IRAS 19475+3119

Lore & Background

The nebula IRAS 19475+3119 was identified as a protoplanetary nebula, a short-lived transitional phase between a red giant and a planetary nebula. Its central star, V2513 Cygni, is an F-type post-AGB star. The brightest portion of the nebula displays a quadrupolar morphology, featuring elongated bipolar lobes embedded within a faint halo. The distance to the object is uncertain; assumptions about the star's luminosity have been used to derive distance and other stellar parameters.

At an assumed kinematical distance, the luminosity and radius are given, and the star was originally at least a certain mass and is now a different mass. Assuming a different luminosity yields a different distance. Estimates based on oxygen spectral line strengths suggest much higher luminosities, with an absolute magnitude of at least −8.

In 2006, Vera P. Arkhipova et al. announced that the star is variable, and it received the variable star designation V2513 Cygni in 2013. The star varies in brightness from about magnitude 9.33 to 9.50. A primary period of 41 days has been determined, but a slightly shorter secondary period produces long beats, causing variations in amplitude and apparent period from year to year. These variations arise from stellar pulsations; the star is brightest when it is hottest, and its temperature varies by up to a certain amount.

Reader's Guide

IRAS 19475+3119 is significant as a protoplanetary nebula that offers insight into the late evolutionary stages of intermediate-mass stars. Its quadrupolar structure, with elongated bipolar lobes and a surrounding halo, is a relatively rare morphology that provides clues about the shaping mechanisms at work during the post-AGB phase. The central star, V2513 Cygni, is an F-type post-AGB star whose pulsations cause brightness variations with a primary period of 41 days and a secondary period that creates long beats. This pulsational behavior, with the star brightest when hottest, helps constrain stellar interior models.

The distance to the object remains uncertain, with estimates ranging from an assumed kinematical distance to values derived from different luminosity assumptions or oxygen spectral line strengths, which imply an absolute magnitude of at least −8. This uncertainty underscores the challenges in characterizing such objects. The nebula's legacy lies in its contribution to understanding the transition from asymptotic giant branch stars to planetary nebulae, the development of complex nebular shapes, and the pulsational properties of post-AGB stars.