I recently carried out photometry of the short period pulsating variable star SX Phoenicis.
This star has a very short period of 79 minutes over which it ranges between around magnitude 6.8 and 7.5! Contrast this with a Cepheid variable whose period is measured in many days or weeks and Miras with pulsation periods of many months.
The light curve above was derived from photometry of more than 400 images, using median stacking to group images close in time in order to reduce the scatter between datapoints. Almost two cycles were captured here. There are not many observations of SX Phoenicis in the AAVSO International Database, so I will very likely contribute more.
SX Phoenicis is the prototype (the first example) of a class of variable stars which has two pulsation modes, one with a period of around 79 minutes (as shown in my light curve above), the other around 62 minutes. The temperature of the star varies between 7,230 and 8,170 degrees Kelvin at minimum and maximum brightness, smallest and largest radius, respectively.
The origin of this kind of star is unclear but one possibility is that it comes from the merger of two stars, creating a single star that is more luminous and more blue than expected of the older galactic halo population in which it resides, a so-called blue straggler.