PHR J1724-3859: A Bipolar Planetary Nebula in Open Cluster Trumpler 25*

Abstract Planetary nebulae (PNs) studies are essential for understanding the late stellar evolution of low-to-intermediate mass stars. PNs in open clusters (OC) are rare but valuable since their study directly links their properties to those of their progenitors, something that cannot be achieved for field PNs. Here, we report the identification of one more OC-PN association to add to the small sample of, now, five pairs. The physical properties of the host cluster, PN, and its central star (CSPN) have been explored using high and intermediate-resolution spectral and deep photometric data. The close agreement of the radial velocities of the PN and host cluster, together with concordance of reddening and distance, shows that the PN PHR J1724-3859 is highly likely to be physically associated with the OC Trumpler 25. Deep photometric data allowed clear identification of the CSPN. We find a CSPN effective temperature of around 250 kK and a nebular kinematic age of 23 kyr, both at the extreme end, like the other members of this small class. The progenitor and final CSPN masses have been estimated to be 5.12 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow/> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.15</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.16</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> M ⊙ and 0.95 ± 0.12 M ⊙ respectively. These latest results agree with the emerging trend for our other OC-PNs, falling below, but approximately parallel to, the latest initial-to-final-mass relation estimates derived from cluster white dwarfs, and have important implications for stellar evolution models. All OC-PNs also possess some other common properties (e.g., all are Type I PNs and bipolars) to be explored in future studies.