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

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.

💡 Research Summary

This paper presents a systematic investigation and discovery of 88 new Beta Cephei (BCEP) variable stars and candidates by synergistically integrating data from two major astronomical missions: NASA’s Transiting Exoplanet Survey Satellite (TESS) and ESA’s Gaia mission.

The research methodology hinges on a multi-survey approach. The team utilized high-precision time-series photometry from TESS, specifically the short-cadence (SC, 2-minute) data for Sectors 1-69 and the SPOC-processed full-frame image (FFI-SPOC, 30-minute) data for Sectors 1-55. This photometric data was combined with fundamental stellar parameters from Gaia’s Data Release 3 (DR3), notably parallaxes for distance/luminosity determination and effective temperatures derived from the Extended Stellar Parametrizer for Hot Stars (ESP-HS) pipeline, which is optimized for hot stars like BCEPs. The identification of BCEP stars followed rigorous criteria established in the authors’ previous work, involving a comprehensive analysis of Fourier spectra from light curves, and the stars’ positions in Hertzsprung-Russell (H-R) diagrams, temperature-period, and luminosity-period diagrams.

The search yielded 88 new objects: 85 from the TESS SC data and 3 from the FFI-SPOC data. Two of these (TIC386693012 and TIC459105076) were previously noted as candidate pulsators and are now conclusively confirmed as BCEP stars. The physical parameters of the new sample align well with known BCEP populations, validating the classification criteria: visual magnitudes of 8.0-12.0 mag, parallaxes between 0.11 and 1.74 mas, effective temperatures from 18,000 to 30,000 K, and luminosities spanning 1,500 to 38,000 solar luminosities.

The analysis reveals three key findings. First, a significant detection bias exists between the two TESS datasets. While 30% of the targets found in the SC data have temperatures exceeding 18,000 K, only 0.7% of those from the FFI data do. This reflects an inherent observational bias, as the SC target list is pre-selected to include brighter, often more luminous and hotter stars, whereas the FFI data provides a more uniform, magnitude-limited survey.

Second, four of the newly discovered stars are located near the theoretical “red edge” of the BCEP instability strip. These stars exhibit sparse pulsation modes and represent critical testbeds for pulsation models under low-mass, low-temperature boundary conditions, challenging and refining current stellar astrophysics theories.

Third, the spatial distribution of the sample shows strong clustering within the Galactic disk (|b| < 20°), consistent with the active formation regions of massive stars. However, two high Galactic latitude outliers were identified, which are likely runaway stars ejected from the disk via dynamical interactions, offering intriguing targets for studying Galactic dynamics.

In conclusion, this work underscores the indispensable role of space-based, high-cadence photometry (like TESS) in detecting low-amplitude pulsators and the transformative power of integrating multi-mission survey data (TESS + Gaia) in the era of time-domain astronomy. The discovery of 88 new BCEP stars and candidates substantially enriches the known sample of these massive pulsators, providing a valuable new dataset to constrain stellar pulsation theory, probe the internal structure of massive stars via asteroseismology, and investigate their distribution and kinematics within the Milky Way.