Photometric multi-site campaign on the open cluster NGC 884 I. Detection of the variable stars

Abstract

CONTEXT: Recent progress in the seismic interpretation of field beta Cep stars has resulted in improvements of the physics in the stellar structure and evolution models of massive stars. Further asteroseismic constraints can be obtained from studying ensembles of stars in a young open cluster, which all have similar age, distance and chemical composition. AIMS: To improve our comprehension of the beta Cep stars, we studied the young open cluster NGC 884 to discover new B-type pulsators, besides the two known beta Cep stars, and other variable stars. METHODS: An extensive multi-site campaign was set up to gather accurate CCD photometry time series in four filters (U, B, V, I) of a field of NGC884. Fifteen different instruments collected almost 77500 CCD images in 1286 hours. The images were calibrated and reduced to transform the CCD frames into interpretable differential light curves. Various variability indicators and frequency analyses were applied to detect variable stars in the field. Absolute photometry was taken to deduce some general cluster and stellar properties. RESULTS: We achieved an accuracy for the brightest stars of 5.7 mmag in V, 6.9 mmag in B, 5.0 mmag in I and 5.3 mmag in U. The noise level in the amplitude spectra is 50 micromag in the V band. Our campaign confirms the previously known pulsators, and we report more than one hundred new multi- and mono-periodic B-, A- and F-type stars. Their interpretation in terms of classical instability domains is not straightforward, pointing to imperfections in theoretical instability computations. In addition, we have discovered six new eclipsing binaries and four candidates as well as other irregular variable stars in the observed field.

Accepted for publication in Astronomy and Astrophysics, 21 pages, 14 figures, 4 tables. The full appendix is available at http://www.ster.kuleuven.be/~sophies/Appendix.pdf (74 MB, 169 pages, 343 figures, 1 table)

References in corpus (9)

• The generalised Lomb-Scargle periodogram. A new formalism for the floating-mean and Keplerian periodograms
• Automated supervised classification of variable stars I. Methodology
• An asteroseismic study of the beta Cephei star theta Ophiuchi: constraints on global stellar parameters and core overshooting
• Statistical properties of a sample of periodically variable B-type supergiants - Evidence for opacity-driven gravity-mode oscillations
• Instability strips of SPB and beta Cephei stars: the effect of the updated OP opacities and of the metal mixture
• The two hybrid B-type pulsators: Nu Eridani and 12 Lacertae
• CoRoT's view of newly discovered B-star pulsators: results for 358 candidate B pulsators from the initial run's exoplanet field data
• An asteroseismic study of the beta Cephei star beta Canis Majoris
• Automated supervised classification of variable stars II. Application to the OGLE database

Cited by in corpus (30)

• Domains of pulsational instability of low-frequency modes in rotating upper main-sequence stars
• Gaia Data Release 3: Pulsations in main sequence OBAF-type stars
• Stellar variability in open clusters. I. A new class of variable stars in NGC 3766
• Extended main-sequence turnoffs in the double cluster $h$ and $\chi$ Persei: The complex role of stellar rotation
• The puzzling new class of variable stars in NGC 3766 : old friend pulsators?
• Seismic probing of the first dredge-up event through the eccentric red-giant & red-giant spectroscopic binary KIC9163796
• NGC 7419 as a template for red supergiant clusters
• The Monitor Project: Stellar rotation at 13~Myr: I. A photometric monitoring survey of the young open cluster h~Per
• Isochrone-cloud fitting of the extended Main-Sequence Turn-Off of young clusters
• Pulsating B-type stars in the open cluster NGC 884: frequencies, mode identification and asteroseismology
• Detection of solar-like oscillations in the bright red giant stars $\gamma$ Psc and ${\theta }^1$ Tau from a 190-day high-precision spectroscopic multisite campaign
• Photometric Study and Detection of Variable Stars in the Open Clusters - I : NGC 6866
• Main-sequence variable stars in young open cluster NGC 1893
• Pre-main sequence variable stars in young open cluster NGC 1893
• Pulsating B stars in the Scorpius-Centaurus Association with TESS
• Theoretical seismic properties of pre-main sequence gamma Doradus pulsators
• Physical Properties of the B and Be Star Populations of h and chi Persei
• Ensemble asteroseismology of pulsating B-type stars in NGC 6910
• Searching for the orbital period of the ultraluminous X-ray source NGC 1313 X-2
• Analysis of high-resolution FEROS spectroscopy for a sample of variable B-type stars assembled from TESS photometry
• Multiscale entropy analysis of astronomical time series. Discovering subclusters of hybrid pulsators
• The ESO UVES/FEROS Large Programs of TESS OB pulsators. I. Global stellar parameters from high-resolution spectroscopy
• Stellar Parameters for Pulsating B Star Candidates in the Kepler Field
• Variable stars in the field of intermediate-age open cluster NGC 559
• Towards ensemble asteroseismology of the young open clusters Chi Persei and NGC 6910
• Constraining the properties of delta Scuti stars using spectroscopic eclipsing binary systems
• NGC 1893: a young open cluster rich in multi-type variable stars
• Probing the models: Abundances for high-mass stars in binaries
• A Pipeline for the ROTSE-IIId Archival Data
• Theoretical study of $\gamma$ Doradus pulsations in pre-main sequence stars