Abstract Details
| Name: Sushan Konar Affiliation: NCRA-TIFR, Pune Conference ID: ASI2015_376 Title : Nuling Radio Pulsars : A Statistical Study Authors and Co-Authors : 1. Devansh Agarwal IISER, Trivandrum India 2. Vishal Gajjar Xinjian Astronomical Observatory, Xinjiang, China 3. Yashwant Gupta NCRA-TIFR, Pune India Abstract Type : Poster Abstract Category : Stars, The Milky Way Galaxy and its neighbours Abstract : Radio pulsars are strongly magnetized rotating neutron stars and are characterized by their short spin periods ($P \sim 10^{-3} - 10^2$~s) and large inferred surface magnetic fields ($B \sim 10^8 - 10^{15}$~G). Abrupt cessation of their pulsed radio emission for several pulse periods, observed in some hundred odd pulsars, is known as the phenomenon of nulling. The nature and degree of this nulling varies from pulsar to pulsar. Detailed investigations of the nulling behaviour of individual pulsars and theoretical modeling of the phenomenon have been undertaken by many individuals/groups. However, except for some of the pioneering studies (Rankin 1986; Biggs 19992; Wang, Manchester & Johnston 2007) comprehensive statistical study of nulling has not been given a lot of attention. Given the existing data it is now possible to find the statistical characteristics of the population of nulling pulsars. We investigate this. In the analysis, we also include the intermittent pulsars and the rotating radio transients (RRAT). Recently, it has been suggested that there may exist a trend for nulling activity, going from ordinary nulling pulsars to intermittents to RRATs. Here we try to quantify the nulling behaviour to check for any difference between these different classes of pulsars. With that aim we find the proximity of a given object to the death-line. We quantify this proximity by a parameter $q_d$ such that, $q_d = \tau_d / \tau_c$. Here $\tau_d$ is the time left for a pulsar to reach the death line assuming its magnetic field to remain constant at the present value. And $\tau_c$ is the characteristic age of a pulsar given by $P/\dot{P}$. Evidently, the value of $\tau_d$ depends on the choice of a particular death-line. We find that for any assumed death-line the statistical distribution of $q_d$ for ordinary nulling pulsars is very different from that of the RRATs. We also address the issue of birthrates which has been considered by Keane & Kramer (2008). The observed and the predicted birth rates of the neutron stars differ by a large amount, the predicted one being higher. The major problem is concerning the birthrate of the RRATs, which is highest among rotation powered pulsars (RPP), X-ray dim neutron stars (XDINS) and Magnetars. This suggests that somehow RRATs need to be linked with these populations through some evolutionary pathways. Statistical tests performed by us again indicate that RRATs are different from the nulling/non-nulling pulsars, i.e., the population of RPPs. References : 1. Biggs J. D., 1992, ApJ, 394, 574 2. Keane, E. F., Kramer, M., 2008, MNRAS, 391, 2009 3. Rankin J., 1986, ApJ, 301, 901 4. Wang N., Manchester R. N., Johnston S., 2007, MNRAS, 377, 1383 |