The same input field is used for either name resolution or coordinate input and the service dynamically determines its content. IRSA accepts both decimal degree and sexagesimal character mode inputs. If the input field contains a string which can be interpreted as a coordinate representation, it is used as such. If not, the string is sent first to NED, then to SIMBAD to attempt name resolution. The range of name formats acceptable is set by those projects.
Coordinates entered into the interface allow for all information to be contained in a single string. The parser is very forgiving, so all of the following are valid (and give the results you would expect):
Putting all the information in one field has the advantages that cutting and pasting from other sources can be done quickly and data entry in general can be performed without moving back and forth between the keyboard and mouse.
This same entry field appears in many other IRSA services where names or coordinates are required.
The circular geometric search about a single position is the standard method to identify sources in proximity to the input target. Specify the search radius in arcsec.