We present new 1–1.25 \mu m ( z and J band ) Subaru/IRCS and 2 \mu m ( K band ) VLT/NaCo data for HR 8799 and a rereduction of the 3–5 \mu m MMT/Clio data first presented by Hinz et al .
( 33 ) .
Our VLT/NaCo data yields a detection of a fourth planet at a projected separation of \sim 15 AU – “ HR 8799e ” .
We also report new , albeit weak detections of HR 8799b at 1.03 \mu m and 3.3 \mu m .
Empirical comparisons to field brown dwarfs show that at least HR 8799b and HR8799c , and possibly HR 8799d , have near-to-mid IR colors/magnitudes significantly discrepant from the L/T dwarf sequence .
Standard cloud deck atmosphere models appropriate for brown dwarfs provide only ( marginally ) statistically meaningful fits to HR 8799b and c for unphysically small radii .
Models with thicker cloud layers not present in brown dwarfs reproduce the planets ’ SEDs far more accurately and without the need for rescaling the planets ’ radii .
Our preliminary modeling suggests that HR 8799b has log ( g ) = 4–4.5 , T _ { eff } = 900K , while HR 8799c , d , and ( by inference ) e have log ( g ) = 4–4.5 , T _ { eff } = 1000–1200K .
Combining results from planet evolution models and new dynamical stability limits implies that the masses of HR 8799b , c , d , and e are 6–7 M _ { J } , 7–10 M _ { J } , 7–10 M _ { J } and 7–10 M _ { J } .
” Patchy ” cloud prescriptions may provide even better fits to the data and may lower the estimated surface gravities and masses .
Finally , contrary to some recent claims , forming the HR 8799 planets by core accretion is still plausible , although such systems are likely rare .