The Eclipsing $γ$ Doradus Star V421 Pegasi

TL;DR

The paper investigates V421 Peg, a short-period, early-F detached eclipsing binary with a candidate $\gamma$ Dor pulsator in the primary. Using high-precision TESS short-cadence photometry combined with existing spectroscopic constraints, the authors perform a Wilson-Devinney binary analysis to refine stellar masses, radii, and orbital parameters, finding a circular, detached configuration with radii measured to about $1\%$ and a distance of $159 \pm 6$ pc. A multi-frequency analysis of the out-of-eclipse residuals reveals four independent $\gamma$ Dor pulsation frequencies in the range $0.73$--$1.02$ day$^{-1}$, with pulsation constants $Q$ in the $0.63$--$0.88$ days, consistent with gravity-mode pulsations from the primary; several other signals are identified as orbital harmonics or aliases. The results demonstrate a coexisting, multi-period $\gamma$ Dor pulsator within a well-characterized detached EB, providing valuable constraints for stellar structure and evolution models and highlighting the potential for future spectroscopic follow-up to further refine atmospheric parameters and pulsation properties.

Abstract

We present high-precision TESS photometry of V421 Peg (TIC 301747091), an early F-type eclipsing binary containing a candidate $γ$ Dor component. The observed short-cadence data allow the detection of pulsation signals, along with revision of the fundamental properties of the component stars. Detailed binary modeling indicated that the program target is a partially-eclipsing detached system in a circular orbit and that both components are currently in super-synchronous states. The radii of each star were measured with an accuracy of about 1 \%. By periodogram analysis of the outside-eclipse residual lights obtained from the binary star model, we extracted nine significant signals, five of which are likely aliasing frequencies due to sampling artifacts and uncorrected trends in the data used. The other signals of $f_1$, $f_2$, $f_3$, and $f_6$ are considered to be independent pulsations with frequencies ranging from 0.73 day$^{-1}$ to 1.02 day$^{-1}$, corresponding to pulsation constants of 0.63$-$0.88 days. These frequencies, pulsation constants, and position on the H-R diagram reveal that the pulsating signals are $γ$ Dor variables arising from the V421 Peg primary component.

Figures (4)

• Figure 1: TESS observations of V421 Peg distributed in BJD (top panel) and orbital phase (second panel). The circles are individual measurements and the solid line represents the synthetic curve obtained with our binary modeling. The corresponding residuals are plotted in the bottom panel. Alt text: TESS light curve observed at 120-s cadence in Sector 57.
• Figure 2: Roche-lobe geometrical surfaces of V421 Peg at three orbital phases (from top to bottom, 0.0, 0.25, and 0.50). The A and B represent the primary and secondary components, respectively. Alt text: Geometrical representations of the Roche lobe surfaces.
• Figure 3: Light curve residuals after subtracting the binary effect from the W-D modeling fit to the TESS data. The lower panel shows a zoomed-in view of the residuals marked using the inset box in the upper panel. The synthetic curve is computed from the 9-frequency fit to the outside-eclipse part of the residuals. The vertical solid and dotted lines indicate the primary and secondary minima measured from the observed TESS data, respectively. Alt text: TESS residual lights distributed in BJD instead of orbital phase.
• Figure 4: Amplitude spectra before (top panel) and after prewhitening the first three frequencies (middle) and all nine frequencies (bottom) from the PERIOD04 program for the out-of-eclipse residuals. The dotted line in the bottom panel corresponds to five times the noise spectrum. Alt text: PERIOD04 periodogram for the residual light curve of V421 Peg.