New Cepheid variables in the young open clusters Berkeley 51 and Berkeley 55

Abstract

As part of a wider investigation of evolved massive stars in Galactic open clusters, we have spectroscopically identified three candidate classical Cepheids in the little-studied clusters Berkeley 51, Berkeley 55 and NGC 6603. Using new multi-epoch photometry, we confirm that Be 51 #162 and Be 55 #107 are bona fide Cepheids, with pulsation periods of 9.83+/-0.01 d and 5.850+/-0.005 d respectively, while NGC 6603 star W2249 does not show significant photometric variability. Using the period-luminosity relationship for Cepheid variables, we determine a distance to Be 51 of 5.3(+1.0,-0.8) kpc and an age of 44(+9,-8) Myr, placing it in a sparsely-attested region of the Perseus arm. For Be 55, we find a distance of 2.2+/-0.3 kpc and age of 63(+12,-11) Myr, locating the cluster in the Local arm. Taken together with our recent discovery of a long-period Cepheid in the starburst cluster VdBH222, these represent an important increase in the number of young, massive Cepheids known in Galactic open clusters. We also consider new Gaia (data release 2) parallaxes and proper motions for members of Be 51 and Be 55; the uncertainties on the parallaxes do not allow us to refine our distance estimates to these clusters, but the well-constrained proper motion measurements furnish further confirmation of cluster membership. However, future final Gaia parallaxes for such objects should provide valuable independent distance measurements, improving the calibration of the period-luminosity relationship, with implications for the distance ladder out to cosmological scales.

arXiv comment8 pages, 10 figures, accepted for publication in Monthly Notices of the Royal Astronomical Society. Author details corrected

References in corpus (22)

• Gaia Data Release 2. Summary of the contents and survey properties
• Las Cumbres Observatory Global Telescope Network
• Achieving better than 1 minute accuracy in the Heliocentric and Barycentric Julian Dates
• Global survey of star clusters in the Milky Way II. The catalogue of basic parameters
• Astrophysical parameters of Galactic open clusters
• Classical Be Stars: Rapidly Rotating B Stars with Viscous Keplerian Decretion Disks
• New Parallaxes of Galactic Cepheids from Spatially Scanning the Hubble Space Telescope: Implications for the Hubble Constant
• Gaia Data Release 1: Catalogue validation
• Hubble Space Telescope Fine Guidance Sensor Parallaxes of Galactic Cepheid Variable Stars: Period-Luminosity Relations
• Evidence for a systematic offset of -80 micro-arcseconds in the Gaia DR2 parallaxes
• Classical Cepheid Pulsation Models. X. The Period-Age Relation
• Trigonometric Parallaxes of Star Forming Regions in the Perseus Spiral Arm
• A third red supergiant rich cluster in the Scutum-Crux Arm
• Cepheids in Open Clusters: An 8-D All-sky Census
• A massive association around the obscured open cluster RSGC3
• Consistent metallicity scale for cool dwarfs and giants. A benchmark test using the Hyades
• An LTE effective temperature scale for red supergiants in the Magellanic clouds
• A search for open cluster Cepheids in the Galactic plane
• Berkeley 51, a young open cluster with four yellow supergiants
• The red supergiant population in the Perseus arm
• A long-period Cepheid variable in the starburst cluster VdBH222
• Optical photometry and basic parameters of 10 unstudied open clusters

Cited by in corpus (9)

• Wide-field Infrared Survey Explorer (WISE) Catalog of Periodic Variable Stars
• Photometric, kinematic and variability study in the young open cluster NGC 1960
• Three open clusters containing Cepheids: NGC 6649, NGC 6664 and Berkeley 55
• A revisited study of Cepheids in open clusters in the Gaia era
• Galactic open cluster Cepheids -- a census based on Gaia EDR3
• Search for Classical Cepheids in Galactic Open Clusters and Calibration of the Period Wesenheit Metallicity Relation in the Gaia Bands
• A massive open cluster hiding in full sight
• On the nature of VX Sagitarii: Is it a TZO, a RSG or a high-mass AGB star?
• UBVI CCD Photometry of Berkeley 55 Open Cluster