Using the Very Long Base Array , we observed the young stellar object EC 95 in the Serpens cloud core at eight epochs from December 2007 to December 2009 .
Two sources are detected in our field , and are shown to form a tight binary system .
The primary ( EC 95a ) is a 4–5 M _ { \odot } proto-Herbig AeBe object ( arguably the youngest such object known ) , whereas the secondary ( EC 95b ) is most likely a low-mass T Tauri star .
Interestingly , both sources are non-thermal emitters .
While T Tauri stars are expected to power a corona because they are convective while they go down the Hayashi track , intermediate-mass stars approach the main sequence on radiative tracks .
Thus , they are not expected to have strong superficial magnetic fields , and should not be magnetically active .
We review several mechanisms that could produce the non-thermal emission of EC 95a , and argue that the observed properties of EC 95a might be most readily interpreted if it possessed a corona powered by a rotation-driven convective layer .
Using our observations , we show that the trigonometric parallax of EC 95 is \pi = 2.41 \pm 0.02 mas , corresponding to a distance of 414.9 ^ { +4.4 } _ { -4.3 } pc .
We argue that this implies a distance to the Serpens core of 415 \pm 5 pc , and a mean distance to the Serpens cloud of 415 \pm 25 pc .
This value is significantly larger than previous estimates ( d \sim 260 pc ) based on measurements of the extinction suffered by stars in the direction of Serpens .
A possible explanation for this discrepancy is that these previous observations picked out foreground dust clouds associated with the Aquila Rift system rather than Serpens itself .