Caught in the Act: Discovery of a Physical Quasar Triplet
  We present the discovery of a triplet of quasars at z~1.51. The whole system
is well accommodated within 25 arcsec (i.e., 200 kpc in projected distance).
The velocity differences among the three objects (as measured through the broad
MgII emission line) are less than 1000 km/s, suggesting that the quasars belong
to the same physical structure. Broad band NIR images of the field do not
reveal evidence of galaxies or galaxy clusters that could act as a
gravitational lens, ruling out the possibility that two or all the three
quasars are multiple images of a single, strongly lensed source. QQQ J1519+0627
is the second triplet of quasars known up to date. We estimate that these
systems are extremely rare in terms of simple accidental superposition. The
lack of strong galaxy overdensity suggests that this peculiar system is
harboured in the seeds of a yet-to-be-formed massive structure.
  Based on observations collected at the La Silla Observatory with the New
Technology Telescope (NTT) of the European Southern Observatory (ESO) and at
the Calar Alto Observatory with the 3.5m telescope of the Centro Astron\'omico
Hispano Alem\'an (CAHA).
