Optical observations of PSR J0205+6449 – the next optical pulsar?

Abstract

PSR J0205+6449 is a young (∼ 5400 years), Crab-like pulsar detected in radio and at X and γ-ray energies and has the third largest spin-down flux among known rotationpowered pulsars. It also powers a bright synchrotron nebula detected in the optical and X-rays. At a distance of ∼ 3.2 kpc and with an extinction comparable to the Crab, PSR J0205+6449 is an obvious target for optical observations. We observed PSR J0205+6449 with several optical facilities, including 8m class ground-based telescopes, such as the Gemini and the Gran Telescopio Canarias. We detected a point source, at a significance of 5.5σ, of magnitude i'∼25.5, at the centre of the optical synchrotron nebula, coincident with the very accurate Chandra and radio positions of the pulsar. Thus, we discovered a candidate optical counterpart to PSR J0205+6449. The pulsar candidate counterpart is also detected in the g' (∼27.4) band and weakly in the r' (∼26.2) band. Its optical spectrum is fit by a power law with photon index Γ O = 1.9 ± 0.5, proving that the optical emission if of non-thermal origin, is as expected for a young pulsar. The optical photon index is similar to the X-ray one (Γ X = 1.77±0.03), although the optical fluxes are below the extrapolation of the X-ray power spectrum. This would indicate the presence of a double spectral break between the X-ray and optical energy range, at variance with what is observed for the Crab and Vela pulsars, but similar to the Large Magellanic Cloud pulsar PSR B0540−69.

A CANDIDATE OPTICAL COUNTERPART TO THE MIDDLE AGED Γ-Ray PULSAR PSR J1741–2054*

“…This yields F opt /F X ∼ 3.1 × 10 −4 and F opt /F γ ∼ 3.5 × 10 −6 . All of these values are in the range of those computed for the other middle aged pulsars identified in the optical (see, e.g., Table 4 of Moran et al 2013). This confirms that middle aged pulsars tend to have similar multi-wavelength emission properties.…”

“…Furthermore, candidate counterparts have been found for PSR J0205+6449 (Moran et al 2013) and PSR J1357−6429 (Zyuzin et al 2016). Here, we found a candidate counterpart to another γ-ray pulsar, PSR J1741−2054.…”

“…PSR J1741−2054 would then be the third γ-ray pulsar discovered by Fermi for which a candidate optical/ infrared counterpart has been found, after PSR J0205+6449 (Moran et al 2013) and PSR J1357−6429 (Zyuzin et al 2016). Multi-epoch optical observations will allow us to measure the proper motion of the PSR J1741−2054 candidate counterpart and confirm the optical identification, whereas multi-band photometry will be needed to determine the pulsar spectrum in the optical.…”

The First Ultraviolet Detection of the Large Magellanic Cloud Pulsar PSR B0540–69 and Its Multi-wavelength Properties

“…Owing to their intrinsic faintness, the number of pulsar detections at optical energies by and large lag behind those at high energies. After the Crab pulsar (PSR B0531+21; Cocke et al 1969), which was the first one identified through its optical pulsations at the radio period (Cocke et al 1969), only eight isolated pulsars (i.e., not in binary systems) have been firmly identified in the optical plus two candidates (see, Mignani 1 See, ATNF pulsar catalogue (Manchester et al 2005) 2011 for a review), and three more identifications have been recently proposed (Moran et al 2013;Mignani et al 2016a;Rangelov et al 2017). Optical pulsations have been detected only for some of them, though.…”

A candidate optical counterpart to the middle-aged gamma-ray pulsar PSR J1741-2054

“…Owing to their faintness, only eight of the over 200 γ-ray pulsars discovered to date 6 have been detected at optical wavelengths (see Abdo et al 2013 and references therein), the number accounting also for PSR B0540−69 (Caraveo et al 1992), only recently found to be a γ-ray pulsar (Ackermann et al 2015). Furthermore, candidate counterparts have been found for PSR J0205+6449 (Moran et al 2013) and PSR J1357−6429 (Zyuzin et al 2016). Here, we found a candidate counterpart to another γray pulsar, PSR J1741−2054.…”