Observational Properties of $β$ Cephei Stars: 88 new samples discovered Based on TESS and Gaia Data

TL;DR

This work leverages the high-precision, space-based photometry of TESS in conjunction with Gaia DR3 ESP-HS parameters to systematically identify and characterize β Cephei stars. By combining short-cadence (SC) and full-frame (FFI) photometry with Gaia parallaxes and Teff estimates, the authors compile 88 BCEP stars and candidates, revealing pulsation periods primarily in the range $P \sim 0.06$–$0.27$ days and amplitudes up to tens of millimagnitudes. The study highlights observational biases between SC and FFI data, identifies rare red-edge pulsators and runaway stars, and demonstrates the value of multi-survey integration for constraining massive star pulsation models and Galactic dynamics. The findings expand the BCEP sample to enable improved tests of instability strip boundaries, core overshooting, and rotation effects, while underscoring the need for follow-up spectroscopy and higher-resolution observations to mitigate contamination and confirm binarity.

Abstract

We present a systematic investigation of $β$ Cephei (BCEP) stars by integrating photometric data from the Transiting Exoplanet Survey Satellite (TESS) with astrometric parameters from Gaia Data Release 3. Utilizing TESS's short-cadence (SC) and full-frame image (FFI) photometry, along with Gaia parallaxes and temperatures derived from the Extended Stellar Parametrizer for Hot Stars (ESP-HS) pipeline, we identify 88 new BCEP stars and candidates--85 from SC data and 3 from SPOC-processed FFI observations. These targets exhibit visual magnitudes ranging from 8.0 to 12.0 mag, parallaxes between 0.11 and 1.74 mas, effective temperatures of 18,000 to 30,000 K, and luminosities from 1,500--38,000 $L_\odot$, consistent with previously cataloged BCEP populations, thereby demonstrating the robustness of our classification criteria. Key findings include: (1) a significant detection disparity between SC and FFI datasets, with 30\% of SC targets exceeding 18,000 K compared to only 0.7\% in FFI, reflecting observational biases toward high-luminosity, hotter stars in SC data; (2) four samples near the red edge of the theoretical instability strip, exhibiting sparse pulsation modes that are important samples for testing pulsation models under low-mass, low-temperature conditions; and (3) spatial clustering within the Galactic disk ($|b| < 20^\circ$), with two high-latitude outliers likely representing runaway stars ejected from disk environments. Our analysis underscores the critical role of space-based photometry in detecting low-amplitude pulsators and the transformative potential of multi-survey integration in the era of time-domain astronomy. These results provide new samples to constrain stellar pulsation theories of massive stars and to study Galactic dynamics.

Figures (7)

• Figure 1: Fourier spectra of new BCEP stars and candidates. The red dotted lines are the rough boundary (3 $d^{-1}$) for low-frequency and high-frequency.
• Figure 2: (Continued.)
• Figure 3: The Hertzsprung--Russell (H--R) diagram of BCEP stars. In this diagram, confirmed BCEP stars and candidates from this work are marked as filled red circles. For comparative analysis, previously published BCEP and SPB stars from Paper I--III are also plotted as open red circles and black circles, respectively. Theoretical stellar evolution frameworks are shown, Black solid curves: Zero-age main sequence (ZAMS) and evolutionary tracks for masses 7--20 $M_{\odot}$ at solar metallicity (Z = 0.02); Blue/magenta dashed curves: the theoretical instability strips for SPB/BCEP stars at Z = 0.02, modeling low-degree pulsation modes $l \leq$ 3 2007CoAst.151...48M; Black cross: a standard error box.
• Figure 4: The effective temperature and the dominant pulsating period relation diagram of these BCEP stars and candidates. Similar symbols to those in Figure \ref{['fig:L-T']} are used, but the size of the circles denotes their pulsation amplitude at the dominant frequency.
• Figure 5: The luminosity and the dominant pulsating period relation diagram of these BCEP stars and candidates. Symbols are similar to those in Figure \ref{['fig:L-P']}. The red dashed line and the black solid line represent the relationship derived by Paper I for BCEP and SPB stars, respectively. The red solid line represents the new relation derived in Paper III.