We have made a multiwavelength study of the overlapping error boxes of the unidentified \gamma -ray sources TeV J2032+4130 and 3EG J2033+4118 in the direction of the Cygnus OB2 association ( d = 1.7 kpc ) in order to search for a point-source counterpart of the first unidentified TeV source .
Optical identifications and spectroscopic classifications for the brighter X-ray sources in ROSAT PSPC and Chandra ACIS images are obtained , without finding a compelling counterpart .
The classified X-ray sources are a mix of early and late-type stars , with one exception .
The brightest source in the Chandra observation is a new , hard absorbed source that is both transient and rapidly variable .
It lies 7 ^ { \prime } from the centroid of the TeV emission , which places it outside of the claimed 2 \sigma location ( r \approx 4. ^ { \prime } 8 ) .
A possible eclipse or “ dip ” transition is seen in its light curve .
With a peak 1–10 keV luminosity of \approx 7 \times 10 ^ { 32 } ( d / 1.7 { kpc } ) ^ { 2 } ergs s ^ { -1 } , this source could be a quiescent low-mass X-ray binary that lies beyond the Cyg OB2 association .
A coincident , reddened optical object of R = 20.4 , J = 15.4 , H = 14.2 , and K = 13.4 is observed , but not yet classified due to the lack of obvious emission or absorption features in its spectrum .
Alternatively , this Chandra and optical source might be a considered a candidate for a “ proton blazar , ” a long hypothesized type of radio-weak \gamma -ray source .
More detailed observations will be needed to determine the nature of this variable X-ray source , and to assess the possibility of its connection with TeV J2032+4130 .