On the nature of the intermittent pulsar PSR B1931+24

PSR B1931+24 is the first intermittent radio pulsar discovered to date, characterized by a 0.8 s pulsation which turns on and off quasi-periodically every ~35 days, with a duty cycle of ~10%. We present here X-ray and optical observations of PSR B1931+24 performed with the Chandra X-ray Observatory and Isaac Newton Telescope, respectively. Simultaneous monitoring from the Jodrell Bank Observatory showed that this intermittent pulsar was in the radio-on phase during our observations. We do not find any X-ray or optical counterpart to PSR B1931+24 translating into an upper limit of ~2x10^{31} erg/s on the X-ray luminosity, and of g' > 22.6 on the optical magnitude. If the pulsar is isolated, these limits cannot constrain the dim X-ray and optical emission expected for a pulsar of that age (~1.6 Myr). We discuss the possibility that the quasi-periodic intermittent behavior of PSR B1931+24 is due to the presence of a low mass companion star or gaseous planet, tight with the pulsar in an eccentric orbit. In order to constrain the parameters of this putative binary system we re-analysed the pulsar radio timing residuals and we found that (if indeed hosted in a binary system), PSR B1931+24 should have a very low mass companion and an orbit of low inclination.Comment: 6 pages; accepted for publication in MNRA

Supernova Kicks and Misaligned Be Star Binaries

Be stars are rapidly spinning B stars surrounded by an outflowing disc of gas in Keplerian rotation. Be star/X-ray binary systems contain a Be star and a neutron star. They are found to have non-zero eccentricities and there is evidence that some systems have a misalignment between the spin axis of the star and the spin axis of the binary orbit. The eccentricities in these systems are thought to be caused by a kick to the neutron star during the supernova that formed it. Such kicks would also give rise to misalignments. In this paper we investigate the extent to which the same kick distribution can give rise to both the observed eccentricity distribution and the observed misalignments. We find that a Maxwellian distribution of velocity kicks with a low velocity dispersion, $\sigma_k \approx 15\rm km s^{-1}$, is consistent with the observed eccentricity distribution but is hard to reconcile with the observed misalignments, typically $i \ge 25^\circ$. Alternatively a higher velocity kick distribution, $\sigma_k = 265 \rm km s^{-1}$, is consistent with the observed misalignments but not with the observed eccentricities, unless post-supernova circularisation of the binary orbits has taken place. We discuss briefly how this might be achieved.Comment: Accepted for publication in MNRA

Study of measured pulsar masses and their possible conclusions

We study the statistics of 61 measured masses of neutron stars (NSs) in binary pulsar systems, including 18 double NS (DNS) systems, 26 radio pulsars (10 in our Galaxy) with white dwarf (WD) companions, 3 NSs with main-sequence companions, 13 NSs in X-ray binaries, and one undetermined system. We derive a mean value of M = 1.46 +/- 0.30 solar masses. When the 46 NSs with measured spin periods are divided into two groups at 20 milliseconds, i.e., the millisecond pulsar (MSP) group and others, we find that their mass averages are, respectively, M=1.57 +/- 0.35 solar masses and M=1.37+/- 0.23 solar masses. In the framework of the pulsar recycling hypothesis, this suggests that an accretion of approximately 0.2 solar mass is sufficient to spin up a neutron star and place it in the millisecond pulsar group. An empirical relation between the accreting mass and MSP spin period is \Delta M=0.43 (solar mass)(P/1 ms)^{-2/3}. UNlike the standard recycling process, if a MSP is formed by the accretion induced collapse (AIC) of a white dwarf with a mass less than Chandrasekha limit, e.g. 1.35 solar mass, then the binary MSPs involved in AICs is not be higher than 20%, which imposes a constraint on the AIC origin of MSPs.Comment: 6 pages, 5 figures, in press, Astronomy and Astrophysics 2011, 527, 8

Nodal and Periastron Precession of Inclined Orbits in the Field of a Rapidly Rotating Neutron Star

We derive a formula for the nodal precession frequency and the Keplerian period of a particle at an arbitrarily inclined orbit (with a minimum latitudinal angle reached at the orbit) in the post-Newtonian approximation in the external field of an oblate rotating neutron star (NS). We also derive formulas for the nodal precession and periastron rotation frequencies of slightly inclined low-eccentricity orbits in the field of a rapidly rotating NS in the form of asymptotic expansions whose first terms are given by the Okazaki--Kato formulas. The NS gravitational field is described by the exact solution of the Einstein equation that includes the NS quadrupole moment induced by rapid rotation. Convenient asymptotic formulas are given for the metric coefficients of the corresponding space-time in the form of Kerr metric perturbations in Boyer--Lindquist coordinates.Comment: 12 page

Binary and Millisecond Pulsars at the New Millennium

We review the properties and applications of binary and millisecond pulsars. Our knowledge of these exciting objects has greatly increased in recent years, mainly due to successful surveys which have brought the known pulsar population to over 1300. There are now 56 binary and millisecond pulsars in the Galactic disk and a further 47 in globular clusters. This review is concerned primarily with the results and spin-offs from these surveys which are of particular interest to the relativity community.Comment: 59 pages, 26 figures, 5 tables. Accepted for publication in Living Reviews in Relativity (http://www.livingreviews.org

Participation‐related constructs and participation of children with additional support needs in schools

From Wiley via Jisc Publications RouterHistory: received 2022-03-07, rev-recd 2022-07-21, accepted 2022-07-25, pub-electronic 2022-09-25Article version: VoRPublication status: PublishedFunder: City of Edinburgh CouncilFunder: National Health Service LothianFunder: Scottish Government; Id: http://dx.doi.org/10.13039/100012095Funder: Queen Margaret University, Edinburgh; Id: http://dx.doi.org/10.13039/100010033Abstract: Aim: To investigate associations between participation‐related constructs and participation frequency and involvement in inclusive schools. Method: In this cross‐sectional study, teachers of children with additional support needs, including intellectual disability, autism, and learning difficulties, completed measures. Participation‐related constructs were measured using the School Participation Questionnaire; participation frequency and involvement were measured using the Participation and Environment Measure for Children and Youth. A series of multilevel linear mixed‐effects regression models with maximum likelihood estimates and bootstrap confidence intervals with p‐values were obtained. Final models included participation‐related constructs and participation, controlling for demographic and diagnostic confounders (including age, sex, language, level of school support, and autism). Results: Six hundred and eighty‐eight children (448 [65.1%] males; mean age 8 years 7 months [range 4 years 10 months–12 years 13 months, standard deviation 2 years 1 months]) were assessed by 252 teachers. Across a series of models, participation‐related constructs were consistently associated with more intensive participation (competence, environment, identity p < 0.001; symptoms p = 0.007), independent of confounders. More frequent participation remained associated with three of four participation‐related constructs (competence, identity p < 0.001; environment p = 0.021). Age (p = 0.046), language (p = 0.002), and level of school support (p = 0.039) also remained significantly associated with frequency of participation. Interpretation: Children with additional support needs in inclusive schools may have several participation barriers. Policies and interventions to improve participation are needed

Sporadic Cryptosporidiosis, North Cumbria, England, 1996–2000

Risk factors for sporadic cryptosporidiosis were determined in 152 patients and 466 unmatched controls who resided in two local government districts in North Cumbria, North West England, from March 1, 1996, to February 29, 2000. Risk was associated with the usual daily volume of cold unboiled tap water drunk (odds ratio [OR] 1.40, 95% confidence intervals [CI] 1.14 to 1.71 per pint consumed per day [p = 0.001]) and short visits to farms (OR 2.02, 95% CI 1.04 to 3.90, p = 0.04). Fifty-six (84%) of 67 fecal specimens from patients obtained from January 1, 1998, and February 29, 2000, were Cryptosporidium parvum genotype 2 (animal and human strain). Livestock fecal pollution of water sources appears to be the leading cause of human sporadic cryptosporidiosis in this population and shows the need for better protection of water catchments from livestock and improved drinking water treatment in this area of England

Magnetic Field Generation in Stars

Enormous progress has been made on observing stellar magnetism in stars from the main sequence through to compact objects. Recent data have thrown into sharper relief the vexed question of the origin of stellar magnetic fields, which remains one of the main unanswered questions in astrophysics. In this chapter we review recent work in this area of research. In particular, we look at the fossil field hypothesis which links magnetism in compact stars to magnetism in main sequence and pre-main sequence stars and we consider why its feasibility has now been questioned particularly in the context of highly magnetic white dwarfs. We also review the fossil versus dynamo debate in the context of neutron stars and the roles played by key physical processes such as buoyancy, helicity, and superfluid turbulence,in the generation and stability of neutron star fields. Independent information on the internal magnetic field of neutron stars will come from future gravitational wave detections. Thus we maybe at the dawn of a new era of exciting discoveries in compact star magnetism driven by the opening of a new, non-electromagnetic observational window. We also review recent advances in the theory and computation of magnetohydrodynamic turbulence as it applies to stellar magnetism and dynamo theory. These advances offer insight into the action of stellar dynamos as well as processes whichcontrol the diffusive magnetic flux transport in stars.Comment: 41 pages, 7 figures. Invited review chapter on on magnetic field generation in stars to appear in Space Science Reviews, Springe

Phenomenology of the Lense-Thirring effect in the Solar System

Recent years have seen increasing efforts to directly measure some aspects of the general relativistic gravitomagnetic interaction in several astronomical scenarios in the solar system. After briefly overviewing the concept of gravitomagnetism from a theoretical point of view, we review the performed or proposed attempts to detect the Lense-Thirring effect affecting the orbital motions of natural and artificial bodies in the gravitational fields of the Sun, Earth, Mars and Jupiter. In particular, we will focus on the evaluation of the impact of several sources of systematic uncertainties of dynamical origin to realistically elucidate the present and future perspectives in directly measuring such an elusive relativistic effect.Comment: LaTex, 51 pages, 14 figures, 22 tables. Invited review, to appear in Astrophysics and Space Science (ApSS). Some uncited references in the text now correctly quoted. One reference added. A footnote adde