Detection of Planetary and Stellar Companions to Neighboring Stars via a Combination of Radial Velocity and Direct Imaging Techniques

Abstract

The sensitivities of radial velocity (RV) surveys for exoplanet detection are extending to increasingly long orbital periods, where companions with periods of several years are now being regularly discovered. Companions with orbital periods that exceed the duration of the survey manifest in the data as an incomplete orbit or linear trend, a feature that can either present as the sole detectable companion to the host star, or as an additional signal overlain on the signatures of previously discovered companion(s). A diagnostic that can confirm or constrain scenarios in which the trend is caused by an unseen stellar, rather than planetary, companion is the use of high-contrast imaging observations. Here, we present RV data from the Anglo-Australian Planet Search (AAPS) for twenty stars that show evidence of orbiting companions. Of these, six companions have resolved orbits, with three that lie in the planetary regime. Two of these (HD 92987b and HD 221420b) are new discoveries. Follow-up observations using the Differential Speckle Survey Instrument (DSSI) on the Gemini South telescope revealed that five of the twenty monitored companions are likely stellar in nature. We use the sensitivity of the AAPS and DSSI data to place constraints on the mass of the companions for the remaining systems. Our analysis shows that a planetary-mass companion provides the most likely self-consistent explanation of the data for many of the remaining systems.

Joint Radial Velocity and Direct Imaging Planet Yield Calculations. I. Self-consistent Planet Populations

“…Demograph-ics information will be informed from a variety of largescale surveys, many of which were conducted using observations of nearby stellar systems (Johnson et al 2010;Bowler et al 2015;Stone et al 2018;Nielsen et al 2019). Although each planet-detection technique confers different observational biases, complementary sensitivities such as radial velocity (RV) and high-contrast imaging also present an opportunity to combine results in an effort to form a more holistic picture of exoplanetary system architectures (Montet et al 2014;Kane et al 2019).…”

Frequency of Planets in Binaries

“…The mass flag indicates the source for the companion mass: a: M comp from VF06; b: M comp from Reid and Gizis [64], Delfosse et al [65]; c: M comp from individual papers (see Reference list below), d: minimum M comp compatible with ∆µ and/or RV trend and null detection in GDR2, and e: preliminary orbital solution based on available RV measurements. HD 52447: Star with a long-term RV trend [38] and Gaia2/TGAS ∆µ. From the properties of the long-term trend, it results that, most likely, the companion is stellar.…”

“…HD 80913: Star with a long-term RV trend [38] and Gaia2/TGAS ∆µ. From the properties of the long-term trend, it results that, most likely, the companion has mass larger than 20 M Jup .…”

“…The companion is a white dwarf. The star has also a long-term RV trend [38] and ∆µ signature, which might be due to the WD (projected separation of about 160 au).…”

“…Several dedicated adaptive optics (AO) surveys targeting stars with RV planets [9,10,37], objects with RV long-term trends [38,39], and stars with astrometric acceleration from Tycho and Hipparcos [40], all published after BD07.…”