The near-infrared companion to HD 94660 (=KQ Vel)

¹ European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany
e-mail: mschoell@eso.org
² Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany
³ Centre for Space Research, Physics Department, North West University, Mahikeng 2745, South Africa
⁴ Jeremiah Horrocks Institute, University of Central Lancashire, Preston PR1 2HE, UK
⁵ European Southern Observatory, Alonso de Cordova 3107, Vitacura, Santiago, Chile
⁶ Hamburger Sternwarte, Gojenbergsweg 112, 21029 Hamburg, Germany

Received: 16 July 2020
Accepted: 10 September 2020

Abstract

Context. The Bp star HD 94660 is a single-lined spectroscopic binary. Some authors have suggested that the unseen companion of at least 2 M_⊙ may be a compact object.

Aims. We intend to study this multiple system in detail, especially to learn more about the thus far unseen companion.

Methods. We have collected and analyzed PIONIER (Precision Integrated-Optics Near-infrared Imaging ExpeRiment) H-band data from the Very Large Telescope Interferometer, TESS (Transiting Exoplanet Survey Satellite) visible photometric data, and X-ray observations with Chandra of HD 94660.

Results. Using PIONIER, we were able to detect the companion to HD 94660, which is absent from high quality spectra at visible wavelengths, with a magnitude difference of 1.8 in the H band at a separation of 18.72 mas. The TESS light curve shows variations with a period of 2.1 d and also flaring. The Chandra spectrum is well described by emission from hot thermal plasma, yet it might include a nonthermal component. The X-ray properties are compatible with a magnetically active companion, while it is also possible that there might be some magnetospheric contributions from the primary.

Conclusions. We can rule out that the companion to HD 94660 is a compact source. It is also very unlikely that this companion is a single star, as the estimated mass of more than 2 M_⊙, the magnitude difference of 1.8 in the H band, and its nondetection in visible spectra are difficult to realize in a single object. One alternative could be a pair of late F stars, which would also be responsible for the detected photometric variations. Interferometric observations over the full binary orbit are necessary to determine the real mass of the companion and to add constraints on the overall geometry of the system.