Relentless and complex transits from a planetesimal debris disc

This article reports quasi-continuous transiting events towards WD 1054–226 at d = 36.2 pc and V = 16.0 mag, based on simultaneous, high-cadence, multiwavelength imaging photometry using ULTRACAM over 18 nights from 2019 to 2020 March. The predominant period is 25.02 h and corresponds to a circular orbit with blackbody Teq = 323 K, where a planetary surface can nominally support liquid water. The light curves reveal remarkable night-to-night similarity, with changes on longer time-scales, and lack any transit-free segments of unocculted starlight. The most pronounced dimming components occur every 23.1 min – exactly the 65th harmonic of the fundamental period – with depths of up to several per cent, and no evident colour dependence. Myriad additional harmonics are present, as well as at least two transiting features with independent periods. High-resolution optical spectra are consistent with stable, photospheric absorption by multiple, refractory metal species, with no indication of circumstellar gas. Spitzer observations demonstrate a lack of detectable dust emission, suggesting that the otherwise hidden circumstellar disc orbiting WD 1054–226 may be typical of polluted white dwarfs, and detected only via favourable geometry. Future observations are required to constrain the orbital eccentricity, but even if periastron is near the Roche limit, sublimation cannot drive mass loss in refractory parent bodies, and collisional disintegration is necessary for dust production

Mammary immunoglobulin transfer rates following prepartum milking

Colostrum formation is thought to occur slowly over an extended period (4wk) prepartum. Furthermore, colostrum formation is highly variable among cows in total volume, IgG1 concentration, and mass obtained at first postpartum milking. Recent work has suggested that a rapid transfer of IgG1 to secretions may occur if animals are milked prepartum. Our objective was to establish the concentration, mass, and mass transfer rates of IgG1 in multiparous Holstein cows (n=11, parity=3.6±1.1) milked prepartum (-74 to -1h) and again around 4h postpartum. Blood concentrations of IgG1 were very low (<1mg/mL) in 7 cows at prepartum milking and did not decline following prepartum milking. Cows showed variability in the capacity to recover total volume, IgG1 concentration, and IgG1 mass. Three groupings of cows were considered based on the time between the 2 milkings (prepartum + 4h postpartum): long-time (-74 to -54h, n=3), medium-time (-25 to -17h, n=4), and short-time (< -13h, n=4) groups. The average rates of transfer of these groups were 1.4±0.8, 3.0±1.3, and 25.1±15.8g/h, respectively. The data indicate that a longer time between prepartum and postpartum milking is not a main factor in IgG1 secretion transfer. Furthermore, because blood concentrations did not change after prepartum milking and the mass of blood plasma IgG1 was not sufficient to account for the mass occurring in postpartum colostrum, a source of IgG1 other than blood circulation appears to be present during colostrogenesis