PG 1325+101 and PG 2303+019: Two new large amplitude subdwarf B pulsators

We report the detection of short period oscillations in the sdB stars PG 1325+101 (B=13.8) and PG 2303+019 (alias HS 2303+0152, B=16.0) from time-series photometry made at the Nordic Optical Telescope of a sample of 21 candidates. Both stars are multi-mode pulsators with at least three distinct periods in the range 100-140 s, and relatively large amplitudes up to 2.6 and 1.6% respectively. Moreover PG 1325+101 shows the shortest pulsation period ever registered among sdBV stars, 68.9 s, which corresponds to the first harmonic of the main signal. Following previous temperature and gravity determinations for PG 1325+101 (T_eff = 34 500 K, log g=6.1) and our NLTE model atmosphere analysis for PG 2303+019 (T_eff = 35 200 K, log g=5.7), both stars are well inside the theoretical sdBV instability strip. Based on observations obtained at the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias; and at the German-Spanish Astronomical Center, Calar Alto, operated by the Max-Plank-Institute für Astronomie Heidelberg jointly with the Spanish National Commission for Astronomy.