  We present the discovery and follow-up observations of a broad-line type-Ic
supernova (SN), PTF 10bzf (SN 2010ah), detected by the Palomar Transient
Factory (PTF) on 2010 February 23. The SN distance is \cong 218 Mpc, greater
than GRB 980425 / SN 1998bw and GRB 060218 / SN 2006aj, but smaller than the
other SNe firmly associated with gamma-ray bursts (GRBs). We conducted a
multi-wavelength follow-up campaign with Palomar-48 inch, Palomar 60-inch,
Gemini-N, Keck, Wise, Swift, the Allen Telescope Array, CARMA, WSRT, and EVLA.
Here we compare the properties of PTF 10bzf with those of SN 1998bw and other
broad-line SNe. The optical luminosity and spectral properties of PTF 10bzf
suggest that this SN is intermediate, in kinetic energy and amount of 56Ni,
between non GRB-associated SNe like 2002ap or 1997ef, and GRB-associated SNe
like 1998bw. No X-ray or radio counterpart to PTF 10bzf was detected. X-ray
upper-limits allow us to exclude the presence of an underlying X-ray afterglow
as luminous as that of other SN-associated GRBs like GRB 030329 or GRB 031203.
Early-time radio upper-limits do not show evidence for mildly-relativistic
ejecta. Late-time radio upper-limits rule out the presence of an underlying
off-axis GRB, with energy and wind density similar to the SN-associated GRB
030329 and GRB 031203. Finally, by performing a search for a GRB in the time
window and at the position of PTF 10bzf, we find that no GRB in the IPN catalog
could be associated with this SN.
