Radial Velocities from the N2K Project: Six New Cold Gas Giant Planets Orbiting HD 55696, HD 98736, HD 148164, HD 203473, and HD 211810

Abstract

The N2K planet search program was designed to exploit the planet-metallicity correlation by searching for gas giant planets orbiting metal-rich stars. Here, we present the radial velocity measurements for 378 N2K target stars that were observed with the HIRES spectrograph at Keck Observatory between 2004 and 2017. With this data set, we announce the discovery of six new gas giant exoplanets: a double-planet system orbiting HD 148164 (M sin i of 1.23 and 5.16 M JUP ) and single planet detections around HD 55696 (M sin i = 3.87 M JUP ), HD 98736 (M sin i= 2.33 M JUP ), HD 203473 (M sin i = 7.8 M JUP ), and HD 211810 (M sin i = 0.67 M JUP ). These gas giant companions have orbital semi-major axes between 1.0 and 6.2 AU and eccentricities ranging from 0.13 to 0.71. We also report evidence for three gravitationally bound companions with M sin i between 20 to 30 M JUP , placing them in the mass range of brown dwarfs, around HD 148284, HD 214823, and HD 217850, and four low mass stellar companions orbiting HD 3404, HD 24505, HD 98630, and HD 103459. In addition, we present updated orbital parameters for 42 previously announced planets. We also report a nondetection of the putative companion HD 73256 b. Finally, we highlight the most promising candidates for direct imaging and astrometric detection, and find that many hot Jupiters from our sample could be detectable by state-of-the-art telescopes such as Gaia.

Ca II H&K stellar activity parameter: a proxy for extreme ultraviolet stellar fluxes

“…For each star in the France et al ( 2018) sample, we collected measurements of the log R HK activity parameter from the literature and retained only the stars for which we found at least one measurement (Isaacson & Fischer 2010;Boro Saikia et al 2018;Jenkins et al 2011Jenkins et al , 2006Caillault et al 1991;Mamajek & Hillenbrand 2008;Gray et al 2006Gray et al , 2003Moutou et al 2014;Arriagada 2011;Robertson et al 2012;Anderson et al 2014;Wittenmyer et al 2009;Laws et al 2003;Henry et al 1996;Canto Martins et al 2011;Pace 2013;Astudillo-Defru et al 2017;Hinkel et al 2017;Ment et al 2018;Wright et al 2004;Hall et al 2009;Morris et al 2017). The total number of collected log R HK measurements is 498.…”

Reinvestigation of the Multi-Epoch Direct Detections of HD 88133 b and Upsilon Andromedae b

“…We ran a few sets of simulations to determine what physical or observational factors would allow for the detection of HD88133b. We note that HD88133A has a rather large stellar radius of 2.20 R (Ment et al 2018), meaning that this system has an even lower planet to star contrast than most hot Jupiters, though we cannot measure it directly because of the unknown planetary radius. Our first simulations ask how large the planetary radius would have to be for the planetary peak to be detectable in the six L band epoch observed (Section 3.2.2).…”

“…The secondary velocities are calculated by plugging the f values in Table 1, This work, into Equation 2 using Piskorz et al 2016 orbital parameters and a K p of 40 km/s. For these simulations, we assume a planetary radius of 1 R Jup (except in the planetary radius simulations) and a stellar radius of 2.20 R (Ment et al 2018). After combination, the continuum is removed using a third order polynomial fit from 2.8 to 4.0 µm in wavenumber space.…”

“…Because there seems to be no clear peak at a positive K p in Figure 1, we use simulations to see how much larger the planetary radius would have to be for its peak to be distinguishable. For these simulations, we set the K p at 40 km/s and the stellar radius at 2.20 R (Ment et al 2018), and step the planetary radius up from 1 R Jup to 4 R Jup in increments of 0.5 R Jup . Figure 2 shows the results of these simulations in the top panel.…”

Hiding Planets Near and Far: The Parameter Space of Hidden Companions for Known Planetary Systems

“…This trend was suggested by radial velocity surveys that showed a large population of giant planets may exist at large distances from stars that host one or more inner planets (e.g., Knutson et al 2014;Konopacky et al 2016;Zhu & Wu 2018;Bryan et al 2016Bryan et al , 2019a. Additionally, several systems have been discovered where the configuration is strictly hierarchical, with a giant planet on a wide orbit outside of one or more very close-in planets (e.g., Bonomo et al 2017;Ment et al 2018;Barbato et al 2018;Mills et al 2019). Furthermore, the most generic example is our solar system, with Jupiter at 5 au, or even with the possible planet 9 (Batygin & Brown 2016).…”