Early spectroscopic observations of four extragalactic novae

• We performed spectroscopic observations of four extragalactic novae in M31 and M33.
• Nova M31 2009-10b is one of the most luminous novae ever observed in M31.
• Nova M33 2010-07a is the first recorded nova in M33 that underwent a second mass ejection.

We report the spectroscopic observations of four extragalactic novae in M31 and in M33, secured at Loiano Observatory, Italy. Nova M31 2009-10b is a luminous nova that needed some days to achieve the peak brightness. We confirm that it is a Fe II nova and we show that it is one of the most luminous novae ever observed in M31, showing an evolution close to that of the bright extragalactic novae M31 2007-11d, LMC 1991 and SN 2010U. The novae M31 2010-07a and M31 2011-07b are standard Fe II novae. Nova M33 2010-07a is a Fe II nova that showed a peculiar rebrightening, during which we observed emission lines with P Cyg profiles: we suggest that it is the first observed nova in M33 that underwent a second mass ejection.