Bibcode
Zapatero Osorio, M. R.; Lodieu, N.; Béjar, V. J. S.; Martín, E. L.; Ivanov, V. D.; Bayo, A.; Boffin, H. M. J.; Mužić, K.; Minniti, D.; Beamín, J. C.
Referencia bibliográfica
Astronomy and Astrophysics, Volume 592, id.A80, 9 pp.
Fecha de publicación:
8
2016
Revista
Número de citas
9
Número de citas referidas
8
Descripción
Aims: We aim at obtaining near-infrared photometry and deriving
the mass, age, temperature, and surface gravity of WISE
J085510.74-071442.5 (J0855-0714), which is the coolest object beyond the
solar system currently known. Methods: We used publicly available
data from the archives of the Hubble Space Telescope (HST) and the Very
Large Telescope (VLT) to determine the emission of this source at 1.153
μm (F110W) and 1.575 μm (CH4-off). J0855-0714 was
detected at both wavelengths with a signal-to-noise ratio of ≈10
(F110W) and ≈4 (CH4-off) at the peak of the corresponding
point-spread-functions. Results: This is the first detection of
J0855-0714 in the H-band wavelengths. We measured 26.31 ± 0.10
and 23.22 ± 0.35 mag in F110W and CH4-off (Vega
system). J0855-0714 remains unresolved in the HST images that have a
spatial resolution of 0.22''. Companions at separations of 0.5 AU
(similar mass and brightness) and at ~1 AU (≈1 mag fainter in the
F110W filter) are discarded. By combining the new data with published
photometry, including non-detections, we build the spectral energy
distribution of J0855-0714 from 0.89 through 22.09 μm, and contrast
it against current solar-metallicity models of planetary atmospheres. We
determine that the best spectral fit yields a temperature of 225-250 K,
a bolometric luminosity of log L/L⊙ = -8.57, and a high
surface gravity of log g = 5.0 (cm s-2), which suggests an
old age although a gravity this high is not fully compatible with
evolutionary models. After comparing our data with the cooling theory
for brown dwarfs and planets, we infer a mass in the interval 2-10
MJup for ages of 1-12 Gyr and high atmospheric gravities of
log g ⪆ 3.5 (cm s-2). If it had the age of the Sun,
J0855-0714 would be a ≈5-MJup free-floating planetary-mass
object. Conclusions: J0855-0714 meets the mass values previously
determined for free-floating planetary-mass objects discovered in
star-forming regions and young stellar clusters. Based on extrapolations
of the substellar mass functions of young clusters to the field, as many
J0855-0714-like objects as M5-L2 stars may be expected to populate the
solar neighborhood.