(Possible spiral in the disk around HD34282

An inner clearing or cavity extending up to r<0.28" (88au) is surrounded by a bright inclined (i=56{deg}) ring with a position angle of 119{deg}. The center of this ring is offset from the star along the minor axis with 0.07", which can be explained with a disk height of 26au above the midplane. Outside this ring, beyond its southeastern ansa we detect an azimuthal asymmetry or blob at r~0.4".

At larger separation, we detect an outer disk structure that can be fitted with an ellipse, which is compatible with a circular ring seen at r=0.62" (=190au) and a height of 77au. After applying a height-corrected deprojection we see a circular ring centered on the star at 88 au; what had seemed to be a separate blob and outer ring could now both be part of a single-armed spiral. We present the first scattered-light image of the disk around HD 34282 and resolve a disk with an inner cavity up to r~90au and a highly structured scattering surface of an inclined disk at a large height H_scat_/r=0.29" above the midplane at the inner edge of the outer disk.

Based on the current data it is not possible to conclude decisively whether H_scat_/r remains constant or whether the surface is flared with at most H_scat_ {prop.to} r^1.35^, although we favor the constant ratio based on our deprojections. The height-corrected deprojection allows for a more detailed interpretation of the observed structures, from which we discern the first detection of a single-armed spiral in a protoplanetary disk.