Dark Matter Hot Spots and Neutrino Telescopes

We perform a new dark matter hot spot analysis using ten years of public IceCube data. In this analysis we assume dark matter self-annihilates to neutrino pairs and treat the production sites as discrete point sources. For neutrino telescopes these sites will appear as hot spots in the sky, possibly outshining other standard model neutrino sources. Comparing to galactic center analyses, we show that this approach is a powerful tool and capable of setting the highest neutrino detector limits for dark matter masses between 10 TeV and 100 PeV. This is due to the inclusion of spatial information in addition to the typically used energy deposition in the analysis.

Multiple Star Systems in the Orion Nebula

This work presents an interferometric study of the massive-binary fraction in the Orion Trapezium Cluster with the recently comissioned GRAVITY instrument. We observe a total of 16 stars of mainly OB spectral type. We find three previously unknown companions for $theta ^1$ Ori B, $theta ^2$ Ori B, and $theta ^2$ Ori C. We determine a separation for the previously suspected companion of NU Ori. We confirm four companions for $theta ^1$ Ori A, $theta ^1$ Ori C, $theta ^1$ Ori D, and $theta ^2$ Ori A, all with substantially improved astrometry and photometric mass estimates. We refine the orbit of the eccentric high-mass binary $theta ^1$ Ori C and we are able to derive a new orbit for $theta ^1$ Ori D. We find a system mass of 21.7 $M_{odot}$ and a period of $53$ days. Together with other previously detected companions seen in spectroscopy or direct imaging, eleven of the 16 high-mass stars are multiple systems. We obtain a total number of 22 companions with separations up to 600 AU. The companion fraction of the early B and O stars in our sample is about 2, significantly higher than in earlier studies of mostly OB associations. The separation distribution hints towards a bimodality. Such a bimodality has been previously found in A stars, but rarely in OB binaries, which up to this point have been assumed to be mostly compact with a tail of wider companions. We also do not find a substantial population of equal-mass binaries. The observed distribution of mass ratios declines steeply with mass, and like the direct star counts, indicates that our companions follow a standard power law initial mass function. Again, this is in contrast to earlier findings of flat mass ratio distributions in OB associations. We exclude collision as a dominant formation mechanism but find no clear preference for core accretion or competitive accretion.