Orbital Parameters of Binary Radio Pulsars : Revealing Their Structure, Formation, Evolution and Dynamic History

Orbital parameters of binary radio pulsars reveal the history of the pulsars' formation and evolution including dynamic interactions with other objects. Advanced technology has enabled us to determine these orbital parameters accurately in most of the cases. Determination of post-Keplerian parameters of double neutron star binaries (especially of the double pulsar) provide clean tests of GTR and in the future may lead us to constrain the dense matter EoS. For binary pulsars with MS or WD companions, knowledge about the values of the orbital parameters as well as of the spin periods and the masses of the pulsars and the companions might be useful to understand the evolutionary history of the systems. As accreting neutron star binaries lead to orbit circularization due to the tidal coupling during accretion, their descendants i.e. binary MSPs are expected to be in circular orbits. On the other hand, dense stellar environments inside globular clusters (GCs) cause different types of interactions of single stars with pulsar binaries. These interactions can impart high eccentricities to the pulsar binaries. So it is quite common to get eccentric millisecond pulsar binaries in GCs and we find that "fly-by" causes intermediate values of eccentricities while "exchange" or "merger" causes high values of eccentricities. We also show that "ionization" is not much effective in the present stage of GCs. Even in the absence of such kinds of stellar interactions, a millisecond pulsar can have an eccentric orbit as a result of Kozai resonance if the pulsar binary is a member of a hierarchical triple system. PSR J1903+0327 is the only one eccentric millisecond pulsar binary in the galactic disk where stellar interactions are negligible. The possibility of this system to be a member of a hierarchical triple system or past association of a GC have been studied and found to be less likely.Comment: Invited chapter in "Pulsars: Theory, Categories and Applications", Editor: Alexander D. Morozov, 2010, Nova Science Publishers, ISBN: 978-1-61668-919-3; Typos correcte

Prospects of constraining the dense matter equation of state from the timing analysis of pulsars in double neutron star binaries: the cases of PSR J0737-3039A and PSR J1757-1854

The Lense-Thirring effect from spinning neutron stars in double neutron star binaries contribute to the periastron advance of the orbit. This extra term involves the moment of inertia of the neutron stars. Moment of inertia, on the other hand, depends on the mass and spin of the neutron star as well as the equation of state of the matter. If at least one member of the double neutron star binary (better the faster one) is a radio pulsar, then accurate timing analysis might lead to the estimation of the contribution of the Lense-Thirring effect to the periastron advance, which will lead to the measurement of the moment of inertia of the pulsar. Combination of the knowledge on the values of the moment of inertia, the mass, and the spin of the pulsar, will give a new constraint on the equation of state. Pulsars in double neutron star binaries are the best for this purpose as short orbits and moderately high eccentricities make the Lense-Thirring effect substantial, whereas tidal effects are negligible (unlike pulsars with main sequence or white-dwarf binaries). The most promising pulsars are PSR J0737-3039A and PSR J1757-1854. The spin-precession of pulsars due to the misalignment between the spin and the orbital angular momentum vectors affect the contribution of the Lense-Thirring effect to the periastron advance. This effect has been explored for both PSR J0737-3039A and PSR J1757-1854, and as the misalignment angles for both of these pulsars are small, the variation in the Lense-Thirring term is not much. However, to extract the Lense-Thirring effect from the observed rate of the periastron advance, more accurate timing solutions including precise proper motion and distance measurements are essential.Comment: To appear in the special issue of `Universe' dedicated to the conference: "Compact Stars in the QCD Phase Diagram VI" held at The Joint Institute for Nuclear Research (JINR), Dubna, Russia; during 26 - 29 September, 201

Factors affecting Child Labour in India

Child labour in India is a critical socio-economic problem that needs special attention of policy makers. In order to make effective policies to reduce child labour it is important to understand the specific factors that affect it in different situations. The paper empirically examines these factors across 35 Indian states and union territories at three levels of aggregation: total population, rural/urban, and male/female. The results showed that education, fertility, and workforce participation are the major influencing factors in our models. Interestingly, impact of economic indicators of poverty and income differed among total, rural, urban, male, and female population. The explanatory powers of models showed large variations across different levels of aggregation and were stronger for total, rural and female population.

Strategic Human Resource Management: Three-Stage Process and Influencing Organisational Factors

A three-stage model for the process of strategic human resource management is developed in this paper. The three stages cover strategy formulation, implementation and evaluation. The inter-linkages in this dynamic model have been explored. The organisational factors that have enabling or deterring influence on the success of each of these three stages have been discussed. The paper highlights the key role played by HR professionals in these three stages.