Radio pulsar sub-populations (II): The mysterious RRATs

Abstract

Several conjectures have been put forward to explain rotating radio transients (RRATs), the newest subclass of neutron stars, and their connections to other radio pulsars. This work discusses these conjectures in the context of the characteristic properties of the RRAT population. Contrary to expectations, it is seen that: (a) the RRAT population is statistically un-correlated with the nulling pulsars and (b) the RRAT phenomenon is unlikely to be related to old age or death-line proximity. It is perhaps more likely that the special emission property of RRATs is a signature of them being later evolutionary phases of other types of neutron stars which may have resulted in restructuring their magnetic fields.

Appendix. The RRATs

Table 5 lists the known RRATs, detected till date, which we have used for our calculations in this work. Majority of the sources are obtained from the RRATalog site maintained by Bingyi Cui and Maura McLaughlin. For the rest, discovery papers have been referred. The parameter values for spin period ($P_s$), dispersion measure (DM), characteristic age ($\tau _c$) and surface dipolar field ($B_s$) are taken from the ATNF pulsar catalog (Manchester & Hobbs 2005), except where the objects are not yet included in the ATNF list. Parameter values for these second set of objects are taken from the discovery papers and the references are marked with a -P. For some sources, different names have been used by different groups. We have primarily used the ATNF names and indicated the alternative names in the ‘Other-Name’ column. The references cited in the tables with numbers ranging from 1 to 9 correspond to the following:

• (1) RRATalog (last update September 2016);

• (2) Weltevrede et al. (2011);

• (3) Esamdin et al. (2012);

• (4) Deneva et al. (2013);

• (5) Cui et al. (2017);

• (6) Tyul’bashev et al. (2018);

• (7) Good (2021);

• (8) Logvinenko et al. (2020);

• (9) Tyul’bashev et al. (2021).

RRATalog: http://astro.phys.wvu.edu/rratalog/

ATNF: http://www.atnf.csiro.au/research/pulsar/psrcat/