Modeling isolated magnetar spin-down evolution and implications for long-period radio transients

Abstract

Long-period radio transients (LPTs) are a new class of radio sources characterized by long spin periods ($P_{\text{spin}}>10^3$ s) and highly variable radio emission. While known magnetars are relatively young ($\tau <10^5$ yrs) with spin periods clustered between $1-10$ sec, it has been proposed that LPTs may be linked to a missing population of older magnetars. In this paper, we present an extensive parametric analysis of isolated magnetar spin evolution using various propeller spin-down models. In general, at higher initial magnetar B-fields ($B_0>\sim 10^{15}$ G) and larger ambient densities ($n_0>\sim 10^2$ cm${}^{-3}$), magnetars will transition to the propeller phase earlier, and they start accreting gas from the ISM or molecular clouds after $\tau \sim 10^8$ yrs. We found that a transition from the pulsar to the propeller phase is required to reach the observed LPT period range of $P>10^3$ s. More specifically, our population synthesis study based on Monte-Carlo simulations shows that two propeller models can account for most of the observed LPT periods ($P\sim 1-400$ [min]) and their period derivative constraints ($\dot{P}<10^{-9}$ s s${}^{-1}$). Our spin-down models predict that (1) nearby radio-quiet neutron stars with the estimated dipole $B$-field range of $B\sim (1-5)\times 10^{13}$ G will transition to the propeller phase eventually after $\tau >\sim 10^7$ yrs; (2) thermal X-ray emission from accretion-phase magnetars becomes too faint for detection after traveling ($d>\sim 10$ kpc) from their birth places; (3) sporadic radio outbursts observed from LPTs may not be explained by regular radio pulsar and magnetar emission mechanisms that operate during the propeller phase.

References in corpus (26)

• Unifying the observational diversity of isolated neutron stars via magneto-thermal evolution models
• Magnetic field dissipation in neutron star crusts: from magnetars to isolated neutron stars
• A powerful bursting radio source towards the Galactic Centre
• A radio transient with unusually slow periodic emission
• A long-period radio transient active for three decades
• Galactic neutron stars I. Space and velocity distributions in the disk and in the halo
• The impact of magnetic field on the thermal evolution of neutron stars
• Evidence for Heating of Neutron Stars by Magnetic Field Decay
• MHD Simulations of Bondi Accretion to a Star in the "Propeller" Regime
• An emission state switching radio transient with a 54 minute period
• Evidence for an abundant old population of Galactic ultra long period magnetars and implications for fast radio bursts
• Sporadic radio pulses from a white dwarf binary at the orbital period
• Isolated magnetar spin-down, soft X-ray emission and RXJ1856.5-3754
• The emission of interpulses by a 6.45-hour period coherent radio transient
• GLEAM-X J16279.5-523504.3 as a White Dwarf Pulsar
• Constraining the nature of the 18-min periodic radio transient GLEAM-X J162759.5-523504.3 via multi-wavelength observations and magneto-thermal simulations
• On The Evolution of The Radio Pulsar PSR J1734-3333
• Spectroscopic Detection of a 2.9-hour Orbit in a Long Period Radio Transient
• Interaction Between Supernova Remnant G22.7-0.2 And The Ambient Molecular Clouds
• Detection of X-ray Emission from a Bright Long-Period Radio Transient
• Evolution of isolated neutron stars till accretion. The role of initial magnetic field
• CHIME/FRB/Pulsar discovery of a nearby long period radio transient with a timing glitch
• Evolution of the long-period pulsar GLEAM-X J162759.5-523504.3
• The CRAFT Coherent (CRACO) upgrade I: System Description and Results of the 110-ms Radio Transient Pilot Survey
• The Galactic population of magnetars : a simulation-based inference study
• Deep Synoptic Array Science: Searching for Long Duration Radio Transients with the DSA-110