On the origin of LS 5039 and PSR J1825−1446

Abstract

Context. The gamma-ray binary LS 5039 and the isolated pulsar PSR J1825−1446 were proposed to have been formed in the supernova remnant (SNR) G016.8−01.1. Aims. We aim to obtain the Galactic trajectory of LS 5039 and PSR J1825−1446 to find their origin in the Galaxy, and in particular to check their association with SNR G016.8−01.1 to restrict their age. Methods. By means of radio and optical observations we obtained the proper motion and the space velocity of the sources. Results. The proper motion of PSR J1825−1446 corresponds to a transverse space velocity of 690 km s −1 at a distance of 5 kpc. Its Galactic velocity at different distances is not compatible with the expected Galactic rotation. The velocity and characteristic age of PSR J1825−1446 make it incompatible with SNR G016.8−01.1. There are no clear OB associations or SNRs crossing the past trajectory of PSR J1825−1446. We estimate the age of the pulsar to be 80-245 kyr, which is compatible with its characteristic age. The proper motion of LS 5039 is μ α cos δ = 7.09 and μ δ = −8.82 mas yr −1 . The association of LS 5039 with SNR G016.8−01.1 is unlikely, although we cannot discard it. The system would have had to be formed in the association Ser OB2 (at 2.0 kpc) if the age of the system is 1.0-1.2 Myr, or in the association Sct OB3 (distance 1.5-2 kpc) for an age of 0.1-0.2 Myr. If the system were not formed close to Ser OB2, the pseudo-synchronization of the orbit would be unlikely. Conclusions. PSR J1825−1446 is a high-velocity isolated pulsar ejected from the Galaxy. The distance to LS 5039, which needs to be constrained by future astrometric missions such as Gaia, is a key parameter for restricting its origin and age.

Refining the origins of the gamma-ray binary 1FGL J1018.6–5856

“…Therefore it is unclear if the derived peculiar motion originates from a kick during the stellar core collapse or if it was intrinsic to the system beforehand. We note that the derived motion is similar to the motion of 26 ± 8 km s −1 observed in the gamma-ray binary PSR B1259−63 (Miller-Jones et al 2018), but lower than the motion of ∼ 140 km s −1 observed in LS 5039 (Moldón et al 2012b), and higher than the motion of ∼ 16 km s −1 observed in LS I +61 303 (Wu et al 2018). In any case, these motions are well below the velocities observed in isolated pulsars (see e.g., Chatterjee et al 2005), as expected for binary systems.…”

Vlbi Astrometry of PSR J2222-0137: A Pulsar Distance Measured to 0.4% Accuracy

“…This effect is particularly severe when the number of degrees of freedom is relatively small, as is typically the case for astrometric observations. Accordingly, a useful cross-check is a bootstrap test, which has been widely used in past pulsar astrometry projects (Chatterjee et al 2009;Deller et al 2012;Moldón et al 2012), since it can be used to estimate errors on fitted parameters when the underlying measurement errors are poorly known (Efron & Tibshirani 1991). Bootstrapping involves creating a large number of test data sets, where each data set is constructed by sampling with replacement from the pool of measured astrometric positions.…”

Locating the intense interstellar scattering towards the inner Galaxy

“…Proper motion of PSR B1822−14 in RA and Dec (top two panels) and the residuals of the VLBI data compared to the best linear fit (bottom two panels). The first two epochs are from archival VLA data (Frail & Scharringhausen 1997), the next four are VLA and VLBA observations (Moldón et al 2012), and the final point is from our recent VLBA observation. Our position is consistent with the proper motion measured by Moldón et al (2012).…”