way or its satellite galaxies. However, such events are rare, with nearby stars exploding only every few decades. The most recent occurrence was in 1987, when a supernova erupted in the Large Magellanic Cloud, a satellite galaxy of the Milky Way. Although the Solar Maximum Mission gamma-ray telescope was directed toward this supernova, its sensitivity was insufficient to detect the predicted gamma-ray intensity, as analyzed by the UC Berkeley team.

"A modern gamma-ray telescope observing a supernova like 1987A could confirm or eliminate the existence of the QCD axion—a fascinating theoretical particle—over a vast range of parameter space," said Benjamin Safdi, UC Berkeley associate professor of physics and senior author of a paper published on November 19 in Physical Review Letters. "This includes nearly all parameter regions unreachable by laboratory methods and a considerable portion that laboratories are currently investigating, and it would happen within 10 seconds."

The Proposed GALAXIS Satellite Network

The Urgency of Detecting Axions

The researchers express concern that when the long-anticipated supernova occurs in the nearby universe, the opportunity to observe gamma rays produced by axions might be missed. To address this, they are collaborating with colleagues involved in gamma-ray telescope development to explore the possibility of deploying a fleet of satellites capable of monitoring the entire sky continuously. They have even proposed a name for this ambitious constellation of full-sky gamma-ray satellites: the GALactic Axion Instrument for Supernova, or GALAXIS.

The Risks of Missing the Opportunity

"We're all deeply concerned about the possibility of the next supernova occurring before the necessary instruments are in place," said Safdi. "Missing the chance to detect axions due to a supernova happening tomorrow would be a profound loss—such an opportunity may not arise again for another 50 years."

Safdi's co-researchers are graduate student Yujin Park and postdoctoral scholars Claudio Andrea Manzari and Inbar Savoray. Together, they are part of UC Berkeley's physics department and the Theoretical Physics Grou p at Lawrence Berkeley National Laboratory.

Understanding the QCD Axion

Dark Matter and the Search for Axions

Dark matter searches began by focusing on faint, massive compact halo object (MACHOs), which were expected to be spread throughout our galaxy and beyond. When MACHOs couldn't be detected, attention turned to theoretical elementary particles that should be ubiquitous and detectable in lab experiments on Earth. Yet, the hunt for weakly interacting massive particles (WIMPs) also yielded no results.

Axions and Their Role in Physics

The axion is currently the leading candidate for dark matter, a particle that seamlessly integrates into the standard model of physics while addressing several unresolved issues in particle physics.

Additionally, axions arise naturally from string theory, a theoretical framework for the universe's fundamental geometry, and could potentially reconcile gravity, which governs large-scale interactions, with quantum mechanics, which governs the microscopic.

According to Safdi, it appears nearly impossible to formulate a consistent theory that integrates gravity with quantum mechanics without including particles such as the axion.

The leading candidate for an axion, known as the QCD axion—so named after the prevailing theory of the strong face, quantum chromodynamics—hypothetically interacts with all forms of matter, albeit weakly, through the four fundamental forces: gravity, electromagnetism, the strong force (which binds atoms), and the weak force (which governs atomic decay).

One consequence is that in a powerful magnetic field, an axion should occasionally transform into an electromagnetic wave, or photon. This contrasts with the neutrino, a similarly lightweight, weakly-interacting particle, which only engages with gravity and the weak force, entirely disregarding the electromagnetic force.

Experimental Efforts and Simulations

Axion Detection in Laboratory Experiments

Experiments in laboratory settings, such as the ALPHA Consortium (Axion Longitudinal Plasma HAloscope), DMradion, and ABRACADABRA, all involving UC Berkeley researchers, utilize compact cavities that resonate like a tuning fork, enhancing the faint electromagnetic field or photon produced when a low-mass axion undergoes transformation in the presence of a strong magnetic field.

Supercomputer Simulations and Neutron Stars

Rather than focusing on distant galactic magnetic fields, the researchers investigated the generation of gamma rays by axions within the strong magnetic fields surrounding the star that produced them. Supercomputer simulations revealed that this process efficiently generates a burst of gamma rays, with intensity linked to the mass of the axion.

Neutron Stars as Axion Laboratories

The Role of Neutron Stars and Magnetars

Gamma ray burst should coincide with a burst of neutrinos from within the neutron star. However, this axion burst only lasts for 10 seconds following the formation of the neutron star, after which the production rate rapidly decreases, hours before the outer layers of the star begin to explode.

"This has prompted us to consider neutron stars as ideal locations for axion searches, effectively turning them into 'axion laboratories,'" Safdi explained. "Neutron stars offer many advantages. Not only are they incredibly hot, but they also possess some of the strongest magnetic fields in the universe. Magnetars, a type of neutron star, for instance, generate magnetic fields that are tens of billions of times stronger than anything we can produce in a laboratory. These intense magnetic fields help convert axions into detectable signals."

Setting Limits on Axion Mass

Two years ago, Safdi and his team established the most precise upper limit on the mass of the QCD axion, pegging it at roughly 16 million electron volts, which is about 32 times smaller than the electron's mass. This conclusion was drawn from analyzing the cooling rate of neutron stars, which would accelerate if axions were produced alongside neutrinos within these dense celestial objects.

The Future of Axion Research

Predictions and Opportunities for Gamma-Ray Detection

In their latest publication, the UC Berkeley team details the generation of gamma rays following a core collapse into a neutron star. Additionally, they utilize the lack of gamma ray detection from the 1987A supernova to set the most stringent constraints on the mass of axion-like particles, which differ from QCD axions in their lack of interaction with the strong force.

The researchers predict that detecting gamma rays enable them to determine the mass of the QCD axion, provided it exceeds 50 microelectron volts (μeV), roughly one 10-billionth of the electron's mass. A single observation could redirect ongoing experiments to verify the axion's mass, according to Safdi. Although a network of dedicated gamma-ray telescopes is the optimal solution for detecting gamma rays from a nearby supernova, a fortunate event with Fermi would be an even more advantageous scenario.

The Role of Fermi in Axion Research

The optimal scenario for detecting axions would be for Fermi to capture a supernova. However, Safdi notes that the probability of this hap pening is low. "But if Fermi were to observe it, we would be able to measure the axion's mass and interaction strength, providing us with the critical information about the axion. The signal would be highly reliable, as no ordinary matter could produce such an event," he said.

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axion-clouds-neutron-stars-dark-matter-insight

Physicists Propose Axion Clouds Around Neutron Stars: A New Insight into Dark Matter

Introduction

Physicists from Amsterdam, Princeton, and Oxford suggest that axions, extremely light particles, could exist in large clouds around neutron stars, potentially offering insight into the elusive dark matter. Moreover, these axions may not be too challenging to observe.

Continuation of Research

Previous Work

The study was published in Physical Review X as a continuation of earlier research, where the authors explored axions and neutron stars from a different perspective.

In their earlier research, the team focused on axions escaping from neutron stars. Now, they shift their attention to the axions trapped by the stars' gravity, which over time form a faint cloud around the star, one that might be detectable by telescopes. But what makes these hazy clouds around distant stars so intriguing to astronomers and physicists?

Axions: A Surprising Link Between Soap and Dark Matter Mysteries

The Nature of Axions

Protons, neutrons, electrons, and photons, many of us recognize these fundamental particles. The axion, however, remains less familiar, and for good reason; it's still a theoretical particle, one that is yet to be detected.

The axion, named after a soap brand, was theorized in the 1970s to "clean up" a problem in our understanding of the neutron. However, despite its elegant theory, if axions exist, their lightness makes them nearly impossible to detect.

Axions and Dark Matter

Today, axions stand as a prominent candidate for dark matter, one of the biggest unsolved puzzles in contemporary physics. Multiple lines of evidence suggest that roughly 85% of the universe's matter is "dark", composed of particles we have yet to detect.

The existence of dark matter is inferred indirectly, based on its gravitational effects on visible matter. Fortunately, this doesn't imply it has no interaction with visible matter at all, but if such interactions exist, they are incredibly weak. As its name implies, detecting dark matter directly is exceedingly challenging.

By connecting the dots, physicists have speculated that the axion might hold the key to solving the dark matter puzzle. This elusive, unobserved particle--extremely light and weakly interacting--could it be part of the answer to the dark matter enigma?

Neutron Stars: A Unique Magnification Tool in Astrophysics

The Challenge of Detection

While the concept of the axion as a dark matter particle is appealing, in physics, a theory is truly valuable only if it yields observable consequences. Is there a way to detect axions, fifty years after their potential existence was initially proposed?

Axions and Photon Interaction

Axions are anticipated to convert into photons-particles of light-when subjected to electric and magnetic fields, and vice versa. While light is detectable, the interaction strength between axions and photons is expected to be minimal, resulting in a limited production of light from axions. However, this changes in environments with a significant concentration of axions, especially under strong electromagnetic fields.

The Role of Neutron Stars

As a result, the researchers turned their attention to neutron stars, the most densely packed stars in the universe. These objects have masses akin to our Sun, yet they are condensed into a diameter of only 12 to 15 kilometers.

The extreme densities of neutron stars give rise to an equally extreme environment, characterized by immense magnetic fields that are billions of times stronger than those found on Earth. Recent studies indicate that if axions exist, these magnetic fields enable neutron stars to produce these particles in large quantities near their surfaces.

The Ones that Linger

Focus on Trapped Axions

In their prior study, the authors examined the axions that were produced and subsequently escaped the star. They determined the amounts of axions generated, the paths they would traverse, and how their transformation into light could create a subtle but potentially observable signal.

This time, the researchers examine the axions that do not succeed in escaping; these are the particles that, despite their negligible mass, are ensnared by the neutron star's powerful gravitational pull.

Formation of Axion Clouds

Owing to the axion's extremely weak interactions, these particles will remain in the vicinity, gradually accumulating around the neutron star over timescales of up to millions of years. This accumulation can lead to the formation of highly dense axion clouds surrounding neutron stars, presenting remarkable new avenues for axion research.

In their paper, the researchers investigate the formation, properties, and subsequent evolution of these axion clouds, emphasizing that they are expected to, and in many instances must, exist.

Observational Signatures

In fact, the authors propose that, axions should exist, axion clouds are likely to be widespread, forming around a broad spectrum of neutron stars. They assert that these clouds should generally possess very high densities--potentially twenty orders of magnitude above local dark matter densities--leading to pronounced observational signatures.

The latter may manifest in various forms, of which the authors explore two: a continuous signal emitted throughout much of a neutron star's lifespan and a one-time burst of light occurring at the end of its life, when it ceases to produce electromagnetic radiation. Both types of signatures could be detected and utilized to investigate the interaction between axions and photons beyond current thresholds; potentially employing existing radio telescopes.

What Comes Next?

Future Directions

While axion clouds have yet to be observed, the new results clarify exactly what to look for, enhancing the feasibility of a comprehensive search for axions. Thus, the main item on the agenda is to "search for axion clouds," while also opening several intriguing theoretical avenues for further exploration.

Collaborative Efforts

One important aspect is that one of the authors is already pursuing follow-up work focused on how axion clouds could affect neutron star dynamics. Additionally, another vital future research direction involves numerical modeling of these axion clouds: while the present paper shows great potential for discovery, further numerical modeling is needed to gain a more precise understanding of what to search for and where.

Axion Clouds in Binary Systems

Ultimately, the current results pertain solely to individual neutron stars; however, many of these stars exist as components of binary systems--either alongside another neutron star or in conjunction with a black hole. Gaining insight into the physics of axion clouds in these systems, along with their potential observational signals, would be extremely beneficial.

Conclusion:

Consequently, this work represents a significant advancement in an exciting new research direction. Achieving a comprehensive understanding of axion clouds will necessitate collaborative efforts across various scientific disciplines, including particle (astro) physics, plasma physics, and observational radio astronomy.

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