Exoplanets and Stellar Physics

Abstract:

Context. The 16 Myr old star 1SWASP J140747.93-394542.6 (V1400 Cen) underwent a series of complex eclipses in May 2007, interpreted as the transit of a giant Hill sphere filling debris ring system around a secondary companion, J1407b. No other eclipses have since been detected, although other measurements have constrained but not uniquely determined the orbital period of J1407b. Finding another eclipse towards J1407 will help determine the orbital period of the system, the geometry of the proposed ring system and enable planning of further observations to characterize the material within these putative rings.

Aims. We carry out a search for other eclipses in photometric data of J1407 with the aim of constraining the orbital period of J1407b.

Methods. We present photometry from archival photographic plates from the Harvard DASCH survey, and Bamberg and Sonneberg Observatories, in order to place additional constraints on the orbital period of J1407b by searching for other dimming and eclipse events. Using a visual inspection of all 387 plates and a period-folding algorithm we performed a search for other eclipses in these data sets.

Results. We find no other deep eclipses in the data spanning from 1890 to 1990, nor in recent time-series photometry from 2012–2018.

Conclusions. We rule out a large fraction of putative orbital periods for J1407b from 5 to 20 yr. These limits are still marginally consistent with a large Hill sphere filling ring system surrounding a brown dwarf companion in a bound elliptical orbit about J1407. Issues with the stability of any rings combined with the lack of detection of another eclipse, suggests that J1407b may not be bound to J1407.

Abstract:

We provide the catalogue of all transit-like features, including false alarms, detected by the CoRoT exoplanet teams in the 177 454 light curves of the mission. All these detections have been re-analysed with the same softwares so that to ensure their homogeneous analysis. Although the vetting process involves some human evaluation, it also involves a simple binary flag system over basic tests: detection significance, presence of a secondary, difference between odd and even depths, colour dependence, V-shape transit, and duration of the transit. We also gathered the information from the large accompanying ground-based programme carried out on the planet candidates and checked how useful the flag system could have been at the vetting stage of the candidates. In total, we identified and separated 824 false alarms of various kind, 2269 eclipsing binaries among which 616 are contact binaries and 1653 are detached ones, 37 planets and brown dwarfs, and 557 planet candidates. For the planet candidates, the catalogue gives not only their transit parameters but also the products of their light curve modelling, together with a summary of the outcome of follow-up observations when carried out and their current status. Among the planet candidates whose nature remains unresolved, we estimate that 8 +/- 3 planets are still to be identified. We derived planet and brown dwarf occurrences and confirm disagreements with Kepler estimates: small-size planets with orbital period less than ten days are underabundant by a factor of three in the CoRoT fields whereas giant planets are overabundant by a factor of two. These preliminary results would however deserve further investigations using the recently released CoRoT light curves that are corrected of the various instrumental effects and a homogeneous analysis of the stellar populations observed by the two missions.

Abstract:

We investigate the properties of the interstellar medium, star formation, and the current-day stellar population in the strongly lensed star-forming galaxy H-ATLAS J091043.1-000321 (SDP.11), at z = 1.7830, using new Herschel and Atacama Large Millimeter/submillimeter Array (ALMA) observations of far-infrared fine-structure lines of carbon, oxygen, and nitrogen. We report detections of the [O iii] 52 μm, [N iii] 57 μm, and [O i] 63 μm lines from Herschel/PACS, and present high-resolution imaging of the [C ii] 158 μm line, and underlying continuum, using ALMA. We resolve the [C ii] line emission into two spatially offset Einstein rings, tracing the red and blue velocity components of the line, in the ALMA/Band 9 observations at 0farcs2 resolution. The values seen in the [C ii]/far-infrared (FIR) ratio map, as low as ~0.02% at the peak of the dust continuum, are similar to those of local ULIRGs, suggesting an intense starburst in this source. This is consistent with the high intrinsic FIR luminosity (~3 × 1012 L ⊙), ~16 Myr gas depletion timescale, and lesssim8 Myr timescale since the last starburst episode, estimated from the hardness of the UV radiation field. By applying gravitational lensing models to the visibilities in the uv-plane, we find that the lensing magnification factor varies by a factor of two across SDP.11, affecting the observed line profiles. After correcting for the effects of differential lensing, a symmetric line profile is recovered, suggesting that the starburst present here may not be the result of a major merger, as is the case for local ULIRGs, but instead could be powered by star formation activity spread across a 3–5 kpc rotating disk.

Abstract:

Phase curves are the best technique to probe the three-dimensional structure of exoplanets' atmospheres. In this chapter we first review current exoplanets' phase curve observations and the particular challenges they face. We then describe the different physical mechanisms shaping the atmospheric phase curves of highly irradiated tidally locked exoplanets. Finally, we discuss the potential for future missions to further advance our understanding of these new worlds.

Abstract:

The spectrum of an exoplanet reveals the physical, chemical, and biological processes that have shaped its history and govern its future. However, observations of exoplanet spectra are complicated by the overwhelming glare of their host stars. This chapter focuses on high-resolution spectroscopy (HRS) (R = 25, 000–100, 000), which helps to disentangle and isolate the exoplanet’s spectrum. At high spectral resolution, molecular features are resolved into a dense forest of individual lines in a pattern that is unique for a given molecule. For close-in planets, the spectral lines undergo large Doppler shifts during the planet’s orbit, while the host star and Earth’s spectral features remain essentially stationary, enabling a velocity separation of the planet. For slower-moving, wide-orbit planets, HRS, aided by high contrast imaging, instead isolates their spectra using their spatial separation. The lines in the exoplanet spectrum are detected by comparing them with high resolution spectra from atmospheric modelling codes; essentially a form of fingerprinting for exoplanet atmospheres. This measures the planet’s orbital velocity and helps define its true mass and orbital inclination. Consequently, HRS can detect both transiting and non-transiting planets. It also simultaneously characterizes the planet’s atmosphere, due to its sensitivity to the depth, shape, and position of the planet’s spectral lines. These are altered by the planet’s atmospheric composition, structure, clouds, and dynamics, including day-to-night winds and its rotation period. This chapter describes the HRS technique in detail, highlighting its successes in exoplanet detection and characterization, and concludes with the future prospects of using HRS to identify biomarkers on nearby rocky worlds and map features in the atmospheres of giant exoplanets.