ChandraDetection of a Synchrotron Nebula around the Vela‐like Pulsar J1016−5857

We report on a 19 ks observation of the pulsar J1016-5857 with the ChandraX-ray Observatory. This "Vela-like" pulsar has rotation period 107 ms,characteristic age 21 kyr, and spin-down power 2.6e36 ergs/s. A relativelybright centrally peaked source of radius ~25" around the radio pulsar positionhas a spectrum that is well fitted by an absorbed power law with photon index1.32+-0.25. We regard this as a newly identified pulsar wind nebula that wedesignate PWN G284.0-1.8. We do not detect the pulsar either as a point X-raysource or as a pulsed source in a 55 ks observation with the Rossi X-ray TimingExplorer. The isotropic PWN luminosity is 3e32 ergs/s in the 2-10 keV range,for a distance of 3 kpc that is consistent with the measured neutral hydrogencolumn density. The unpulsed flux from the pulsar is less than 30% of themeasured PWN flux. The brightest component of the PWN, near the pulsar, showsextended emission of size ~2" that may indicate, by analogy with other youngpulsars, the wind termination shock. In the Chandra image we also detect a veryfaint extended structure ~1' by 2' in size that is highly asymmetric about thepulsar position. This structure is a good match in width and position angle tothe tip of a "finger" of radio emission that appears to connect to the nearbysupernova remnant G284.3-1.8, but we cannot characterize it further with theavailable data. There is a variable X-ray point source only 1.5 arcmin from thepulsar, which we identify using optical spectroscopy as an accreting binary.Comment: To appear in The Astrophysical Journal, 11 pages, 6 figure