Stellar Remnants at the Junction

There is a meeting on Comparing Accreating White Dwarfs, Neutron Stars, and Black Holes in the Junction, Texas, USA. Dr. Natalie Webb ask me to write a short abstract for the meeting.

Globular clusters are compact group of stars, probably remnants of early star formation from when our own galaxy was forming. Due to their age and the nature of the gravitational interaction dominating the dynamics of the members, they are predicted to have a significant fraction of binaries in them. Many of these binaries are known to be formed from compact objects, hosts of strong accretion disks. The formation and evolution of these kind of binaries is still not completely understood, but globular clusters constitute perfect nearby laboratories to try to better understand their nature.

Of special interest is the globular cluster NGC 6397. It constitutes the seconds closest globular cluster from Earth. This cluster have been extensively studied in different wavelengths with instruments like XMM, Chandra, Hubble Space telescope, and more recently in the optical with the Multi Unit Spectroscopic Explorer (MUSE). Integral field spectrographs, like MUSE, has some advantages compare to traditional long slit spectroscopy. MUSE field of view allow us to acquire longer wavelength range of complete stellar populations within the cluster.

This work explores the possibility to analyze the obtained spectra by MUSE of the cataclysmic variables population in NGC 6397. The goal is to further understand the characteristics of the proposed bimodal population of cataclysmic in the cluster. We are particularly interest in studying in detail the signs of accretion in these spectra, e.g. H\(\alpha\) and He lines, to get further insight into the nature of the accretion disks present in this binary population. This way we hope to extent to CVs in globular cluster the know relation for fields CVs of the double peak H\(\alpha\) emission to mass ratio.

After a word with Dr. Webb:

Globular clusters are very old groups of stars. Due to their age and the gravitational interactions dominating the dynamics of the clusters, they are home to a significant fraction of compact binaries. The formation and evolution of these kinds of binaries is still not completely understood.

Of special interest is the globular cluster NGC 6397 as it is the closest core collapsed cluster and has therefore been extensively studied with instruments like XMM, Chandra, Hubble Space Telescope, and more recently in the optical with the Multi Unit Spectroscopic Explorer (MUSE), installed on the Very Large Telescope (VLT). Integral field spectrographs, like MUSE, have many advantages compared to traditional long slit spectroscopy, as spectra are obtained for every pixel and thus every object in the large field of view (1’ x 1’).

Here we present analysis of the compact binary population in NGC 6397 taken with MUSE. The goal is to further understand the characteristics of the proposed bimodal population of cataclysmic variables in the cluster, which have been suggested to be of primordial and dynamically formed origin. Spectral analysis will allow us to examine the origin of these two populations.

The flight

Proposed flight:

https://www.kayak.fr/flights/PAR-SAT/2016-05-01/2016-05-07/f7d1a7597212dca19f0759f70e5056620

To arrive like Dr. Webb at San Antonio on Sunday and leave Saturday. 09h40 CDG 16h38 SAT 13h58 1 escale (ORD) 14h32 SAT 09h35 CDG 12h03 1 escale (DFW)

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