1SWASP J140747.93-394542.6 - Exoplanet, rings and moons?

It was reported some time ago that in 2007 that a transit of 1SWASP J140747.93-394542.6 seemed to be rather complex, likely explained by the existence of structured rings.

Monitoring of J1407 for next extrasolar ring system transit
http://www.aavso.org/aavso-alert-notice-462

Planetary Construction Zones in Occultation: Discovery of an Extrasolar Ring System Transiting a Young Sun-like Star and Future Prospects for Detecting Eclipses by Circumsecondary and Circumplanetary Disks
http://arxiv.org/abs/1108.4070

A re-analysis of the data is quite interesting:

Analysis and modeling of a giant transiting multiple ring system around the substellar companion J1407b
http://www.ast.cam.ac.uk/talks/archive/3495

Quote :

In May 2007 the nearby young (17 Myr) pre-MS star J1407 underwent a series of deep complex eclipses that lasted over 60 days. These eclipses were interpreted by Mamajek et al. (2012) to be caused by a giant ring system of up to 60 million km in diameter surrounding an unseen substellar companion, J1407b. A re-analysis of the photometry shows structure down to timescales of 1 hour, consistent with the movement of ring edges across the diameter of the stellar disk. We present our model of this giant exo-Saturn ring system, showing how we can simultaneously solve for the geometry of the ring system and the detection of over 20 individual rings. The presence of highly structured multiple rings is a signpost of the presence of exomoons. Future transits of this ring system will provide a unique observing opportunity to study a young ring system in formation.

van Werkhoven, Kenworthy and Mamajek (2014) "Analysis of 1SWASP J140747.93-394542.6 eclipse fine-structure: hints of exomoons"

Also available on Eric Mamajek's home page.

Kenworth et al. "Mass and period limits on the ringed companion transiting the young star J1407"
http://arxiv.org/abs/1410.6577

Further constraints from photometric and radial velocity observations. The central object hosting the ring system is likely to be either a brown dwarf or a planet, and the rings are substantially larger than the Roche radius, suggesting they may go on to form exomoons.

Page 20 :

Observations at longer wavelengths may be able to detect
and possibly resolve the ring system around J1407b.
Heating from the secondary companion combined with the
large surface area of the ring system results in significant flux
at submm wavelengths, detectable with the Atacama Large
Millimeter Array (ALMA) or a large single dish submm telescope.
When the full ALMA suite of telescopes is deployed,
a high precision astrometric detection can constrain the orbit
of the secondary companion and measure the mass of the
ring system
(…)
The ringed system around J1407b represents a unique laboratory to both spatially
and spectrally resolve a young 16 Myr old disk around
a likely substellar object and probe its structure to unprecedented
spatial scales. Photometric monitoring is underway
to look for the beginning of the next eclipse, and will signal
the start of intensive observational campaigns over the
subsequent weeks.

Listed in EPE:

http://exoplanet.eu/catalog/1swasp_j1407_b/

Any idea as to when we will see the results?

-M-

Modeling giant extrasolar ring systems in eclipse and the case of J1407b: sculpting by exomoons?
http://arxiv.org/abs/1501.05652

Quote :

The light curve of 1SWASP J140747.93-394542.6, a ∼16 Myr old star in the Sco-Cen OB association, underwent a complex series of deep eclipses that lasted 56 days, centered on April 2007. This light curve is interpreted as the transit of a giant ring system that is filling up a fraction of the Hill sphere of an unseen secondary companion, J1407b. We fit the light curve with a model of an azimuthally symmetric ring system, including spatial scales down to the temporal limit set by the star's diameter and relative velocity. The best ring model has 37 rings and extends out to a radius of 0.6 AU (90 million km), and the rings have an estimated total mass on the order of 100MMoon. The ring system has one clearly defined gap at 0.4 AU (61 million km), which we hypothesize is being cleared out by a <0.8M⊕ exosatellite orbiting around J1407b. This eclipse and model implies that we are seeing a circumplanetary disk undergoing a dynamic transition to an exosatellite-sculpted ring structure and is one of the first seen outside our Solar system.

http://spaceref.com/astronomy/gigantic-ring-system-around-exoplanet-j1407b.html

"...A new analysis of the data, led by Leiden's Matthew Kenworthy, shows that the ring system consists of over 30 rings, each of them tens of millions of kilometers in diameter. Furthermore, they found gaps in the rings, which indicate that satellites ("exomoons") may have formed. The result has been accepted for publication in the Astrophysical Journal...."

The image of the ring data is worth a look.

Wonder if there will be a similar event at the conjunction of Beta Pic b.

http://vimeo.com/117757625

Computer model that fits the light curve of the star J1407 seen in SuperWASP data in 2007

Rieder & Kenworthy "Constraints on the size and dynamics of the J1407b ring system"
http://arxiv.org/abs/1609.08485

They infer that J1407b is likely a massive brown dwarf or a small star (60–100 M_Jupiter), and the disc is likely in a retrograde orbit with respect to the companion's orbital motion.

This is largely inconsistent with the mass constraints found by Kenworthy et al., which are based on the combined results of various complimentary methods. Note that Kenworthy is a co-author for this paper, however.

While correct for its purpose, I suspect the methodology used here is too greatly simplified to make broad conclusions - in particular only the ~minimum possible period (11 yrs) is considered, which forces the companion mass to be large to maintain a large hill sphere. I would like to see what constraints are possible for periods of a few decades.

Looks like there's an update in the works... https://twitter.com/RobinMentel/status/1037014130853601283

Here it is.
Constraining the period of the ringed secondary companion to the young star J1407 with photographic plates
https://arxiv.org/abs/1810.05171

Quote :

Context. The 16 Myr old star 1SWASP J140747.93-394542.6 (V1400 Cen) underwent a series of complex eclipses in May 2007, interpreted as the transit of a giant Hill sphere filling debris ring system around a secondary companion, J1407b. No other eclipses have since been detected, although other measurements have constrained but not uniquely determined the orbital period of J1407b. Finding another eclipse towards J1407 will help determine the orbital period of the system, the geometry of the proposed ring system and enable planning of further observations to characterize the material within these putative rings. Aims. We carry out a search for other eclipses in photometric data of J1407 with the aim of constraining the orbital period of J1407b. Methods. We present photometry from archival photographic plates from the Harvard DASCH survey, and Bamberg and Sonneberg Observatories, in order to place additional constraints on the orbital period of J1407b by searching for other dimming and eclipse events. Using a visual inspection of all 387 plates and a period-folding algorithm we performed a search for other eclipses in these data sets. Results. We find no other deep eclipses in the data spanning from 1890 to 1990, nor in recent time-series photometry from 2012-2018. Conclusions. We rule out a large fraction of putative orbital periods for J1407b from 5 to 20 years. These limits are still marginally consistent with a large Hill sphere filling ring system surrounding a brown dwarf companion in a bound elliptical orbit about J1407. Issues with the stability of any rings combined with the lack of detection of another eclipse, suggests that J1407b may not be bound to J1407.

The transiting ringed planet candidate at 1SWASP J1407 may have been directly imaged with ALMA, if it is a non-bound planet, but there are other possibilities, too (background galaxy for example).

ALMA and NACO observations towards the young exoring transit system J1407 (V1400 Cen)
https://arxiv.org/abs/1912.03314

Quote :

Our aim was to directly detect the thermal emission of the putative exoring system responsible for the complex deep transits observed in the light curve for the young Sco-Cen star 1SWASP J140747.93-394542.6 (V1400 Cen, hereafter J1407), confirming it as the occulter seen in May 2007, and to determine its orbital parameters with respect to the star. We used the Atacama Large Millimeter/submillimeter Array (ALMA) to observe the field centred on J1407 in the 340 GHz (Band 7) continuum in order to determine the flux and astrometric location of the ring system relative to the star. We used the VLT/NACO camera to observe the J1407 system in March 2019 and to search for the central planetary mass object at thermal infrared wavelengths. We detect no point source at the expected location of J1407, and derive an upper limit 3σ level of 57.6 μJy. There is a point source detected at an angular separation consistent with the expected location for a free-floating ring system that occulted J1407 in May 2007, with a flux of 89 μJy consistent with optically thin dust surrounding a massive substellar companion. At 3.8 microns with the NACO camera, we detect the star J1407 but no other additional point sources within 1.3 arcseconds of the star, with a lower bound on the sensitivity of 6MJup at the location of the ALMA source, and down to 4MJup in the sky background limit. The ALMA upper limit at the location of J1407 implies that a hypothesised bound ring system is composed of dust smaller than 1 mm in size, implying a young ring structure. The detected ALMA source has multiple interpretations, including: (i) it is an unbound substellar object surrounded by warm dust in Sco-Cen with an upper mass limit of 6MJup, or (ii) it is a background galaxy.

Twitter thread from Matthew Kenworthy about the ALMA/NACO observations here.