Y2V

Thus far WISE J1828+2650 appears to be the only object classified Y2
so far (Kirkpatrick20), but it appears to be somewhat pathological
compared to other Ys. Kirkpatrick20 assigns Y2 to WISE 1828+2650 and
Y4 to WISE 0855−0714.

Teff(Y2V) =  250 K ; Leggett15 (although this was w/WISE J0855 at Y2)
Teff(Y2V) = 288 K ; Kirkpatrick20 (Table 13 polynomial)
Teff(Y2V) = 323 K ; interp Y1V(360K)-Y4V(250K)
Teff(Y2V) = 325 K ; WISE J1828+2650 (Cushing21)
Teff(Y2V) = 406 K ; WISE J1828+2650 (Kirkpatrick20)
Teff(Y2V) = 412 K ; WISE J1828+2650 (Kirkpatrick19; plx=100.7+-2.3mas)
=> adopt Teff(Y2V) = 320 K (logT = 2.505) [updated 2/2/2021]

M_J(MKO)(Y2V)  = 23.62 ; WISE_J1828+2650
=> adopt M_J(MKO)(Y2V) = 23.6 [updated 12/5/2020]

M_H(Y2V)  = 22.46 ; WISE_J1828+2650
=> adopt M_H(MKO)(Y2V) = 22.5 [updated 12/5/2020]

M_K(MKO)(Y2V) = 23.49 ; WISE_1828+2650 calc using Kirkpatrick20
=> adopt M_K(MKO)(Y2V) = 23.5 [updated 12/5/2020]

M_W2(Y2V) = 14.40 ; WISE_J1828+2650
=> adopt M_W2(Y2V) = 14.4 [updated 12/5/2020]

W1-W2(Y2V) = 4.71 ; Kirkpatrick19 polynomial
=> adopt (W1-W2)(Y2V) = 4.7 [updated 12/5/2020]

log(L/Lsun) = -6.50 ; WISE J1828+2650 (Cushing21)

Mbol = 21.00 ; WISE J1828+2650 (Cushing21)

BC_K = -2.49 ; WISE J1828+2650 (Mbol - M_K = 21.00 - 23.49 = -2.49)


# Others

WISE J1828+2650 = WISE J182831.08+265037.7 = WISEPA J182831.08+265037.8 = EQ J1828+2650 
  >=Y2: Kirkpatrick12,Kirkpatrick19,Kirkpatrick20,Cushing21
  Y1.5: Leggett17

  Only Y2 in Kirkpatrick20 but
  ">=Y2". plx=100.3+-2.0mas(Kirkpatrick20).  Teffs:
  406+-88K(Kirkpatrick20). J=23.57+-0.35(Kirkpatrick11,Beichman13),
  J=23.61(Leggett17), H=22.45+-0.08(Beichman13),
  W2=14.39+-0.06(Beichman13) => using Kirkpatrick20 plx => M_J=23.62,
  M_H=22.46, M_W2=14.40.  M_K(MKO)=23.49(calc using Kirkpatrick20).
  fbol=(1.015+-0.01)e-16 W/m2(Cushing21) => mbol = 20.9864+-0.0107
  (IAU2015 scale), adopting plx=100.3+-2.0mas(K20) => Mbol=21.001+-0.051.
  log(L/Lsun)=-6.50+-0.02(Cushing21). Beichman13
  2013ApJ...764..101B:
  d=11.2+1.3-1.0pc. M_H=22.21+0.25-0.22. Mass=0.5-20Mjup for age 0.1-1
  Gyr => age of 2-4 Gyr => 3-6 Mjup.  Teff=250-400K. B13: "No single
  model adequately represents the 1-5 um SED". Kirkpatrick19: "This
  >=Y2 dwarf is overluminous for its spectral type in MW2 and Mch2 and
  is also overluminous in MH for its H–W2 color (Figure 8). On the MW2
  versus H–W2 plot, it falls ∼1 mag above the trend, and in the Mch1
  versus H–W2 plot, it falls at least 1 mag above the trend. However,
  WISE 1828+2650 falls in line with other Y dwarfs on the plot of MH
  versus ch1−ch2. This Y dwarf has been an object of much speculation
  since its broadband colors cannot be fit by any of the current suite
  of models (e.g., Beichman et al. 2013). Leggett et al. (2017)
  speculate that the object may be an equal-magnitude binary (which
  explains only 0.75 mag worth of overluminosity) as well as having a
  subsolar metallicity ([M H] » -0.5), the latter based on model
  atmosphere trends seen in the Mch2 versus J−ch2
  diagram. Inexplicably, though, their best fitting atmospheric model
  suggests a young system (∼1.5 Gyr). Such a young age is hard to
  reconcile with the subsolar metallicity, so the more likely
  explanation is that the current suite of atmospheric models simply
  fails to contain the physics necessary to explain this object’s
  near-infrared spectrum and broadband colors." Cushing21: "Since the
  spectrum of WISE 1828+2650 smoothly extends the Y dwarf spec-tral
  sequence beyond Y1, its spectral type should remain ≥Y2 until the
  near-infrared spectra of cooler objects like WISE 0855−0714 are
  obtained." Cushin: "the ebst overall match to the observed
  properties of WISE 1828+2650 is a ~1 Gyr old binary composed of two
  Teff~325K ~5 Mjup brown dwarfs withs subsolar [C/O] ratios."