A search for binaries with massive companions in the core of the closest globular cluster M4
Abstract
We propose to constrain the number of binaries with massive companions {black holes, neutron stars, or white dwarfs} in the core of M4 by measuring the "wobble" of the bright {main-sequence} companion around the center of mass of the pair. The wobble will be measured by leveraging the high-precision spatial resolution of WFC3/UVIS with our expertise in high-accuracy astrometry on HST images. We will constrain the total number of binaries with massive companions and periods between 0.5 months < P < 15 years. Mass segregation predicts these binaries should be strongly concentrated in the core and we will measure their radial distribution. Moreover, as a by-product, we can identify and measure the mass of a central black hole, if this cluster happens to host one. This proposal will complement other ongoing investigations on the binary population in M4, and will allow us to construct a dynamical model of the cluster to help us understand why its core is not collapsed.Stellar-mass black holes, neutron stars, and white dwarfs must form as a result of normal stellar evolution, and we have designed this program to leave no chance of failing to see their influence on their binary companions.
- Publication:
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HST Proposal
- Pub Date:
- October 2012
- Bibcode:
- 2012hst..prop12911B