We perform population synthesis studies of different types of neutron stars (NSs) (thermally emitting isolated NSs, normal radio pulsars, magnetars) taking into account the magnetic field decay and using results from the most recent advances in NS cooling theory. For the first time, we confront our results with observations using simultaneously the log N–log S distribution for nearby isolated NSs, the log N–log L distribution for magnetars, and the distribution of radio pulsars in the diagram. For this purpose, we fix a baseline NS model (all microphysics input), and other relevant parameters to standard values (velocity distribution, mass spectrum, birth rates, etc.), allowing us to vary the initial magnetic field strength. We find that our theoretical model is consistent with all sets of data if the initial magnetic field distribution function follows a lognormal law with 〈log (B0/G)〉∼ 13.25 and . The typical scenario includes about 10 per cent of NSs born as magnetars, significant magnetic field decay during the first million years of a NS life (only about a factor of 2 for low‐field NSs but more than an order of magnitude for magnetars), and a mass distribution function dominated by low‐mass objects. This model explains satisfactorily all known populations. Evolutionary links between different subclasses may exist, although robust conclusions are not yet possible.

An overview of the results of observations for the transient X-ray pulsar 4U 0115+63, a member of a binary system with a Be star, since its discovery to the present day (∼40 years) based on data from more than dozen observatories and instruments is presented. A overall light curve and the history of change in the spin frequency of the neutron star over the entire history of its observations, which also includes the results of recent measurements made by the INTEGRAL observatory during the 2004, 2008, and 2011 outbursts, are provided. The source's energy spectra have also been constructed from the INTEGRAL data obtained during the 2011 outburst for a dynamic range of its luminosities (10 37 − 7 × 10 37 erg s −1 ). We show that apart from the fundamental harmonic of the cyclotron absorption line at energy ∼11 keV, its four higher harmonics at energies ≃ 24, 35.6, 48.8, and 60.7 keV are detected in the spectrum. We have performed a detailed analysis of the source's spectra in the 4-28 keV energy band based on all of the available RXTE archival data obtained during bright outbursts in 1995 − 2011. We have confirmed that modifying the source's continuum model can lead to the disappearance of the observed anticorrelation between the energy of the fundamental harmonic of the cyclotron absorption line and the source's luminosity. Thus, the question about the evolution of the cyclotron absorption line energy with the luminosity of the X-ray pulsar 4U 0115+63 remains open and a physically justified radiation model for X-ray pulsars is needed to answer it. INTRODUCTIONThe X-ray pulsar 4U 0115+63 has a long history of observations and is well suited for testing models for the evolution of binary systems, models for the structure and evolution of decretion disks around Be stars, and models for the structure of emitting regions (accretion columns) in neutron stars. The source was discovered in the UHURU satellite survey (Giacconi et al., 1972;Forman et al., 1978). Later on, this object was found in the Vela-5B satellite archival data since 1969 (Whitlock et al., 1989). Accurate measurements of its position in the sky were subsequently made by the SAS-3, Ariel-V, and HEAO-1 observatories Johnston et al., 1978). These measurements allowed the optical component in this binary system

We study the evolution of isolated neutron stars on long time‐scales and calculate the distribution of these sources in the main evolutionary stages: ejector, propeller, accretor and georotator. We make comparisons among different initial magnetic field distributions taking into account the possibility of magnetic field decay, and include in our calculations the stage of subsonic propeller. It is shown that though the subsonic propeller stage can be relatively long, initially highly magnetized neutron stars (B0≳ 1013 G) reach the accretion regime within the Galactic lifetime if their kick velocities are not too large. The fact that in previous studies made >10 yr ago such objects were not considered results in a slight increase of the accretor fraction in comparison with earlier conclusions. Most of the neutron stars similar to the Magnificent Seven are expected to become accreting from the interstellar medium after a few billion years of their evolution. They are the main predecessors of accreting isolated neutron stars.

Recently, we discovered a bug in our population synthesis (PS) code presented in A&A 2008, 482, 617. This bug concerns the application of the improved ISM models to calculate the absorbed X-ray flux. The code erroneously did not cover the whole Galactic coordinate (l, b) range of the ISM-models to obtain the absorbing column density N(H). Instead, only a small region ( l ≈ 7 deg, b ≈ 7 deg) around the Galactic Center was used, which led to a significant overestimation of the absorption translating into an underestimation of the predicted neutron star number.While all our main conclusions remain valid we report in the following on some details regarding the corrected results. Comparison of log N-log S distributions for different model modificationsThe log N-log S curves in Figs. 3 and 4 of the original paper remain unchanged. The log N-log S curves for the new analytical as well as for the Hakkila ISM model in Fig. 5 of the original paper are updated in Fig. 1. The corrected curves for both ISM models are now situated ≈0.3 dex above the observational points. The differences between the Hakkila ISM and the improved ISM analytical model are smaller than those obtained by the original PS-code. However, as before, the application of the Hakkila ISM model results in lower N for high count rates than obtained by using the analytical ISM model, and in higher N for low count rates. Comparison of our new results with observations of bright, cooling NSs indicates that the model overpredicts the number of NSs by roughly a factor of two for both ISM models. The possible reasons for this discrepancy are an inadequate treatment of the NS birth rate or of their thermal evolution, or yet other, not in this paper investigated properties like atmospheres, magnetic fields, or statistical fluctuations. Birth rates of neutron stars are highly uncertain, especially at larger distances (see, e.g.,