Simultaneous X-ray and radio observations of the radio-mode-switching pulsar PSR B1822−09

Abstract

We report on simultaneous X-ray and radio observations of the radio-mode-switching pulsar PSR B1822−09 with ESA's XMM-Newton and the WSRT, GMRT and Lovell radio telescopes. PSR B1822−09 switches between a radio-bright and radio-quiet mode, and we discovered a relationship between the durations of its modes and a known underlying radiomodulation timescale within the modes. We discovered X-ray (energies 0.2−1.4 keV) pulsations with a broad sinusoidal pulse, slightly lagging the radio main pulse in phase by 0.094 ± 0.017, with an energy-dependent pulsed fraction varying from ∼ 0.15 at 0.3 keV to ∼ 0.6 at 1 keV. No evidence is found for simultaneous X-ray and radio mode switching. The total X-ray spectrum consists of a cool component (T ∼ 0.96 × 10 6 K, hot-spot radius R ∼ 2.0 km) and a hot component (T ∼ 2.2 × 10 6 K, R ∼ 100 m). The hot component can be ascribed to the pulsed emission and the cool component to the unpulsed emission. The high-energy characteristics of PSR B1822−09 resemble those of middle-aged pulsars such as PSR B0656+14, PSR B1055−52 and Geminga, including an indication for pulsed highenergy gamma-ray emission in Fermi LAT data. Explanations for the high pulsed fraction seem to require different temperatures at the two poles of this orthogonal rotator, or magnetic anisotropic beaming effects in its strong magnetic field. In the X-ray skymap we found a harder source at only (5.1 ± 0.5) ′′ from PSR B1822−09, which might be a pulsar wind nebula.

Periodic Q-mode modulation in PSR J1825−0935 (PSR B1822−09)

“…Latham et al (2012) associated the periodic Q-mode modulation with subpulse drifting. However, no organized drifting pattern has been detected (Hermsen et al 2017).…”

“…Dyks et al (2005) proposed that the IP and the PC originate from the same emission region and that the PC emission intermittently reverses its direction to form the IP. Although it is much harder to understand the IP-PC correlation in two-pole models, on the basis of the separation between the IP and the MP and/or polarization properties of this pulsar, many investigators argued that PSR J1825−0935 is an almost orthogonal rotator and that the IP and the PC are emitted from two opposite magnetic poles (Backus et al 2010;Maciesiak et al 2011;Latham et al 2012;Hermsen et al 2017). Another curious property of PSR J1825−0935 is the periodic modulation in the Q-mode.…”

Periodic mode changing in PSR J1048−5832

“…In a recent work by Basu & Mitra (2019), the periodic amplitude modulation has also been seen in the core single pulsar PSR J0826+2637. A periodic phase-stationary intensity modulation occurring in the interpulse and the main pulse was observed in PSR J1825−0935 (Fowler & Wright 1982;Gil et al 1994;Backus et al 2010;Latham et al 2012;Hermsen et al 2017;Yan et al 2019). Similar to PSR J1048−5832, the main pulse of PSR J1825−0935 is partially modulated with an unmodulated trailing component.…”

The Radio and X-ray Mode-Switching Pulsar PSR B0943+10

“…Very interesting results were obtained by applying a 3-D maximum likelihood analysis [28] to simultaneously derive the spectra of the pulsed and unpulsed emission. The findings of [1] for the Q-mode were confirmed (Fig.…”