The Young Binary DQ Tau: A Hunt For X-ray Emission From Colliding
  Magnetospheres
  The young high-eccentricity binary DQ Tau exhibits powerful recurring
millimeter-band (mm) flaring attributed to collisions between the two stellar
magnetospheres near periastron, when the stars are separated by only ~8Rstar.
These magnetospheric interactions are expected to have scales and magnetic
field strengths comparable to those of large X-ray flares from single
pre-main-sequence (PMS) stars observed in the Chandra Orion Ultradeep Project
(COUP). To search for X-rays arising from processes associated with colliding
magnetospheres, we performed simultaneous X-ray and mm observations of DQ Tau
near periastron phase. We report here several results. 1) As anticipated, DQ
Tau was caught in a flare state in both mm and X-rays. A single long X-ray
flare spanned the entire 16.5 hour Chandra exposure. 2) The inferred
morphology, duration, and plasma temperature of the X-ray flare are typical of
those of large flares from COUP stars. 3) However, our study provides three
lines of evidence that this X-ray flare likely arises from colliding
magnetospheres: the chance of capturing a large COUP-like flare within the span
of our observation is small; the relative timing of the X-ray and mm flares
indicates the Neupert effect and is consistent with a common coronal structure;
the size of the emitting coronal structure (4-5Rstar) inferred from our
analysis (which is admittedly model-dependent and should be considered with
caution) is comparable to half the binary separation. 4) The peak flare X-ray
luminosity is in agreement with an estimate of the power dissipated by magnetic
reconnection within the framework of a simple model of interacting
magnetospheres.
