Rotational and X-ray luminosity evolution of high-B radio pulsars

Abstract

In continuation of our earlier work on the long-term evolution of the so-called high--B radio pulsars (HBRPs) with measured braking indices, we have investigated the long-term evolution of the remaining five HBRPs for which braking indices have not been measured yet. This completes our source-by-source analyses of HBRPs in the fallback disc model that was also applied earlier to anomalous X-ray pulsars (AXPs), soft gamma repeaters (SGRs), and dim isolated neutron stars (XDINs). Our results show that the X-ray luminosities and the rotational properties of these rather different neutron star populations can be acquired by neutron stars with fallback discs as a result of differences in their initial conditions, namely the initial disc mass, initial period and the dipole field strength. For the five HBRPs, unlike for AXPs, SGRs and XDINs, our results do not constrain the dipole field strengths of the sources. We obtain evolutionary paths leading to the properties of HBRPs in the propeller phase with dipole fields sufficiently strong to produce pulsed radio emission.Comment: 14 pages, 3 figures, 1 table, accepted for publication in New Astronom

Long-term evolution of RRAT J1819–1458

“…The estimated B0,min values seen in Fig. 2 is important in that it is compatible with a continuous distribution for the B0 values of all single neutron star populations (AXP/SGR, XDIN, HBRP, RRAT and CCO) in the fallback disc model, filling the gap between B0 ∼ 10 9 G for CCOs (Benli & Ertan 2018a) and B0 10 11 G for the other populations (Alpar 2001;Ekşi & Alpar 2003;Ertan et al 2007Ertan et al , 2009Ertan et al , 2014Ertan 2017;Benli & Ertan 2017, 2018b.…”

“…To test these ideas, a long-term evolution model for neutron stars with fallback discs was developed including the effects of X-ray irradiation with contribution of the intrinsic cooling of the neutron star, and the inactivation of the disc at low temperatures on the evolution of the star (Ertan et al 2009;Alpar et al 2011;Çalışkan et al 2013). Later, it was shown that the individual source properties of AXP/SGRs (Benli & Ertan 2016), XDINs (Ertan et al 2014, high magnetic-field radio pulsars (HBRPs) (Çalışkan et al 2013;Benli & Ertan 2017, 2018b, and CCOs (Benli & Ertan 2018a) can be reproduced in the same long-term evolution model with very similar main disc parameters, supporting the idea proposed by Alpar (2001).…”

“…In the longterm evolution, rout decreases with decreasing X-ray irradiation flux that can be written as Firr 1.2CLx/(πr 2 ) (Fukue 1992), where r is radial distance from the star, Lx is the Xray luminosity of the star, and C is the irradiation parameter which depends on the disc geometry and the albedo of the disc surfaces. Individual source properties of AXP/SGRs, XDINs, HBRPs, and CCOs could be reproduced self consistently with TP ∼ 50 − 150 K (Benli & Ertan 2016, 2017, 2018b and C ∼ (1 − 7) × 10 −4 (Ertan &Çalışkan 2006; Ertan et al 2007). The TP values estimated in our model are in agreement with results indicating that the disc is likely to be active at temperatures ∼ 300 K (Inutsuka & Sano 2005), while our C range is similar to that estimated for the lowmass X-ray binaries (see e.g.…”

Is PSR J0726-2612 a dim isolated neutron star progenitor?

“…In the fallback disc model, B 0 values are estimated to be one to three orders smaller than the values inferred from the dipole torque formula. The long-term evolution of XDINs and HBRPs with fallback discs was studied earlier by Ertan et al (2014) and Benli & Ertan (2017, 2018a. The model can reproduce P, P and L x of individual XDIN and HBRP sources with B 0 in the ranges of (0.3 -1.3) ×10 12 G for XDINs and (0.3 -6) × 10 12 G for HBRPs.…”

“…The model can reproduce P, P and L x of individual XDIN and HBRP sources with B 0 in the ranges of (0.3 -1.3) ×10 12 G for XDINs and (0.3 -6) × 10 12 G for HBRPs. These relatively weak fields together with the long periods place XDINs well below the pulsar death line (see Ertan et al 2014, figure 4) in the B 0 − P diagram (Chen & Ruderman 1993), while HBRPs with relatively strong fields and/or short periods are located above the death line (Benli & Ertan 2017, 2018a. In other words, in the fallback disc model, the lack of radio pulses from XDINs is due to their weak dipole fields, rather than the beaming geometry.…”