Diameter, geometric albedo and compositional constraints for (298) Baptistina through visible and mid-infrared photometry

Here we present visible and mid-infrared observations of the asteroid (298) Baptistina, obtained with the Gemini South telescope, the 2.2-m European Southern Observatory (ESO) telescope in La Silla and the 1.5-m telescope at the Observatorio do Pico dos Dias (OPD). From photometry at the R band and observations with a solar phase angle separation of 11 degrees we have determined H-R = 10.92(-0.11)(+0.13) and G(R) = 0.25(-0.11)(+0.13). From VRI photometry we determined V - R = 0.38 +/- 0.03 and R - I = 0.39 +/- 0.02. Finally, from thermal photometry in the N band, and using the derived values of H and G, we obtained p(V) = 0.347(0.076)(+0.109) -, eta = 0.969(-0.210)(+0.221) and D = 12.4 km, for the geometric albedo, beaming parameter and diameter, respectively. If one assumes that Baptistina is indeed a member of the family it names, these results rule out the recently suggested link between the dynamical family associated with this asteroid and the cretaceous/tertiary (K/T) event since (1) this albedo is incompatible with the mineralogy of the impactor and (2) the age of the family derived through Yarkovisky spreading would be too young to be related to that event.