Asteroseismic Detection of a Massive Unseen Companion to the $\delta$ Scuti Star TIC 160582982

Abstract

We present TIC 160582982, an eccentric $\delta$ Scuti binary with a dynamically massive unseen companion. Six coherent high-frequency pressure modes used as pulsation clocks yield a phase-modulation orbit with $P_{\mathrm{orb}}=89.29\pm 0.19$ d, $e=0.539_{-0.037}^{+0.040}$, and $a_1\sin i/c=145.6_{-3.4}^{+3.7}$ s, corresponding to $K_1=42.2_{-1.8}^{+2.2}$ km s${}^{-1}$ and $f(M)=0.416_{-0.028}^{+0.032}{M}_{\odot }$. An independent frequency-modulation analysis of the two strongest modes gives a consistent orbital solution. Rotating MIST isochrones constrained by the atmospheric parameters and spectral energy distribution (SED) give $M_1=1.93\pm 0.19M_{\odot }$ and $R_1=2.65\pm 0.23R_{\odot }$. The mass function implies a formal edge-on minimum companion mass of approximately $1.80M_{\odot }$. Assuming a luminous main-sequence companion and including the non-eclipsing geometry gives $M_2=2.19_{-0.34}^{+1.24}{M}_{\odot }$ and $i=61.5_{-19.6}^{+16.6}$ deg. However, no clear evidence for the presence of a luminous counterpart is found, either photometrically or spectroscopically. This suggests the presence of a massive compact object, such as a neutron star or even a stellar-mass black hole, as the massive unseen binary companion. Future phase-resolved high-resolution spectroscopy will be crucial for obtaining an independent orbital constraint and clarifying the nature of the companion.

arXiv comment14 pages, 6 figures. Accepted for publication in The Astrophysical Journal