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See detail$\textit{Gaia}$ white dwarfs within 40 pc I: spectroscopic observations of new candidates
Tremblay, P.-E.; Hollands, M. A.; Gentile Fusillo, N. P. et al

in Monthly Notices of the Royal Astronomical Society (in press)

We present a spectroscopic survey of 230 white dwarf candidates within 40 pc of the Sun from the William Herschel Telescope and Gran Telescopio Canarias. All candidates were selected from $\textit{Gaia ... [more ▼]

We present a spectroscopic survey of 230 white dwarf candidates within 40 pc of the Sun from the William Herschel Telescope and Gran Telescopio Canarias. All candidates were selected from $\textit{Gaia}$ Data Release 2 (DR2) and in almost all cases had no prior spectroscopic classifications. We find a total of 191 confirmed white dwarfs and 39 main-sequence star contaminants. The majority of stellar remnants in the sample are relatively cool ($\langle T_{\rm eff} \rangle$ = 6200 K), showing either hydrogen Balmer lines or a featureless spectrum, corresponding to 89 DA and 76 DC white dwarfs, respectively. We also recover two DBA white dwarfs and 9--10 magnetic remnants. We find two carbon-bearing DQ stars and 14 new metal-rich white dwarfs. This includes the possible detection of the first ultra-cool white dwarf with metal lines. We describe three DZ stars for which we find at least four different metal species, including one which is strongly Fe- and Ni- rich, indicative of the accretion of a planetesimal with core-Earth composition. We find one extremely massive (1.31 $\pm$ 0.01 M$_{\odot}$) DA white dwarf showing weak Balmer lines, possibly indicating stellar magnetism. Another white dwarf shows strong Balmer line emission but no infrared excess, suggesting a low-mass sub-stellar companion. High spectroscopic completeness ($>$99%) has now been reached for $\textit{Gaia}$ DR2 sources within 40 pc sample, in the northern hemisphere ($\delta >$ 0 deg) and located on the white dwarf cooling track in the Hertzsprung-Russell diagram. A statistical study of the full northern sample is presented in a companion paper. [less ▲]

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See detailVolume uncertainty of (7) Iris shape models from disk-resolved images.
Dudziński, G.; Podlewska-Gaca, E.; Bartczak, P. et al

in Monthly Notices of the Royal Astronomical Society (2020)

High angular resolution disk-resolved images of (7) Iris collected by VLT/SPHERE instrument allowed for the detailed shape modelling of this large asteroid revealing its surface features. If (7) Iris did ... [more ▼]

High angular resolution disk-resolved images of (7) Iris collected by VLT/SPHERE instrument allowed for the detailed shape modelling of this large asteroid revealing its surface features. If (7) Iris did not suffer any events catastrophic enough to disrupt the body (which is very likely) by studying its topography we might get insights into the early Solar System's collisional history. When it comes to internal structure and composition, thoroughly assessing the volume and density uncertainties is necessary. In this work we propose a method of uncertainty calculation of asteroid shape models based on lightcurve and Adaptive Optics images. We apply this method on four models of (7) Iris produced from independent SAGE and ADAM inversion techniques and photoclinometry (MPCD). Obtained diameter uncertainties stem from both the observations from which the models were scaled and the models themselves. We show that despite the availability of high resolution AO images, the volume and density of (7) Iris have substantial error bars that were underestimated in the previous studies. [less ▲]

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See detailTESS light curves of γ Cas stars
Nazé, Yaël ULiege; Rauw, Grégor ULiege; Pigulski, Andrzej

in Monthly Notices of the Royal Astronomical Society (2020), 498

γ Cas stars constitute a subgroup of Be stars showing unusually hard and bright X-ray emission. In search for additional peculiarities, we analysed the TESS light curves of 15 γ Cas analogues. Their ... [more ▼]

γ Cas stars constitute a subgroup of Be stars showing unusually hard and bright X-ray emission. In search for additional peculiarities, we analysed the TESS light curves of 15 γ Cas analogues. Their periodograms display broad frequency groups and/or narrow isolated peaks, often superimposed over red noise. The detected signals appear at low frequencies, with few cases of significant signals beyond 5 d[SUP]-1[/SUP] (and all of them are faint). The signal amplitudes, and sometimes the frequency content, change with time, even in the absence of outburst events. On the basis of their optical photometric variability, γ Cas stars reveal no distinctive behaviour and thus appear similar to Be stars in general. [less ▲]

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See detailGlobal analysis of the TRAPPIST Ultra-Cool Dwarf Transit Survey
Lienhard, F.; Queloz, D.; Gillon, Michaël ULiege et al

in Monthly Notices of the Royal Astronomical Society (2020), 497(3), 3790

We conducted a global analysis of the TRAPPIST Ultra-Cool Dwarf Transit Survey - a prototype of the SPECULOOS transit search conducted with the TRAPPIST-South robotic telescope in Chile from 2011 to 2017 ... [more ▼]

We conducted a global analysis of the TRAPPIST Ultra-Cool Dwarf Transit Survey - a prototype of the SPECULOOS transit search conducted with the TRAPPIST-South robotic telescope in Chile from 2011 to 2017 - to estimate the occurrence rate of close-in planets such as TRAPPIST-1b orbiting ultra-cool dwarfs. For this purpose, the photometric data of 40 nearby ultra-cool dwarfs were reanalysed in a self-consistent and fully automated manner starting from the raw images. The pipeline developed specifically for this task generates differential light curves, removes non-planetary photometric features and stellar variability, and searches for transits. It identifies the transits of TRAPPIST-1b and TRAPPIST-1c without any human intervention. To test the pipeline and the potential output of similar surveys, we injected planetary transits into the light curves on a star-by-star basis and tested whether the pipeline is able to detect them. The achieved photometric precision enables us to identify Earth-sized planets orbiting ultra-cool dwarfs as validated by the injection tests. Our planet-injection simulation further suggests a lower limit of 10 per cent on the occurrence rate of planets similar to TRAPPIST-1b with a radius between 1 and 1.3 R[SUB]⊕[/SUB] and the orbital period between 1.4 and 1.8 d. [less ▲]

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See detailH0LiCOW - XI. A weak lensing measurement of the external convergence in the field of the lensed quasar B1608+656 using HST and Subaru deep imaging
Tihhonova, O.; Courbin, F.; Harvey, D. et al

in Monthly Notices of the Royal Astronomical Society (2020), 498

We investigate the environment and line of sight (LoS) of the H0LiCOW (H[SUB]0[/SUB] Lenses in COSMOGRAIL's Wellspring) lens B1608+656 using Subaru Suprime-Cam and the Hubble Space Telescope (HST) to ... [more ▼]

We investigate the environment and line of sight (LoS) of the H0LiCOW (H[SUB]0[/SUB] Lenses in COSMOGRAIL's Wellspring) lens B1608+656 using Subaru Suprime-Cam and the Hubble Space Telescope (HST) to perform a weak lensing analysis. We compare three different methods to reconstruct the mass map of the field, i.e. the standard Kaiser-Squires inversion coupled with inpainting and Gaussian or wavelet filtering, and ${\rm {\small {glimpse}}}$ , a method based on sparse regularization of the shear field. We find no substantial difference between the 2D mass reconstructions, but we find that the ground-based data are less sensitive to small-scale structures than the space-based observations. Marginalizing over the results obtained with all the reconstruction techniques applied to the two available HST filters F606W and F814W, we estimate the external convergence, κ[SUB]ext[/SUB], at the position of B1608+656 is $\kappa _{\mathrm{ext}}= 0.11^{+0.06}_{-0.04}$ , where the error bars correspond, respectively, to the 16th and 84th quartiles. This result is compatible with previous estimates using the number counts technique, suggesting that B1608+656 resides in an overdense LoS, but with a completely different technique. Using our mass reconstructions, we also compare the convergence at the position of several groups of galaxies in the field of B1608+656 with the mass measurements using various analytical mass profiles, and find that the weak lensing results favour truncated halo models. [less ▲]

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See detailCharacterizing brown dwarf companions with IRDIS long-slit spectroscopy: HD 1160 B and HD 19467 B
Mesa, D.; D'Orazi, V.; Vigan, A. et al

in Monthly Notices of the Royal Astronomical Society (2020), 495

The determination of the fundamental properties (mass, separation, age, gravity, and atmospheric properties) of brown dwarf companions allows us to infer crucial informations on their formation and ... [more ▼]

The determination of the fundamental properties (mass, separation, age, gravity, and atmospheric properties) of brown dwarf companions allows us to infer crucial informations on their formation and evolution mechanisms. Spectroscopy of substellar companions is available to date only for a limited number of objects (and mostly at very low resolution, R < 50) because of technical limitations, I.e. contrast and angular resolution. We present medium resolution (R = 350), coronagraphic long-slit spectroscopic observations with SPHERE of two substellar companions, HD 1160 B and HD 19467 B. We found that HD 1160 B has a peculiar spectrum that cannot be fitted by spectra in current spectral libraries. A good fit is possible only considering separately the Y+J and the H spectral band. The spectral type is between M5 and M7. We also estimated a T[SUB]eff[/SUB] of 2800-2900 K and a log g of 3.5-4.0 dex. The low surface gravity seems to favour young age (10-20 Myr) and low mass (∼20 M[SUB]Jup[/SUB] ) for this object. HD 19467 B is instead a fully evolved object with a T[SUB]eff[/SUB] of ∼1000 K and log g of ∼5.0 dex. Its spectral type is T6 ± 1. [less ▲]

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See detailPhotometry and performance of SPECULOOS-South
Murray, C. A.; Delrez, Laetitia ULiege; Pedersen, P. P. et al

in Monthly Notices of the Royal Astronomical Society (2020), 495

SPECULOOS-South, an observatory composed of four independent 1-m robotic telescopes, located at ESO Paranal, Chile, started scientific operation in 2019 January. This Southern hemisphere facility operates ... [more ▼]

SPECULOOS-South, an observatory composed of four independent 1-m robotic telescopes, located at ESO Paranal, Chile, started scientific operation in 2019 January. This Southern hemisphere facility operates as part of the Search for Habitable Planets EClipsing ULtra-cOOl Stars (SPECULOOS), an international network of 1-m-class telescopes surveying for transiting terrestrial planets around the nearest and brightest ultracool dwarfs (UCDs). To automatically and efficiently process the observations of SPECULOOS-South, and to deal with the specialized photometric requirements of UCD targets, we present our automatic pipeline. This pipeline includes an algorithm for automated differential photometry and an extensive correction technique for the effects of telluric water vapour, using ground measurements of the precipitable water vapour. Observing very red targets in the near-infrared can result in photometric systematics in the differential light curves, related to the temporally-varying, wavelength-dependent opacity of the Earth's atmosphere. These systematics are sufficient to affect the daily quality of the light curves, the longer time-scale variability study of our targets and even mimic transit-like signals. Here we present the implementation and impact of our water vapour correction method. Using the 179 nights and 98 targets observed in the I + z' filter by SPECULOOS-South since 2019 January, we show the impressive photometric performance of the facility (with a median precision of ∼1.5 mmag for 30-min binning of the raw, non-detrended light curves) and assess its detection potential. We compare simultaneous observations with SPECULOOS-South and TESS, to show that we readily achieve high- precision, space-level photometry for bright, UCDs, highlighting SPECULOOS-South as the first facility of its kind. [less ▲]

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See detailVLA and ALMA observations of the lensed radio-quiet quasar SDSS J0924+0219: a molecular structure in a 3 μJy radio source
Badole, Shruti; Jackson, Neal; Hartley, Philippa et al

in Monthly Notices of the Royal Astronomical Society (2020), 496

We present Karl G. Jansky Very Large Array (VLA) and Atacama Large Millimetre Array (ALMA) observations of SDSS J0924+0219, a z = 1.524 radio-quiet lensed quasar with an intrinsic radio flux density of ... [more ▼]

We present Karl G. Jansky Very Large Array (VLA) and Atacama Large Millimetre Array (ALMA) observations of SDSS J0924+0219, a z = 1.524 radio-quiet lensed quasar with an intrinsic radio flux density of about 3 $\, \mu$ Jy. The four lensed images are clearly detected in the radio continuum and the CO(5-4) line, whose centroid is at z = 1.5254 ± 0.0001, with a marginal detection in the submillimetre continuum. The molecular gas displays ordered motion, in a structure approximately 1-2.5 kpc in physical extent, with typical velocities of 50-100 km s[SUP]-1[/SUP]. Our results are consistent with the radio emission being emitted from the same region, but not with a point source of radio emission. SDSS J0924+0219 shows an extreme anomaly in the flux ratios of the two merging images in the optical continuum and broad emission lines, suggesting the influence of microlensing by stars in the lensing galaxy. We find the flux ratio in the radio, submillimetre continuum and CO lines to be slightly greater than 1 but much less than that in the optical, which can be reproduced with a smooth galaxy mass model and an extended source. Our results, supported by a microlensing simulation, suggest that the most likely explanation for the optical flux anomaly is indeed microlensing. [less ▲]

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See detailThe flatness problem and the age of the Universe
Helbig, Phillip ULiege

in Monthly Notices of the Royal Astronomical Society (2020), 495(4), 35713575

Several authors have made claims, none of which has been rebutted, that the flatness problem, as formulated by Dicke and Peebles, is not really a problem but rather a misunderstanding. Nevertheless, the ... [more ▼]

Several authors have made claims, none of which has been rebutted, that the flatness problem, as formulated by Dicke and Peebles, is not really a problem but rather a misunderstanding. Nevertheless, the flatness problem is still widely perceived to be real. Most of the arguments against the idea of a flatness problem are based on the change with time of the density parameter Ω and normalized cosmological constant λ and, since the Hubble constant H is not considered, are independent of time-scale. An independent claim is that fine-tuning is required in order to produce a Universe which neither collapsed after a short time nor expanded so quickly that no structure formation could take place. I show that this claim does not imply that fine-tuning of the basic cosmological parameters is necessary, in part for similar reasons as in the more restricted flatness problem and in part due to an incorrect application of the idea of perturbing the early Universe in a gedankenexperiment; I discuss some typical pitfalls of the latter. [less ▲]

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See detailDiscovery of a pre-cataclysmic binary with unusual chromaticity of the eclipsed white dwarf by the GPX survey
Krushinsky, Vadim; Benni, Paul; Burdanov, Artem et al

in Monthly Notices of the Royal Astronomical Society (2020), 493

We report the discovery of a relatively bright eclipsing binary system, which consists of a white dwarf (WD) and a main-sequence K7 star with clear signs of chromospheric and spot activity. The light ... [more ▼]

We report the discovery of a relatively bright eclipsing binary system, which consists of a white dwarf (WD) and a main-sequence K7 star with clear signs of chromospheric and spot activity. The light curve of this system shows ∼0.2 mag ellipsoidal variability with a period of 0.297549 d and a short total eclipse of the WD. Based on our analysis of the spectral and photometric data, we estimated the parameters of the system. The K7V star is tidally deformed but does not fill its Roche lobe (the filling factor is about 0.86). The orbital inclination is i = 73.1° ± 0.2°, and the mass ratio is q = M[SUB]2[/SUB]/M[SUB]1[/SUB] ≈ 0.88. The parameters of the K7V star are M[SUB]2[/SUB] ≈ 0.64 M[SUB]☉[/SUB], R[SUB]2[/SUB] = 0.645 ± 0.012R[SUB]☉[/SUB], and T[SUB]2[/SUB] ≈ 4070 K. The parameters of the WD are M[SUB]1[/SUB] ≈ 0.72 M[SUB]☉[/SUB], R[SUB]1[/SUB] = 0.013 ± 0.003R[SUB]☉[/SUB], and T[SUB]1[/SUB] = 8700 ± 1100 K. Photometric observations in different bands revealed that the maximum depth of the eclipse is in the SDSS r filter, which is unusual for a system of a WD and a late main-sequence star. We suspect that this system is a product of the evolution of a common-envelope binary star, and that the WD accretes the stellar wind from the secondary star (the so-called low-accretion-rate polar, hereafter LARP). [less ▲]

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See detailThree discoveries of γ Cas analogues from dedicated XMM-Newton observations of Be stars
Nazé, Yaël ULiege; Motch, Christian; Rauw, Grégor ULiege et al

in Monthly Notices of the Royal Astronomical Society (2020), 493

In the last years, a peculiarity of some Be stars - their association with unusually hard and intense X-ray emission - was shown to extend beyond a mere few cases. In this paper, we continue our search ... [more ▼]

In the last years, a peculiarity of some Be stars - their association with unusually hard and intense X-ray emission - was shown to extend beyond a mere few cases. In this paper, we continue our search for new cases by performing a limited survey of 18 Be stars using XMM-Newton. The targets were selected either on the basis of a previous X-ray detection (EXOSAT,ROSAT, XMM-slew survey) without spectral information available or because of the presence of a peculiar spectral variability. Only two targets remain undetected in the new observations and three other stars display only faint and soft X-rays. Short-term and/or long- term variations were found in one third of the sample. The spectral characterization of the X-ray brightest 13 stars of the sample led to the discovery of three new γ Cas (HD 44458, HD 45995, and V558 Lyr), bringing the total to 25 known cases, and another γ Cas candidate (HD 120678), bringing the total to two. [less ▲]

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See detailSTRIDES: a 3.9 per cent measurement of the Hubble constant from the strong lens system DES J0408-5354
Shajib, A. J.; Birrer, S.; Treu, T. et al

in Monthly Notices of the Royal Astronomical Society (2020), 494

We present a blind time-delay cosmographic analysis for the lens system DES J0408-5354. This system is extraordinary for the presence of two sets of multiple images at different redshifts, which provide ... [more ▼]

We present a blind time-delay cosmographic analysis for the lens system DES J0408-5354. This system is extraordinary for the presence of two sets of multiple images at different redshifts, which provide the opportunity to obtain more information at the cost of increased modelling complexity with respect to previously analysed systems. We perform detailed modelling of the mass distribution for this lens system using three band Hubble Space Telescope imaging. We combine the measured time delays, line-of-sight central velocity dispersion of the deflector, and statistically constrained external convergence with our lens models to estimate two cosmological distances. We measure the 'effective' time- delay distance corresponding to the redshifts of the deflector and the lensed quasar $D_{\Delta t}^{\rm eff}=$ $3382_{-115}^{+146}$ Mpc and the angular diameter distance to the deflector D[SUB]d[/SUB] = $1711_{-280}^{+376}$ Mpc, with covariance between the two distances. From these constraints on the cosmological distances, we infer the Hubble constant H[SUB]0[/SUB]= $74.2_{-3.0}^{+2.7}$ km s[SUP]-1 [/SUP]Mpc[SUP]-[/SUP][SUP]1[/SUP] assuming a flat ΛCDM cosmology and a uniform prior for Ω[SUB]m[/SUB] as $\Omega _{\rm m} \sim \mathcal {U}(0.05, 0.5)$ . This measurement gives the most precise constraint on H[SUB]0[/SUB] to date from a single lens. Our measurement is consistent with that obtained from the previous sample of six lenses analysed by the H[SUB]0[/SUB] Lenses in COSMOGRAIL's Wellspring (H0LiCOW) collaboration. It is also consistent with measurements of H[SUB]0[/SUB] based on the local distance ladder, reinforcing the tension with the inference from early Universe probes, for example, with 2.2σ discrepancy from the cosmic microwave background measurement. [less ▲]

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See detailLet there be more variability in two γ Cas stars
Nazé, Yaël ULiege; Pigulski, Andrzej; Rauw, Grégor ULiege et al

in Monthly Notices of the Royal Astronomical Society (2020), 494

We investigate the short-term optical variability of two γ Cas analogues, πAqr and BZ Cru, thanks to intensive ground-based spectroscopic and space-borne photometric monitorings. For both stars, low ... [more ▼]

We investigate the short-term optical variability of two γ Cas analogues, πAqr and BZ Cru, thanks to intensive ground-based spectroscopic and space-borne photometric monitorings. For both stars, low-amplitude (mmag) coherent photometric variability is detected. The associated signals display long-term amplitude variations, as in other Be stars. However, these signals appear at high frequencies, especially in πAqr, indicating p modes with a high degree l, a quite unusual feature amongst Be stars. While BZ Cru presents only low-level spectral variability, without clear periodicity, this is not the case of πAqr. In this star, the dominant photometric frequencies, near ∼12 d[SUP]-1[/SUP], are confirmed spectroscopically in separate monitorings taken during very different disc activity levels; the spectroscopic analysis suggests a probable tesseral nature for the mode. [less ▲]

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See detailDouble dark matter vision: twice the number of compact-source lenses with narrow-line lensing and the WFC3 grism
Nierenberg, A. M.; Gilman, D.; Treu, T. et al

in Monthly Notices of the Royal Astronomical Society (2020), 492

The magnifications of compact-source lenses are extremely sensitive to the presence of low-mass dark matter haloes along the entire sightline from the source to the observer. Traditionally, the study of ... [more ▼]

The magnifications of compact-source lenses are extremely sensitive to the presence of low-mass dark matter haloes along the entire sightline from the source to the observer. Traditionally, the study of dark matter structure in compact-source strong gravitational lenses has been limited to radio-loud systems, as the radio emission is extended and thus unaffected by microlensing which can mimic the signal of dark matter structure. An alternate approach is to measure quasar nuclear-narrow- line emission, which is free from microlensing and present in virtually all quasar lenses. In this paper, we double the number of systems which can be used for gravitational lensing analyses by presenting measurements of narrow-line emission from a sample of eight quadruply imaged quasar lens systems, WGD J0405-3308, HS 0810+2554, RX J0911+0551, SDSS J1330+1810, PS J1606-2333, WFI 2026-4536, WFI 2033-4723, and WGD J2038-4008. We describe our updated grism spectral modelling pipeline, which we use to measure narrow-line fluxes with uncertainties of 2-10 per cent, presented here. We fit the lensed image positions with smooth mass models and demonstrate that these models fail to produce the observed distribution of image fluxes over the entire sample of lenses. Furthermore, typical deviations are larger than those expected from macromodel uncertainties. This discrepancy indicates the presence of perturbations caused by small-scale dark matter structure. The interpretation of this result in terms of dark matter models is presented in a companion paper. [less ▲]

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See detailThe first observed stellar occultations by the irregular satellite Phoebe (Saturn IX) and improved rotational period
Gomes-Júnior, A. Ramos; Assafin, Marcelo; Braga-Ribas, Felipe et al

in Monthly Notices of the Royal Astronomical Society (2020), 492

We report six stellar occultations by Phoebe (Saturn IX), an irregular satellite of Saturn, obtained between mid-2017 and mid-2019. The 2017 July 6 event was the first stellar occultation by an irregular ... [more ▼]

We report six stellar occultations by Phoebe (Saturn IX), an irregular satellite of Saturn, obtained between mid-2017 and mid-2019. The 2017 July 6 event was the first stellar occultation by an irregular satellite ever observed. The occultation chords were compared to a 3D shape model of the satellite obtained from Cassini observations. The rotation period available in the literature led to a sub-observer point at the moment of the observed occultations where the chords could not fit the 3D model. A procedure was developed to identify the correct sub-observer longitude. It allowed us to obtain the rotation period with improved precision compared to the currently known value from literature. We show that the difference between the observed and the predicted sub-observer longitude suggests two possible solutions for the rotation period. By comparing these values with recently observed rotational light curves and single- chord stellar occultations, we can identify the best solution for Phoebe's rotational period as 9.27365 ± 0.00002 h. From the stellar occultations, we also obtained six geocentric astrometric positions in the ICRS as realized by the Gaia DR2 with uncertainties at the 1-mas level. [less ▲]

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See detailModelling the photometric variability of magnetic massive stars with the Analytical Dynamical Magnetosphere model
Munoz, M. S.; Wade, Gregg; Nazé, Yaël ULiege et al

in Monthly Notices of the Royal Astronomical Society (2020), 492(1), 1199-1213

In this paper, we investigate the photometric variability of magnetic O-type stars. Such stars possess oblique, predominantly dipolar magnetic fields that confine their winds roughly axisymmetrically ... [more ▼]

In this paper, we investigate the photometric variability of magnetic O-type stars. Such stars possess oblique, predominantly dipolar magnetic fields that confine their winds roughly axisymmetrically about the magnetic equator, thus forming a magnetosphere. We interpret their photometric variability as phase-dependent magnetospheric occultations. For massive star winds dominated by electron scattering opacity in the optical and NIR, we can compute synthetic light curves from simply knowing themagnetosphere'smass density distribution.We exploit the newly developed Analytical Dynamical Magnetosphere (ADM) model in order to obtain the predicted circumstellar density structures of magnetic O-type stars. The simplicity in our light-curve synthesis model allows us to readily conduct a parameter space study. For validation purposes, we first apply our algorithm to HD 191612, the prototypical Of?p star. Next, we attempt to model the photometric variability of the Of?p-type stars identified in the Magellanic Clouds using OGLE photometry. We evaluate the compatibility of the ADM predictions with the observed photometric variations and discuss the magnetic field properties that are implied by our modelling. © 2019 The Author(s). [less ▲]

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See detailA SHARP view of H0LiCOW: H[SUB]0[/SUB] from three time-delay gravitational lens systems with adaptive optics imaging
Chen, Geoff C.-F.; Fassnacht, Christopher D.; Suyu, Sherry H. et al

in Monthly Notices of the Royal Astronomical Society (2019), 490

We present the measurement of the Hubble constant, H[SUB]0[/SUB], with three strong gravitational lens systems. We describe a blind analysis of both PG 1115+080 and HE 0435-1223 as well as an extension of ... [more ▼]

We present the measurement of the Hubble constant, H[SUB]0[/SUB], with three strong gravitational lens systems. We describe a blind analysis of both PG 1115+080 and HE 0435-1223 as well as an extension of our previous analysis of RXJ 1131-1231. For each lens, we combine new adaptive optics (AO) imaging from the Keck Telescope, obtained as part of the SHARP (Strong-lensing High Angular Resolution Programme) AO effort, with Hubble Space Telescope (HST) imaging, velocity dispersion measurements, and a description of the line-of-sight mass distribution to build an accurate and precise lens mass model. This mass model is then combined with the COSMOGRAIL-measured time delays in these systems to determine H[SUB]0[/SUB]. We do both an AO-only and an AO + HST analysis of the systems and find that AO and HST results are consistent. After unblinding, the AO-only analysis gives H[SUB]0[/SUB]=82.8^{+9.4}_{-8.3} km s^{-1} Mpc^{-1} for PG 1115+080, H[SUB]0[/SUB]=70.1^{+5.3}_{-4.5} km s^{-1} Mpc^{-1} for HE 0435-1223, and H[SUB]0[/SUB]=77.0^{+4.0}_{-4.6} km s^{-1} Mpc^{-1} for RXJ 1131-1231. The joint AO-only result for the three lenses is H[SUB]0[/SUB]=75.6^{+3.2}_{-3.3} km s^{-1} Mpc^{-1}. The joint result of the AO + HST analysis for the three lenses is H[SUB]0[/SUB]=76.8^{+2.6}_{-2.6} km s^{-1} Mpc^{-1}. All of these results assume a flat Λ cold dark matter cosmology with a uniform prior on Ω[SUB]m[/SUB] in [0.05, 0.5] and H[SUB]0[/SUB] in [0, 150] km s^{-1} Mpc^{-1}. This work is a collaboration of the SHARP and H0LiCOW teams, and shows that AO data can be used as the high-resolution imaging component in lens-based measurements of H[SUB]0[/SUB]. The full time- delay cosmography results from a total of six strongly lensed systems are presented in a companion paper. <P /> [less ▲]

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See detailTOI-150b and TOI-163b: two transiting hot Jupiters, one eccentric and one inflated, revealed by TESS near and at the edge of the JWST CVZ
Kossakowski, Diana; Espinoza, Néstor; Brahm, Rafael et al

in Monthly Notices of the Royal Astronomical Society (2019), 490

We present the discovery of TYC9191-519-1b (TOI-150b, TIC 271893367) and HD271181b (TOI-163b, TIC 179317684), two hot Jupiters initially detected using 30-min cadence Transiting Exoplanet Survey Satellite ... [more ▼]

We present the discovery of TYC9191-519-1b (TOI-150b, TIC 271893367) and HD271181b (TOI-163b, TIC 179317684), two hot Jupiters initially detected using 30-min cadence Transiting Exoplanet Survey Satellite (TESS) photometry from Sector 1 and thoroughly characterized through follow-up photometry (CHAT, Hazelwood, LCO/CTIO, El Sauce, TRAPPIST-S), high- resolution spectroscopy (FEROS, CORALIE), and speckle imaging (Gemini/DSSI), confirming the planetary nature of the two signals. A simultaneous joint fit of photometry and radial velocity using a new fitting package JULIET reveals that TOI-150b is a 1.254± 0.016 {R}_ {J}, massive (2.61^{+0.19}_{-0.12} {M}_ {J}) hot Jupiter in a 5.857-d orbit, while TOI-163b is an inflated (R_ {P} = 1.478^{+0.022}_{-0.029} R_ {J}, M_ {P} = 1.219± 0.11 {M}_ {J}) hot Jupiter on a P = 4.231-d orbit; both planets orbit F-type stars. A particularly interesting result is that TOI-150b shows an eccentric orbit (e=0.262^{+0.045}_{-0.037}), which is quite uncommon among hot Jupiters. We estimate that this is consistent, however, with the circularization time-scale, which is slightly larger than the age of the system. These two hot Jupiters are both prime candidates for further characterization - in particular, both are excellent candidates for determining spin-orbit alignments via the Rossiter-McLaughlin (RM) effect and for characterizing atmospheric thermal structures using secondary eclipse observations considering they are both located closely to the James Webb Space Telescope (JWST) Continuous Viewing Zone (CVZ). [less ▲]

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See detailA Gaia view of the two OB associations Cygnus OB2 and Carina OB1: the signature of their formation process
Lim, Beomdu ULiege; Nazé, Yaël ULiege; Gosset, Eric ULiege et al

in Monthly Notices of the Royal Astronomical Society (2019), 490

OB associations are the prime star-forming sites in galaxies. However, the detailed formation process of such stellar systems still remains a mystery. In this context, identifying the presence of ... [more ▼]

OB associations are the prime star-forming sites in galaxies. However, the detailed formation process of such stellar systems still remains a mystery. In this context, identifying the presence of substructures may help in tracing the footprints of their formation process. Here, we present a kinematic study of the two massive OB associations Cygnus OB2 and Carina OB1 using the precise astrometry from the Gaia Data Release 2 and radial velocities. From the parallaxes of stars, these OB associations are confirmed to be genuine stellar systems. Both Cygnus OB2 and Carina OB1 are composed of a few dense clusters and a halo which have different kinematic properties: the clusters occupy regions of 5-8 parsecs in diameter and display small dispersions in proper motion, while the haloes spread over tens of parsecs with two to three times larger dispersions in proper motion. This is reminiscent of the so-called line width-size relation of molecular clouds related to turbulence. Considering that the kinematics and structural features were inherited from those of their natal clouds would then imply that the formation of OB associations may result from structure formation driven by supersonic turbulence, rather than from the dynamical evolution of individual embedded clusters. [less ▲]

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See detailH0LiCOW - X. Spectroscopic/imaging survey and galaxy-group identification around the strong gravitational lens system WFI 2033-4723
Sluse, Dominique ULiege; Rusu, C. E.; Fassnacht, C. D. et al

in Monthly Notices of the Royal Astronomical Society (2019), 490

Galaxies and galaxy groups located along the line of sight towards gravitationally lensed quasars produce high-order perturbations of the gravitational potential at the lens position. When these ... [more ▼]

Galaxies and galaxy groups located along the line of sight towards gravitationally lensed quasars produce high-order perturbations of the gravitational potential at the lens position. When these perturbation are too large, they can induce a systematic error on H[SUB]0[/SUB] of a few per cent if the lens system is used for cosmological inference and the perturbers are not explicitly accounted for in the lens model. In this work, we present a detailed characterization of the environment of the lens system WFI 2033-4723 (z_src = 1.662, z_lens= 0.6575), one of the core targets of the H0LiCOW project for which we present cosmological inferences in a companion paper. We use the Gemini and ESO- Very Large telescopes to measure the spectroscopic redshifts of the brightest galaxies towards the lens, and use the ESO-MUSE integral field spectrograph to measure the velocity-dispersion of the lens (σ _{los}= 250^{+15}_{-21} km s[SUP]-1[/SUP]) and of several nearby galaxies. In addition, we measure photometric redshifts and stellar masses of all galaxies down to i < 23 mag, mainly based on Dark Energy Survey imaging (DR1). Our new catalogue, complemented with literature data, more than doubles the number of known galaxy spectroscopic redshifts in the direct vicinity of the lens, expanding to 116 (64) the number of spectroscopic redshifts for galaxies separated by less than 3 arcmin (2 arcmin ) from the lens. Using the flexion-shift as a measure of the amplitude of the gravitational perturbation, we identify two galaxy groups and three galaxies that require specific attention in the lens models. The ESO MUSE data enable us to measure the velocity-dispersions of three of these galaxies. These results are essential for the cosmological inference analysis presented in Rusu et al. [less ▲]

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