Ligo, Virgo, Kagra and Beyond: the Future of Ground-Based Gravitational- Wave Observatories

The Space Astrophysics Landscape 2019 (LPI Contrib. No. 2135) 5021.pdf LIGO, VIRGO, KAGRA AND BEYOND: THE FUTURE OF GROUND-BASED GRAVITATIONAL- WAVE OBSERVATORIES. Peter S. Shawhan1 for the LIGO Scientific Collaboration and the Virgo Collabora- tion, 1University of Maryland and Joint Space-Science Institute (4296 Stadium Drive, College Park, MD 20742- 2440), [email protected]. Introduction: Beginning with LIGO’s first direct sensitivity at the existing LIGO observatories. At the detection of a gravitational-wave (GW) signal, in 2015, same time, “third-generation” (3G) design studies are the LIGO and Virgo observatories have confidently exploring the benefits of new, larger observatories identified 11 GW signals so far [1]. Ten of these were which could reach an order of magnitude farther into binary black hole (BBH) mergers, with total system the universe, sampling the cosmological evolution of masses ranging from about 18 to 85 solar masses, and GW sources and what they can tell us about stellar and we are starting to get a picture of the population of galactic astrophysics over cosmic time. In all phases, black holes in merging binaries [2]. The remaining multi-messenger science with astrophysics missions event was the spectacular binary neutron star (BNS) and observing facilities will significantly extend the merger GW170817 [3], which was accompanied by a scientific reach beyond what can be learned from gravi- short-hard gamma-ray burst [4], a distinctive “kilono- tational waves alone. va” light curve signature traced out by UV/visible/IR References: [1] B. P. Abbott et al. (2018), submit- telescopes around the world for weeks, and afterglow ted to PRX, arXiv:1811.12907. [2] B. P. Abbott et al. emission detectable in X-ray and radio for months [5]. (2018), submitted to ApJ, arXiv:1811.12940. [3] B. P. This event proved the rich possibilities of multi- Abbott et al. (2017), PRL, 119, 161101. [4] B. P. Ab- messenger astronomy involving gravitational-wave bott et al. (2017), ApJL, 848, L13. [5] B. P. Abbott et events. al. (2017), ApJL, 848, L12. The Advanced LIGO and Virgo observatories are planning to begin their third observing run, O3, in April 2019, with better sensitivities and thus an expec- tation that many more GW events will be detected in this ~year-long run. The rate of BBH mergers is now reasonably well known, but the rate of BNS mergers still has a large uncertainty. It remains to be seen how many events will lead to multi-messenger observations and whether any new source type(s) will be detected, such as a neutron-star–black-hole binary or a transient signal not from a binary merger. The KAGRA detector in Japan is being commissioned with the goal of join- ing LIGO and Virgo for the last part of the O3 run, in early 2020. The Future: An upgrade project called A+ is now getting started to extend the range of the LIGO detec- tors with targeted technology improvements (better mirror coatings and frequency-dependent squeezing), and a corresponding upgrade, AdV+, is planned for Virgo. Construction of a third LIGO observatory, in India, is scheduled to begin soon and the observatory is projected to come online in 2025. Thus, by the mid- 2020s there will be five highly sensitive observatories operating as a coherent network. With a substantial rate of detected events, excellent all-sky response and good localization, this network will offer many oppor- tunities for multi-messenger science with astronomical facilities on the ground and in orbit. Designs are now being studied for substantially up- graded interferometers with silicon mirror substrates and farther-infrared lasers which could achieve greater .

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