SPIRITS catalog of IR long period variables

These were identified in 20 nearby galaxies by the ongoing SPitzer InfraRed Intensive Transients Survey survey with the Spitzer Space Telescope. Of these, 359 variables have M_[4.5]_ (phase-weighted mean magnitudes) fainter than -12 and periods and luminosities consistent with previously reported variables in the Large Magellanic Cloud (LMC).

However, 58 variables are more luminous than M_[4.5]_=-12, including 11 that are brighter than M_[4.5]_=-13, with the brightest having M_[4.5]_=-15.51. Most of these bright variable sources have quasi-periods longer than 1000 days, including four over 2000 days. We suggest that the fundamental period-luminosity relationship, previously measured for the LMC, extends to much higher luminosities and longer periods in this large galaxy sample.