98 research outputs found
Proof of polar ejection fom the close-binary core of the planetary nebula Abell 63
We present the first detailed kinematical analysis of the planetary nebula
Abell 63, which is known to contain the eclipsing close-binary nucleus UU Sge.
Abell 63 provides an important test case in investigating the role of
close-binary central stars on the evolution of planetary nebulae.
Longslit observations were obtained using the Manchester echelle spectrometer
combined with the 2.1-m San Pedro Martir Telescope. The spectra reveal that the
central bright rim of Abell 63 has a tube-like structure. A deep image shows
collimated lobes extending from the nebula, which are shown to be high-velocity
outflows. The kinematic ages of the nebular rim and the extended lobes are
calculated to be 8400+/-500 years and 12900+/-2800 years, respectively, which
suggests that the lobes were formed at an earlier stage than the nebular rim.
This is consistent with expectations that disk-generated jets form immediately
after the common envelope phase.
A morphological-kinematical model of the central nebula is presented and the
best-fit model is found to have the same inclination as the orbital plane of
the central binary system; this is the first proof that a close-binary system
directly affects the shaping of its nebula. A Hubble-type flow is
well-established in the morphological-kinematical modelling of the observed
line profiles and imagery.
Two possible formation models for the elongated lobes of Abell 63 are
considered (1) a low-density, pressure-driven jet excavates a cavity in the
remnant AGB envelope; (2) high-density bullets form the lobes in a single
ballistic ejection event.Comment: 11 pages, 8 figures, accepted by MNRAS for publicatio
SuperWASP Observations of the 2007 Outburst of Comet 17P/Holmes
We present wide-field imaging of the 2007 outburst of Comet 17P/Holmes
obtained serendipitously by SuperWASP-North on 17 nights over a 42-night period
beginning on the night (2007 October 22-23) immediately prior to the outburst.
Photometry of 17P's unresolved coma in SuperWASP data taken on the first night
of the outburst is consistent with exponential brightening, suggesting that the
rapid increase in the scattering cross-section of the coma could be largely due
to the progressive fragmentation of ejected material produced on a very short
timescale at the time of the initial outburst, with fragmentation timescales
decreasing from t(frag)~2x10^3 s to t(frag)~1x10^3 s over our observing period.
Analysis of the expansion of 17P's coma reveals a velocity gradient suggesting
that the outer coma was dominated by material ejected in an instantaneous,
explosive manner. We find an expansion velocity at the edge of the dust coma of
v(exp) = 0.55+/-0.02 km/s and a likely outburst date of t_0=2007 October
23.3+/-0.3, consistent with our finding that the comet remained below
SuperWASP's detection limit of m(V)~15 mag until at least 2007 October 23.3.
Modelling of 17P's gas coma indicates that its outer edge, which was observed
to extend past the outer dust coma, is best explained with a single pulse of
gas production, consistent with our conclusions concerning the production of
the outer dust coma.Comment: 36 pages, 8 figures, accepted for publication in MNRA
WASP-120b, WASP-122b and WASP-123b: Three newly discovered planets from the WASP-South survey
We present the discovery by the WASP-South survey of three planets transiting
moderately bright stars (V ~ 11). WASP-120b is a massive (5.0MJup) planet in a
3.6-day orbit that we find likely to be eccentric (e = 0.059+0.025-0.018)
around an F5 star. WASP-122b is a hot-Jupiter (1.37MJup, 1.79RJup) in a 1.7-day
orbit about a G4 star. Our predicted transit depth variation cause by the
atmosphere of WASP-122b suggests it is well suited to characterisation.
WASP-123b is a hot-Jupiter (0.92MJup, 1.33RJup) in a 3.0-day orbit around an
old (~ 7 Gyr) G5 star.Comment: 15 pages, 10 figures, 5 table
WASP-80b has a dayside within the T-dwarf range
AHMJT is a Swiss National Science Foundation (SNSF) fellow under grant number P300P2-147773. MG and EJ are Research Associates at the F.R.S-FNRS; LD received the support the support of the F.R.I.A. fund of the FNRS. DE, KH, and SU acknowledge the financial support of the SNSF in the frame of the National Centre for Competence in Research ‘PlanetS’. EH and IR acknowledge support from the Spanish Ministry of Economy and Competitiveness (MINECO) and the ‘Fondo Europeo de Desarrollo Regional’ (FEDER) through grants AYA2012-39612-C03-01 and ESP2013-48391-C4-1-R.WASP-80b is a missing link in the study of exo-atmospheres. It falls between the warm Neptunes and the hot Jupiters and is amenable for characterisation, thanks to its host star's properties. We observed the planet through transit and during occultation with Warm Spitzer. Combining our mid-infrared transits with optical time series, we find that the planet presents a transmission spectrum indistinguishable from a horizontal line. In emission, WASP-80b is the intrinsically faintest planet whose dayside flux has been detected in both the 3.6 and 4.5 m Spitzer channels. The depths of the occultations reveal that WASP-80b is as bright and as red as a T4 dwarf, but that its temperature is cooler. If planets go through the equivalent of an L-T transition, our results would imply this happens at cooler temperatures than for brown dwarfs. Placing WASP-80b's dayside into a colour-magnitude diagram, it falls exactly at the junction between a blackbody model and the T-dwarf sequence; we cannot discern which of those two interpretations is the more likely. Flux measurements on other planets with similar equilibrium temperatures are required to establish whether irradiated gas giants, like brown dwarfs, transition between two spectral classes. An eventual detection of methane absorption in transmission would also help lift that degeneracy. We obtained a second series of high-resolution spectra during transit, using HARPS. We reanalyse the Rossiter-McLaughlin effect. The data now favour an aligned orbital solution and a stellar rotation nearly three times slower than stellar line broadening implies. A contribution to stellar line broadening, maybe macroturbulence, is likely to have been underestimated for cool stars, whose rotations have therefore been systematically overestimated. [abridged]Publisher PDFPeer reviewe
The thermal emission of the exoplanets WASP-1b and WASP-2b
We present a comparative study of the thermal emission of the transiting
exoplanets WASP-1b and WASP-2b using the Spitzer Space Telescope. The two
planets have very similar masses but suffer different levels of irradiation and
are predicted to fall either side of a sharp transition between planets with
and without hot stratospheres. WASP-1b is one of the most highly irradiated
planets studied to date. We measure planet/star contrast ratios in all four of
the IRAC bands for both planets (3.6-8.0um), and our results indicate the
presence of a strong temperature inversion in the atmosphere of WASP-1b,
particularly apparent at 8um, and no inversion in WASP-2b. In both cases the
measured eclipse depths favor models in which incident energy is not
redistributed efficiently from the day side to the night side of the planet. We
fit the Spitzer light curves simultaneously with the best available radial
velocity curves and transit photometry in order to provide updated measurements
of system parameters. We do not find significant eccentricity in the orbit of
either planet, suggesting that the inflated radius of WASP-1b is unlikely to be
the result of tidal heating. Finally, by plotting ratios of secondary eclipse
depths at 8um and 4.5um against irradiation for all available planets, we find
evidence for a sharp transition in the emission spectra of hot Jupiters at an
irradiation level of 2 x 10^9 erg/s/cm^2. We suggest this transition may be due
to the presence of TiO in the upper atmospheres of the most strongly irradiated
hot Jupiters.Comment: 10 pages, submitted to Ap
Results from the Wide Angle Search for Planets Prototype (WASP0) I: Analysis of the Pegasus Field
WASP0 is a prototype for what is intended to become a collection of
wide-angle survey instruments whose primary aim is to detect extra-solar
planets transiting across the face of their parent star. The WASP0 instrument
is a wide-field (9-degree) 6.3cm aperture F/2.8 Apogee 10 CCD camera (2Kx2K
chip, 16-arcsec pixels) mounted piggy-back on a commercial telescope. We
present results from analysis of a field in Pegasus using the WASP0 camera,
including observations of the known transiting planet around HD 209458. We also
present details on solving problems which restrict the ability to achieve
photon limited precision with a wide-field commercial CCD. The results
presented herein demonstrate that millimag photometry can be obtained with this
instrument and that it is sensitive enough to detect transit due to extra-solar
planets.Comment: 9 pages, 10 figures, Accepted for publication in MNRA
One of the closest exoplanet pairs to the 3:2 Mean Motion Resonance: K2-19b \& c
The K2 mission has recently begun to discover new and diverse planetary
systems. In December 2014 Campaign 1 data from the mission was released,
providing high-precision photometry for ~22000 objects over an 80 day timespan.
We searched these data with the aim of detecting further important new objects.
Our search through two separate pipelines led to the independent discovery of
K2-19b \& c, a two-planet system of Neptune sized objects (4.2 and 7.2
), orbiting a K dwarf extremely close to the 3:2 mean motion
resonance. The two planets each show transits, sometimes simultaneously due to
their proximity to resonance and alignment of conjunctions. We obtain further
ground based photometry of the larger planet with the NITES telescope,
demonstrating the presence of large transit timing variations (TTVs), and use
the observed TTVs to place mass constraints on the transiting objects under the
hypothesis that the objects are near but not in resonance. We then
statistically validate the planets through the \texttt{PASTIS} tool,
independently of the TTV analysis.Comment: 18 pages, 10 figures, accepted to A&A, updated to match published
versio
WASP-80b has a dayside within the T-dwarf range
WASP-80b is a missing link in the study of exoatmospheres. It falls between the warm Neptunes and the hot Jupiters and is amenable for characterization, thanks to its host star's properties. We observed the planet through transit and during occultation with Warm Spitzer. Combining our mid-infrared transits with optical time series, we find that the planet presents a transmission spectrum indistinguishable from a horizontal line. In emission, WASP-80b is the intrinsically faintest planet whose dayside flux has been detected in both the 3.6 and 4.5 μm Spitzer channels. The depths of the occultations reveal that WASP-80b is as bright and as red as a T4 dwarf, but that its temperature is cooler. If planets go through the equivalent of an L-T transition, our results would imply that this happens at cooler temperatures than for brown dwarfs. Placing WASP-80b's dayside into a colour-magnitude diagram, it falls exactly at the junction between a blackbody model and the T-dwarf sequence; we cannot discern which of those two interpretations is the more likely. WASP-80b's flux density is as low as GJ436b at 3.6 μm; the planet's dayside is also fainter, but bluer than HD189733Ab's nightside (in the [3.6] and [4.5]Spitzer bands). Flux measurements on other planets with similar equilibrium temperatures are required to establish whether irradiated gas giants, such as brown dwarfs, transition between two spectral classes. An eventual detection of methane absorption in transmission would also help lift that degeneracy. We obtained a second series of high-resolution spectra during transit, using HARPS. We reanalyse the Rossiter-McLaughlin effect. The data now favour an aligned orbital solution and a stellar rotation nearly three times slower than stellar line broadening implies. A contribution to stellar line broadening, maybe macroturbulence, is likely to have been underestimated for cool stars, whose rotations have therefore been systematically overestimate
The EBLM project. VII. Spin-orbit alignment for the circumbinary planet host EBLM J0608-59 A/TOI-1338 A
Funding: This work was inpart funded by the U.S.–Norway Fulbright Foundation and a NASATESSGI grant G022253 (PI: Martin). AHMJT received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant 803193/BEBOP), and from a Leverhulme Trust Research Project grant (RPG-2018-418). VKH is also supported by a Birmingham Doctoral Scholarship, and by a studentship from Birmingham’s School of Physics & Astronomy. DVM received funding from the Swiss National Science Foundation (grant P 400P2 186735). SG has been supported by STFC through consolidated grants ST/L000733/1and ST/P000495/1.A dozen short-period detached binaries are known to host transiting circumbinary planets. In all circumbinary systems so far, the planetary and binary orbits are aligned within a couple of degrees. However, the obliquity of the primary star, which is an important tracer of their formation, evolution, and tidal history, has only been measured in one circumbinary system until now. EBLM J0608-59/TOI-1338 is a low-mass eclipsing binary system with a recently discovered circumbinary planet identified by TESS. Here, we perform high-resolution spectroscopy during primary eclipse to measure the projected stellar obliquity of the primary component. The obliquity is low, and thus the primary star is aligned with the binary and planetary orbits with a projected spin-orbit angle β = 2.°8 ± 17.°1. The rotation period of18.1 ± 1.6 d implied by our measurement of vsinI⋆ suggests that the primary has not yet pseudo-synchronized with the binary orbit, but is consistent with gyrochronology and weak tidal interaction with the binary companion. Our result, combined with the known coplanarity of the binary and planet orbits, is suggestive of formation from a single disc. Finally, we considered whether the spectrum of the faint secondary star could affect our measurements. We show through simulations that the effect is negligible for our system, but can lead to strong biases in vsinI⋆ and β for higher flux ratios. We encourage future studies in eclipse spectroscopy test the assumption of a dark secondary for flux ratios ≳1ppt.Publisher PDFPeer reviewe
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