High-energy characteristics of the schizophrenic pulsar PSR J1846-0258 in Kes 75

Abstract

Aims. PSR J1846−0258 is a young rotation-powered pulsar with one of the highest surface magnetic field strengths, located in the centre of SN-remnant Kes-75. In June 2006 a magnetar-like outburst took place. Using multi-year RXTE and INTEGRAL observations covering the epoch of the outburst, we aim to study the temporal and spectral characteristics of PSR J1846−0258 over a broad ∼3-300 keV energy range to derive constraints on theoretical scenarios aiming to explain this schizophrenic behaviour. Methods. We explored all publically available RXTE observations of PSR J1846−0258 to generate accurate ephemerides over the period January 30, 2000-November 7, 2007. Phase-folding procedures yielded pulse profiles for RXTE PCA (∼3-30 keV), RXTE HEXTE (∼15-250 keV) and INTEGRAL ISGRI (∼20-300 keV). The pulsed spectrum over the full ∼3-300 keV energy range was derived, as well as the total spectrum (including the pulsar wind nebula) over the 20-300 keV band with the ISGRI. The timing, spatial, and spectral analyses were applied for epochs before, during, and after the magnetar-like outburst to study the evolution of the high-energy characteristics. Results. ISGRI detected PSR J1846−0258/Kes-75 before outburst during 2003-2006 with a power-law-shape spectrum over the 20-300 keV energy range with photon index Γ = 1.80 ± 0.06 and energy flux (20-300 keV) of (6.62 ± 0.35) × 10 −11 erg/cm 2 s. More than 90 days after the onset of the outburst, still during the decay phase, the same spectral shape was measured (Γ = 1.75 +0.27 −0.31 ) with an indication for a 52% (2.3σ) enhanced total emission, while one year after the outburst the hard X-ray non-thermal emission of PSR J1846−0258/Kes-75 was found to be back to its pre-outburst values. PCA monitoring of PSR J1846−0258 before the outburst yielded phase-coherent ephemerides confirming the earlier derived breaking index of the spindown. During the outburst, incoherent solutions have been derived. We show that the radiative outburst was triggered by a major spin-up glitch near MJD 53 883 ± 3 with a glitch size Δν/ν in the range (2.0−4.4) × 10 −6 . Using all pre-outburst observations of ISGRI and HEXTE for the first time pulse profiles have been obtained up to 150 keV with a broad single asymmetric pulse. The pulse shape did not vary with energy over the 2.9-150 keV energy range, nor did it change during the magnetar-like outburst. The time-averaged pre-outburst ∼3-300 keV pulsed spectrum measured with the PCA, HEXTE, and ISGRI was fitted with a power-law model with Γ = 1.20 ± 0.01. A fit with a curved power-law model gives an improved fit. Around 150 keV the pulsed fraction approaches 100%. For the first 32 days of the magnetarlike outburst, the 3-30 keV pulsed spectrum can be represented with two power laws, a soft component with index Γ s = 2.96 ± 0.06 and a hard component with the pre-outburst value Γ h ∼ 1.2. Above ∼9 keV, all spectra during outburst are consistent with the latter single power-law shape with index ∼1.2. The 2-10 keV flux increased by a factor ∼5 and the 10...

The rotation-powered nature of some soft gamma-ray repeaters and anomalous X-ray pulsars

“…It was there found that a glitch with fractional change of period |∆P|/P ∼ (1.73-2.2) × 10 −6 could explain the outburst of 2006. This theoretical result is in full agreement with the observational analysis by Kuiper & Hermsen (2009), who showed that indeed a major glitch with |∆P|/P ∼ (2-4.4) × 10 −6 is associated with the outburst. Very recently, Archibald et al (2016) reported another example of an X-ray outburst from a radio pulsar, PSR J1119-6127, which also has L X <Ė rot .…”

Possible rotation-power nature of SGRs and AXPs

“…In view of the possible NS rotation-power nature of PSR J1846-0258, Malheiro et al [8] assumed that the outburst with energy (3.8-4.8) × 10 41 erg [20] was triggered by a glitch in the NS, and found that a glitch of |∆P |/P ∼ (1.73-2.2) × 10 −6 could explain the outburst of 2006. This theoretical result is in full agreement with the observational analysis of [21], who showed that indeed a major glitch with |∆P |/P ∼ (2-4.4) × 10 −6 occurred.…”

“…From this set of nine sources, the only glitch detected was the one of PSR J1846-0258 in June 2006 [21], whose observed value of |∆P |/P is shown with the gray-shaded area in these plots. Indeed a minimum mass for the NS can be established for this source by requesting that 1) the entire moment of inertia is involved in the glitch and 2) that the theoretical value of |∆P |/P coincides with the observed value: we obtain M min = 0.72 M ⊙ and M min = 0.61 M ⊙ for the global and local charge neutrality cases, respectively.…”

Pulsars and Magnetars

“…The bursting activity was accompanied by a large spin-up glitch and marked the start of an enhancement in the pulsed X-ray flux which lasted about one month [121]. Spectral and flux variations associated with this event were seen also in the hard X-ray range [110]. All these phenomena are typical of magnetars.…”