We present Atacama Large Millimeter/submillimeter Array ( ALMA ) observations at 0.3 \arcsec -resolution of EX Lup , the prototype of the EXor class of outbursting pre-main sequence stars .
The circumstellar disk of EX Lup is resolved for the first time in 1.3 mm continuum emission and in the J =2–1 spectral line of three isotopologues of CO. At the spatial resolution and sensitivity achieved , the compact dust continuum disk shows no indications of clumps , fragments , or asymmetries above 5-sigma level .
Radiative transfer modeling constrains the characteristic radius of the dust disk to 23 au and a total dust mass of 1.0 \times 10 ^ { -4 } M _ { \odot } ( 33 M _ { \earth } ) , similar to other EXor sources .
The ^ { 13 } CO and C ^ { 18 } O line emission trace the disk rotation and are used to constrain the disk geometry , kinematics , and a total gas disk mass of 5.1 \times 10 ^ { -4 } M _ { \odot } .
The ^ { 12 } CO emission extends out to a radius of 200 au and is asymmetric , with one side deviating from Keplerian rotation .
We detect blue-shifted , ^ { 12 } CO arc-like emission located 0.8 \arcsec to the north-west , and spatially disconnected from the disk emission .
We interpret this extended structure as the brightened walls of a cavity excavated by an outflow , which are more commonly seen in FUor sources .
Such outflows have also been seen in the borderline FU/EXor object V1647 Ori , but not towards EXor objects .
Our detection provides evidence that the outflow phenomenon persists into the EXor phase , suggesting that FUor and EXor objects are a continuous population in which outflow activity declines with age , with transitional objects such as EX Lup and V1647 Ori .