Variability Survey of the Cepheus Flare Star Forming Region Using TESS Light Curves

Aerts, C. (2021), RMP, 93, 015001. Aerts, C., et al. (2025), A&A, 695, A214. Cody, A. M., et al. (2014), AJ, 147, 82. Cody, A. M., Hillenbrand L. A. (2018), AJ, 156, 71. Green, G. M., et al. (2019), ApJ, 887, 93. Szylágyi, et al. (2021), MNRAS, 505, 5164–5182. VARIABILITY SURVEY OF THE CEPHEUS FLARE STAR FORMING REGION Nena Scheller, Konstanze Zwintz Institut fr Astround Teilchenphysik, Universität Innsbruck We present a variability survey of young stellar objects (YSOs) in the Cepheus Flare Star Forming Region, based on high-cadence photometric data from the Transiting Exoplanet Survey Satellite (TESS). Our goal is to classify light curve morphologies indicative of underlying physical processes such as accretion, rotation, disk interaction, and pulsations in pre-main sequence (pre-MS) stars. The Cepheus Flare (CF) is a nearby (< 500 pc) star-forming region located in the northern constellation of Cepheus. Its location near the ecliptic north pole makes it exceptionally well-suited for TESS observations, providing extended temporal coverage. This variability mapping offers insight into the dynamic environments of YSOs and contributes to a broader understanding of stellar evolution during the pre-MS phase. The survey also lays groundwork for future asteroseismic studies of young, evolving stellar populations. Motivation CONTACT INFO: [email protected] [email protected] Variability types through visual inspection, supported by the metrics Q and M, quantifying the degree of periodicity and flux asymmetry, respectively. Periodic: Typically, rotational modulation due to cool star spots; clean, sinusoidal variations reflect the stellar rotation period. Semi-regular: Likely a combination of periodic spot behavior and aperiodic changes (e.g., accretion) or variable extinction by circumstellar material. Irregular: Stochastic, non-periodic brightness variations; potentially inner disk instabilities or magnetic turbulence. Eclipsing binaries: Stars periodically obscure each other, producing symmetric dips; planetary transits can appear similar but shallower and narrower. Multiperiodic: Possibly intrinsic variability due to stellar oscillations; in this sample, a young SPB (g-mode) pulsator candidate. No variability: No significant variability beyond noise or gaps (TESS 13.7d). Distribution of Q and M values across all observed targets is shown, with symbols indicating visual classifications. Boundaries drawn empirically in Q–M space define nine categories of metric-based classification. Q values are particularly sensitive to systematics in the data; classification boundaries should be interpreted as gradual transitions rather than sharp divisions. In most cases, the Q-M framework complements visual classification, though semi-regular and irregular types may overlap due to data artifacts or noise. Q-M METRIC CLASSIFICATION LIGHTCURVE MORPHOLOGIES COLOR-MAGNITUDE DIAGRAM De-reddened color–absolute magnitude diagram, based on Gaia EDR3 data. Extinction corrections were applied using the Bayestar 3D dust maps. Symbols denote the different variability classes, as determined by visual classification. Black hexagons identify known disk-bearing stars. PARSEC isochrones from 0.5 to 10 Myr are plotted shown as solid lines and CIFIST isochrones (𝑀 < 1.4 M☉) as dashed lines. The 0.5 Myr isochrone is marked in black, and the 10 Myr isochrone in red (both solid and dashed). Our newly discovered SPB candidate is highlighted with a cyan asterisk. A promising candidate for a young Slowly Pulsating B (SPB) star, characterized by g-mode pulsations. The star has 𝑇eff = 12.534 Kand log(𝑔) = 3.761. The light curve was modeled using Fourier frequency analysis. Residuals reveal additional unresolved frequencies. Figure to the left: (a) Amplitude spectrum with the dominant frequency marked. (b) g-mode period spacing diagram. A linear relation to the dominant gravitoinertial mode suggests a near-core rotation rate of 𝑓rot = 1.824 c/d. The slope in the period spacing pattern is likely induced by rotation. YOUNG SPB CANDIDATE