Vladimir V. Sokolov

Subaru optical observations of the two middle-aged pulsars PSR B0656+14 and Geminga

Aims. We carried out a deep subarcsecond BRI imaging of the two middle-aged pulsars to establish their properties in the optical range Methods. Astrometry and photometry methods are applied to identify the pulsars and to measure their fluxes. We also reanalyze arch ival ESO/NTT and HST broadband data and find that some published fluxes f or Geminga were estimated inaccurately. The resulting dereddened broadband spectra in the near-IR-UV range are analyzed and compared with available data from the radio through gamma-rays. Results. Both pulsars are detected at>10σ level. Geminga is for the first time reliably detected in the I band with a magnitude of 25. 10±0.14. The dereddened spectra of both pulsars are remarkably similar to each other and show significant flux increases towards th e far-UV and near-IR, and a wide flux excess in V-I bands. This suggests a multicomponent structure of the optical emission. The nonthermal power law component of the pulsar magnetospheric origin dominates in the most part of the optical range. For PSR B0656+14 it is compatible with a low energy extension of the power law tail seen in hard X-rays. For Geminga the respective extension overshoots by a factor of 100 the nonthermal optical flux, which has a less steep spectral slope than in X-r ays. This implies a spectral break at a photon energy∼1 keV. The flux increases towards the far-UV are compatible with contributions of the Rayleigh-Jeans parts of the blackbody components from whole surfaces of the neutron stars dominating in soft X-rays. The V-I excess, which is most significant for PSR B0656+14, suggests a third spectral component of still unidentified origin. Faint, a few arcseconds in size ne bulae extended perpendicular to the proper motion directions of the pulsars, are seen around both objects in our deepest I band images. They can be optical counterparts of the bow-shock head of Geminga and of the tentative pulsar wind nebula of PSR B0656+14 observed in X-rays.

Subaru optical observations of the old pulsar PSR B0950+08 ⋆

We report the B band optical observations of an old (τ ∼ 17.5 Myr) radiopulsar PSR B0950+08 obtained with the Suprime-Cam at the Subaru telescope. We detected a faint object, B = 27. m 07 ± 0.16. Within our astrometrical accuracy it coincides with the radio position of the pulsar and with the object detected earlier by Pavlov et al. (1996) in UV with the HST/FOC/F130LP. The positional coincidence and spectral properties of the object suggest that it is the optical counterpart of PSR B0950+08. Its flux in the B band is two times higher than one would expect from the suggested earlier Rayleigh-Jeans interpretation of the only available HST observations in the adjacent F130LP band. Based on the B and F130LP photometry of the suggested counterpart and on the available X-ray data we argue in favour of nonthermal origin of the broad-band optical spectrum of PSR B0950+08, as it is observed for the optical emission of the younger, middle-aged pulsars PSR B0656+14 and Geminga. At the same time, the optical efficiency of PSR B0950+08, estimated from its spin-down power and the detected optical flux, is by several orders of magnitude higher than for these pulsars, and comparable with that for the much younger and more energetic Crab pulsar. We cannot exclude the presence of a compact, ∼1 �� , faint pulsar nebula around PSR B0950+08, elongated perpendicular to the vector of its proper motion, unless it is not a projection of a faint extended object on the pulsar position.

Some astrophysical consequences of a dynamical interpretation of gravitation

In the framework of a dynamical (field-theoretical) interpretation of gravitation, it is shown that in the case of spherical collapse of a body to about R/sub g/ the energy radiated in the form of scalar gravitational waves may reach aboutMc/sup 2/. Instead of producing a black hole, the gravitational collapse will result in a powerful pulse (or train of pulses) of scalar gravitational radiation. This opens up new possibilities for interpreting supernova explosions and the high peculiar velocities of some O-B stars. Strong scalar radiation is also expected from the active nuclei of galaxies. The superluminal expansion observed in some compact extragalactic radio sources may be due to scalar radiation. The possibility of detecting scalar gravitational waves is discussed.

Antigravitation in gravidynamics

In the bounds of the consistent dynamic interpretation of gravitation (gravidynamics) a gravitational field is divided into two components: scalar and tensor, each interacting with its sources by the same coupling constant. Generated by a massive object, a spherically-symmetrical gravitational field in vacuum has an effect on test bodies as an algebraic sum of attraction (proper gravitation) and repulsion (or antigravitation). The source of the scalar part of the field (or the source of antigravitation) is the trace of the energy-momentum tensor of the gravitating body, which is determined in the end by the total mass M or the total energy Mc2 of this body, including its “coat” consisting of virtual gravitons.

High time resolution multi-band photo-polarimetric observations of the binary millisecond redback pulsar J1023+0038 with the BTA

We briefly report first results of high time resolution optical multiband panoramic photopolarimetric observations of the eclipsing binary millisecond redback pulsar J1023+0038 obtained in February 2017 with the 6 m BTA telescope. Our data show that the pulsar still remained in the lowmass X-ray binary stage, which is characterised by rapid flaring at time scales of 10-100 s with amplitudes of 0.2-0.5 mag. We resolved a fine structure of the flares at time scales of 0.1–10 s. The polarimetry at the time scale of 12 s shows no variable polarization with an upper limit of 2-4% for the linear polarization degree in the flaring and quiet stages. We shortly outline implications of the results.