A Strongly Magnetized Pulsar Within the Grasp of the Milky Way's Supermassive Black Hole

Abstract

The center of our Galaxy hosts a supermassive black hole, Sagittarius (Sgr) A *. Young, massive stars within 0.5 pc of Sgr A * are evidence of an episode of intense star formation near the black hole a few million years ago, which might have left behind a young neutron star traveling deep into Sgr A * 's gravitational potential. On 2013 April 25, a short X-ray burst was observed from the direction of the Galactic center. With a series of observations with the Chandra and the Swift satellites, we pinpoint the associated magnetar at an angular distance of 2.4 ± 0.3 arcsec from Sgr A * , and refine the source spin period and its derivative (P = 3.7635537(2) s andṖ = 6.61(4) × 10 −12 s s −1), confirmed by quasi simultaneous radio observations performed with the Green Bank Telescope and Parkes Radio Telescope, which also constrain a dispersion measure of DM = 1750 ± 50 pc cm −3 , the highest ever observed for a radio pulsar. We have found that this X-ray source is a young magnetar at ≈0.07-2 pc from Sgr A *. Simulations of its possible motion around Sgr A * show that it is likely (∼90% probability) in a bound orbit around the black hole. The radiation front produced by the past activity from the magnetar passing through the molecular clouds surrounding the Galactic center region might be responsible for a large fraction of the light echoes observed in the Fe fluorescence features.

A New Electron-Density Model for Estimation of Pulsar and FRB Distances

“…All eight have DMs 1000 cm -3 pc and could plausibly lie close to the Galactic Center. However, only for the closest one, PSR J1745−2900, which is only 2 4 from Sgr A * (Bower et al 2015), has a case been made for a physical association (Rea et al 2013;Bower et al 2015). As well as having the highest DM of the eight, it also has a very large rotation measure (Eatough et al 2013;Shannon & Johnston 2013), strengthening the case for a physical association.…”

“…Table 11 lists 14 pulsars that are associated with SNR or pulsar wind nebulae (PWN) and have a known DM and an estimated distance based on the association. In this table, we also include a pulsar (PSR J0248 +6021) that is believed to lie in or near the H II region W5 (Theureau et al 2011) and the magnetar PSR J1745−2900 that is believed to lie close to the Galactic Center (Eatough et al 2013;Rea et al 2013). …”

A powerful flare from Sgr A* confirms the synchrotron nature of the X-ray emission

“…′′ from Sgr A ⋆ SGR J1745-2900 is a magnetar located at a small projected distance from Sgr A ⋆ Kennea et al 2013), and it is most likely in orbit around the supermassive BH (Rea et al 2013). Coti-Zelati et al (2015) fitted the full XMM-Newton and Chandra dataset available on SGR J1745-2900, without considering the effects of the dust scattering halo, and found NH = (1.90 ± 0.02) × 10 23 cm −2 for Chandra and NH = (1.86…”

The X-ray outburst of the Galactic Centre magnetar as monitored by Chandra and XMM-Newton

“…The first observation was performed with the HRC to have the best spatial accuracy to localize the source in the crowded region of the Galactic Centre ( [10]). The remaining observations were performed with the ACIS in faint timed-exposure imaging mode with a 1/8 sub-array (time resolution of 0.4 s), and in three cases with the HETG.…”

“…In 2013 April a new magnetar, SGR 1745−2900, was discovered as it entered an outburst at only 2.4 arcsec from the supermassive black hole at the Centre of the Milky Way, Sgr A * ( [8], [9], [10]). SGR 1745−2900 has a spin-down magnetic field of ∼ 2 × 10 14 G and holds the record as the closest neutron star to a black hole detected to date.…”