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Short-term rapid depressions in Galactic cosmic ray (GCR) flux, historically referred to as Forbush decreases (FDs), have long been recognized as important events in the observation of cosmic ray (CR) activity. Although theories and empirical results on the causes, characteristics, and varieties of FDs have been well established, detection of FDs, from either isolated detectors' or arrays of neutron monitor data, remains a subject of interest. Efforts to create large catalogues of FDs began in the 1990s and have continued to the present. In an attempt to test some of the proposed CR theories, several analyses have been conducted based on the available lists. Nevertheless, the results obtained depend on the FD catalogues used. This suggests a need for an examination of consistency between FD catalogues. This is the aim of the present study. Some existing lists of FDs, as well as FD catalogues developed in the current work, were compared, with an emphasis on the FD catalogues selected by the global survey method (GSM). The Forbush effects and interplanetary disturbances database (FEID), created by the Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radiowave Propagation Russian Academy of Sciences (IZMIRAN), is the only available comprehensive and up to date FD catalogue. While there are significant disparities between the IZMIRAN FD and other event lists, there is a beautiful agreement between FDs identified in the current work and those in the FEID. This may be a pointer to the efficiency of the GSM and the automated approach to FD event detection presented here.

In this paper, a large homogenous sample of Jodrell Bank Observatory (JBO) radio pulsars was used to investigate the statistical effects of interstellar medium (ISM) parameters: dispersion and rotation measure (DM and RM, respectively) on non-discrete timing irregularities of our sample (whose observed timing activity timescales span over 40 years). This is done by using the correlations between the measured DM and RM, and some parameters that have been commonly used to measure non-discrete timing irregularities [timing activity parameter (A), the amount of timing fluctuations absorbed by the cubic term (σR23), measure of pulsar rotational stability (σz ) and stability parameter (∆8)]. Our results show that ISM parameters positively correlate (r > 0.60) with the pulsar timing irregularities parameters of our sample. The significant relationships observed are discussed. Â

The relationship between coronal mass ejections (CMEs) and Forbush decreases (FDs) has been investigated in the past. But the selection of both solar events are difficult. Researchers have developed manual and automated methods in efforts to identify CMEs as well as FDs. While scientists investigating CMEs have made significant advancement, leading to several CME catalogues, including manual and automated events catalogues, those analyzing FDs have recorded relatively less progress. Till date, there are no comprehensive manual FD catalogues, for example. There are also paucity of automated FD lists. Many investigators, therefore, attempt to manually select FDs which are subsequently used in the analysis of the impact of CMEs on galactic cosmic-ray (GCR) flux depressions. However, some of the CME versus FD correlation results might be biased since manual event identification is usually subjective, unable to account for the presence of solar-diurnal anisotropy which characterizes GCR flux variations. The current paper investigates the relation between CMEs and FDs with emphasis on accurate and careful Forbush event selection.

Using a large homogenous sample of Jodrell Bank Observatory (JBO) rotation-powered pulsars with derived pulsar parameter obtained from the Australian Telescope National Facility (ATNF) catalogue, we investigated the degree of statistical dependence of timing noise on surface magnetic field for our sample. The distributions of the timing irregularities parameters reveal a striking trend, in which pulsars with large timing noise parameters on average, have large surface magnetic field with up to 5 orders of magnitude. Regression analysis of the data reveals significant correlations (r ≥ 0.80) between timing noise parameters and the surface magnetic field. The implications of the observed significant relationships are discussed.

The number of sudden spin-ups in radio pulsars known as pulsar glitches has increased over the years. Though a consensus has not been reached with regards to the actual cause of the phenomenon, the electromagnetic braking torque on the crust quantified via the magnitude of pulsar spin frequency first derivative, $ \dot{\nu} $ is a key factor in mechanisms put across toward the understanding of the underlying principles involved. The glitch size has been used to establish a quantity used to constrain the mean possible change in pulsar spin frequency $ (\nu) $ per year due to a glitch known as the `glitch activity'. Traditionally, the glitch activity parameter $ A_{g} $ is calculated from the cumulative glitch sizes in a pulsar at a certain observational time span. In this analysis, we test the possibility of of quantifying the $ A_{g} $ with the pulsars main spin frequency derivatives (i.e. $ \dot{\nu} $ and $\ddot{\nu} $). In this approach, the ratio of the frequency derivatives, i.e. $ |\ddot{\nu}|/\dot{\nu}^{2} $ is seen to constrains the glitch activity in radio pulsars. The glitch size is found to be independent of the magnitude of the ratio, however, based on the recorded glitch events, the lower end of $ |\ddot{\nu}|/\dot{\nu}^{2} $ distribution appear to have more glitches. The minimum inter-glitch time interval in the ensemble of pulsars scale with the ratio as $t_{g} \sim 3.35(|\ddot{\nu}|/\dot{\nu}^{2})^{0.23} $. The $ A_{g} $ quantified in this analysis supports the idea of neutron star inner-crust superfluid being the reservoir of momentum transferred during glitches. It suggests that the moment of inertia of the inner-crust to be at most 10 % of the entire neutron star moment of inertia., Comment: This article is to be published in Astrophysics and Space Science (12 pages, 6 figures and 3 tables)

We present statistical analyses of a large homogenous data sample of Fermi-detected blazars thoroughly studied in order to reassess the relationship between flat-spectrum radio quasars (FSRQs) and subclasses of BL Lacertae objects (BL Lacs) blazar populations. We discovered from the average values of gamma-ray and X-ray spectral indices that the sequence of distribution is indicative of the blazar orientation scheme. Analyses of FSRQs and BL Lacs data show difference in the shape of gamma-ray and X-ray indices: significant anti-correlation (r~ greater than - 0.79) exists between gamma-ray and X-ray spectral indices. The spectral energy distributions of the blazar subclasses show that FSRQs and BL Lacs have similar spectral properties which can be unified through an evolutionary sequence. Nevertheless, there is a significant difference between the shapes of X-ray and gamma-ray spectra of blazars suggesting that different mechanisms are responsible for spectral variations in the two energy bands. All these results suggest that there is a form of a unified scheme for all blazars., 18 pages, 11 figures, 2 Tables. Accepted for Publication in New Astronomy

The distribution of radio core-dominance is consistent with average projection angles of 13.5, 14.8, 16.8, 20.4, and 28.2 for ISPs, LSPs, FSRQs, HSPs, and radio galaxies, respectively. Linear regression analyses of our data yield significant anti-correlation r greater than 0.60 between core-dominance parameter and extended luminosity in each individual subsample, the correlation is significant only when individual subsamples are considered. There is a systematic sequence of the distribution of the different subclasses on the Core-dominance parameter-extended luminosity plane. Nevertheless, little or no correlation between Core-dominance parameter and core luminosity or between Core dominance parameter and gamma-ray luminosity r, less than 0.50 was observed. There is a clear dichotomy between high synchrotron-peaking BL Lacs and other BL Lac subclasses. The results are consistent with a unified view for blazars and can be understood in terms of relativistic beaming persisting at the largest scales., 23 pages, 9 figures. Accepted for publication in Astrophysics and Space Science

Our understanding of the unification of jetted AGNs has advanced greatly as the size of extragalactic sources increased. In the present paper, based on the large sample of radio sources, we compiled 680 blazars (279 FSRQs and 401 BL Lacs) from the 3FGL sample and 64 Seyfert galaxies (3 Narrow-line, 34 and 27 regular Seyfert 1 and Seyfert 2 respectively) from the INTEGRAL survey to statistically test the relationship between Seyfert galaxies and the blazar samples of FSRQs and BL Lacs. We compute the synchrotron (SS), Compton (CS) and inverse Compton (IC) continuous spectra from the low energy components of radio to X-ray, radio to gamma-ray and the high energy component of X-ray to gamma-ray bands, respectively. Results show from the distributions of the continuous spectra that Seyfert galaxies form the tail of the distributions, suggestive of similar underlying history and evolution. A two-sample Kolmogorov-Smirnov test (K.S test) of the continuous spectra showed that Seyfert galaxies differ from BL Lacs and FSRQs in the low energy components of the spectra, while there is no clear difference between them in the high energy component, which implies that high energy emissions in Seyfert galaxies, BL Lacs and FSRQs may be as a result of the same emission mechanism. There is a regular sequence of the distributions on SS/CS and IC/CS planes in each individual subsample. Linear regression analyses of our sample yield significant positive correlations (r greater than 0.60) between SS/CS and IC/CS data. This upturns into an anti-correlation (r greater than -0.60) in IC/SS data. These results are not only consistent with unified scheme for blazars but also show that Seyfert galaxies can be unified with the classical radio-loud AGNs counterparts., Comment: 24 pages, 9 figures, 8 Tables. Accepted for Publication in the Journal of Astrophysics and Astronomy

We use the distributions of spectral indices of a large homogenous sample of Fermi-detected blazars to re-investigate the relationship between flat spectrum radio quasars (FSRQs) and subclasses of BL Lac objects (BL Lacs). We compute the broadband synchrotron and Compton spectral indices from radio-to-X-ray and X-ray to gamma-ray bands, respectively. Analyses of our data show continuity in the distributions of the spectral indices from FSRQs to HSP through LSP and ISP subclasses of BL Lacs. We find from gamma-ray luminosity distribution that the jetted radio galaxies form the low-luminosity tail of the distribution, suggestive that the sequence can be extended to the young jetted galaxy populations. We observe a significant difference in the shape of Compton and synchrotron spectra: significant anti-correlation (r ~ -0.80) exists between the broadband Compton and synchrotron spectral indices. Furthermore, the broadband spectral indices vary significantly with redshift (z) at low redshift (z less than 0.3) and remain fairly constant at high (z greater than or egual to 0.3) redshift. The trend of the variations suggests a form of the evolutionary connection between subclasses of blazars. Thus, while the selection effect may be significant at low redshift, an evolutionary sequence can also be important. Our results are not only consistent with a unified scheme for blazars and their young jetted galaxy counterparts but also suggest that the broadband spectral sequence of blazars is not a secondary effect of redshift dependence., 10 pages, 10 figures

Detailed long-term timing observations have revealed that the expected smooth spin- down of many pulsars is prone to a variety of discrete disruptions often referred to as glitches. Although the nature and behaviour of small glitches are still poorly understood compared to large glitches, it is widely believed that both originate from some complex dynamical changes within the neutron star interior and their study could provide valuable information about the internal structure and dynamics of the neutron stars. In this paper, the distribution of glitch sizes, glitch patterns and possible relationships between glitch parameters and pulsar rotational parameters were statistically investigated using 482 glitches reported in 168 pulsars. The distribution of glitch sizes showed predominance of large glitches for J0537-6910, J0835-4510, J1341-6220 and J18001-2304; small glitches for J0534+2200, J0631+1036 and J1740-3015 and continuous glitch size distribution for J0534+2200, J1341-6220, J1740-3015 and J1801-2304. PSRs J0537-6910 and J0835-4510 showed specific regular pattern with J1740-3015 showing a quasi-regular pattern. The mean glitch size of these pulsars relates considerably with rotational frequency (ν) and spin down rate ( ) in simple power laws. Similarly, variation of glitch activity with the characteristic age (τ) traces a curve that peaks at τ = 104 yr and decays with age for older pulsars with τ ≥ 104yr. The angular momentum transfer resulting to glitches appears to be maximum at youthful age (≈ 104-106yr) of pulsars when certain rotational properties as well as temperature of the star best supports vortex pinning and unpinning of the superfluid of the star interior.