Integral Field Spectroscopy of the Low-mass Companion HD 984 B with the Gemini Planet Imager

Abstract

We present new observations of the low-mass companion to HD 984 taken with the Gemini Planet Imager (GPI) as a part of the GPI Exoplanet Survey campaign. Images of HD 984 B were obtained in the J (1.12-1.3 μm) and H (1.50-1.80 μm) bands. Combined with archival epochs from 2012 and 2014, we fit the first orbit to the companion to find an 18 au (70-year) orbit with a 68% confidence interval between 14 and 28 au, an eccentricity of 0.18 with a 68% confidence interval between 0.05 and 0.47, and an inclination of 119°with a 68% confidence interval between 114°and 125°. To address the considerable spectral covariance in both spectra, we present a method of splitting the spectra into low and high frequencies to analyze the spectral structure at different spatial frequencies with the proper spectral noise correlation. Using the split spectra, we compare them to known spectral types using field brown dwarf and low-mass star spectra and find a best-fit match of a field gravity M6.5±1.5 spectral type with a corresponding temperature of 2730 180 120 -+ K. Photometry of the companion yields a luminosity of L log bol ( /L 2.88 0.07 = - ) ☉ dex with DUSTY models. Mass estimates, again from DUSTY models, find an age-dependent mass of 34±1 to 95±4M Jup . These results are consistent with previous measurements of the object.

Characterizing brown dwarf companions with IRDIS long-slit spectroscopy: HD 1160 B and HD 19467 B

“…HD 1160 is an A0V (Houk & Swift 1999) star at a distance of 125.9 ± 1.2 pc (Gaia Collaboration 2018). Around this star, Nielsen et al (2012) detected two companions, HD 1160 B and HD 1160 C at separations of ∼80 and 530 au, respectively, using NICI at the Gemini telescope.…”

Revised astrometric calibration of the Gemini Planet Imager

“…The changes to the pipeline described in Section 3 and the revised astrometric calibration of the instrument described in Section 6 both necessitate a revision of previously-published relative astrometry of substellar companions measured using GPI observations. Revisions for β Pictoris b Here, we present corrections to the astrometry for the exoplanets in the HR 8799 5 and HD 95086 7 systems, and the brown dwarfs HR 2562 B 34 and HD 984 B, 35 that correct for the changes to the pipeline and the revised astrometric calibration of the instrument. We reduced the same images used in the previous studies with the latest version of the GPI DRP.…”

Gemini Planet Imager Spectroscopy of the Dusty Substellar Companion HD 206893 B

“…As the raw IFS data include over 36,000 microspectra, the process of spectral extraction and interpolation (from the 16 pixel microspectra to 37 wavelength elements) introduces correlations between the resulting 37 spectral channels in the final data cubes. Applying the methodology of Greco & Brandt (2016), we calculate the covariance between channels to better estimate spectral uncertainties (see Appendix A), an approach that has been applied to other recent analyses of GPI companion spectra (see De Rosa et al 2016;Johnson-Groh et al 2017;Rajan et al 2017). This effect can then be incorporated into the error budget of the individual spectrophotometric points for model fitting, as described in Section 5.3.…”