55 Cancri e -- Transits detected!!

Sulis et al. "Multi-season optical modulation phased with the orbit of the super-Earth 55 Cnc e"
https://arxiv.org/abs/1910.00383

Possibilities for the modulation include star-planet interactions and a circumstellar dust torus similar to the Io torus at Jupiter.

No evidence for transits of the outer planets.

Detection of a ~15 ppm eclipse with TESS, with a preliminary albedo of ~0.5.

Detection of the Occultation of 55 Cancri e with TESS
http://arxiv.org/abs/2009.12601v1

No escaping helium from 55 Cnc e
https://arxiv.org/abs/2012.02198

Quote :

We search for escaping helium from the hot super Earth 55 Cnc e by taking high-resolution spectra of the 1083 nm line during two transits using Keck/NIRSPEC. We detect no helium absorption down to a 90% upper limit of 250 ppm in excess absorption or 0.27 milli-Angstrom in equivalent width. This corresponds to a mass loss rate of less than ∼109 g/s, although the precise constraint is heavily dependent on model assumptions. This rate is notably below that predicted by both the 1D hydrodynamical simulations of Salz et al 2016 and our own 2.5D models, even for implausibly thin hydrogen/helium atmospheres with surface pressures of less than 100 microbar. We consider both hydrogen- and helium-dominated atmospheric compositions, and find similar bounds on the mass loss rate in both scenarios. Together with the non-detection of Lyman α absorption by Ehrenreich et al 2012, our helium non-detection indicates that 55 Cnc e either never accreted a primordial atmosphere in the first place, or lost its primordial atmosphere shortly after the dissipation of the gas disk.

CHEOPS Precision Phase Curve of the Super-Earth 55 Cnc e
https://arxiv.org/abs/2106.07443

Apparently a non-detection of the planet's secondary eclipse or reflected light with CHEOPS, though some modulation in phase with the planet needs to be explained.

Quote :

CHEOPS observations confirm that the 55 Cnc system varies in flux over the orbital period of planet e. The origin of these flux variations is unclear. Two scenarios ruled unlikely by this work are that the flux variations are the result of reflection from the planet's surface (observed amplitude is too large and asymmetric), or that magnetospheric interactions are inducing excess emission from the star (observed amplitude is too large). A surviving hypothesis for explaining the optical and infrared observations is that dust is orbiting either the star or planet, obscuring the secondary eclipse in the optical but not the infrared.

Detection of the occultation of 55 Cnc e with CHEOPS

Demory et al. "55 Cancri e's occultation captured with CHEOPS"
https://arxiv.org/abs/2211.03582

The occultation depth gives a 2σ upper limit on the geometric albedo of 0.55. There appears to be a 47.3-day cycle in the occultation depths which is yet to be explained.

Another go at measuring the Rossiter-McLaughlin effect:

Zhao et al. "Measured Spin-Orbit Alignment of Ultra-Short Period Super-Earth 55 Cancri e"
https://arxiv.org/abs/2212.03953

They obtain a sky-projected angle λ=10°⁺¹⁷_-20, corresponding to an unprojected angle ψ=23°⁺¹⁴_-12.