We report the detection of the extremely red object ( ERO ) , HR 10 ( I - K \sim 6.5 , z =1.44 ) , at 4.9 and 6.1 \mu m ( rest-frame ) with ISOCAM , the mid-infrared ( MIR ) camera onboard the Infrared Space Observatory ( ISO ) .
HR 10 is the first ERO spectroscopically identified to be associated with an ultra-luminous IR galaxy ( ULIG ) detected in the radio , MIR and sub-millimeter .
The rest-frame spectral energy distribution ( SED ) of HR 10 is amazingly similar to the one of Arp 220 , scaled by a factor 3.8 \pm 1.3 .
The corresponding 8-1000 \mu m luminosity ( \sim 7 \times 10 ^ { 12 } ~ { } h _ { 70 } ^ { -2 } L _ { \sun } ) translates into a star formation rate of about 1200 ~ { } h _ { 70 } ^ { -2 } M _ { \odot } yr ^ { -1 } if HR 10 is mostly powered by star formation .
We address the key issue of the origin of the powerful luminosity of HR 10 , i.e .
starburst versus active galactic nucleus ( AGN ) , by using the similarity with its closeby clone , Arp 220 .