  We report the detection of an anomalous accretion flare in the tight
eccentric pre-main-sequence binary system DQ Tau. In a multi-epoch survey
consisting of randomly acquired low to moderate resolution near-infrared
spectra obtained over a period of almost ten years, we detect a significant and
simultaneous brightening of four standard accretion indicators (CaII infrared
triplet, the Paschen and Brackett series HI lines, and HeI 1.083 um), on
back-to-back nights (phase = 0.372, 0.433) with the flare increasing in
strength as the system approached apastron (phase = 0.5). The mass accretion
rate measured for the anomalous flare is nearly an order of magnitude stronger
than the average quiescent rate. While previous observations established that
frequent, periodic accretion flares phased with periastron passages occur in
this system, these data provide evidence that orbitally-modulated accretion
flares occur near apastron, when the stars make their closest approach to the
circumbinary disk. The timing of the flare suggests that this outburst is due
to interactions of the stellar cores (or the highly truncated circumstellar
disks) with material in non-axisymmetric structures located at the inner edge
of the circumbinary disk. We also explore the optical/infrared spectral type
mismatch previously observed for T Tauri stars and successfully model the shape
of the spectra from 0.8 to 1.0 um and the strengths of the TiO and FeH bands as
manifestations of large cool spots on the surfaces of the stellar companions in
DQ Tau. These findings illustrate that a complete model of near-infrared
spectra of many T Tauri stars must include parameters for spot filling factors
and temperatures.
