Figure 3 : Magellan-Baade moderate-resolution spectra at opposite phases of the cycle of the prototype object OGLE-BLAP-001.

From: Blue large-amplitude pulsators as a new class of variable stars

Figure 3

Best fits of stellar atmosphere models to the observed spectra are shown by coloured lines. The different effective temperatures derived indicate that the observed variability is indeed caused by pulsations. With increasing temperature, lines of ionized elements become stronger, for example He ii 4,686 Å. Short-period pulsations result in striking changes in the shape of neutral helium lines (He i). Parameters derived from the combined spectrum can be treated as mean values for this prototype object. The uncertainties shown are formal errors returned by the χ2 fitting procedure.