The Fermi-LAT detection of magnetar-like pulsar PSR J1846−0258 at high-energy gamma-rays

Abstract

We report the detection of the pulsed signal of the radio-quiet magnetar-like pulsar PSR J1846-0258 in the high-energy γ-ray data of the Fermi Large Area Telescope (Fermi LAT). We produced phase-coherent timing models exploiting RXTE PCA and Swift XRT monitoring data for the post-(magnetar-like) outburst period from 2007 August 28 to 2016 September 4, with independent verification using INTEGRAL ISGRI and Fermi GBM data. Phase-folding barycentric arrival times of selected Fermi LAT events from PSR J1846-0258, resulted in a 4.2σ detection (30-100 MeV) of a broad pulse consistent in shape and aligned in phase with the profiles that we measured with Swift XRT (2.5-10 keV), INTEGRAL ISGRI (20-150 keV) and Fermi GBM (20-300 keV). The pulsed flux (30-100 MeV) is (3.91 ± 0.97) × 10 −9 photons cm −2 s −1 MeV −1 . Declining significances of the INTEGRAL ISGRI 20-150 keV pulse profiles suggest fading of the pulsed hard X-ray emission during the post-outburst epochs. We revisited with greatly improved statistics the timing and spectral characteristics of PSR B1509-58 as measured with the Fermi LAT. The broad-band pulsed emission spectra (from 2 keV up to GeV energies) of PSR J1846-0258 and PSR B1509-58 can be accurately described with similarly curved shapes, with maximum luminosities at 3.5 ± 1.1 MeV (PSR J1846-0258) and 2.23 ± 0.11 MeV (PSR B1509-58). We discuss possible explanations for observational differences between Fermi LAT detected pulsars that reach maximum luminosities at GeV energies, like the second magnetar-like pulsar PSR J1119-6127, and pulsars with maximum luminosities at MeV energies, which might be due to geometric differences rather than exotic physics in high-B fields.

Spectral characterization of the non-thermal X-ray emission of gamma-ray pulsars

“…A few pulsars are dimmer in the highenergy gamma-ray band, with only a few data points available in their SEDs. This is the case of J1513−5908 (Kuiper et al 2018), J1846−0258 (Kuiper & Dekker 2016;Kuiper et al 2018) and J2022+3842 (Pilia et al 2010;Ohuchi et al 2015;Smith 2016).…”

“…We consider here the pulsars with GeV emission reported in the 2PC catalogue and in subsequent publications (e.g., Guillemot et al 2012;Xing & Wang 2016;Kuiper et al 2018). All of them have a publicly available phase-averaged gamma-ray SED.…”

“…We also include in our sample the pulsars J1846−0258 and J2022+3842, which were detected as gamma-ray pulsars only after the release of the 2PC catalogue (e.g. Kuiper et al 2018), as well as the three pulsars B1821−24, B1937+21 and J0218+4232, as analysed by Gotthelf & Bogdanov (2017). As mentioned above, the SEDs of the pulsars J1747−2958, J1826−1256 and J2021+3651, have been already extracted by us before (Li et al 2018b) using the same procedure adopted in this paper (see Section 5.2).…”

“…We have also included the SEDs extracted by Li et al (2018b), as well as those corresponding to the pulsed X-ray emission as reported by Kuiper & Hermsen (2015) (see their Figure 28) and by Gotthelf & Bogdanov (2017). The Fermi LAT high-energy gamma-ray spectra are taken from Abdo et al (2010a,b); Pilia et al (2010); Lemoine-Goumard et al (2011); Abdo et al (2013); Ackermann et al (2015); Ohuchi et al (2015); Kuiper & Dekker (2016); Li et al (2016); Smith (2016); Xing & Wang (2016); Li et al (2018a); Kuiper et al (2018). The broad-band SED of the Crab pulsar is shown in all panels for comparison.…”

Resonant Inverse Compton Scattering Spectra from Highly Magnetized Neutron Stars

“…In the context of high-field pulsars such as PSRs B1509-58 and J1846-0258, detailed consideration of spectral modeling via this inner magnetosphere scenario, perhaps focusing on their states after magnetar-like outbursts, is deferred to future studies. Yet it is clear that Lorentz factors γ e > ∼ 10 2 will probably be needed in order to generate the spectral turnovers that match those observed in the 1-10 MeV range (e.g., see Kuiper, Hermsen & Dekker 2018), modulo attenuation mechanisms as discussed in Section 5.2 and in Harding, Baring & Gonthier (1997).…”