We present a study of the core collapse supernova ( CCSN ) rate in nuclei A and B1 , of the luminous infrared galaxy ( LIRG ) Arp 299 , based on \sim 11 years of Very Large Array ( VLA ) monitoring of their radio emission at 8.4 GHz .
Significant variations in the nuclear radio flux density can be used to identify the CCSN activity in the absence of high-resolution very long baseline interferometry ( VLBI ) observations .
In the case of the B1-nucleus , the small variations in its measured diffuse ( synchrotron plus free-free ) radio emission are below the fluxes expected from radio supernovae ( RSNe ) , thus making it well-suited to detect RSNe through flux density variability .
In fact , we find strong evidence for at least three RSNe this way , which results in a lower limit for the CCSN rate ( \nu _ { \mathrm { \mbox { \tiny SN } } } ) of > 0.28 \pm 0.16 yr ^ { -1 } .
This value agrees within the uncertainties with the infrared ( IR ) luminosity based SN rate estimate , and with previously reported radio estimates .
In the A-nucleus , we did not detect any significant variability and found a SN detection threshold luminosity of \approx 3.1 \times 10 ^ { 28 } \mathrm { erg s ^ { -1 } Hz ^ { -1 } } , allowing only the detection of the most luminous RSNe known .
Our method is basically blind to normal CCSN explosions occurring within the A-nucleus , which result in too small variations in the nuclear flux density , remaining diluted by the strong diffuse emission of the nucleus itself .
Additionally , we have attempted to find near-infrared ( NIR ) counterparts for the earlier reported RSNe in the Arp 299 nucleus A , by comparing NIR adaptive optics images from the Gemini-N telescope with contemporaneous observations from the European VLBI Network ( EVN ) .
However , we were not able to detect NIR counterparts for the reported radio SNe within the innermost regions of nucleus A .
While our NIR observations were sensitive to typical CCSNe at \sim 300 mas ( or 70 pc projected distance ) from the centre of the nucleus A , suffering from extinction up to A _ { V } \sim 15 mag , they were not sensitive to such highly obscured SNe within the innermost nuclear regions where most of the EVN sources were detected .