Irradiated brown dwarfs

We have observed the post common envelope binary WD0137-349 in the near infrared $J$, $H$ and $K$ bands and have determined that the photometry varies on the system period (116 min). The amplitude of the variability increases with increasing wavelength, indicating that the brown dwarf in the system is likely being irradiated by its 16500 K white dwarf companion. The effect of the (primarily) UV irradiation on the brown dwarf atmosphere is unknown, but it is possible that stratospheric hazes are formed. It is also possible that the brown dwarf (an L-T transition object) itself is variable due to patchy cloud cover. Both these scenarios are discussed, and suggestions for further study are made

Novae in the SuperWASP data base

We present the results of trawling through the SuperWASP data base for classical and recurrent novae. We report light curves for a nova in eruption, and for classical novae and a recurrent nova in quiescence. For five objects in quiescence, we report periodicity, arising in most cases from orbital modulation of the light from the cool secondary star. The stability of the SuperWASP system means that these data have huge potential for the study not only of novae in eruption, but also of the long-term modulations of light during quiescence

Multiwaveband photometry of the irradiated brown dwarf WD0137-349B

WD0137−349 is a white dwarf–brown dwarf binary system in a 116 min orbit. We present radial velocity observations and multiwaveband photometry from V, R and I in the optical, to J, H and Ks in the near-IR and [3.6], [4.5], [5.8] and [8.0] μm in the mid-IR. The photometry and light curves show variability in all wavebands, with the amplitude peaking at [4.5] μm, where the system is also brightest. Fluxes and brightness temperatures were computed for the heated and unheated atmosphere of the brown dwarf (WD0137−349B) using synthetic spectra of the white dwarf using model atmosphere simulations. We show that the flux from the brown dwarf dayside is brighter than expected in the Ks and [4.5] μm bands when compared to models of irradiated brown dwarfs with full energy circulation and suggest this overluminosity may be attributed to H2 fluorescence or H+3 being generated in the atmosphere by the UV irradiation

Discovery of a stripped red giant core in a bright eclipsing binary system

We have identified a star in the Wide Angle Search for Planets (WASP) archive photometry with an unusual light curve due to the total eclipse of a small, hot star by an apparently normal A-type star and with an orbital period of only 0.668 d. From an analysis of the WASP light curve together with V-band and IC-band photometry of the eclipse and a spectroscopic orbit for the A-type star we estimate that the companion star has a mass of 0.23 ± 0.03 M⊙ and a radius of 0.33 ± 0.01 R⊙, assuming that the A-type star is a main-sequence star with the metallicity appropriate for a thick-disc star. The effective temperature of the companion is 13 400 ± 1200 K from which we infer a luminosity of 3 ± 1 L⊙. From a comparison of these parameters to various models we conclude that the companion is most likely to be the remnant of a red giant star that has been very recently stripped of its outer layers by mass transfer on to the A-type star. In this scenario, the companion is currently in a shell hydrogen-burning phase of its evolution, evolving at nearly constant luminosity to hotter effective temperatures prior to ceasing hydrogen burning and fading to become a low-mass white dwarf composed of helium (He-WD). The system will then resemble the pre-He-WD/He-WD companions to A- and B-type stars recently identified from their Kepler satellite light curves (KOI-74, KOI-81 and KIC 10657664). This newly discovered binary offers the opportunity to study the evolution of a stripped red giant star through the pre-He-WD stage in great detail

WASP-25b: A 0.6M planet in the Southern hemisphere

We report the detection of a 0.6 MJ extrasolar planet by WASP-South, WASP-25b, transiting its solar-type host star every 3.76 d. A simultaneous analysis of the WASP, FTS and Euler photometry and CORALIE spectroscopy yields a planet of Rp= 1.22 RJ and Mp= 0.58 MJ around a slightly metal-poor solar-type host star, [Fe/H]=− 0.05 ± 0.10, of R*= 0.92 R⊙ and M*= 1.00 M⊙. WASP-25b is found to have a density of ρp= 0.32 ρJ, a low value for a sub-Jupiter mass planet. We investigate the relationship of planetary radius to planetary equilibrium temperature and host star metallicity for transiting exoplanets with a similar mass to WASP-25b, finding that these two parameters explain the radii of most low-mass planets well

WASP-52b, WASP-58b, WASP-59b, and WASP-60b: Four new transiting close-in giant planets

We present the discovery of four new transiting hot Jupiters, detected mainly from SuperWASP-North and SOPHIE observations. These new planets, WASP-52b, WASP-58b, WASP-59b, and WASP-60b, have orbital periods ranging from 1.7 to 7.9 days, masses between 0.46 and 0.94 MJup, and radii between 0.73 and 1.49 RJup. Their G1 to K5 dwarf host stars have V magnitudes in the range 11.7−13.0. The depths of the transits are between 0.6 and 2.7%, depending on the target. With their large radii, WASP-52b and WASP-58b are new cases of low-density, inflated planets, whereas WASP-59b is likely to have a large, dense core. WASP-60 shows shallow transits. In the case of WASP-52 we also detected the Rossiter-McLaughlin anomaly via time-resolved spectroscopy of a transit. We measured the sky-projected obliquity λ = 24° +17-9, indicating that WASP-52b orbits in the same direction as its host star isrotating and that this prograde orbit is slightly misaligned with the stellar equator. These four new planetary systems increase our statistics on hot Jupiters and provide new targets for follow-up studies