WISEPC J121756.91+162640.2 (designation abbreviated to WISE 1217+1626, or WISE J1217+1626) is a binary brown dwarf system of spectral classes T9 + Y0, located in constellation Coma Berenices at approximately 30.4 light-years from Earth.

History of observations

Discovery WISE 1217+1626 A was discovered in 2011 by J. Davy Kirkpatrick et al. from data, collected by Wide-field Infrared Survey Explorer (WISE) Earth-orbiting satellite—NASA infrared-wavelength 40 cm (16 in) space telescope, which mission lasted from December 2009 to February 2011. In 2011 Kirkpatrick et al. published a paper in The Astrophysical Journal Supplement, where they presented discovery of 98 new found by WISE brown dwarf systems with components of spectral types M, L, T and Y, among which also was WISE 1217+1626.These 98 brown dwarf systems are only among first, not all brown dwarf systems, discovered from data, collected by WISE: six discoveries were published earlier (however, also listed in Kirkpatrick et al. (2011)) in Mainzer et al. (2011) and Burgasser et al. (2011), and the other discoveries were published later.

Initial estimate of spectral type Initial estimate of WISE 1217+1626' spectral type (before discovery of its binarity) was T9 (the same as the component's A type estimate made after this discovery).

Discovery of component B WISE 1217+1626 B was discovered in 2012 by Liu et al. with laser guide star (LGS) adaptive optics (AO) system of the 10-m Keck II Telescope on Mauna Kea, Hawaii, using infrared camera NIRC2 (the observations were made on 2012 January 29 (UT)). On 2012 April 1 (UT) Liu et al. observed WISE J1217+1626AB using the near-IR camera NIRI on the Gemini-North 8.1-m telescope on Mauna Kea, Hawaii and the binary was marginally resolved. On 12 April 2012 (UT) they obtained resolved spectroscopy of WISE J1217+1626AB with the near-IR spectrograph NIRSPEC again on the Keck II Telescope. In 2012 Liu et al. published a paper in The Astrophysical Journal where they presented results of observations with Keck II LGS-AO of three brown dwarf binary systems, binarity of one of which was known before, and binarity of the other two, including WISE 1217+1626, was first presented in this paper.

Physical properties Using three models, Liu et al. calculated physical properties of WISE 1217+1626 components for ages of 1 and 5 billion years. Later, models corresponding to age of the system equal to 1 billion years, were found to be poorly fitting and were discarded.

From Burrows et al. (2003) models and M(J): Component andassumed age Mass, Teff,K log g,cm/s2 P,yr A (for 5 Gyr) B (for 5 Gyr)

From Lyon/COND models and M(J): Component andassumed age Mass, Teff,K log g,cm/s2 P,yr A (for 5 Gyr) B (for 5 Gyr)

From Lyon/COND models and Lbol: Component andassumed age Mass, Teff,K log g,cm/s2 P,yr A (for 5 Gyr) B (for 5 Gyr) Both components have a thin cloud layers in atmosphere. Despite being cold enough to have a chloride and sulfide clouds in atmosphere, component B atmosphere is not as cloudy as expected, possibly because of the system been metal-poor.

See also WISE J0336−0143 – first Y + Y binary brown dwarf system discovered The other two brown dwarf binary systems, observed by Liu et al. with Keck II LGS-AO in 2012: WISE 1711+3500 (T8 + T9.5, binarity was newly discovered) CFBDSIR 1458+10 (T9 + Y0, binarity was known before) Lists: List of star systems within 30–35 light-years List of Y-dwarfs

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References