emamajek on 24-Dec-2024 03:07:43 GMT about HD 1388
A separate entry for the companion to HD 1388 (GJ 9008) could be created and WDS IDs assigned to each and the unresolved pair:
Unresolved pair HD 1388 = GJ 9008 = WDS J00180-1327AB = LLO 2
A = Gaia DR3 2423292879948720000 = WDS J00180-1327A = ** LLO 2A
B = Gaia DR3 2423292879947492608 = WDS J00180-1327B = ** LLO 2B
The WDS numbers appear to reflect the initial discovery and followup observations from Jamie Lloyd's PhD thesis (2002PhDT........14L). WDS lists the pair at epoch 2002 having PA=87deg, separation 1.40", mag1=4.99, mag2=7.80 with component spectral types G0V and M2V. Lloyd (2002) reported magnitude differences of del(Ks)=2.69mag and del(Brgamma)=2.86 and measured multiple epochs spanning 2001 and 2002 confirming common proper motion.
While "B" lacks proper motion and parallax in Gaia DR2 and DR3, the association with "A" is supported several ways:
1) The position of B with respect to A in Gaia DR3 (epoch 2016.0) is consistent with separation 1".7980+-0".0002, PA=85.92 deg, close to the last observed separation and PA in WDS from epoch 2002.
2) The Gaia DR3 magnitude difference (Gmag(A)=6.369294, Gmag(B)=11.411153, delta(Gmag)=5.04186) is not far from that reported in WDS, which appears to be tied to 2MASS Ks band (WDS has mag1=4.99, mag2=7.80, del(mag)=2.81), consistent with what would be expected for a G dwarf+M dwarf pair. If the Gaia and WDS "B" components actually match and are co-distant with "A", then the absolute magnitudes for "B" would be M_G(B)=9.26, M_Ks(B)=5.65, which would be consistent with ~M2V and ~M1.5V dwarf stars, respectively (hence, consistent with the spectral type M2V listed in WDS).
3) Kervella+2022(2022A&A...657A...7K) estimated tangential velocity anomaly for A of 383.07+-5.27 m/s between Hipparcos and Gaia, with the pertrubation consistent with a companion at PA=85.98+-0.41deg. This corresponds perfectly to the "B" object in Gaia DR3, and the binary companion reported in WDS for WDS J00180-1327 (LLO 2): PA=87deg.
4) Medan+2023(2023AJ....166..218M) also included the pair in their "Gaia EDR3 red candidate binaries within 200pc" catalog.
5) Dalba+2021(2021AJ....161..123D) report independent speckle observations in 2017 with WIYN/NESSI, detecting the companion to HD 1388 at PA=85.8+-0.6deg, sep=1".8459+-0".0013, del(mag)=4.98 in 832nm band, consistent with both the WDS companion at epoch 2002 and the epoch 2016 Gaia DR3 detection of Gaia DR3 2423292879947492608 ("B") if it were a companion to Gaia DR3 2423292879948720000 ("A").
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