Radio Phase-Resolved Spectra of the Conal-Double Pulsar B1133+16

Based on dividing the profile into a number of absolute phase intervals, the phaseresolved spectra （PHRS） are derived from published time-aligned average profiles at radio frequencies over two decades for the classic conal-double pulsar B1133＋16. The relative spectral index, defined as the difference between the spectral indices of a reference and the given arbitrary phase interval, is obtained by power-law fit at each phase interval. The derived phase-resolved spectra show an ＂M-like＂ shape, of which the leading part and trailing part are approximately symmetrical. The basic feature of the PHRS is that the spectrum first flattens then steepens as the pulse phase sweeps from the profile center to the profile edges. The PHRS provide a coherent explanation of the major features of profile evolution of B 1133＋ 16, namely, the pulse width shrinkage with increasing frequency and the frequency evolution of the relative intensity between the leading and trailing conal components, and the bridge emission. The PHRS may be an indicator for emission spectral variation across the pulsar magnetosphere. Possible mapping from PHRS to emission-location-dependent spectral variation is presented, and some intrinsic mechanisms are discussed.

The Bright Single Pulse Emission from PSR B1133+16

We have conducted a comprehensive investigation into the bright single pulse emission from PSR B1133+16using the Giant Metrewave Radio Telescope.High time resolution data(61μs)were obtained at a center frequency of 322 MHz with a bandwidth of 32 MHz over a continuous observation period of 7.45 hr.A total of 1082 bright pulses were sporadically detected with peak flux densities ranging from 10 to 23 times stronger than the average pulse profile.However,no giant pulse-like emission with a relative pulse energy larger than 10 and extremely short duration was detected,indicating that these bright pulses cannot be categorized as giant pulse emission.The majority of these bright pulses are concentrated in pulse phases at both the leading and trailing windows of the average pulse profile,with an occurrence ratio of approximately 2.74.The pulse energy distribution for all individual pulses can be described by a combination of two Gaussian components and a cutoff power-law with an index of α=-3.2.An updated nulling fraction of 15.35%±0.45% was determined from the energy distribution.The emission of individual pulses follows a log-normal distribution in peak flux density ratio.It is imperative that regular phase drifting in bright pulse sequence is identified in both the leading and trailing components for the first time.Possible physical mechanisms are discussed in detail to provide insights into these observations.

Testing Lorentz violation with binary pulsars:constraints on standard model extension

Under the standard model extension （SME） framework, Lorentz invariance is tested in five binary pulsars： PSR J0737-3039, PSR B 1534＋12, PSR J1756-2251, PSR B1913＋16 and PSR B2127＋11C. By analyzing the advance of periastron, we obtain the constraints on a dimensionless combination of SME parameters that is sen- sitive to timing observations. The results imply no evidence for the break of Lorentz invariance at the 10-l level, one order of magnitude larger than the previous estima- tion.

The silicate and carbon-rich models of CoRoT-7b,Kepler-9d and Kepler-10b

Possible bulk compositions of the super-Earth exoplanets CoRoT-7b, Kepler-9d, and Kepler-10b are investigated by applying a commonly used silicate model and a non-standard carbon model. Their internal structures are deduced using a suitable equation of state for the materials. The degeneracy problems of their compo- sitions can be partly overcome, based on the fact that all three planets are extremely close to their host stars. By analyzing the numerical results, we conclude： 1） the iron core of CoRoT-7b is not more than 27% of its total mass within lc~ mass-radius error bars, so an Earth-like composition is less likely, but its carbon rich model can be com- patible with an Earth-like core/mantle mass fraction; 2） Kepler-10b is more likely to have a Mercury-like composition, with its old age implying that its high iron content may be a result of strong solar wind or giant impact; 3） the transiting-only super-Earth Kepler-9d is also discussed. Combining its possible composition with the formation theory, we can place some constraints on its mass and bulk composition.

Preliminary limits of a logarithmic correction to the Newtonian gravitational potential in binary pulsars

We obtain preliminary limits on a logarithmic correction to the Newtonian gravitational potential by using five binary pulsars： PSR J0737-3039, PSR B 1534＋12, PSR J 1756-2251, PSR B 1913＋ 16 and PSR B2127＋ 11C. This kind of correction may originate from fundamental frameworks, like string theories, effective models of grav- ity due to quantum effects and the non-local gravity scheme. We estimate the upper limit of the Tohline-Kuhn-Kruglyak parameter A and the lower limit of the Fabris- Campos parameter α, which parameterize the correction and are connected to each other by αλ = -1. By analyzing the advances of periastron of these binary pulsars, we find that the preliminary upper limit of a is 0.19 ± 0.14 kpc^-1 and the prelimi- nary lower limit of ）, is -5.2 4± 3.8 kpc. They are compatible with the bounds based on dynamics of spiral galaxies but quite different from those given by solar system dynamics. These results indicate that this logarithmic correction might be more ob- servable in current timings of binary pulsars than in motions of the solar system.

Search for giant pulses of radio pulsars at frequency 111 MHz with LPA radio telescope

We have used the unique low frequency sensitivity of the Large Phased Array （LPA） radio telescope of Pushchino Radio Astronomy Observatory to collect a dataset consisting of single pulse observations of second period pulsars in the Northern Hemisphere. During observation sessions in 2011- 2017, we collected data on 71 pulsars at a frequency of 111 MHz using a digital pulsar receiver. We have discovered Giant Radio Pulses （GRPs） from pulsars B0301＋09 and B 1237＋25, and confirmed earlier reported generation of anomalously strong （probable giant） pulses from B 1133＋16 in a statistically significant dataset. Data for these pulsars and from B0950＋08 and B 1112＋50, earlier reported as pulsars generating GRPs, were analyzed to evaluate their behavior over long time intervals. It was found that the statistical criterion （power-law spectrum of GRP distribution of energy and peak flux density） seems not to be strict for pulsars with a low magnetic field at their light cylinder. Moreover, spectra of some of these pulsars demonstrate unstable behavior with time and have a complex multicomponent shape. In the dataset for B0950＋08, we have detected the strongest GRP from a pulsar with a low magnetic field at its light cylinder ever reported, having a peak flux density as strong as 16.8 kJy.