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Table 1.

Circumstances and light-curve fitting results of the 6 October 2022 occultation.

Occulted star
Identification (Gaia DR3 (a)) 2639239368824994944
Geocentric astrometric position
at observational epoch (ICRF (b))
Parallax (mas) 2.2717
G-mag/BP-mag/RP-mag 11.55/11.85/11.08
Radius, Rs (in solar radius) 1.526
Triton’s body (c)
Mass, GMb (km3 s−2) 1428
Radius, Rb (km) 1353
Triton’s atmosphere (c)
N2 molecular mass, μ (kg) 4.652 × 10−26
N2 molecular 1.091 × 10−23
refractivity, K (cm3)
Boltzmann constant, kB (J K−1) 1.380626 × 10−23
Given reference radius, rref (km) 1400
Template temperature profile (K) T(r) (d)
Other information on Triton
Ephemerides DE440/NEP097
Apparent magnitude 13.45
Geocentric distance, D (km) 4.3341 × 109
Projected Rs at D (km) 0.3362
Light-curve fitting results (with 1σ error bars)
Pressure (e) at rref, pref (μbar)
Surface pressure (e) at Rb, psurf (μbar)
Geocentric C/A distance (f), ρcag (km) 4068.98 ± 0.64
Geocentric C/A time (g), tcag (UTC) 14:39:46.223 ± 34 ms

Notes.

(a)

Gaia Collaboration (2023), with the astrometric, photometric, and astrophysical parameters of the star obtained from VizieR online gaiadr3 (https://vizier.cds.unistra.fr/viz-bin/VizieR-6?-out.form=%2bH-source=I/355/gaiadr3%2aSource=2639239368824994944) and paramsup (https://vizier.cds.unistra.fr/viz-bin/VizieR-6?-out.form=%2bH-source=I/355/paramsup%2aSource=2639239368824994944) tables of the Gaia DR3 Part 1. Main source.

(b)

International Celestial Reference Frame.

(c)

All the input parameters of Triton’s body and atmosphere are the same as in MO22, with nitrogen gas (N2) assumed to be the only constituent in the light-curve model. This is mainly to ensure that comparisons are free from systematic discrepancies attributable to differences in ray-tracing codes.

(d)

Using parameters in Table B.1 of MO22.

(e)

Using a ratio psurf/pref = 12.0 given in MO22.

(f)

C/A mean closest approach to shadow axis. Positive (negative) distance values mean that the shadow center passes north (south) of the geocenter.

(g)

Timings by QHY174M-GPS cameras and PMO-GPSBOX devices are used as time references, considering their reliability and accuracy.

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