A magnetar parallax

Abstract

XTE J1810−197 (J1810) was the first magnetar identified to emit radio pulses, and has been extensively studied during a radio-bright phase in 2003–2008. It is estimated to be relatively nearby compared to other Galactic magnetars, and provides a useful prototype for the physics of high magnetic fields, magnetar velocities, and the plausible connection to extragalactic fast radio bursts. Upon the re-brightening of the magnetar at radio wavelengths in late 2018, we resumed an astrometric campaign on J1810 with the Very Long Baseline Array, and sampled 14 new positions of J1810 over 1.3 years. The phase calibration for the new observations was performed with two phase calibrators that are quasi-colinear on the sky with J1810, enabling substantial improvement of the resultant astrometric precision. Combining our new observations with two archival observations from 2006, we have refined the proper motion and reference position of the magnetar and have measured its annual geometric parallax, the first such measurement for a magnetar. The parallax of 0.40 ± 0.05 mas corresponds to a most probable distance $2.5^{\, +0.4}_{\, -0.3}$ kpc for J1810. Our new astrometric results confirm an unremarkable transverse peculiar velocity of ≈200 $\rm km~s^{-1}$ for J1810, which is only at the average level among the pulsar population. The magnetar proper motion vector points back to the central region of a supernova remnant (SNR) at a compatible distance at ≈70 kyr ago, but a direct association is disfavored by the estimated SNR age of ∼3 kyr.

Localized Fast Radio Bursts Are Consistent with Magnetar Progenitors Formed in Core-collapse Supernovae

“…The millisecond magnetar hypothesis also predicts large kick velocities of order 10 3 km s −1 (Duncan & Thompson 1992). However, the distribution of magnetar kick velocities is similar to that of the general NS population (Deller et al 2012;Tendulkar 2014;Ding et al 2020). In addition, there is evidence that the stellar progenitors of magnetars span a wide range of masses (Muno et al 2006;Davies et al 2009;Zhou et al 2019), while the progenitors of engine-driven explosions are likely more massive than a typical CCSN (Blanchard et al 2020).…”

The orbital-decay test of general relativity to the 2% level with 6-year VLBA astrometry of the double neutron star PSR J1537+1155

“…In the following discussion, we adopt the astrometric results derived with Bayesian analysis, which incorporates the VLBI and timing measurements. For those who want to use VLBI-only results (such as pulsar timers of J1537), we recommend the bootstrap results in Table 2, as bootstrap can potentially correct improper error estimations to an appropriate level (see Ding et al 2020b as a good example), especially when the number of measurements is relatively large ( 10 for VLBI astrometry). Accordingly, the reference position errors do not take into account the position errors of the main and second phrase calibrators.…”

Probing magnetar formation channels with high-precision astrometry: The progress of VLBA astrometry of the fastest-spinning magnetar Swift J1818.0-1607

“…This visibility allows precise astrometry for the magnetars. Historically, 7 magnetars have been precisely measured astrometrically, including 4 infrared-bright magnetars (Tendulkar et al 2013) and 3 radio magnetars (Deller et al 2012;Bower et al 2015;Ding et al 2020b). The primary motivations of previous astrometric campaigns of magnetars are to 1) establish supernova remnant associations and 2) test whether magnetars receive extraordinary kick velocities ( 1000 km s −1 ) as predicted by Duncan & Thompson (1992).…”

“…On one hand, FRBs have been localized to specific environments (i.e., spiral arms) of spiral galaxies (Mannings et al 2021). On the other hand, magnetar astrometry could potentially pinpoint the 3-D magnetar location (Ding et al 2020b) in the Galaxy. Hence, comparing the Galactic magnetar distribution against FRB sites (localized to spiral galaxies) can test the link between FRBs and magnetars.…”

“…To enhance astrometric accuracy of our observations, we have employed the 1-D interpolation tactic (e.g. Fomalont & Kopeikin 2003;Ding et al 2020b) for all the 6 VLBA observations. After data reduction and analysis, we obtained a compelling proper motion µ α = −3.54±0.05 mas yr −1 , µ δ = −7.65±0.09 mas yr −1 , alongside a tentative (5 σ) parallax (see Figure 2).…”