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See detailOGLE-2014-BLG-1186: gravitational microlensing providing evidence for a planet orbiting the foreground star or for a close binary source?
Dominik, M.; Bachelet, E.; Bozza, V. et al

in Monthly Notices of the Royal Astronomical Society (2019), 484

Discussing the particularly long gravitational microlensing event OGLE-2014-BLG-1186 with a time-scale t[SUB]E[/SUB] ˜ 300 d, we present a methodology for identifying the nature of localised deviations ... [more ▼]

Discussing the particularly long gravitational microlensing event OGLE-2014-BLG-1186 with a time-scale t[SUB]E[/SUB] ˜ 300 d, we present a methodology for identifying the nature of localised deviations from single-lens point-source light curves, which ensures that (1) the claimed signal is substantially above the noise floor, (2) the inferred properties are robustly determined and their estimation is not subject to confusion with systematic noise in the photometry, (3) alternative viable solutions within the model framework are not missed. Annual parallax and binarity could be separated and robustly measured from the wing and the peak data, respectively. We find matching model light curves that involve either a binary lens or a binary source, and discover hitherto unknown model ambiguities. Our binary-lens models indicate a planet of mass M[SUB]2[/SUB] = (45 ± 9) M[SUB]⊕[/SUB], orbiting a star of mass M[SUB]1[/SUB] = (0.35 ± 0.06) M[SUB]⊙[/SUB], located at a distance D[SUB]L[/SUB] = (1.7 ± 0.3) kpc from Earth, whereas our binary-source models suggest a brown-dwarf lens of M = (0.046 ± 0.007) M[SUB]⊙[/SUB], located at a distance D[SUB]L[/SUB] = (5.7 ± 0.9) kpc, with the source potentially being a (partially) eclipsing binary involving stars predicted to be of similar colour given the ratios between the luminosities and radii. Further observations might resolve the ambiguity in the interpretation in favour of either a lens or a source binary. We experienced that close binary source stars pose a challenge for claiming the detection of planets by microlensing in events where the source passes very close to the lens star hosting the planet. [less ▲]

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See detailH0LiCOW - IX. Cosmographic analysis of the doubly imaged quasar SDSS 1206+4332 and a new measurement of the Hubble constant
Birrer, S.; Treu, T.; Rusu, C. E. et al

in Monthly Notices of the Royal Astronomical Society (2019), 484

We present a blind time-delay strong lensing (TDSL) cosmographic analysis of the doubly imaged quasar SDSS 1206+4332 . We combine the relative time delay between the quasar images, Hubble Space Telescope ... [more ▼]

We present a blind time-delay strong lensing (TDSL) cosmographic analysis of the doubly imaged quasar SDSS 1206+4332 . We combine the relative time delay between the quasar images, Hubble Space Telescope imaging, the Keck stellar velocity dispersion of the lensing galaxy, and wide-field photometric and spectroscopic data of the field to constrain two angular diameter distance relations. The combined analysis is performed by forward modelling the individual data sets through a Bayesian hierarchical framework, and it is kept blind until the very end to prevent experimenter bias. After unblinding, the inferred distances imply a Hubble constant H[SUB]0[/SUB] = 68.8^{+5.4}_{-5.1} km s[SUP]-1[/SUP] Mpc[SUP]-1[/SUP], assuming a flat Λ cold dark matter cosmology with uniform prior on Ω[SUB]m[/SUB] in [0.05, 0.5]. The precision of our cosmographic measurement with the doubly imaged quasar SDSS 1206+4332 is comparable with those of quadruply imaged quasars and opens the path to perform on selected doubles the same analysis as anticipated for quads. Our analysis is based on a completely independent lensing code than our previous three H0LiCOW systems and the new measurement is fully consistent with those. We provide the analysis scripts paired with the publicly available software to facilitate independent analysis (footnote with link to www.h0licow.org). The consistency between blind measurements with independent codes provides an important sanity check on lens modelling systematics. By combining the likelihoods of the four systems under the same prior, we obtain H[SUB]0[/SUB] = 72.5^{+2.1}_{-2.3} km s[SUP]-1[/SUP] Mpc[SUP]-1[/SUP]. This measurement is independent of the distance ladder and other cosmological probes. [less ▲]

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See detailExtreme resonance line profile variations in the ultraviolet spectra of NGC 1624-2: probing the giant magnetosphere of the most strongly magnetized known O-type star
David-Uraz, A.; Erba, C.; Petit, V. et al

in Monthly Notices of the Royal Astronomical Society (2019), 483

In this paper, we present high-resolution HST/COS observations of the extreme magnetic O star NGC 1624-2. These represent the first ultraviolet spectra of this archetypal object. We examine the ... [more ▼]

In this paper, we present high-resolution HST/COS observations of the extreme magnetic O star NGC 1624-2. These represent the first ultraviolet spectra of this archetypal object. We examine the variability of its wind-sensitive resonance lines, comparing it to that of other known magnetic O stars. In particular, the observed variations in the profiles of the C IV and Si IV doublets between low state and high state are the largest observed in any magnetic O-type star, consistent with the expected properties of NGC 1624-2's magnetosphere. We also observe a redshifted absorption component in the low state, a feature not seen in most stars. We present preliminary modelling efforts based on the Analytic Dynamical Magnetosphere (ADM) formalism, demonstrating the necessity of using non-spherically symmetric models to determine wind/magnetospheric properties of magnetic O stars. [less ▲]

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See detailA remarkable change of the spectrum of the magnetic Of?p star HD 148937 reveals evidence of an eccentric, high-mass binary
Wade, G. A.; Smoker, J. V.; Evans, C. J. et al

in Monthly Notices of the Royal Astronomical Society (2019), 483

We report new spectroscopic observations of the magnetic Of?p star HD 148937 obtained since 2015 that differ qualitatively from its extensive historical record of weak, periodic spectral variations. This ... [more ▼]

We report new spectroscopic observations of the magnetic Of?p star HD 148937 obtained since 2015 that differ qualitatively from its extensive historical record of weak, periodic spectral variations. This remarkable behaviour represents clear evidence for an unprecedented change in the character of variability of the star. In this paper, we describe the new spectral properties and compare them to the previous line profiles. Based on measurements of the radial velocities of the C III/N III emission lines near 4640 Å and the C IV absorption lines near 5800 Å, we infer that HD 148937 is likely a high-mass, double-lined spectroscopic binary. Combining the spectroscopic orbit with an archival interferometric measurement of the apparent separation of the equal brightness components, we tentatively conclude that HD 148937 consists of two O-type stars with masses of approximately 34 and 49 M[SUB]⊙[/SUB], orbiting in an eccentric (e = 0.75), long-period (P[SUB]orb[/SUB] ˜ 26 yr) orbit. We discuss the potential relationship of the binary system to the peculiar properties of HD 148937, and propose future observations to refine the orbital and stellar properties. [less ▲]

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See detailMean density inversions for red giants and red clump stars
Buldgen, Gaël ULiege; Rendle, B.; Sonoi, T. et al

in Monthly Notices of the Royal Astronomical Society (2019), 482(2), 2305-2319

Since the CoRoT and Kepler missions, the availability of high-quality seismic spectra for red giants has made them the standard clocks and rulers for Galactic Archeology. With the expected excellent data ... [more ▼]

Since the CoRoT and Kepler missions, the availability of high-quality seismic spectra for red giants has made them the standard clocks and rulers for Galactic Archeology. With the expected excellent data from the TESS and PLATO missions, red giants will again play a key role in Galactic studies and stellar physics, thanks to the precise masses and radii determined by asteroseismology. The determination of these quantities is often based on so-called scaling laws, which have been used extensively for main-sequence stars. We show how the SOLA inversion technique can provide robust determinations of the mean density of red giants within 1 per cent of the real value, using only radial oscillations. Combined with radii determinations from Gaia of around 2 per cent precision, this approach provides robust, less model-dependent masses with an error lower than 10 per cent. It will improve age determinations, helping to accurately dissect the Galactic structure and history. We present results on artificial data of standard models, models including an extended atmosphere from averaged 3D simulations and non-adiabatic frequency calculations to test surface effects, and on eclipsing binaries. We show that the inversions provide very robust mean density estimates, using at best seismic information. However, we also show that a distinction between red-giant branch and red-clump stars is required to determine a reliable estimate of the mean density. The stability of the inversion enables an implementation in automated pipelines, making it suitable for large samples of stars. [less ▲]

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See detailNew transiting hot Jupiters discovered by WASP-South, Euler/CORALIE, and TRAPPIST-South
Hellier, Coel; Anderson, D. R.; Bouchy, F. et al

in Monthly Notices of the Royal Astronomical Society (2019), 482

We report the discovery of eight hot-Jupiter exoplanets from the WASP-South transit survey. WASP-144b has a mass of 0.44 M[SUB]Jup[/SUB], a radius of 0.85 R[SUB]Jup[/SUB], and is in a 2.27-d orbit around ... [more ▼]

We report the discovery of eight hot-Jupiter exoplanets from the WASP-South transit survey. WASP-144b has a mass of 0.44 M[SUB]Jup[/SUB], a radius of 0.85 R[SUB]Jup[/SUB], and is in a 2.27-d orbit around a V = 12.9, K2 star which shows a 21-d rotational modulation. WASP-145Ab is a 0.89 M[SUB]Jup[/SUB] planet in a 1.77-d orbit with a grazing transit. The host is a V = 11.5, K2 star with a companion 5 arcsec away and 1.4 mag fainter. WASP-158b is a relatively massive planet at 2.8 M[SUB]Jup[/SUB] with a radius of 1.1 R[SUB]Jup[/SUB] and a 3.66-d orbit. It transits a V = 12.1, F6 star. WASP-159b is a bloated hot Jupiter (1.4 R[SUB]Jup[/SUB] and 0.55 M[SUB]Jup[/SUB]) in a 3.8-d orbit around a V = 12.9, F9 star. WASP-162b is a massive planet in a relatively long and highly eccentric orbit (5.2 M[SUB]Jup[/SUB], P = 9.6 d, e = 0.43). It transits a V = 12.2, K0 star. WASP-168b is a bloated hot Jupiter (0.42 M[SUB]Jup[/SUB]; 1.5 R[SUB]Jup[/SUB]) in a 4.15-d orbit with a grazing transit. The host is a V = 12.1, F9 star. WASP-172b is a bloated hot Jupiter (0.5 M[SUB]Jup[/SUB]; 1.6 R[SUB]Jup[/SUB]) in a 5.48-d orbit around a V = 11.0, F1 star. WASP-173Ab is a massive planet (3.7 M[SUB]Jup[/SUB]) with a 1.2 R[SUB]Jup[/SUB] radius in a circular orbit with a period of 1.39 d. The host is a V = 11.3, G3 star, being the brighter component of the double-star system WDS23366 - 3437, with a companion 6 arcsec away and 0.8 mag fainter. One of the two stars shows a rotational modulation of 7.9 d. [less ▲]

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See detailConstraining the microlensing effect on time delays with a new time-delay prediction model in H0 measurements
Chen, Geoff C.-F.; Chan, James H. H.; Bonvin, Vivien et al

in Monthly Notices of the Royal Astronomical Society (2018), 481

Time-delay strong lensing provides a unique way to directly measure the Hubble constant (H0). The precision of the H0measurement depends on the uncertainties in the time-delay measurements, the mass ... [more ▼]

Time-delay strong lensing provides a unique way to directly measure the Hubble constant (H0). The precision of the H0measurement depends on the uncertainties in the time-delay measurements, the mass distribution of the main deflector(s), and the mass distribution along the line of sight. Tie & Kochanek have proposed a new microlensing effect on time delays based on differential magnification of the coherent accretion disc variability of the lensed quasar. If real, this effect could significantly broaden the uncertainty on the time-delay measurements by up to 30 per cent for lens systems such as PG 1115+080, which have relatively short time delays and monitoring over several different epochs. In this paper we develop a new technique that uses the cosmological time-delay ratios and simulated microlensing maps within a Bayesian framework in order to limit the allowed combinations of microlensing delays and thus to lessen the uncertainties due to the proposed effect. We show that, under the assumption of Tie & Kochanek, the uncertainty on the time-delay distance (D∆t, which is proportional to 1/H0) of the short time-delay (18 d) lens, PG 1115+080, increases from 7 per cent to ̃10 per cent by simultaneously fitting the three time-delay measurements from the three different data sets across 20 yr, while in the case of the long time-delay (̃90 d) lens, the microlensing effect on time delays is negligible as the uncertainty on D[SUB]∆t[/SUB] of RXJ 1131-1231 only increases from ̃2.5 per cent to 2.6 per cent. [less ▲]

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See detailDiscovery of WASP-174b: Doppler tomography of a near-grazing transit
Temple, L. Y.; Hellier, C.; Almleaky, Y. et al

in Monthly Notices of the Royal Astronomical Society (2018), 480

We report the discovery and tomographic detection of WASP-174b, a planet with a near-grazing transit on a 4.23-d orbit around a V= 11.9, F6V star with [Fe/H] = 0.09 ± 0.09. The planet is in a moderately ... [more ▼]

We report the discovery and tomographic detection of WASP-174b, a planet with a near-grazing transit on a 4.23-d orbit around a V= 11.9, F6V star with [Fe/H] = 0.09 ± 0.09. The planet is in a moderately misaligned orbit with a sky-projected spin-orbit angle of λ = 31° ± 1°. This is in agreement with the known tendency for orbits around hotter stars to be misaligned. Owing to the grazing transit, the planet's radius is uncertain with a possible range of 0.8-1.8 R[SUB]Jup[/SUB]. The planet's mass has an upper limit of 1.3 M[SUB]Jup[/SUB]. WASP-174 is the faintest hot-Jupiter system so far confirmed by tomographic means. [less ▲]

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See detailWASP-147b, 160Bb, 164b and 165b: two hot Saturns and two Jupiters, including two planets with metal-rich hosts
Lendl, M.; Anderson, D. R.; Bonfanti, Andrea ULiege et al

in Monthly Notices of the Royal Astronomical Society (2018)

We report the discovery of four transiting hot Jupiters, WASP-147, WASP-160B, WASP-164 and WASP-165 from the WASP survey. WASP-147b is a near Saturn-mass (M[SUB]P[/SUB] = 0.28M[SUB]J[/SUB]) object with a ... [more ▼]

We report the discovery of four transiting hot Jupiters, WASP-147, WASP-160B, WASP-164 and WASP-165 from the WASP survey. WASP-147b is a near Saturn-mass (M[SUB]P[/SUB] = 0.28M[SUB]J[/SUB]) object with a radius of 1.11 R[SUB]J[/SUB] orbiting a G4 star with a period of 4.6 d. WASP-160Bb has a mass and radius (M[SUB]p[/SUB] = 0.28 M[SUB]J[/SUB], R[SUB]p[/SUB] = 1.09 R[SUB]J[/SUB]) near-identical to WASP-147b, but is less irradiated, orbiting a metal-rich ([Fe/H][SUB]*[/SUB] = 0.27) K0 star with a period of 3.8 d. WASP-160B is part of a near equal-mass visual binary with an on-sky separation of 28.5 arcsec. WASP-164b is a more massive (M[SUB]P[/SUB] = 2.13 M[SUB]J[/SUB], R[SUB]p[/SUB] = 1.13 R[SUB]J[/SUB]) hot Jupiter, orbiting a G2 star on a close-in (P = 1.8 d), but tidally stable orbit. WASP-165b is a classical (M[SUB]p[/SUB] = 0.66 M[SUB]J[/SUB], R[SUB]P[/SUB] = 1.26 R[SUB]J[/SUB]) hot Jupiter in a 3.5 d period orbit around a metal-rich ([Fe/H][SUB]*[/SUB] = 0.33) star. WASP-147b and WASP-160Bb are promising targets for atmospheric characterization through transmission spectroscopy, while WASP-164b presents a good target for emission spectroscopy. [less ▲]

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See detailA cosmology-independent calibration of type Ia supernovae data
Hauret, Clémentine ULiege; Magain, Pierre ULiege; Biernaux, Judith ULiege

in Monthly Notices of the Royal Astronomical Society (2018), 479(3), 3996-4003

Recently, the common methodology used to transform type Ia supernovae (SNe Ia) into genuine standard candles has been suffering criticism. Indeed, it assumes a par- ticular cosmological model (namely the ... [more ▼]

Recently, the common methodology used to transform type Ia supernovae (SNe Ia) into genuine standard candles has been suffering criticism. Indeed, it assumes a par- ticular cosmological model (namely the flat LambdaCDM) to calibrate the standardisation corrections parameters, i.e. the dependency of the supernova peak absolute magnitude on its colour, post-maximum decline rate and host galaxy mass. As a result, this as- sumption could make the data compliant to the assumed cosmology and thus nullify all works previously conducted on model comparison. In this work, we verify the viability of these hypotheses by developing a cosmology-independent approach to standardise SNe Ia data from the recent JLA compilation. Our resulting corrections turn out to be very close to the LambdaCDM-based corrections. Therefore, even if a LambdaCDM-based calibra- tion is questionable from a theoretical point of view, the potential compliance of SNe Ia data does not happen in practice for the JLA compilation. Previous works of model comparison based on these data do not have to be called into question. However, as this cosmology-independent standardisation method has the same degree of complex- ity than the model-dependent one, it is worth using it in future works, especially if smaller samples are considered, such as the superluminous type Ic supernovae. [less ▲]

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See detailWASP-128b: a transiting brown dwarf in the dynamical-tide regime
Hodžić, Vedad; Triaud, Amaury H. M. J.; Anderson, David R. et al

in Monthly Notices of the Royal Astronomical Society (2018)

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 ... [more ▼]

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, M[SUB]⋆[/SUB] = 1.16 ± 0.04M[SUB]⊙[/SUB], R[SUB]⋆[/SUB] = 1.16 ± 0.02R[SUB]⊙[/SUB], and for the companion, M[SUB]b[/SUB] = 37.5 ± 0.8Mj, R[SUB]b[/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. [less ▲]

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See detailH0LiCOW VIII. A weak-lensing measurement of the external convergence in the field of the lensed quasar HE 0435-1223
Tihhonova, O.; Courbin, F.; Harvey, D. et al

in Monthly Notices of the Royal Astronomical Society (2018), 477

We present a weak gravitational lensing measurement of the external convergence along the line of sight to the quadruply lensed quasar HE 0435-1223. Using deep r-band images from Subaru Suprime Cam, we ... [more ▼]

We present a weak gravitational lensing measurement of the external convergence along the line of sight to the quadruply lensed quasar HE 0435-1223. Using deep r-band images from Subaru Suprime Cam, we observe galaxies down to a 3σ limiting magnitude of ˜26 mag resulting in a source galaxy density of 14 galaxies per square arcminute after redshift-based cuts. Using an inpainting technique and multiscale entropy filtering algorithm, we find that the region in close proximity to the lens has an estimated external convergence of κ =-0.012^{+0.020}_{-0.013} and is hence marginally underdense. We also rule out the presence of any halo with a mass greater than M[SUB]vir[/SUB] = 1.6 × 10[SUP]14[/SUP]h[SUP]-1[/SUP]M[SUB]⊙[/SUB] (68 per cent confidence limit). Our results, consistent with previous studies of this lens, confirm that the intervening mass along the line of sight to HE 0435-1223 does not affect significantly the cosmological results inferred from the time-delay measurements of that specific object. [less ▲]

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See detailHigh-contrast imaging of HD 163296 with the Keck/NIRC2 L'-band vortex coronograph
Guidi, G.; Ruane, G.; Williams, J. P. et al

in Monthly Notices of the Royal Astronomical Society (2018), 479

We present observations of the nearby (D~100 pc) Herbig star HD 163296 taken with the vortex coronograph at Keck/NIRC2 in the L' band (3.7 μm) to search for planetary mass companions in the ringed disc ... [more ▼]

We present observations of the nearby (D~100 pc) Herbig star HD 163296 taken with the vortex coronograph at Keck/NIRC2 in the L' band (3.7 μm) to search for planetary mass companions in the ringed disc surrounding this pre-main-sequence star. The images reveal an arc-like region of scattered light from the disc surface layers that is likely associated with the first bright ring detected with ALMA in the λ = 1.3mm dust continuum at ~65 au. We also detect a point-like source at ~0.5 arcsec projected separation in the north-east direction, close to the inner edge of the second gap in the millimetre images. Comparing the point source photometry with the atmospheric emission models of non-accreting giant planets, we obtain a mass of 6-7 MJ for a putative protoplanet, assuming a system age of 5 Myr. Based on the contrast at a 95 per cent level of completeness calculated on the emission-free regions of our images, we set upper limits for the masses of giant planets of 8-15 MJ, 4.5-6.5 MJ, and 2.5-4.0MJ at the locations of the first, second, and third gap in the millimetre dust continuum, respectively. Further deep, high-resolution thermal IR imaging of the HD 163296 system are warranted to confirm the presence and nature of the point source and to better understand the structure of the dust disc. © 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. [less ▲]

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See detailCircumbinary, not transitional: on the spiral arms, cavity, shadows, fast radial flows, streamers, and horseshoe in the HD 142527 disc
Price, Daniel J.; Cuello, Nicolás; Pinte, Christophe et al

in Monthly Notices of the Royal Astronomical Society (2018), 477

We present 3D hydrodynamical models of the HD 142527 protoplanetary disc, a bright and well-studied disc that shows spirals and shadows in scattered light around a 100 au gas cavity, a large horseshoe ... [more ▼]

We present 3D hydrodynamical models of the HD 142527 protoplanetary disc, a bright and well-studied disc that shows spirals and shadows in scattered light around a 100 au gas cavity, a large horseshoe dust structure in mm continuum emission, together with mysterious fast radial flows and streamers seen in gas kinematics. By considering several possible orbits consistent with the observed arc, we show that all of the main observational features can be explained by one mechanism - the interaction between the disc and the observed binary companion. We find that the spirals, shadows, and horseshoe are only produced in the correct position angles by a companion on an inclined and eccentric orbit approaching periastron - the `red' family from Lacour et al. Dust-gas simulations show radial and azimuthal concentration of dust around the cavity, consistent with the observed horseshoe. The success of this model in the HD 142527 disc suggests other mm-bright transition discs showing cavities, spirals, and dust asymmetries may also be explained by the interaction with central companions. [less ▲]

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See detailKinematic evidence for feedback-driven star formation in NGC 1893
Lim, Beomdu ULiege; Sung, Hwankyung; Bessell, Michael S. et al

in Monthly Notices of the Royal Astronomical Society (2018), 477

OB associations are the prevailing star-forming sites in the Galaxy. Up to now, the process of how OB associations were formed remained a mystery. A possible process is self-regulating star formation ... [more ▼]

OB associations are the prevailing star-forming sites in the Galaxy. Up to now, the process of how OB associations were formed remained a mystery. A possible process is self-regulating star formation driven by feedback from massive stars. However, although a number of observational studies uncovered various signposts of feedback-driven star formation, the effectiveness of such feedback has been questioned. Stellar and gas kinematics is a promising tool to capture the relative motion of newborn stars and gas away from ionizing sources. We present high-resolution spectroscopy of stars and gas in the young open cluster NGC 1893. Our findings show that newborn stars and the tadpole nebula Sim 130 are moving away from the central cluster containing two O-type stars, and that the time-scale of sequential star formation is about 1 Myr within a 9 pc distance. The newborn stars formed by feedback from massive stars account for at least 18 per cent of the total stellar population in the cluster, suggesting that this process can play an important role in the formation of OB associations. These results support the self-regulating star formation model. [less ▲]

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See detailTheoretical study of ArH+ dissociative recombination and electron-impact vibrational excitation
Abdoulanziz, A.; Colboc, F.; Little, D. A. et al

in Monthly Notices of the Royal Astronomical Society (2018)

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See detailThe X-ray footprint of the CircumNuclear Disk
Mossoux, Enmanuelle ULiege; Eckart, Andreas

in Monthly Notices of the Royal Astronomical Society (2018), 474(3), 3787-3807

We studied the central regions of the Galactic Centre to determine if the CircumNuclear Disk (CND) acts as an absorber or a barrier for the central X-rays diffuse emission. After reprocessing 4.6Ms of ... [more ▼]

We studied the central regions of the Galactic Centre to determine if the CircumNuclear Disk (CND) acts as an absorber or a barrier for the central X-rays diffuse emission. After reprocessing 4.6Ms of Chandra observations, we were able to detect, for the first time, a depression in the X-ray luminosity of the diffuse emission whose size and location correspond to those of the CND. We extracted the X-ray spectra for various regions inside the CND footprint as well as for the region where the footprint is observed and for a region located outside the footprint. We simultaneously fitted these spectra as an optically thin plasma whose absorption by the interstellar medium and by the local plasma were fitted independently using the MCMC method. The hydrogen column density of the ISM is 7.5x10^22 cm^-2. The X-ray diffuse emission inside the CND footprint is formed by a 2T plasma of 1 and 4keV with slightly super-solar abundances except for the iron and carbon which are sub-solar. The plasma from the CND, in turn, is better described by a 1T model with abundances and local hydrogen column density which are very different to those of the innermost regions. The large iron abundance in this region confirms that the CND is dominated by the shock-heated ejecta of the Sgr A East supernova remnant. We deduced that the CND rather acts as a barrier for the Galactic Centre plasma and that the plasma located outside the CND may correspond to the collimated outflow possibly created by Sgr A* or the interaction between the wind of massive stars and the mini-spiral material. [less ▲]

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See detailUnmasking the hidden NGTS-3Ab: A hot Jupiter in an unresolved binary system
Günther, M. N.; Queloz, D.; Gillen, E. et al

in Monthly Notices of the Royal Astronomical Society (2018), 478(4), 4720-4737

We present the discovery of NGTS-3Ab, a hot Jupiter found transiting the primary star of an unresolved binary system. We develop a joint analysis of multicolour photometry, centroids, radial velocity (RV ... [more ▼]

We present the discovery of NGTS-3Ab, a hot Jupiter found transiting the primary star of an unresolved binary system. We develop a joint analysis of multicolour photometry, centroids, radial velocity (RV) cross-correlation function (CCF) profiles, and their bisector inverse slopes (BIS) to disentangle this three-body system. Data from the Next Generation Transit Survey (NGTS), SPECULOOS and HARPS are analysed and modelled with our new BLENDFITTER software. We find that the binary consists of NGTS-3A (G6V-dwarf) and NGTS-3B (K1Vdwarf) at < 1 arcsec separation. NGTS-3Ab orbits every 1.675 d. The planet radius and mass are Rplanet = 1.48 ± 0.37 RJ and Mplanet = 2.38 ± 0.26MJ, suggesting it is potentially inflated. We emphasize that only combining all the information frommulticolour photometry, centroids and RV CCF profiles can resolve systems like NGTS-3. Such systems cannot be disentangled from single-colour photometry and RV measurements alone. Importantly, the presence of a BIS correlation indicates a blend scenario, but is not sufficient to determine which star is orbited by the third body. Moreover, even if no BIS correlation is detected, a blend scenario cannot be ruled out without further information. The choice of methodology for calculating the BIS can influence the measured significance of its correlation. The presented findings are crucial to consider for wide-field transit surveys, which require wide CCD pixels (> 5 arcsec) and are prone to contamination by blended objects. With TESS on the horizon, it is pivotal for the candidate vetting to incorporate all available follow-up information from multicolour photometry and RV CCF profiles. © 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. [less ▲]

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See detailHigh-precision multiwavelength eclipse photometry of the ultra-hot gas giant exoplanetWASP-103 b
Delrez, L.; Madhusudhan, N.; Lendl, M. et al

in Monthly Notices of the Royal Astronomical Society (2018), 474(2), 2334-2351

We present 16 occultation and three transit light curves for the ultra-short period hot Jupiter WASP-103b, in addition to five new radial velocity measurements. We combine these observations with archival ... [more ▼]

We present 16 occultation and three transit light curves for the ultra-short period hot Jupiter WASP-103b, in addition to five new radial velocity measurements. We combine these observations with archival data and perform a global analysis of the resulting extensive data set, accounting for the contamination from a nearby star. We detect the thermal emission of the planet in both the z' and KS bands, the measured occultation depths being 699±110 ppm (6.4σ) and 3567-350 +400 ppm (10.2σ), respectively. We use these two measurements, together with recently published HST/WFC3 data, to derive joint constraints on the properties of WASP- 103b's dayside atmosphere. On one hand, we find that the z' band and WFC3 data are best fit by an isothermal atmosphere at 2900K or an atmosphere with a low H2O abundance. On the other hand, we find an unexpected excess in the KS band measured flux compared to these models, which requires confirmation with additional observations before any interpretation can be given. From our global data analysis, we also derive a broad-band optical transmission spectrum that shows a minimum around 700 nm and increasing values towards both shorter and longer wavelengths. This is in agreement with a previous study based on a large fraction of the archival transit light curves used in our analysis. The unusual profile of this transmission spectrum is poorly matched by theoretical spectra and is not confirmed by more recent observations at higher spectral resolution. Additional data, in both emission and transmission, are required to better constrain the atmospheric properties of WASP-103b. © 2017 The Author(s). [less ▲]

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See detailLLAMA: nuclear stellar properties of Swift-BAT AGN and matched inactive galaxies
Lin, M.-Y.; Davies, R. I.; Hicks, E. K. S. et al

in Monthly Notices of the Royal Astronomical Society (2018), 473

In a complete sample of local 14–195 keV selected active galactic nuclei (AGNs) and inactive galaxies, matched by their host galaxy properties, we study the spatially resolved stellar kinematics and ... [more ▼]

In a complete sample of local 14–195 keV selected active galactic nuclei (AGNs) and inactive galaxies, matched by their host galaxy properties, we study the spatially resolved stellar kinematics and luminosity distributions at near-infrared wavelengths on scales of 10–150 pc, using SINFONI on the VLT. In this paper, we present the first half of the sample, which comprises 13 galaxies, eight AGNs and five inactive galaxies. The stellar velocity fields show a disc-like rotating pattern, for which the kinematic position angle is in agreement with the photometric position angle obtained from large scale images. For this set of galaxies, the stellar surface brightness of the inactive galaxy sample is generally comparable to the matched sample of AGN, but extends to lower surface brightness. After removal of the bulge contribution, we find a nuclear stellar light excess with an extended nuclear disc structure, which exhibits a size-luminosity relation. While we expect the excess luminosity to be associated with a dynamically cooler young stellar population, we do not typically see a matching drop in dispersion. This may be because these galaxies have pseudo-bulges in which the intrinsic dispersion increases towards the centre. And although the young stars may have an impact in the observed kinematics, their fraction is too small to dominate over the bulge and compensate the increase in dispersion at small radii, so no dispersion drop is seen. Finally, we find no evidence for a difference in the stellar kinematics and nuclear stellar luminosity excess between these active and inactive galaxies. [less ▲]

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