New radial velocity observations of AH Her: evidence for material outside the tidal radius

• Published in: arXiv.org 2020-11
• Main Authors: Echevarría, J, Hernández Santisteban, J V, O Segura Montero, Ramírez, S H, Ruelas-Mayorga, A, Sánchez, L J, Michel, R, Costero, R, González-Buitrago, D H, Olivares, J
• Format: Article
• Language: English
• Subjects: Inclination; Orbits; Radial velocity; Spectrum analysis; Stellar evolution
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2011.08310

Spectroscopic observations of AH Herculis during a deep quiescent state are put forward. We found the object in a rare long minima, allowing us to derive accurately the semi-amplitudes: \(K_1 =121 \pm \, 4\) \kms\ and \(K_2 =152 \pm 2\) \kms\ and its mass functions \(M_W{ \sin }^{ 3 }i=0.30 \pm 0.01\) M\(_{\odot}\) and \(M_R{ \sin }^{ 3 }i=0.24 \pm 0.02\) M\(_{\odot}\), while its binary separation is given by \(a \sin i =1.39 \pm 0.02\)~R\(_{\odot}\). The orbital period \(P_{orb}\)~=~ 0.25812~\(\pm~0.00032\)~days was found from a power spectrum analysis of the radial velocities of the secondary star. These values are consistent with those determined by \citet{Horne:1986}. Our observations indicate that K5 is the most likely spectral type of the secondary. We discuss why we favour the assumption that the donor in AH Her is a slightly evolved star, in which case we find that the best solution for the inclination yields \(i = 48^\circ \pm 2^\circ\). Nonetheless, should the donor be a ZAMS star, we obtain that the inclination is between \( i = 43^\circ\) and \(i = 44^\circ\). We also present Doppler tomography of H\(\alpha\) and H\(\beta\), and found that the emission in both lines is concentrated in a large asymmetric region at low velocities, but at an opposite position to the secondary star, outside the tidal radius and therefore at an unstable position. We also analyse the H\(\alpha\) and H\(\beta\) line profiles, which show a single broad peak and compare it with the previous quiescent state study which shows a double-peaked profile, providing evidence for its transient nature.