The Gaia parallax discrepancy for the cluster Pismis 19, and separating $δ$ Scutis from Cepheids

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Main Authors: Majaess, Daniel, Bonatto, Charles J., Turner, David G., Saito, Roberto K., Minniti, Dante, Bidin, Christian Moni, González-Díaz, Danilo, Alonso-Garcia, Javier, Bono, Giuseppe, Braga, Vittorio F., Navarro, Maria G., Carraro, Giovanni, Gomez, Matias
Format: Preprint
Published: 2025
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author Majaess, Daniel
Bonatto, Charles J.
Turner, David G.
Saito, Roberto K.
Minniti, Dante
Bidin, Christian Moni
González-Díaz, Danilo
Alonso-Garcia, Javier
Bono, Giuseppe
Braga, Vittorio F.
Navarro, Maria G.
Carraro, Giovanni
Gomez, Matias
author_facet Majaess, Daniel
Bonatto, Charles J.
Turner, David G.
Saito, Roberto K.
Minniti, Dante
Bidin, Christian Moni
González-Díaz, Danilo
Alonso-Garcia, Javier
Bono, Giuseppe
Braga, Vittorio F.
Navarro, Maria G.
Carraro, Giovanni
Gomez, Matias
contents Pre-Gaia distances for the open cluster Pismis 19 disagree with Gaia parallaxes. A 2MASS $JK_s$ red clump distance was therefore established for Pismis 19 ($2.90\pm0.15$ kpc), which reaffirms that zero-point corrections for Gaia are required (e.g., Lindegren et al.~2021). OGLE GD-CEP-1864 is confirmed as a member of Pismis 19 on the basis of DR3 proper motions, and its 2MASS+VVV color-magnitude position near the tip of the turnoff. That $0^{\rm d}.3$ variable star is likely a $δ$ Scuti rather than a classical Cepheid. The case revealed a pertinent criterion to segregate those two populations in tandem with the break in the Wesenheit Leavitt Law ($\simeq 0^{\rm d}.5$). Just shortward of that period discontinuity are $δ$ Scutis, whereas beyond the break lie first overtone classical Cepheids mostly observed beyond the first crossing of the instability strip.
format Preprint
id arxiv_https___arxiv_org_abs_2502_06930
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle The Gaia parallax discrepancy for the cluster Pismis 19, and separating $δ$ Scutis from Cepheids
Majaess, Daniel
Bonatto, Charles J.
Turner, David G.
Saito, Roberto K.
Minniti, Dante
Bidin, Christian Moni
González-Díaz, Danilo
Alonso-Garcia, Javier
Bono, Giuseppe
Braga, Vittorio F.
Navarro, Maria G.
Carraro, Giovanni
Gomez, Matias
Solar and Stellar Astrophysics
Astrophysics of Galaxies
Pre-Gaia distances for the open cluster Pismis 19 disagree with Gaia parallaxes. A 2MASS $JK_s$ red clump distance was therefore established for Pismis 19 ($2.90\pm0.15$ kpc), which reaffirms that zero-point corrections for Gaia are required (e.g., Lindegren et al.~2021). OGLE GD-CEP-1864 is confirmed as a member of Pismis 19 on the basis of DR3 proper motions, and its 2MASS+VVV color-magnitude position near the tip of the turnoff. That $0^{\rm d}.3$ variable star is likely a $δ$ Scuti rather than a classical Cepheid. The case revealed a pertinent criterion to segregate those two populations in tandem with the break in the Wesenheit Leavitt Law ($\simeq 0^{\rm d}.5$). Just shortward of that period discontinuity are $δ$ Scutis, whereas beyond the break lie first overtone classical Cepheids mostly observed beyond the first crossing of the instability strip.
title The Gaia parallax discrepancy for the cluster Pismis 19, and separating $δ$ Scutis from Cepheids
topic Solar and Stellar Astrophysics
Astrophysics of Galaxies
url https://arxiv.org/abs/2502.06930