NGTS-28Ab: A short period transiting brown dwarf

We report the discovery of a brown dwarf orbiting a M1 host star. We first identified the brown dwarf within the Next Generation Transit Survey data, with supporting observations found in TESS sectors 11 and 38. We confirmed the discovery with follow-up photometry from the South African Astronomical Observatory, SPECULOOS-S, and TRAPPIST-S, and radial velocity measurements from HARPS, which allowed us to characterise the system. We find an orbital period of ~1.25 d, a mass of 69.0+5.3-4.8 MJ, close to the Hydrogen burning limit, and a radius of 0.95 +- 0.05 RJ. We determine the age to be >0.5 Gyr, using model isochrones, which is found to be in agreement with SED fitting within errors. NGTS-28Ab is one of the shortest period systems found within the brown dwarf desert, as well as one of the highest mass brown dwarfs that transits an M dwarf. This makes NGTS-28Ab another important discovery within this scarcely populated region.Comment: 20 pages (inc. appendices), 16 figures, accepted for publication in MNRA

NGTS-28Ab:a short period transiting brown dwarf

We report the discovery of a brown dwarf orbiting a M1 host star. We first identified the brown dwarf within the Next Generation Transit Survey data, with supporting observations found in TESS sectors 11 and 38. We confirmed the discovery with follow-up photometry from the South African Astronomical Observatory, SPECULOOS-S, and TRAPPIST-S, and radial velocity measurements from HARPS, which allowed us to characterize the system. We find an orbital period of ∼1.25 d, a mass of 69.0+5.3-4.8 MJ, close to the hydrogen burning limit, and a radius of 0.95 ± 0.05 RJ. We determine the age to be &gt;0.5 Gyr, using model isochrones, which is found to be in agreement with spectral energy distribution fitting within errors. NGTS-28Ab is one of the shortest period systems found within the brown dwarf desert, as well as one of the highest mass brown dwarfs that transits an M dwarf. This makes NGTS-28Ab another important discovery within this scarcely populated region.</div

Complex Modulation of Rapidly Rotating Young M Dwarfs: Adding Pieces to the Puzzle

New sets of young M dwarfs with complex, sharp-peaked, and strictly periodic photometric modulations have recently been discovered with Kepler/K2 (scallop shells) and TESS (complex rotators). All are part of star-forming associations, are distinct from other variable stars, and likely belong to a unified class. Suggested hypotheses include starspots, accreting dust disks, corotating clouds of material, magnetically constrained material, spots and misaligned disks, and pulsations. Here, we provide a comprehensive overview and add new observational constraints with TESS and SPECULOOS Southern Observatory photometry. We scrutinize all hypotheses from three new angles: (1) We investigate each scenario's occurrence rates via young star catalogs, (2) we study the feature's longevity using over one year of combined data, and (3) we probe the expected color dependency with multicolor photometry. In this process, we also revisit the stellar parameters accounting for activity effects, study stellar flares as activity indicators over year-long timescales, and develop toy models to simulate typical morphologies. We rule out most hypotheses, and only (i) corotating material clouds and (ii) spots and misaligned disks remain feasible-with caveats. For (i), corotating dust might not be stable enough, while corotating gas alone likely cannot cause percentage-scale features and (ii) would require misaligned disks around most young M dwarfs. We thus suggest a unified hypothesis, a superposition of large-amplitude spot modulations and sharp transits of corotating gas clouds. While the complex rotators' mystery remains, these new observations add valuable pieces to the puzzle going forward

WASP-193b: An extremely low-density super-Neptune

peer reviewe

An extended low-density atmosphere around the Jupiter-sized planet WASP-193 b

Gas giants transiting bright nearby stars provide crucial insights into planetary system formation and evolution mechanisms. Most of these planets show certain average characteristics, serving as benchmarks for our understanding of planetary systems. However, outliers like the planet we present in this study, WASP-193 b, offer unique opportunities to explore unconventional formation and evolution processes. This planet completes an orbit around its V-band-magnitude 12.2 F9 main-sequence host star every 6.25 days. Our analyses found that WASP-193 b has a mass of 0.139 +/- 0.029 M-J and a radius of 1.464 +/- 0.058 R-J, translating into an extremely low density of 0.059 +/- 0.014g cm(-3), at least one order of magnitude less than standard gas giants like Jupiter. Typical gas giants such as Jupiter have densities that range between 0.2 g cm(-3) and 2 g cm(-3). The combination of its large transit depth (1.4%), extremely low density, high-equilibrium temperature (1,254 +/- 31 K) and the infrared brightness of its host star (K-band magnitude 10.7) makes WASP-193 b an exquisite target for characterization by transmission spectroscopy (transmission spectroscopy metric similar to 600). One single JWST transit observation would yield detailed insights into its atmospheric properties and planetary mass, providing a unique window to explore the mechanisms behind its exceptionally low density and shed light on giant planets' diverse nature

WASP-193b: An extremely low-density super-Neptune

Gas giants transiting bright nearby stars are stepping stones for our understanding of planetary system formation and evolution mechanisms. This paper presents a particularly interesting new specimen of this kind of exoplanet discovered by the WASP-South transit survey, WASP-193b. This planet completes an orbit around its Vmag = 12.2 F9 main-sequence host star every 6.25 d. Our analyses found that WASP-193b has a mass of Mp = 0.139 +/- 0.029 M_Jup and a radius of Rp = 1.464 +/- 0.058 R_ Jup, translating into an extremely low density of rhop = 0.059 +\- 0.014 g/cm^3. The planet was confirmed photometrically by the 0.6-m TRAPPIST-South, the 1.0-m SPECULOOS-South telescopes, and the TESS mission, and spectroscopically by the ESO-3.6-m/HARPS and Euler-1.2-m/CORALIE spectrographs. The combination of its large transit depth (dF~1.4 %), its extremely-low density, its high-equilibrium temperature (Teq = 1254 +/- 31 K), and the infrared brightness of its host star (magnitude Kmag=10.7) makes WASP-193b an exquisite target for characterization by transmission spectroscopy (transmission spectroscopy metric: TSM ~ 600). One single JWST transit observation would yield detailed insights into its atmospheric properties and planetary mass, within ~0.1 dex and ~1% (vs ~20% currently with radial velocity data) respectively

Reduced choroidal neovascularization by AAV-anti-VEGF shRNA delivery

VEGF plays an essential role in ocular angiogenic diseases including the late-stage form of AMD, the primary cause of vision loss in the western world. Over-expression of VEGF leads to development of vasculature emanating from the choroid, invading the subretinal space through breaks in Bruch's membrane. Strategies leading to long-term suppression of inappropriate ocular angiogenesis are required. A panel of 10 shRNAs targeting the coding region of human VEGF165 was tested in HEK293 cells and in the human retinal pigment epithelial cell line, ARPE-19. VEGF knock-down up to 92% was achieved by co-transfecting shRNAexpressing constructs with plasmid encoding the Renilla luciferase gene fused to the VEGF165 sequence. For in vivo delivery of the most potent shRNA cassette, both single-stranded and self-complementary rAAV vectors were packaged in serotype 8 capsids. Intramuscular administration in mice led to localized expression and 96% knock-down of endogenous VEGF. Using eGFP as a marker, efficient gene transfer of retinal pigment epithelial cells, the cells thought to be responsible for the abnormal VEGF production, was obtained by subretinal delivery of rAAV2.8 vectors. The capacity of rAAV-encoded shRNAs to silence endogenous VEGF gene expression was evaluated in the laser-induced murine model of choroidal neovascularization (CNV). In this mouse model of AMD, sizes of the CNV were found to be significantly reduced following rAAV-shRNA subretinal delivery. Thus, our results indicate that gene transfer combining AAV-mediated delivery with triggering of the endogenous RNAi pathway can be used for anti-VEGF therapy and holds great promise for the treatment of AMD

TOI 762 A b and TIC 46432937 b:Two Giant Planets Transiting M Dwarf Stars

We present the discovery of TOI 762 A b and TIC 46432937 b, two giant planets transiting M dwarf stars. Transits of both systems were first detected from observations by the NASA TESS mission, and the transiting objects are confirmed as planets through high-precision radial velocity (RV) observations carried out with VLT/ESPRESSO. TOI 762 A b is a warm sub-Saturn with a mass of 0.251 +- 0.042 M_J, a radius of 0.744 +- 0.017 R_J, and an orbital period of 3.4717 d. It transits a mid-M dwarf star with a mass of 0.442 +- 0.025 M_S and a radius of 0.4250 +- 0.0091 R_S. The star TOI 762 A has a resolved binary star companion TOI 762 B that is separated from TOI 762 A by 3.2" (~ 319 AU) and has an estimated mass of 0.227 +- 0.010 M_S. The planet TIC 46432937 b is a warm Super-Jupiter with a mass of 3.20 +- 0.11 M_J and radius of 1.188 +- 0.030 R_J. The planet's orbital period is P = 1.4404 d, and it undergoes grazing transits of its early M dwarf host star, which has a mass of 0.563 +- 0.029 M_S and a radius of 0.5299 +- 0.0091 R_S. TIC 46432937 b is one of the highest mass planets found to date transiting an M dwarf star. TIC 46432937 b is also a promising target for atmospheric observations, having the highest Transmission Spectroscopy Metric or Emission Spectroscopy Metric value of any known warm Super-Jupiter (mass greater than 3.0 M_J, equilibrium temperature below 1000 K)