The detection of interstellar objects passing through the solar system offers the promise of constraining the physical and chemical processes involved in planetary formation in other extrasolar ...systems. While the effect of outgassing by 1I/2017 U1 ('Oumuamua) was dynamically observed, no direct detection of the ejected material was made. The discovery of the active interstellar comet 2I/Borisov means spectroscopic investigations of the sublimated ices is possible for this object. We report the first detection of gas emitted by an interstellar comet via the near-UV emission of CN from 2I/Borisov at a heliocentric distance of r = 2.7 au on 2019 September 20. The production rate was found to be Q(CN) = (3.7 0.4) × 1024 s−1, using a simple Haser model with an outflow velocity of 0.5 km s−1. No other emission was detected, with an upper limit to the production rate of C2 of 4 × 1024 s−1. The spectral reflectance slope of the dust coma over 3900 < λ < 6000 is steeper than at longer wavelengths, as found for other comets. Broadband Rc photometry on 2019 September 19 gave a dust production rate of Af = 143 10 cm. Modeling of the observed gas and dust production rates constrains the nuclear radius to 0.7-3.3 km assuming reasonable nuclear properties. Overall, we find the gas, dust, and nuclear properties for the first active interstellar object are similar to normal solar system comets.
Cometary Isotopic Measurements Bockelée-Morvan, Dominique; Calmonte, Ursina; Charnley, Steven ...
Space science reviews,
12/2015, Letnik:
197, Številka:
1-4
Journal Article, Web Resource
Recenzirano
Odprti dostop
Isotopic ratios in comets provide keys for the understanding of the origin of cometary material, and the physical and chemical conditions in the early Solar Nebula. We review here measurements ...acquired on the D/H,
14
N/
15
N,
16
O/
18
O,
12
C/
13
C, and
32
S/
34
S ratios in cometary grains and gases, and discuss their cosmogonic implications. The review includes analyses of potential cometary material available in collections on Earth, recent measurements achieved with the Herschel Space Observatory, large optical telescopes, and Rosetta, as well as recent results obtained from models of chemical-dynamical deuterium fractionation in the early solar nebula. Prospects for future measurements are presented.
Many of the known hot Jupiters are formally unstable to tidal orbital decay. The only hot Jupiter for which orbital decay has been directly detected is WASP-12, for which transit-timing measurements ...spanning more than a decade have revealed that the orbital period is decreasing at a rate of , corresponding to a reduced tidal quality factor of about 2 × 105. Here, we present a compilation of transit-timing data for WASP-12 and 11 other systems that are especially favorable for detecting orbital decay: KELT-16; WASP-18, 19, 43, 72, 103, 114, and 122; HAT-P-23; HATS-18; and OGLE-TR-56. For most of these systems we present new data that extend the time baseline over which observations have been performed. None of the systems besides WASP-12 display convincing evidence for period changes, with typical upper limits on dP/dt on the order of 10−9 or 10−10, and lower limits on the reduced tidal quality factor on the order of 105. One possible exception is WASP-19, which shows a statistically significant trend, although it may be a spurious effect of starspot activity. Further observations are encouraged.
Stellar Parameters for Trappist-1 Grootel, Valérie Van; Fernandes, Catarina S.; Gillon, Michael ...
The Astrophysical journal,
01/2018, Letnik:
853, Številka:
1
Journal Article, Web Resource
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Odprti dostop
TRAPPIST-1 is an ultracool dwarf star transited by seven Earth-sized planets, for which thorough characterization of atmospheric properties, surface conditions encompassing habitability, and internal ...compositions is possible with current and next-generation telescopes. Accurate modeling of the star is essential to achieve this goal. We aim to obtain updated stellar parameters for TRAPPIST-1 based on new measurements and evolutionary models, compared to those used in discovery studies. We present a new measurement for the parallax of TRAPPIST-1, 82.4 0.8 mas, based on 188 epochs of observations with the TRAPPIST and Liverpool Telescopes from 2013 to 2016. This revised parallax yields an updated luminosity of , which is very close to the previous estimate but almost two times more precise. We next present an updated estimate for TRAPPIST-1 stellar mass, based on two approaches: mass from stellar evolution modeling, and empirical mass derived from dynamical masses of equivalently classified ultracool dwarfs in astrometric binaries. We combine them using a Monte-Carlo approach to derive a semi-empirical estimate for the mass of TRAPPIST-1. We also derive estimate for the radius by combining this mass with stellar density inferred from transits, as well as an estimate for the effective temperature from our revised luminosity and radius. Our final results are , , and 2516 41 K. Considering the degree to which the TRAPPIST-1 system will be scrutinized in coming years, these revised and more precise stellar parameters should be considered when assessing the properties of TRAPPIST-1 planets.
Searching for Rapid Orbital Decay of WASP-18b Wilkins, Ashlee N.; Delrez, Laetitia; Barker, Adrian J. ...
Astrophysical journal. Letters,
02/2017, Letnik:
836, Številka:
2
Journal Article, Web Resource
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Odprti dostop
The WASP-18 system, with its massive and extremely close-in planet, WASP-18b (Mp = 10.3MJ, a = 0.02 au, P = 22.6 hr), is one of the best-known exoplanet laboratories to directly measure Q′, the ...modified tidal quality factor and proxy for efficiency of tidal dissipation, of the host star. Previous analysis predicted a rapid orbital decay of the planet toward its host star that should be measurable on the timescale of a few years, if the star is as dissipative as is inferred from the circularization of close-in solar-type binary stars. We have compiled published transit and secondary eclipse timing (as observed by WASP, TRAPPIST, and Spitzer) with more recent unpublished light curves (as observed by TRAPPIST and Hubble Space Telescope) with coverage spanning nine years. We find no signature of a rapid decay. We conclude that the absence of rapid orbital decay most likely derives from Q′ being larger than was inferred from solar-type stars and find that Q′ ≥ 1 × 106, at 95% confidence; this supports previous work suggesting that F stars, with their convective cores and thin convective envelopes, are significantly less tidally dissipative than solar-type stars, with radiative cores and large convective envelopes.
2I/Borisov: A C2-depleted interstellar comet Opitom, Cyrielle; Fitzsimmons, Alan; Jehin, Emmanuel ...
Astronomy and astrophysics (Berlin),
11/2019, Letnik:
631
Journal Article, Web Resource
Recenzirano
Odprti dostop
Aims. The discovery of the first active interstellar object 2I/Borisov provides an unprecedented opportunity to study planetary formation processes in another planetary system. In particular, ...spectroscopic observations of 2I allow us to constrain the composition of its nuclear ices. Methods. We obtained optical spectra of 2I with the 4.2 m William Herschel and 2.5 m Isaac Newton telescopes between 2019 September 30 and October 13, when the comet was between 2.5 au and 2.4 au from the Sun. We also imaged the comet with broadband filters on 15 nights from September 11 to October 17, as well as with a CN narrow-band filter on October 18 and 20, with the TRAPPIST-North telescope. Results. Broadband imaging confirms that the dust coma colours (B − V = 0.82 ± 0.02, V − R = 0.46 ± 0.03, R − I = 0.44 ± 0.03, B − R = 1.28 ± 0.03) are the same as for Solar System comets. We detect CN emission in all spectra and in the TRAPPIST narrow-band images with production rates between 1.6 × 1024 and 2.1 × 1024 molec/s. No other species are detected. We determine three-sigma upper limits for C2, C3, and OH production rates of 6 × 1023 molec/s, 2 × 1023 molec/s and 2 × 1027 molec/s, respectively, on October 02. There is no significant increase of the CN production rate or A(0)fρ during our observing period. Finally, we place a three-sigma upper limit on the Q(C2)/Q(CN) ratio of 0.3 (on October 13). From this, we conclude that 2I is highly depleted in C2, and may have a composition similar to Solar System carbon-chain depleted comets.
ABSTRACT
To reduce and analyse astronomical images, astronomers can rely on a wide range of libraries providing low-level implementations of legacy algorithms. However, combining these routines into ...robust and functional pipelines requires a major effort that often ends up in instrument-specific and poorly maintainable tools, yielding products that suffer from a low level of reproducibility and portability. In this context, we present prose, a python framework to build modular and maintainable image processing pipelines. Built for astronomy, it is instrument-agnostic and allows the construction of pipelines using a wide range of building blocks, pre-implemented or user-defined. With this architecture, our package provides basic tools to deal with common tasks, such as automatic reduction and photometric extraction. To demonstrate its potential, we use its default photometric pipeline to process 26 TESS candidates follow-up observations and compare their products to the ones obtained with AstroImageJ, the reference software for such endeavours. We show that prose produces light curves with lower white and red noise while requiring less user interactions and offering richer functionalities for reporting.
Massive companions in close orbits around G dwarfs are thought to undergo rapid orbital decay due to runaway tidal dissipation. We report here the discovery of WASP-128b, a brown dwarf discovered by ...the WASP survey transiting a G0V host on a 2.2 d orbit, where the measured stellar rotation rate places the companion in a regime where tidal interaction is dominated by dynamical tides. Under the assumption of dynamical equilibrium, we derive a value of the stellar tidal quality factor log {Q_\star ^' }} = {6.96 ± 0.19}. A combined analysis of ground-based photometry and high-resolution spectroscopy reveals a mass and radius of the host, MSUB⋆/SUB = 1.16 ± 0.04MSUB⊙/SUB, RSUB⋆/SUB = 1.16 ± 0.02RSUB⊙/SUB, and for the companion, MSUBb/SUB = 37.5 ± 0.8Mj, RSUBb/SUB = 0.94 ± 0.02Rj, placing WASP-128b in the driest parts of the brown dwarf desert, and suggesting a mild inflation for its age. We estimate a remaining lifetime for WASP-128b similar to that of some ultra-short period massive hot Jupiters, and note it may be a propitious candidate for measuring orbital decay and testing tidal theories.
We observed the transiting super-Earth exoplanet GJ1214b using warm Spitzer at 4.5 mu m wavelength during a 20 day quasi-continuous sequence in 2011 May. The goals of our long observation were to ...accurately define the infrared transit radius of this nearby super-Earth, to search for the secondary eclipse, and to search for other transiting planets in the habitable zone of GJ1214. We here report results from the transit monitoring of GJ1214b, including a reanalysis of previous transit observations by Desert et al. In total, we analyze 14 transits of GJ1214b at 4.5 mu m, 3 transits at 3.6 mu m, and 7 new ground-based transits in the I + z band. Our new Spitzer data by themselves eliminate cloudless solar composition atmospheres for GJ1214b, and methane-rich models from Howe & Burrows. Using our new Spitzer measurements to anchor the observed transit radii of GJ1214b at long wavelengths, and adding new measurements in I + z, we evaluate models from Benneke & Seager and Howe & Burrows using a chi super(2) analysis. We find that the best-fit model exhibits an increase in transit radius at short wavelengths due to Rayleigh scattering. Pure water atmospheres are also possible. However, a flat line (no atmosphere detected) remains among the best of the statistically acceptable models, and better than pure water atmospheres. We explore the effect of systematic differences among results from different observational groups, and we find that the Howe & Burrows tholin-haze model remains the best fit, even when systematic differences among observers are considered.
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