The First Science Results From Sphere: Disproving the Predicted Brown Dwarf Around V471 Tau

Hardy, Adam; Schreiber, M. R.; Parsons, S. G.; Cáceres, C.; Retamales, G.; Wahhaj, Z.; Mawet, Dimitri; Cánovas, H.; Cieza, Lucas A.; Marsh, T. R.; Bours, Madelon C. P.; Dhillon, V. S.; Bayo, A.

doi:10.1088/2041-8205/800/2/l24

Cited by 50 publications

(69 citation statements)

References 39 publications

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“…Again, from an orbital stability standpoint, Horner et al (2014) challenged the two planet systems of three other binaries. Hardy et al (2015), using the new extreme-AO instrument SPHERE, imaged the prototype eclipsing post-common envelope binary V471 Tau in search of a brown dwarf that was predicted to be responsible for LTT effects. They found no direct evidence of such an object.…”

Section: A Changing Landscapementioning

confidence: 99%

The quest for stable circumbinary companions to post-common envelope sdB eclipsing binaries

Pulley

Faillace

Smith

et al. 2018

A&A

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Context. Period variations have been detected in a number of eclipsing close compact binary subdwarf B stars (sdBs) and these have often been interpreted as caused by circumbinary massive planets or brown dwarfs. According to canonical binary models, the majority of sdB systems are produced from low mass stars with degenerate cores where helium is ignited in flashes. Various evolutionary scenarios have been proposed for these stars, but a definite mechanism remains to be established. Equally puzzling is the formation of these putative circumbinary objects which must have formed either from the remaining post common envelope circumbinary disk or survived its evolution. Aims. In this paper we review the eclipse time variations (ETVs) exhibited by seven such systems (EC10246-2707, HS0705+6700, HS2231+2441, J08205+0008, NSVS 07826147, NSVS 14256825 and NY Vir) and explore if there is conclusive evidence that the ETVs observed over the last two decades can reliably predict the presence of one or more circumbinary bodies. Methods. We report 246 new observations of the seven sdB systems made between 2013 September and 2017 July using a worldwide network of telescopes. We combined our new data with previously published measurements to analyse the ETVs of these systems. Results. Our data shows that period variations cannot be modelled simply on the basis of circumbinary objects. This implies that more complex processes may be taking place in these systems. These difficulties are compounded by the secondary star not being spectroscopically visible. From eclipse time variations, it has historically been suggested that five of the seven binary systems reported herein had circumbinary objects. Based on our recent observations and analysis only three systems remain serious contenders. We find agreement with other observers that at least a decade of observations is required to establish reliable ephemeris. With longer observational baselines it is quite conceivable that the data will support the circumbinary object hypothesis of these binary systems. Also we generally agree with other observers that larger values of (O-C) residuals are found with secondary companions of spectral type M5/6 or earlier possibly as a result of an Applegate type mechanism

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Section: A Changing Landscapementioning

confidence: 99%

The quest for stable circumbinary companions to post-common envelope sdB eclipsing binaries

Pulley

Faillace

Smith

et al. 2018

A&A

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“…V471 Tau (Guinan & Ribas 2001) and SDSS J143547 (Qian et al 2016). Also note that the brown dwarf companion in V471 Tau was excluded by Hardy et al (2015) but a new study agrees with the presence of a brown dwarf companion (Vaccaro et al 2015). Moreover, some possible planets orbiting the eclipsing CVs or pre-CVs were also presented such as V893 Sco (Bruch 2014), V2051 Oph , OY Car , DP Leo Beuermann et al 2011), HU Aqr (Qian et al 2011;Goździewski et al 2015), UZ For Potter et al 2011) and NN Ser (Marsh et al 2014).…”

Section: Discussionmentioning

confidence: 72%

Cyclic Period Oscillation of the Eclipsing Dwarf Nova DV UMa

Han

Qian

Voloshina

et al. 2017

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DV UMa is an eclipsing dwarf nova with an orbital period of ∼ 2.06 h, which lies just at the bottom edge of the period gap. To detect its orbital period changes we present 12 new mid-eclipse times by using our CCD photometric data and archival data. Combining with the published mid-eclipse times in quiescence, spanning ∼ 30 yr, the latest version of the O − C diagram was obtained and analyzed. The best fit to those available eclipse timings shows that the orbital period of DV UMa is undergoing a cyclic oscillation with a period of 17.58(±0.52) yr and an amplitude of 71.1(±6.7) s. The periodic variation most likely arises from the light-travel-time effect via the presence of a circumbinary object because the required energy to drive the Applegate mechanism is too high in this system. The mass of the unseen companion was derived as M 3 sin i ′ = 0.025(±0.004)M ⊙ . If the third body is in the orbital plane (i.e. i ′ = i = 82.9• ) of the eclipsing pair, it would match to a brown dwarf. This hypothetical brown dwarf is orbiting its host star at a separation of ∼ 8.6 AU in an eccentric orbit (e = 0.44).

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“…This β Pic dataset is described in Absil et al (2013) along with the pre-processing procedures applied to generate the calibrated cube (or reduced image sequence) that we used here. The second dataset is a VLT/SPHERE sequence on V471 Tau (Hardy et al 2015) acquired with the Infra-Red Dual-band Imaging and Spectroscopy (IRDIS, Dohlen et al 2008) subsystem. It consists of two sequences (in the H2 and H3 bands 4 ) with 50 frames, each one with 64 sec of integration time, and a total field rotation of 30 degrees.…”

Section: From Unsupervised To Supervised Learningmentioning

confidence: 99%

“…It consists of two sequences (in the H2 and H3 bands 4 ) with 50 frames, each one with 64 sec of integration time, and a total field rotation of 30 degrees. The pre-processing steps applied to the V471 Tau dataset are described in Hardy et al (2015). Throughout this study, and for simplicity, we assume that (1×)FWHM = 1λ/D = 4 pxs.…”

Section: From Unsupervised To Supervised Learningmentioning

confidence: 99%

Supervised detection of exoplanets in high-contrast imaging sequences

González

Absil

Droogenbroeck

2018

A&A

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Context. Post-processing algorithms play a key role in pushing the detection limits of high-contrast imaging (HCI) instruments. State-of-the-art image processing approaches for HCI enable the production of science-ready images relying on unsupervised learning techniques, such as low-rank approximations, for generating a model PSF and subtracting the residual starlight and speckle noise. Aims. In order to maximize the detection rate of HCI instruments and survey campaigns, advanced algorithms with higher sensitivities to faint companions are needed, especially for the speckle-dominated innermost region of the images. Methods. We propose a reformulation of the exoplanet detection task (for ADI sequences) that builds on well-established machine learning techniques to take HCI post-processing from an unsupervised to a supervised learning context. In this new framework, we present algorithmic solutions using two different discriminative models: SODIRF (random forests) and SODINN (neural networks). We test these algorithms on real ADI datasets from VLT/NACO and VLT/SPHERE HCI instruments. We then assess their performances by injecting fake companions and using receiver operating characteristic analysis. This is done in comparison with state-of-the-art ADI algorithms, such as ADI principal component analysis (ADI-PCA).Results. This study shows the improved sensitivity vs specificity trade-off of the proposed supervised detection approach. At the diffraction limit, SODINN improves the true positive rate by a factor ranging from ∼2 to ∼10 (depending on the dataset and angular separation) with respect to ADI-PCA when working at the same false positive level. Conclusions. The proposed supervised detection framework outperforms state-of-the-art techniques in the task of discriminating planet signal from speckles. In addition, it offers the possibility of re-processing existing HCI databases to maximize their scientific return and potentially improve the demographics of directly imaged exoplanets.

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The First Science Results From Sphere: Disproving the Predicted Brown Dwarf Around V471 Tau

Cited by 50 publications

References 39 publications

The quest for stable circumbinary companions to post-common envelope sdB eclipsing binaries

The quest for stable circumbinary companions to post-common envelope sdB eclipsing binaries

Cyclic Period Oscillation of the Eclipsing Dwarf Nova DV UMa

Supervised detection of exoplanets in high-contrast imaging sequences

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