We present near-UV transmission spectroscopy of the highly irradiated transiting exoplanet WASP-12b, obtained with the Cosmic Origins Spectrograph on the Hubble Space Telescope. The spectra cover ...three distinct wavelength ranges: NUVA (2539-2580 A), NUVB (2655-2696 A), and NUVC (2770-2811 A). Three independent methods all reveal enhanced transit depths attributable to absorption by resonance lines of metals in the exosphere of WASP-12b. Light curves of total counts in the NUVA and NUVC wavelength ranges show a detection at a 2.5{sigma} level. We detect extra absorption in the Mg II {lambda}{lambda}2800 resonance line cores at the 2.8{sigma} level. The NUVA, NUVB, and NUVC light curves imply effective radii of 2.69 {+-} 0.24 R {sub J}, 2.18 {+-} 0.18 R {sub J}, and 2.66 {+-} 0.22 R {sub J} respectively, suggesting the planet is surrounded by an absorbing cloud which overfills the Roche lobe. We detect enhanced transit depths at the wavelengths of resonance lines of neutral sodium, tin, and manganese, and at singly ionized ytterbium, scandium, manganese, aluminum, vanadium, and magnesium. We also find the statistically expected number of anomalous transit depths at wavelengths not associated with any known resonance line. Our data are limited by photon noise, but taken as a whole the results are strong evidence for an extended absorbing exosphere surrounding the planet. The NUVA data exhibit an early ingress, contrary to model expectations; we speculate this could be due to the presence of a disk of previously stripped material.
Extended gas clouds have been previously detected surrounding the brightest known close-in transiting hot Jupiter exoplanets, HD 209458 b and HD 189733 b; we observed the distant but more extreme ...close-in hot Jupiter system, WASP-12, with Hubble Space Telescope (HST). Near-UV (NUV) transits up to three times deeper than the optical transit of WASP-12 b reveal extensive diffuse gas, extending well beyond the Roche lobe. Our spectra reveal significantly enhanced absorption (greater than 3sigma below the median) at ~200 individual wavelengths on each of two HST visits; 65 of these wavelengths are consistent between the two visits, using a strict criterion for velocity matching that excludes matches with velocity shifts exceeding ~20 km s super(-1). Our Visit 2 NUV light curves show evidence for a stellar flare. We show that some of the possible transit detections in resonance lines of rare elements may be due instead to non-resonant transitions in common species. We present optical observations and update the transit ephemeris.
We report on the discovery of a new extremely short period transiting extrasolar planet, WASP-19b. The planet has mass M pl = 1.15 +/- 0.08 MJ, radius R pl = 1.31 +/- 0.06 RJ, and orbital period P = ...0.7888399 +/- 0.0000008 days. Through spectroscopic analysis, we determine the host star to be a slightly super-solar metallicity (M/H = 0.1 +/- 0.1 dex) G-dwarf with T eff = 5500 +/- 100 K. In addition, we detect periodic, sinusoidal flux variations in the light curve which are used to derive a rotation period for the star of P rot = 10.5 +/- 0.2 days. The relatively short stellar rotation period suggests that either WASP-19 is somewhat young (~ 600 Myr old) or tidal interactions between the two bodies have caused the planet to spiral inward over its lifetime resulting in the spin-up of the star. Due to the detection of the rotation period, this system has the potential to place strong constraints on the stellar tidal quality factor, Q's, if a more precise age is determined.
We report on the discovery of WASP-12b, a new transiting extrasolar planet with R pl = 1.79+0.09 -0.09 RJ and M pl = 1.41+0.10 -0.10 M J. The planet and host star properties were derived from a Monte ...Carlo Markov Chain analysis of the transit photometry and radial velocity data. Furthermore, by comparing the stellar spectrum with theoretical spectra and stellar evolution models, we determined that the host star is a supersolar metallicity (M/H = 0.3+0.05 -0.15), late-F (T eff = 6300+200 -100 K) star which is evolving off the zero-age main sequence. The planet has an equilibrium temperature of T eq = 2516 K caused by its very short period orbit (P = 1.09 days) around the hot, twelfth magnitude host star. WASP-12b has the largest radius of any transiting planet yet detected. It is also the most heavily irradiated and the shortest period planet in the literature.
We have detected excess absorption in the emission cores of Ca ii H&K during transits of HD 189733b for the first time. Using observations of three transits, we investigate the origin of the ...absorption, which is also seen in Hα and the Na i D lines. Applying differential spectrophotometry methods to the Ca ii H and Ca ii K lines combined, using respective passband widths of Δλ = 0.4 and 0.6 Å yields excess absorption of t
d
= 0.0074 ± 0.0044 (1.7σ; Transit 1) and 0.0214 ± 0.0022 (9.8σ; Transit 2). Similarly, we detect excess Hα absorption in a passband of width Δλ = 0.7 Å, with t
d
= 0.0084 ± 0.0016 (5.2σ) and 0.0121 ± 0.0012 (9.9σ). For both lines, Transit 2 is thus significantly deeper. Combining all three transits for the Na i D lines yields excess absorption of t
d
= 0.0041 ± 0.0006 (6.5σ). By considering the time series observations of each line, we find that the excess apparent absorption is best recovered in the stellar reference frame. These findings lead us to postulate that the main contribution to the excess transit absorption in the differential light curves arises because the normalizing continuum bands form in the photosphere, whereas the line cores contain a chromospheric component. We cannot rule out that part of the excess absorption signature arises from the planetary atmosphere, but we present evidence which casts doubt on recent claims to have detected wind motions in the planet's atmosphere in these data.
White dwarfs are compact stars, similar in size to Earth but approximately 200,000 times more massive. Isolated white dwarfs emit most of their power from ultraviolet to near-infrared wavelengths, ...but when in close orbits with less dense stars, white dwarfs can strip material from their companions and the resulting mass transfer can generate atomic line and X-ray emission, as well as near- and mid-infrared radiation if the white dwarf is magnetic. However, even in binaries, white dwarfs are rarely detected at far-infrared or radio frequencies. Here we report the discovery of a white dwarf/cool star binary that emits from X-ray to radio wavelengths. The star, AR Scorpii (henceforth AR Sco), was classified in the early 1970s as a δ-Scuti star, a common variety of periodic variable star. Our observations reveal instead a 3.56-hour period close binary, pulsing in brightness on a period of 1.97 minutes. The pulses are so intense that AR Sco's optical flux can increase by a factor of four within 30 seconds, and they are also detectable at radio frequencies. They reflect the spin of a magnetic white dwarf, which we find to be slowing down on a 10
-year timescale. The spin-down power is an order of magnitude larger than that seen in electromagnetic radiation, which, together with an absence of obvious signs of accretion, suggests that AR Sco is primarily spin-powered. Although the pulsations are driven by the white dwarf's spin, they mainly originate from the cool star. AR Sco's broadband spectrum is characteristic of synchrotron radiation, requiring relativistic electrons. These must either originate from near the white dwarf or be generated in situ at the M star through direct interaction with the white dwarf's magnetosphere.
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Transiting extrasolar planets constitute only a small fraction of the range of stellar systems found to display periodic, shallow dimmings in wide-field surveys employing small-aperture camera ...arrays. Here we present an efficient selection strategy for follow-up observations, derived from analysis of the light curves of a sample of 67 SuperWASP targets that passed the selection tests we used in earlier papers, but which have subsequently been identified either as planet hosts or as astrophysical false positives. We determine the system parameters using Markov-chain Monte Carlo analysis of the SuperWASP light curves. We use a constrained optimization of χ2 combined with a Bayesian prior based on the main-sequence mass and radius expected from the Two Micron All Sky Survey J−H colour. The Bayesian nature of the analysis allows us to quantify both the departure of the host star from the main-sequence mass–radius relation and the probability that the companion radius is less than 1.5 Jupiter radii. When augmented by direct light-curve analyses that detect binaries with unequal primary and secondary eclipses, and objects with aperture blends that are resolved by SuperWASP, we find that only 13 of the original 67 stars, including the three known planets in the sample, would qualify for follow-up. This suggests that planet discovery ‘hit rates’ better than one-in-five should be achievable. In addition, the stellar binaries that qualify are likely to have astrophysically interesting stellar or substellar secondaries.
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ABSTRACT
Small low-mass stars are favourable targets for the detection of rocky habitable planets. In particular, planetary systems in the solar neighbourhood are interesting and suitable for precise ...characterization. The RedDots campaigns seek to discover rocky planets orbiting nearby low-mass stars. The 2018 campaign targeted GJ 1061, which is the 20th nearest star to the Sun. For three consecutive months we obtained nightly, high-precision radial velocity measurements with the HARPS spectrograph. We analysed these data together with archival HARPS data. We report the detection of three planet candidates with periods of 3.204 ± 0.001, 6.689 ± 0.005, and 13.03 ± 0.03 d, which are close to 1:2:4 period commensurability. After several considerations related to the properties of the noise and sampling, we conclude that a fourth signal is most likely explained by stellar rotation, although it may be due to a planet. The proposed three-planet system (and the potential four-planet solution) is long-term dynamically stable. Planet–planet gravitational interactions are below our current detection threshold. The minimum masses of the three planets range from 1.4 ± 0.2 to 1.8 ± 0.3 M⊕. Planet d, with msin i = 1.64 ± 0.24 M⊕, receives a similar amount of energy as Earth receives from the Sun. Consequently it lies within the liquid-water habitable zone of the star and has a similar equilibrium temperature to Earth. GJ 1061 has very similar properties to Proxima Centauri but activity indices point to lower levels of stellar activity.
The
Ariel
mission will execute an ambitious survey to measure transit and / or secondary eclipse spectra of the atmospheres of about 1000 exoplanets. I outline here some possible scientific ...applications of the exquisite Ariel Core Survey data, beyond the science for which they are primarily designed.
The first WASP public data release Butters, O. W.; West, R. G.; Anderson, D. R. ...
Astronomy & astrophysics,
09/2010, Volume:
520
Journal Article
Peer reviewed
Open access
The WASP (wide angle search for planets) project is an exoplanet transit survey that has been automatically taking wide field images since 2004. Two instruments, one in La Palma and the other in ...South Africa, continually monitor the night sky, building up light curves of millions of unique objects. These light curves are used to search for the characteristics of exoplanetary transits. This first public data release (DR1) of the WASP archive makes available all the light curve data and images from 2004 up to 2008 in both the Northern and Southern hemispheres. A web interface () to the data allows easy access over the Internet. The data set contains 3 631 972 raw images and 17 970 937 light curves. In total the light curves have 119 930 299 362 data points available between them.
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