A Possible X‐Ray and Radio Counterpart of the High‐Energy Gamma‐Ray Source 3EG J2227+6122

Abstract

The identity of the persistent EGRET sources in the Galactic plane is largely a mystery. For one of these, 3EG J2227]6122, our complete census of X-ray and radio sources in its error circle reveals a remarkable superposition of an incomplete radio shell with a Ñat radio spectrum and a compact, powerlaw X-ray source with photon index ! \ 1.5 and with no obvious optical counterpart. The radio shell is polarized at a level of^25%. The anomalous properties of the radio source prevent us from deriving a completely satisfactory theory as to its nature. Nevertheless, using data from ROSAT , ASCA, the VLA, and optical imaging and spectroscopy, we argue that the X-ray source may be a young pulsar with an associated wind-blown bubble or bow-shock nebula and an example of the class of radio-quiet pulsars that are hypothesized to comprise the majority of EGRET sources in the Galaxy. The distance to this source can be estimated from its X-ray absorption as 3 kpc. At this distance, the X-ray and c-ray luminosities would be B1.7 ] 1033 and B3.7 ] 1035 ergs s~1, respectively, which would require an energetic pulsar to power them. If, on the contrary, this X-ray source is not the counterpart of 3EG J2227]6122, then by process of elimination the X-ray luminosity of the latter must be less than 10~4 of its c-ray luminosity, a condition not satisÐed by any established class of c-ray source counterpart. This would require the existence of at least a quantitatively new type of EGRET source, as has been suggested in studies of other EGRET Ðelds.

Catalogue of high-mass X-ray binaries in the Galaxy (4th edition)

“…However, in't Zand et al (2000) identify another Be star as the optical counterpart to its BeppoSAX counterpart, SAX J2239.3+6116. Instead, V669 Cep is identified as the optical counterpart to RX J2226.6+6113 (Halpern et al 2001). Both Hang et al (1999) and Halpern et al (2001) classify V669 Cep as a Herbig Ae/Be star, while Miroshnichenko et al (2002) suggest it as a binary, consisting of a hot, low luminosity B4-B6 star and a cool companion, most likely a late-type giant.…”

Plerions and pulsar-powered nebulae

“…Indeed, Halpern et al [44] have identified a new radio source, G106.6+3.0, which is coincident with the otherwise unidentified EGRET source 3EG J2227+6122 and also with the X-ray source AX J2229.0+6114. This radio source is polarized, has a flat spectral index, and has a possible bow-shock morphology.…”

Radio continuum and near-infrared study of the MGRO J2019+37 region

“…The location of MGRO J2019+37 is consistent with those of the EGRET sources 3EG J2016+3657 and 3EG J2021+3716. The first of them is positionally coincident with the blazar-like source B2013+370 (G74.87+1.22) (Mukherjee et al 2000;Halpern et al 2001), although this blazar is well outside the inner box of MGRO J2019+37. The second is marginally coincident with the pulsar wind nebula PWN G75.2+0.1 (Hessels et al 2004).…”