Well, I don't know what ST stands for, but based on the naming convention I would have to guess it's some kind of system-generated statistic.
You could check to see if there is, by chance, some kind of text associated with the object if it is a module, e.g.:
SELECT OBJECT_DEFINITION(613577224);
SELECT definition FROM sys.all_sql_modules
WHERE object_id = 613577224;
You could also try:
EXEC sp_help N'dbo._ST_OEA33...';
Finally, you could try to brute force discover this object in any of the catalog views. This script tries to find any view that contains a row where the object_id column is equal to that value.
CREATE TABLE #v(v sysname);
DECLARE @sql nvarchar(max) = N'', @obj int = 613577224;
SELECT @sql += N'INSERT #v
SELECT DISTINCT ''sys.' + name + N'''
FROM sys.' + QUOTENAME(name) + N'
WHERE [object_id] = @obj;'
FROM sys.all_views AS v
WHERE EXISTS
(
SELECT 1
FROM sys.all_columns AS c
WHERE c.name = N'object_id'
AND c.[object_id] = v.[object_id]
);
EXEC sys.sp_executesql @sql, N'@obj int', @obj;
SELECT v FROM #v;
DROP TABLE #v;
If this yields nothing, you could expand it to include all int-based columns across all catalog views, since sometimes object_id values are stored in columns with different names, like referenced_major_id or parent_object_id, and any results here might yield clues as well.