11
Table 2. JWST Magnitudes and Estimated Photometric T for Three Y Dwarf Systems
eff
WISE Name Parallaxa F162M F360M F480M Tb
eff
RA/Dec. mas mag mag mag K
J033605.05-014350.4Ac 99.8± 2.1 21.23± 0.10 17.35± 0.07 14.71+0.02 440± 24d
−0.05
J033605.05-014350.4Bc 99.8± 2.1 23.95+0.18 16.51+0.12 295± 10d
−0.30 −0.26
J035934.06-540154.6e 73.6± 2.0 21.32± 0.05 17.82± 0.05 15.36± 0.05 463± 28f
J182831.08+265037.8g 100.3± 2.0 22.25± 0.10 17.19± 0.10 14.21± 0.10 364± 19h
a All parallaxes are from Kirkpatrick et al. (2021).
b T is estimated from the photometry only, by calculating the average value determined from
eff
the color relationships of Table 1, for the adopted gravity and metallicity. The quoted uncertainty
neglects any systematic errors in the models.
c For the WISE 0336 system, F480M is from Calissendorff et al. (2023), and F162M and F360M
are estimated here, see Section 4. Quoted uncertainty is the sum of the squares of measurement
error and color transformation uncertainty.
d The model sequences imply surface gravities for the primary and secondary components of the
WISE 0336 system of log g ≈ 4.5 and log g ∼ 4.0 respectively, and solar metallicity. For the A
component T was estimated using Table 1 with both colors and M . For the B component the
eff F480M
estimate uses M only due to the divergence between the models and the observed F162M −
F480M
F480M color at the lowest temperatures (Figure 2). The gravities and temperatures are consistent
with a coeval system with an age of a few Gyr and a mass ratio around 2 (Marley et al. 2021).
e For WISE 0359, magnitudes and uncertainties are from Beiler et al. (2023).
f The photometric temperature estimate adopts log g = 4.5 and solar metallicity. The result is
consistent with the spectral fit presented in Section 3; the latter is the preferred value.
g For WISE 1828, magnitudes and uncertainties are from De Furio et al. (2023).
h The photometric temperature estimate assumes that WISE 1828 is an equal-mass binary system,
with log g = 4.5 and [m/H] = −1.0. The result is consistent with the spectral-fit temperature
presented by Leggett et al. (2021).
De Furio et al. (2023) present JWST imaging observations of the Y dwarf WISEP
J182831.08+265037.8 (hereafter WISE 1828), observed with NIRCam and NIRISS filters: F090W,
F115W, F162M, F335M, F360M, F470M, and F480M. WISE 1828 is known to be unusual, being very
bright and red in mid-infrared colors. The red colors suggest metal paucity (Figure 2 and Leggett
et al. 2021) and the brightness suggests that the system is multiple. However De Furio et al. exclude
a similarly bright companion at distances greater than 0.5 AU. WISE 1828 continues to be very red
and bright in Figure 2. Leggett et al. (2021) determine T = 375 K, log g = 4.0, and [m/H] = −0.5
eff
from a spectral fit, assuming the system is an equal-mass binary. We estimated T from the F162M,
eff
F380M, and F480M colors using the log g = 4.5 [m/H] = −1 relationships in Table 1, adopting the
binary solution so that the value inferred from M was consistent with that inferred from the
F480M
other two colors. The value of T = 364±19 K agrees well with the Leggett et al. (2021) value.
eff