Neighbours hiding in the Galactic plane, a new M/L dwarf candidate for the 8 pc sample

Abstract

Aims. Using Wide-field Infrared Survey Explorer (WISE) data and previous optical and near-infrared sky surveys, we try to identify still missing stellar and substellar neighbours of the Sun. Methods. When checking the brightest red WISE sources for proper motions and colours expected for nearby M and L dwarfs, we also approached the thin Galactic plane. Astrometry (proper motion and parallax measurements) and the available photometry were used to obtain first estimates of the distance and type of nearby candidates. Results. We have discovered WISE J072003.20−084651.2, an object with moderately high proper motion (µ ≈ 120 mas/yr) that lies at low Galactic latitude (b = +2.3 • ), with similar brightness (J ≈ 10.6, w2 ≈ 8.9) and colours (I − J ≈ 3.2, J − K s ≈ 1.2, w1−w2 ≈ 0.3) as the nearest known M-type brown dwarf LP 944-20. With a photometric classification as an M9 ± 1 dwarf, its photometric distance lies in the range between about 5 and 7 pc, based on comparison with absolute magnitudes of LP 944-20 alone or of a sample of M8-L0 dwarfs. The slightly larger distance derived from our preliminary trigonometric parallax (7.0 ± 1.9 pc) may indicate a close binary nature. The new neighbour is an excellent target for planet search and low-mass star/brown dwarf studies.

WISE J072003.20-084651.2: AN OLD AND ACTIVE M9.5 + T5 SPECTRAL BINARY 6 pc FROM THE SUN

“…With a parallax distance measurement of only 7.0 ± 1.9 pc, this source had been "hiding" in the Galactic plane, its modest proper motion (123 ± 2 mas yr −1 ) preventing it from being picked up in earlier astrometric surveys. Scholz (2014) estimated a photometric classificaiton of M9 ± 1, which was confirmed in near-infrared spectroscopy reported by Kirkpatrick et al (2014). Given its proximity to the Sun, WISE J0720-0846 is an important new system for investigating the M dwarf/L dwarf and star/brown dwarf transitions at high spatial, spectral and temporal resolution.…”

“…With 13 nights of precision TRAPPIST astrometry we attempted to validate and improve the parallax and proper motion measurements reported by Scholz (2014). As our new measurements span less than a year, we combined the survey data reported by Scholz with our TRAPPIST measurements, rejecting only the SuperCosmos Sky Survey Hα and Short-R survey measurements (Parker et al 2005) for which the PSFs were reported to be elliptical.…”

“…Yet, despite their apparent brightness and high proper motion, up to ∼20% of our nearest < ( 20 pc) VLM neighbors remain "missing," particularly toward the Galactic plane Lépine 2005;Henry et al 2006), as exemplified by the very recent discovery of the third (Luhman 16AB;Luhman 2013) and fourth (WISE J085510.83-071442.5; Kirkpatrick et al 2014;Luhman 2014) closest systems to the Sun, comprised of L, T, and Y dwarfs. Several very low-temperature T and Y dwarfs (Artigau et al 2010;Lucas et al 2010;Cushing et al 2011;Kirkpatrick et al 2011;Scholz et al 2011;Bihain et al 2013) and even M dwarfs (e.g., Teegarden et al 2003;Hambly et al 2004;Deacon et al 2005a;Scholz et al 2005;Henry et al 2006;Scholz 2014) have also been uncovered within 5 pc of the Sun in the past decade.…”

“…One of the most recent nearby discoveries is WISE J072003.20-084651.2 (hereafter WISE J0720-0846), a candidate M/L dwarf identified by Scholz (2014) in the WISE survey. With a parallax distance measurement of only 7.0 ± 1.9 pc, this source had been "hiding" in the Galactic plane, its modest proper motion (123 ± 2 mas yr −1 ) preventing it from being picked up in earlier astrometric surveys.…”

A Proper Motion Survey Using the First Sky Pass of Neowise-Reactivation Data

“…Cataloguing the nearest solar neighbors, however, is not a straightforward procedure. Indeed, recent discoveries have demonstrated that some of our closest neighbors have been lurking unseen because of their low temperatures and luminosities (e.g., WISE J052126.29+102528.4 (∼5 pc), Bihain et al 2013;WISE J104915.57-531906.1AB (∼2 pc), Luhman 2013; WISEA J154045.67-510139.3 (∼5.9 pc), Kirkpatrick et al 2014;WISE J085510.83-071442.5 (∼2 pc), Luhman 2014b;and WISE J072003.20-084651.2 (∼7 pc), Scholz 2014).…”