Content uploaded by P. F. Scott
Author content
All content in this area was uploaded by P. F. Scott
Content may be subject to copyright.
Observation of a Rapidly Pulsating Radio Source
Abstract
Unusual signals from pulsating radio sources have been recorded at the Mullard Radio Astronomy Observatory. The radiation seems to come from local objects within the galaxy, and may be associated with oscillations of white dwarf or neutron stars.
... Long-period radio transients (LPTs) represent a new era in radio astronomy. Pulsars were the first radio sources discovered to be stably pulsating at ∼1 s timescales (Hewish et al. 1968), and attributed to rotating neutron stars (NSs; Gold 1968;Pacini 1968). Exploring a new range of periodicity has historically proven to be revolutionary in the field. ...
Long-period radio transients (LPTs) are a mysterious new class of radio transients pulsating on periods of minutes to hours. To date, nine LPTs have been discovered predominantly at low Galactic latitudes, and yet their nature remains unknown. Here I present the first phase-resolved optical spectroscopy of the 2.9 h LPT GLEAM-X J0704–37, acquired with the 10 m Keck I telescope. Radial velocity (RV) shifts of 189 ± 3 km s ⁻¹ of an M5-type star in a binary system are detected on a period nearly equal to the radio period. Weak H α emission is also present, with some of it possibly originating from outside of the M dwarf. Based on the RV amplitude, and assuming a typical M dwarf mass, the companion mass must be M ≥ 0.22 M ⊙ . Calibrating the spectra with space-based Gaia photometry reveals that the system is nearly four times closer than previously reported, at d ≈ 400 pc, suggesting that more systems could be nearby and amenable to optical characterization. The optical spectrum between 3500–10 000 Åis well modeled by a binary comprised of a massive white dwarf (WD; T eff ≈ 7300 K, M ≈ 0.8 − 1.0 M ⊙ ) and an M dwarf ( T eff ≈ 3000 K, M ≈ 0.14 M ⊙ ). Radio pulses arrive when the WD is at nearly maximum blueshift and the M dwarf at nearly maximum redshift, in contrast to what has been reported for a similar LPT, ILT J1101+5521. GLEAM-X J0704–37 is now the second LPT with an orbital period nearly equal to the radio period, establishing a class of LPTs associated with WD + M dwarf binaries; other LPTs are likely related to WD and/or neutron star spins. This work demonstrates that the precise localization of LPTs, which enables optical follow-up, will be key in uncovering the mechanism(s) that power this new class of phenomena.
... Cabeçalho do artigo publicado na revista Nature Fonte:Hewish et al. (1968). ...
Os estudos de gênero e ciências apontam a omissão histórica na escrita sobre contribuições e trajetórias de mulheres cientistas. No âmbito da educação científica, essas narrativas são importantes para que docentes e discentes reconheçam a identidade das/os personagens que construíram a ciência ao longo dos tempos, além da importância da diversidade de pessoas no empreendimento científico. O artigo, com o objetivo de contribuir com pesquisas recentes do ensino de física e de astronomia que discorrem sobre exemplos de mulheres cientistas do século XX, apresenta aspectos da trajetória acadêmica da cientista britânica Jocelyn Bell Burnell, reconhecida por sua atuação no processo de descoberta dos pulsares, um dos eventos científicos mais importantes da história da astronomia. Para o desenvolvimento deste estudo biográfico, foram considerados relatos elaborados pela cientista em artigos e entrevistas, bem como publicações de historiadoras/es sobre a história dos pulsares. Com base em referenciais do campo de gênero e ciências, o artigo destaca aspectos da carreira da astrônoma que possibilitam refletir sobre fatores que favorecem a entrada de mulheres na ciência, bem como dificuldades estruturais encontradas por elas para sua permanência no campo científico e acadêmico.
... Neutron stars (NSs) are among the most extreme astrophysical bodies, serving as invaluable natural laboratories for modern physics. While predicted already in 1934 [1], their first observation was made possible by the radio pulses of the star today known as PSR B1919+21 [2]. In 1982 the first millisecond pulsar, PSR B1937+21, was discovered [3], characterized by a period of around 1.55 ms; the fastest-spinning pulsars currently known are PSR J1748-2446ad, discovered in 2004 [4], with a period of only 1.4 ms (716.36 ...
Millisecond pulsars, representing the older neutron star population, are believed to have undergone a prolonged period of dark matter accumulation, resulting in a higher dark matter content. Their extreme rotation makes them unique laboratories for studying rapidly rotating neutron stars admixed with dark matter. In this work, we model uniformly rotating neutron stars with a dark matter component that rotates independently from the baryon matter, allowing for the investigation of both co-rotating and counter-rotating scenarios. We examine the impact of dark matter rotation on the macroscopic properties of neutron stars, including the mass-radius relation, the mass-shedding Keplerian limit, and moments of inertia, for various dark matter particle masses and total fractions, considering both core and halo distributions. Our findings provide a more comprehensive understanding of how dark matter influences the equilibrium properties of rotating neutron stars, offering new insights into the astrophysical implications of self-interacting dark matter.
... Pulsating Radio Source" Hewish et al. [1968], Pilkington et al. [1968] the following year. ...
This thesis investigates the impact of dark matter on neutron star properties, focusing on mass, radius, and tidal deformability. Using two-fluid and single-fluid models, dark matter is incorporated into the equation of state (EOS) via a Relativistic Mean Field (RMF) approach. The study finds that increasing dark matter content reduces the maximum mass, radius, and tidal deformability. Bayesian inference, supported by LIGO-Virgo gravitational wave data and NICER mass-radius measurements, refines these models. Despite dark matter's influence, the semi-universal C-Love relation remains valid. Machine learning techniques effectively classify dark matter-admixed neutron stars. The thesis also explores a sigma-cut potential in the EOS, which stiffens the EOS at high densities, favoring larger radii and lower f-mode frequencies. The study of non-radial oscillations, particularly f- and p-modes, highlights their sensitivity to neutron star composition and EOS. These findings enhance our understanding of neutron star interiors and dark matter's role, emphasizing the need for further observational and theoretical advancements.
... Initially hesitant, she approached her supervisor, and the team discovered pulsars after a thorough investigation. They published a paper with the student listed second among five authors (Hewish et al., 1968). Years later, when they received the Nobel Prize (1974), Bell Burnell, who discovered the phenomenon and insisted on its accuracy, was excluded from recognition. ...
The journey of a scientific Endeavor often sparks from a glimmer of curiosity: a question, an observation, or a hunch. Researchers then venture into the unknown, formulating hypotheses and gathering data through experiments. They also forge collaborations to enhance their collective capabilities and knowledge, forming strategic networks that meet funding requirements. However, the ultimate goal – a published paper or a groundbreaking discovery – can be hindered by the mode of collaboration itself. Traditional research heavily relies on good intentions and unspoken trust, which can be fragile, especially when dealing with novel, ever-evolving ideas. This reluctance can lead researchers to withhold data or hesitate to share half-formed concepts, stifling scientific progress from potential collaborators on the specific Endeavor and the broader scientific community. The crux of the issue lies in the current collaborative approach. While teamwork fuels innovation across disciplines, the lack of a formal knowledge-sharing framework cultivates a culture of hesitancy, enabling science to progress but impeding significant advancements and paradigm shifts. For instance, two researchers with potentially complementary ideas may be reluctant to collaborate and exchange ideas due to concerns about ownership or recognition. This scenario underscores the need for a new approach, mirroring practices from the startup realm. Startups navigate uncertainties by establishing a Founders' Agreement that outlines roles, responsibilities, and intellectual property (IP) ownership. This Agreement allows individuals to collaborate freely on nascent ideas, knowing potential disputes are addressed beforehand. Similarly, the Scientific Endeavor Management Agreement (SEM) proposed here can be a game-changer for research team collaborations, stimulating safe knowledge sharing and fostering new paradigm shifts across all scientific disciplines.
Magnetohydrodynamic simulations of core-collapse supernovae have become increasingly mature and important in recent years. Magnetic fields take center stage in scenarios for explaining hypernova explosions, but are now also considered in supernova theory more broadly as an important factor even in neutrino-driven explosions, especially in the context of neutron star birth properties. Here we present an overview of simulation approaches currently used for magnetohydrodynamic supernova simulations and sketch essential physical concepts for understanding the role of magnetic fields in supernovae of slowly or rapidly rotating massive stars. We review progress on simulations of neutrino-driven supernovae, magnetorotational supernovae, and the relevant field amplification processes. Recent results on the nucleosynthesis and gravitational wave emission from magnetorotational supernovae are also discussed. We highlight efforts to provide better initial conditions for magnetohydrodynamic supernova models by simulating short phases of the progenitor evolution in 3D to address uncertainties in the treatment of rotation and magnetic fields in current stellar evolution models.
UTC(k) can be considered a shorthand for the local time standard maintained by a country's or region's time‐ frequency laboratory. Each lab uses its local atomic clocks to maintain this standard and synchronizes it with Coordinated Universal Time (UTC). Although local atomic clocks can operate independently, they generally rely on UTC as a reference standard for precision and long‐term stability. To effectively monitor local atomic clocks and improve monitoring efficiency, this paper aims to study new monitoring methods from the perspective of macroscopic astrometry. By utilizing the measurement results of millisecond pulsars and combining them with clock models, this paper focuses on calculating and predicting the deviation data of local atomic clocks. This method not only expands the means of monitoring local atomic clocks but also has significant implications for improving monitoring accuracy and reliability. To validate its effectiveness, we first calculate and analyze the actual and simulated data of millisecond pulsars, then compare the analysis results with the conventional clock deviation data of local clocks based on UTC as a reference. The results indicate that using millisecond pulsars for monitoring can feasibly obtain the phase and frequency deviations of local atomic clocks within a 95% confidence interval. This demonstrates the feasibility of this method. Therefore, monitoring local atomic clocks using millisecond pulsars is reliable and effective. This study provides new insights and methods for the monitoring of local clocks and is significant for improving monitoring accuracy and reliability.
To date, over 4000 pulsars have been detected. In this study, we identify 231 X-ray counterparts of Australia Telescope National Facility (ATNF) pulsars by performing a spatial cross match across the Chandra, XMM-Newton observational catalogs. This data set represents the largest sample of X-ray counterparts ever compiled, including 98 normal pulsars (NPs) and 133 millisecond pulsars (MSPs). Based on this significantly expanded sample, we re-establish the correlation between X-ray luminosity and spin-down power, given by L X ∝ E ̇ 0.85 ± 0.05 across the whole X-ray band. The strong correlation is also observed in hard X-ray band, while in soft X-ray band there is no significant correlation. Furthermore, L X shows a strong correlation with spin period and characteristic age for NPs. For the first time, we observe a strongly positive correlation between L X and the light cylinder magnetic field ( B lc ) for MSPs, with both NPs and MSPs following the relationship L X ∝ B lc 1.14 , consistent with the outer-gap model of pulsars that explains the mechanism of X-ray emission. Additionally, we investigate potential X-ray counterparts for Galactic Plane Pulsar Snapshot pulsars, finding a lower likelihood of detection compared to ATNF pulsars.
DOI:https://doi.org/10.1103/PhysRevLett.15.599
WITH the discovery of X-ray sources in the sky1,2, speculation has arisen that they might be associated with neutron or hyperon stars formed during the internal collapse which triggers off supernova explosions (probably of type I). Rates of cooling of neutron star models have been calculated by Morton3, Chiu and Salpeter4,5, and Tsuruta6. It appears (J. Bahcall, personal communication) that the importance of the early cooling by emission of neutrinos from the ‘Urca’ process has been underestimated in the foregoing investigations. With rough allowance for this effect, the calculations of Miss Tsuruta indicate that a neutron star will rapidly cool to 3 or 4 × 106 °K, but that after 105 years its surface temperature will still be about 2 × 106 °K.
Solar cosmic rays, discussing flare association, solar particle acceleration, recurrence and low energy solar particle events