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- 12.09. Anlaug Amanda Djupvik (NOT): Star formation studies with the Nordic Optical Telescope
Abstract: I will present the Nordic Optical Telescope and two ongoing star formation studies using the NOT. One is based on infrared observations of embedded protostellar jets and another on high-resolution optical spectroscopy to study the UXOR phenomenon. 1) Protostellar jets serve as footprints of the ejection history of a protostar, believed to reflect also the accretion history. A kinematic study of jet knots with infrared imaging and spectroscopy in a dense cloud in Serpes reveals space velocities and locate their driving sources. We find time-variable ejection/accretion and deduce a higher accretion rate, by orders of magnitude, for the youngest protostar. 2) The UXOR phenomenon, a specific and irregular variability in intermediate-mass young stars, is believed to be caused by variable circumstellar extinction. We monitor the variable emission line profiles of hydrogen and other lines formed in the inner part of the circumstellar disk as the star is going through a fading event. Simulations based on hybrid models of magnetospheric accretion and magnetocentrifugal disk winds are used with variable obscuration scenarios. Modelling finds that the disk wind plays a dominant role in the emission line profiles. An obscuration scenario where dust moves vertically up from the disk fits the data best for one of our targets, RR Tau, and it is suggested that the dust is lifted by the disk wind.
- 19.09.. Vittoria Vecchiotti (IFY, NTNU): The high-energy Galactic gamma-ray emission: the diffuse component and the role of unresolved pulsar wind nebulae
Abstract: The study of the Galactic gamma-ray and neutrino diffuse emission represents an indirect way to investigate cosmic-ray propagation in the Galaxy. However, the signal produced by unresolved sources contaminates diffuse emission measurements, making their interpretation challenging. In order to quantify the relevance of the unresolved source component, we performed a population study of the H.E.S.S. Galactic Plane Survey under the assumption of sources powered by pulsar activity. We estimate the total TeV flux produced by all the sources in our Galaxy. In particular, our results show that a non-negligible fraction of this flux is produced by faint sources below the H.E.S.S. detection threshold. In the GeV energy range, a significant fraction of the TeV source population cannot be resolved by Fermi-LAT providing a relevant contribution to the large-scale diffuse emission, ranging within $\sim 4\%-40\%$ of the total diffuse $\gamma$-ray emission in the inner Galaxy. Hence, this unresolved component may account for a large part of the spectral index variation observed by Fermi-LAT as a function of the Galactocentric distance. Lastly, we calculate the hadronic diffuse emission in the sub-PeV energy range under different model assumptions and compare it to the large-scale diffuse emission observed by Tibet AS$\gamma$. We show that a pure hadronic emission underpredicts the measurements requiring the presence of an unresolved source component.
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