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Department of Astronomy 2022-2023 Colloquium Series

Dr. David Bogensberger & Dr. Sorabh Chhabra Post - Doc Colloquium I
Thursday, September 22, 2022
3:30-4:30 PM
411 West Hall Map
Sorabh’s Title: Spectrograph design for the Asgard/BIFROST spectro-interferometric instrument for the VLTI

Abstract: The BIFROST instrument will be the first VLTI instrument optimised for high spectral resolution up to R=25,000 and operate between 1.05 and 1.7 µm. A key component of the instrument will be the spectrograph, where we require a high throughput over a broad bandwidth. In this contribution, we discuss the four planned spectral modes (R=50, R=1000, R=5000, and R=25,000), the key spectral windows that we need to cover, and the technology choices that we have considered. We present our plan to use Volume Phase Holographic Gratings (VPHGs) to achieve high efficiency of > 85%. We present our preliminary optical design and our strategies for wavelength calibration.

David’s Title: "The eROSITA all sky survey, and long term AGN X-ray variability"

Abstract: "The eROSITA all sky survey seeks to map the entire X-ray sky at an unprecedented sensitivity, detecting millions of AGNs, and tens of thousands of clusters of galaxies. I will discuss the mission, its goals, and some early science results. Due to the scanning pattern of eROSITA, thousands of X-ray sources near the ecliptic poles are observed every 6 hours for the duration of the survey. This constitutes a unique dataset, enabling a detailed study of the mid to long term variability properties of a large, unbiased selection of AGNs. I will be discussing some updated variability methods for analysing eROSITA light curves, as well as some of the results of this investigation."
Building: West Hall
Event Type: Lecture / Discussion
Tags: Astronomy
Source: Happening @ Michigan from Department of Astronomy, Michigan Institute for Research in Astrophysics