| 1. |
- Calissendorff, Per, 1989-
(författare)
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Characterising Young Stellar Binaries
- 2018
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Stars are dispersed all over the sky within our Galaxy, appearing in large varieties of ages and sizes. How- ever, estimating said traits proves not to always be trivial, but certain circumstances allow us to probe the characteristics of stellar binaries. Fortunately, most stars are found to be part of binary or multiple systems, and through their brightness we can study their sizes, while their dynamical interactions let us derive masses. Although absolute ages are near-impossible to estimate, we posses several methods for constraining age-limits of stars at various evolutionary stages. Theoretical models can provide us with an idea of some of the attributes of stars, but sometimes require assumptions that are not always validated. When fundamental physical laws can be used to deduce individual masses of stellar systems, we procure means to constrain and calibrate those models. As such, the multiplicity of different types of stars is of high importance, which separation and mass distributions can also help us constrain formation scenarios among the different mass-regimes. In this review we compile information regarding the detection of binary and multiple stellar systems, as well as how one can go about to estimate their most fundamental quantities including mass and age. We also compare the different methods and techniques employed throughout the literature, addressing various caveats, examples of usage and the future outlook with coming improvements. In the final part of the review, we present the results from a recent paper about the orbital motions of a triple system, which yield a dynamical mass of the system which shows inconsistencies with the theoretical mass obtained from current low-mass stellar evolutionary models.
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| 2. |
- Viswanath, Gayathri, 1992-
(författare)
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High-Contrast Investigation of the ε Ind system
- 2021
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This licentiate thesis provides a broad introduction into the methodology of detecting and characterising exoplanets, with the main focus on the method of high-contrast imaging (HCI). Developments in theoretical knowledge as well as instrumentation have, in the past decade, pushed the boundaries of what HCI can achieve, both in terms of detection sensitivity and constraining planet properties. Direct imaging surveys in the near infrared (NIR) and longward wavelengths have proven particularly useful in detecting younger giant planets at wide orbital separations.The scientific work presented as part of this thesis is one such result of an imaging pursuit of the young giant planet, ϵ Ind Ab, which has long eluded NIR imaging surveys in the past, yet revealing its existence via radial velocity trends and astrometry of the parent star. It resides in the very interesting ϵ Ind stellar system, revolving around the primary star ϵ Ind A which is a Sun-like star only ∼12 light years away and visible in the night sky to the naked eye. With the combination of imaging data from two mid infrared (MIR) instruments, advanced post-processing techniques as well as comparative analysis using different planet atmospheric models, this work was able to place tight constraints on the age of the system and mass of the planet, although no detection was achieved. The new constraints set a firm foundation for MIR imaging surveys for the planet in future, especially with the upcoming more sensitive, advanced instruments in the later half of the decade.MIR imaging surveys have gained increasing significance in the recent years, due to their ability to detect colder/ smaller planets. It plays an important role in covering the missing gaps in the planet parameter space, ultimately aiding in improving our knowledge on planet formation and evolution.
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