Astronomers Watch as a Black Hole Eats a Rogue Planet

Maybe it's useless as comment, but right these days I was wondering why no planet orbiting a black hole hasn't been detected so far...

Perhaps it's time I... begin to wonder...

I think the "star" doesn't emit light, so transit and RV detection is impossible. You can detect a planet arround this dead star only if the planet itself emit enough light (tidal heat, formation heat...) on (in this case) the black hole is eating the planet. Or by microlensing, perhaps such planet is already detected because some lensing star where never observed.

Before this one, there is another possible black hole with very low mass companion treated as brown dwarf donor, whose mass appears well within "planetary domain"

A 420 day X-ray/optical modulation and extended X-ray dips in the short-period transient Swift J1753.5-0127

Quote :

We have discovered a ~420d modulation, with associated X-ray dips, in RXTE-ASM/MAXI/Swift-BAT archival light-curves of the short-period (3.2h) black-hole X-ray transient, Swift J1753.5-0127. This modulation only appeared at the end of a gradual rebrightening, approximately 3 years after the initial X-ray outburst in mid-2005. The same periodicity is present in both the 2-20 keV and 15-50 keV bands, but with a ~0.1 phase offset (~40d). Contemporaneous photometry in the optical and near-IR reveals a weaker modulation, but consistent with the X-ray period. There are two substantial X-ray dips (very strong in the 15-50 keV band, weaker at lower energies) that are separated by an interval equal to the X-ray period. This likely indicates two physically separated emitting regions for the hard X-ray and lower energy emission. We interpret this periodicity as a property of the accretion disc, most likely a long-term precession, where the disc edge structure and X-ray irradiation is responsible for the hard X-ray dips and modulation, although we discuss other possible explanations, including Lense-Thirring precession in the inner disc region and spectral state variations. Such precession indicates a very high mass ratio LMXB, which even for a ~10M_Sun BH requires a brown dwarf donor (~0.02M_Sun), making Swift J1753.5-0127 a possible analogue of millisecond X-ray pulsars. We compare the properties of Swift J1753.5-0127 with other recently discovered short-period transients, which are now forming a separate population of high latitude BH transients located in the galactic halo.

Emphasis mine.

With an orbital period of ~3.2 hours, we get a disrupting brown dwarf/exoplanet at ~0.011 AUs.

Planets around black holes is a difficult observation, either you need them to get destroyed or you need lensing. Don't think there's much hope otherwise.

Not sure how many isolated black holes have been detected by microlensing, MACHO-96-BLG-5 might be one.

Then there's the question of how to get planets orbiting black holes in the first place. Presumably it's somewhat similar to getting planets around pulsars.

Let's "resurrect" this paper about a dying extragalactic planet, maybe it's worth being listed until it exists

Tidal disruption of a super-Jupiter by a massive black hole

Quote :

Aims. A strong, hard X-ray flare was discovered (IGR J12580+0134) by INTEGRAL in 2011, and is associated to NGC 4845, a Seyfert 2 galaxy never detected at high-energy previously. To understand what happened we observed this event in the X-ray band on several occasions.

Methods. Follow-up observations with XMM-Newton, Swift, and MAXI are presented together with the INTEGRAL data. Long and short term variability are analysed and the event wide band spectral shape modelled.

Results. The spectrum of the source can be described with an absorbed (NH ~ 7 × 10²² cm^-2) power law (Γ ≃ 2.2), characteristic of an accreting source, plus a soft X-ray excess, likely to be of diffuse nature. The hard X-ray flux increased to maximum in a few weeks and decreased over a year, with the evolution expected for a tidal disruption event. The fast variations observed near the flare maximum allowed us to estimate the mass of the central black hole in NGC 4845 as ~3 × 10⁵ M⊙. The observed flare corresponds to the disruption of about 10% of an object with a mass of 14–30 Jupiter. The hard X-ray emission should come from a corona forming around the accretion flow close to the black hole. This is the first tidal event where such a corona has been observed.

(Relativity actually suggests that it might be gone since so long, right?)

Here is the article version reposted in higher definition:

Black hole wakes up and has a light snack
https://www.esa.int/Science_Exploration/Space_Science/Black_hole_wakes_up_and_has_a_light_snack