Project C2

"Interpretation of Gravitational Wave Signals"

In the observational part of this project we investigate very young, oscillating neutron stars, precessing neutron stars and old binary neutron stars that are the most prominent sources of gravitational waves. We also investigate the birth rate of neutron stars that is enhanced in the so-called Gould Belt, a torus-like structure around the Sun younger than 50 million years with several thousand stars including both young neutron stars and supernova progenitors. Here, the goal is a clear prediction of the neutron stars birth rate and the fraction of neutron star-neutron star binaries in the Gould Belt.

The goal of project C2 is the detection of gravitational wave (GW) signals in detector data, or signicant upper limits constraining, e.g. neutron star physics. We will predict small regions on the sky with significantly more neutron stars. For such regions, data from current GW detectors (like GEO600, LIGO or VIRGO) can be investigated in much more detail than for the blind searches. Following these predictions we will study the feasibility and requirements for a search on the most sensitive data available at the time and perform such search.

From luminosity and temperature of supernova progenitors we calculate their masses and ages and finally residual lifetimes that enable us to predict a spatial and temporal super nova rate for the next few Myrs, that should be comparable in the last few Myrs.

Supernova rate within 600 pc estimated by us, including the Gould Belt (torus like structure of clusters of massive stars, see Poppel 1997), in the near future. Dashed lines: SN in the past 10 Myrs (Grenier 2000), see Hohle, Neuhäuser & Schutz, 2010, AN 331, 349.

Spatially distributed supernova rate. The distribution of the supernova rate for the next 10 Myrs including all massive stars within 600 pc are shown. The colours indicate the normalised rate per Myr and square bin (longitude and latitude both divided into 25 bins). Note, that the supernova rate per area in Orion is 2 to 3 times higher than for the other clusters, see Hohle, Neuhäuser & Schutz, 2010, AN 331, 349.

Our goals are:

• Prediction of small areas on the sky with enhanced probability for supernovae, young neutron stars and gravitational wave events.
• The data set used in Hohle, Neuhäuser & Schutz, 2010, AN 331, 349  will be enlarged to all massive stars within 5 kpc to derive the spatially and temporal supernova rate.
• Most massive stars are formed in a multiple system that will be destroyed after the supernova event, i.e. create runaway stars. We will compile a list of all young runaway stars within 5 kpc to trace them back to their origins (Monte Carlo simulation). We applied this method successfully to determine kinematic ages of radio-quiet neutron stars (Tetzlaff et al. 2009, MNRAS 400, L99; 2010, MNRAS 402, 2369; 2011, MNRAS 417, 617).
• We will also trace back fast-moving neutron stars to their birth places.
• We will compile a catalog of all known supernova remnants.
• Supernova events form radioactivities (²⁶Al, ⁶⁰Fe) with life times of some 10⁵to 10⁶ years detectable due to Gamma-ray emission.

These different evidences point to birth sites of young neutron stars that can be still present near their birth sites, i.e. we will predict the spatial distribution of young neutron stars, including possibly oscillating, precessing and/or accreting neutron stars, among the most prominent sources of gravitational wave signals. Our star sample also delivered data (massive binaries) for the SFB project B6, see Bauswein, ..., Hohle & Neuhäuser, 2009, PRL 103, 1101.

• We will investigate individual compact objects yielding significant constrains on gravitational wave emission (Wette et al. 2008), such as probably precessing neutron stars (Hohle et al. 2009, A&A 498, 811), young isolated neutron stars, central compact objects, supernova remnants. These young nearby neutron stars may emit gravitational waves due to precession, oscillation, and fast spinning if they have an elliptic shape.