Cosmic condensates - vortex, fluxtube and neutron star dynamics

This thesis studies the implications of cosmic condensates, specifically the dynamics of superfluid vortices and superconducting fluxtubes, on astrophysical observables. Firstly, several mutual friction forces, arising from the interactions of vortices and their surroundings, are examined. We separately address mesoscopic mechanisms acting in the neutron star core and crust and analyse the strength of the resulting macroscopic mutual friction for realistic equations of state. It is obtained that the coupling strengths vary significantly within both layers and the dissipation changes drastically across the crust-core boundary. In analogy with helium experiments, the interface should therefore have important implications for the stars’ rotational properties.This is followed by an analysis of mechanisms affecting the superconducting flux-tubes. Their motion governs the dynamics of the interior magnetic field and characteristic evolution timescales are presented for a realistic equation of state. While these results are only preliminary and a more detailed analysis of additional processes is needed, they point towards deficiencies in earlier work on this subject. Subsequently, one of the flux-tube mechanisms is investigated in more detail and the analogy with normal magneto-hydrodynamics is employed to derive a superconducting induction equation. While this equation differs significantly from the normal resistive equivalent, several key notions of standard magnetohydrodynamics are retained. From the field evolution equation we further deduce that the canonical fluxtube dissipation is not strong enough to explain field evolution timescales invoked from observations. To reconcile these, entirely different fluxtube coupling mechanisms are required.Finally, the possibility of using laboratory condensates to study aspects of neutron star physics, only poorly understood, is examined. Specifically helium, ultra-cold gases and superconductors are prime candidates to mimic the behaviour of neutron stars on smaller scales. By looking at typical characteristics such as the two-fluid nature, super-fluid turbulence and pinning, we find that terrestrial quantum states could provide a promising new angle to fill the missing pieces of neutron star astrophysics

Analyzing the Galactic Pulsar Distribution with Machine Learning

We explore the possibility of inferring the properties of the Galactic population of neutron stars through machine learning. In particular, in this paper we focus on their dynamical characteristics and show that an artificial neural network is able to estimate with high accuracy the parameters that control the current positions of a mock population of pulsars. For this purpose, we implement a simplified population-synthesis framework (where selection biases are neglected at this stage) and concentrate on the natal kick-velocity distribution and the distribution of birth distances from the Galactic plane. By varying these and evolving the pulsar trajectories in time, we generate a series of simulations that are used to train and validate a suitably structured convolutional neural network. We demonstrate that our network is able to recover the parameters governing the distribution of kick velocity and Galactic height with a mean relative error of about 10−2. We discuss the limitations of our idealized approach and study a toy problem to introduce selection effects in a phenomenological way by incorporating the observed proper motions of 216 isolated pulsars. Our analysis highlights that by increasing the sample of pulsars with accurate proper-motion measurements by a factor of ∼10, one of the future breakthroughs of the Square Kilometre Array, we might succeed in constraining the birth spatial and kick-velocity distribution of the neutron stars in the Milky Way with high precision through machine learning.M.R., V.G., A.G., and N.R. acknowledge support from the H2020 ERC Consolidator Grant “MAGNESIA”’ under grant agreement No. 817661 (PI: Rea), and grants SGR2017-1383 and PGC2018-095512-B-I00. J.A.P. acknowledges support by the Generalitat Valenciana grant PROMETEO/2019/071 and by AEI grant PGC2018-095984-B-I00. This work has also been partially supported by the PHAROS COST Action (CA16214)

Long-period Radio Pulsars: Population Study in the Neutron Star and White Dwarf Rotating Dipole Scenarios

© 2024 The Author(s). Published by the American Astronomical Society. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY), https://creativecommons.org/licenses/by/4.0/The nature of two recently discovered radio emitters with unusually long periods of 18min (GLEAM-X J1627-52) and 21min (GPM J1839-10) is highly debated. Their bright radio emission resembles that of radio magnetars, but their long periodicities and lack of detection at other wavelengths challenge the neutron-star interpretation. In contrast, long rotational periods are common in white dwarfs but, although predicted, dipolar radio emission from isolated magnetic white dwarfs has never been unambiguously observed. In this work, we investigate these long-period objects as potential isolated neutron-star or white-dwarf dipolar radio emitters and find that both scenarios pose significant challenges to our understanding of radio emission via pair production in dipolar magnetospheres. We also perform population-synthesis simulations based on dipolar spin-down in both pictures, assuming different initial-period distributions, masses, radii, beaming fractions, and magnetic-field prescriptions, to assess their impact on the ultra-long pulsar population. In the neutron-star scenario, we do not expect a large number of ultra-long period pulsars under any physically motivated (or even extreme) assumptions for the period evolution. On the other hand, in the white-dwarf scenario, we can easily accommodate a large population of long-period radio emitters. However, no mechanism can easily explain the production of such bright coherent radio emission in either scenarios.Peer reviewe

A long-period radio transient active for three decades: population study in the neutron star and white dwarf rotating dipole scenarios

The nature of two recently discovered radio emitters with unusually long periods of 18min (GLEAM-X J1627-52) and 21min (GPM J1839-10) is highly debated. Their bright radio emission resembles that of radio magnetars, but their long periodicities and lack of detection at other wavelengths challenge the neutron-star interpretation. In contrast, long rotational periods are common in white dwarfs but, although predicted, dipolar radio emission from isolated magnetic white dwarfs has never been unambiguously observed. In this work, we investigate these long-period objects as potential isolated neutron-star or white-dwarf dipolar radio emitters and find that both scenarios pose significant challenges to our understanding of radio emission via pair production in dipolar magnetospheres. We also perform population-synthesis simulations based on dipolar spin-down in both pictures, assuming different initial-period distributions, masses, radii, beaming fractions, and magnetic-field prescriptions, to assess their impact on the ultra-long pulsar population. In the neutron-star scenario, we cannot reproduce the large number of expected ultra-long period pulsars under any physically motivated (or even extreme) assumptions. Thus, if GLEAM-X J1627-52 and GPM J1839-10 are confirmed as neutron-star pulsars (even if they are magnetars), this would necessarily call for a significant revision of our understanding of birth parameters at the population level. On the other hand, in the white-dwarf scenario, no mechanism can explain the production of such a bright coherent radio emission in isolated magnetic white dwarf systems (binaries with low mass companions are still viable), although we can easily accommodate a large population of long-period radio emitters.Comment: 8 pages, 4 figures; ApJ Letters submitte

Constraining the Nature of the 18 min Periodic Radio Transient GLEAM-X J162759.5-523504.3 via Multiwavelength Observations and Magneto-thermal Simulations

We observed the periodic radio transient GLEAM-X J162759.5-523504.3 (GLEAM-X J1627) using the Chandra X-ray Observatory for about 30 ks on 2022 January 22–23, simultaneously with radio observations from the Murchison Widefield Array, MeerKAT, and the Australia Telescope Compact Array. Its radio emission and 18 min periodicity led the source to be tentatively interpreted as an extreme magnetar or a peculiar highly magnetic white dwarf. The source was not detected in the 0.3–8 keV energy range with a 3σ upper limit on the count rate of 3 × 10−4 counts s−1. No radio emission was detected during our X-ray observations either. Furthermore, we studied the field around GLEAM-X J1627 using archival European Southern Observatory and DECam Plane Survey data, as well as recent Southern African Large Telescope observations. Many sources are present close to the position of GLEAM-X J1627, but only two within the 2'' radio position uncertainty. Depending on the assumed spectral distribution, the upper limits converted to an X-ray luminosity of LX < 6.5 × 1029 erg s−1 for a blackbody with temperature kT = 0.3 keV, or LX < 9 × 1029 erg s−1 for a power law with photon index Γ = 2 (assuming a 1.3 kpc distance). Furthermore, we performed magneto-thermal simulations for neutron stars considering crust- and core-dominated field configurations. Based on our multiband limits, we conclude that (i) in the magnetar scenario, the X-ray upper limits suggest that GLEAM-X J1627 should be older than ∼1 Myr, unless it has a core-dominated magnetic field or has experienced fast cooling; (ii) in the white dwarf scenario, we can rule out most binary systems, a hot sub-dwarf, and a hot magnetic isolated white dwarf (T ≳ 10.000 K), while a cold isolated white dwarf is still compatible with our limits.N.R., F.C.Z., C.D., M.R., V.G., C.P., A.B., and E.P. are supported by the ERC Consolidator Grant "MAGNESIA" under grant agreement No. 817661, and National Spanish grant No. PGC2018-095512-BI00. F.C.Z., A.B., and V.G. are also supported by Juan de la Cierva Fellowships. C.D., M.R., and C.A.'s work has been carried out within the framework of the doctoral program in Physics of the Universitat Autónoma de Barcelona. N.H.W. is supported by an Australian Research Council Future Fellowship (project number FT190100231) funded by the Australian Government. D.d.M. acknowledges financial support from the Italian Space Agency (ASI) and National Institute for Astrophysics (INAF) under agreements ASI-INAF I/037/12/0 and ASI-INAF n.2017-14-H.0 and from INAF "Sostegno alla ricerca scientifica main streams dell'INAF," Presidential Decree 43/2018 and from INAF "SKA/CTA projects," Presidential Decree 70/2016. D.B. acknowledges support from the South African National Research Foundation. D.V. is supported by the ERC Starting Grant "IMAGINE" under grant agreement No. 948582. This work was also partially supported by the program Unidad de Excelencia Maria de Maetzu de Maeztu CEX2020-001058-M and by the PHAROS COST Action (grant No. CA16214)

Menstrual management in adolescent transgender males

Introduction: Gender dysphoria is associated with increased rates of anxiety, depression, and suicidal ideation in adolescents. There is anecdotal evidence that menstruation increases the occurrence of gender dysphoria in adolescent transgender males. We hypothesize that menses are distressing to transgender males and this population would benefit from menstrual management. Methods: We conducted a retrospective chart review of all transgender male patients seen in the Nemours Gender Wellness Program (GWP) and limited our population to those who have reached menarche. Data was extracted from the encounters at the GWP clinic and recorded in REDCap. We compared self-reported symptoms of gender dysphoria at 3 months, 6 months, and one year following an individual’s baseline visit to the GWP. The incidence of gender dysphoria at subsequent visits will highlight the efficacy of treatment. Results: Preliminary results show that a majority of our population reported significant gender dysphoria related to menses. Of patients reporting gender dysphoria at the initial visit, 84% chose to use menstrual suppression. Patients who chose an IUD at the initial visit had a higher incidence of breakthrough bleeding and gender dysphoria at the first follow up visit compared to patients who chose other menstrual suppression methods. Conclusion: Menstruation is associated with increased gender dysphoria in transgender male adolescents. Menstrual suppression has the potential to be a transformative treatment for this population. Further research is necessary to determine whether the potential harm that could result from prolonging the distress associated with menses justifies the benefits of using an IUD