UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS

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Conference: Bucharest University Faculty of Physics 2021 Meeting


Section: Atomic and Molecular Physics. Astrophysics. Applications


Title:
New growth mechanism for black holes and implications for future gravitational wave experiments


Authors:
Răzvan A. BALAȘOV (1,2), Laurențiu I. CARAMETE (1)


*
Affiliation:
1) Institute of Space Science (ISS)

2) Faculty of Physics (University of Bucharest)


E-mail
rabalasov@spacescience.ro


Keywords:
massive black hole star cluster growth accretion merging rate


Abstract:
The future gravitational waves observatories, including ESA’s LISA Space Mission, will study the merging black holes (BHs) processes in great detail and also will shed light on the evolution of the BH masses. In order to estimate the detection rates for the future gravitational wave observatories, we conducted simulations to study the growth process [1-2]. Here, we describe the results of our investigations for a new implementation regarding the BH growth, star gulping (SG), in which stars are absorbed by BHs [3]. There are two main mechanisms for the growth of BHs, accretion of surrounding material and merging with another BH [4-9]. Both must be taken into account when one tries to model the growth processes of the most massive BHs (MBHs) from the moment of their origin to the present. Extensive studies and our own simulations showed that even if you consider these processes at their maximum, it is very difficult to grow BHs to the masses that we measure today. So, we performed detail simulations to study another growth mechanism, SG, that has the potential to add more mass to BHs. Our simulation setup is the following: we start with a Plummer distribution of stars in a star cluster and we perform simulations without a central BH and, afterwards, with a central BH of 10^8 solar masses. We used the only star simulation as a base line to study the potential of stars to travel, in a normal star evolution scenario, close to the center of the star cluster and to enter a gravitational influence sphere generated by a 10^8 solar mass BH. This gave us a simple linear grow potential, the number of stars that enter the gravitational influence sphere increase linearly with time. When we place a BH in the center of our star cluster, the number of stars diminishes and the rate of growth for the BH is a direct characterization of how the star cluster is affected by the newly introduced gravitational potential. This new growth mechanism can affect not only the rate of merger, but also the overall evolution history of BHs and so it is very important to study it in great detail.


References:

[1] Balasov, R. A., & Caramete, L. I. (2020). Simulations and analysis of the first black hole populations. Rom. Rep. Phys., 72(3), 114.

[2] Caramete, L. I., & Balasov, R. A. (2021). Study of the first populations of black holes in the context of gravitational wave observations (in prep.)

[3] Rees, M. J., “Tidal disruption of stars by black holes of 10^6 - 10^8 solar masses in nearby galaxies”. Nature. vol. 333, no. 6173, pp. 523–528, 1988. doi:10.1038/333523a0

[4] Hawking, S. (1971). Gravitationally Collapsed Objects of Very Low Mass. Monthly Notices of the Royal Astronomical Society, 152(1), 75–78. doi:10.1093/mnras/152.1.75.

[5] Carr, B. J., & Hawking, S. W. (1974). Black Holes in the Early Universe. Monthly Notices of the Royal Astronomical Society, 168(2), 399–415. doi:10.1093/mnras/168.2.399.

[6] Chapline, G. F. (1975). Cosmological effects of primordial black holes. 253(5489), 251–252. doi:10.1038/253251a0.

[7] Rees, M. J., & Volonteri, M. (2007). Massive black holes: formation and evolution. In V. Karas, & G. Matt (Eds.), Black Holes from Stars to Galaxies – Across the Range of Masses (pp. 51–58). volume 238. doi:10.1017/ S1743921307004681. arXiv:astro-ph/0701512.

[8] Green, A. M. (2015). Primordial black holes: Sirens of the early universe. In X. Calmet (Ed.), Quantum Aspects of Black Holes (pp. 129–149). Cham: Springer International Publishing. URL: https://doi.org/10.1007/ 978-3-319-10852-0_5. doi:10.1007/978-3-319-10852-0_5.

[9] Sasaki, M., Suyama, T., Tanaka, T., & Yokoyama, S. (2018). Primordial black holes—perspectives in gravitational wave astronomy. Classical and Quantum Gravity, 35(6), 063001. doi:10.1088/1361-6382/aaa7b4. arXiv:1801.05235.

Acknowledgement:
This work was supported by the ESA PRODEX project DSLISALLP and by the LAPLAS VI project. The results reported here were obtained using the Scientific Computing Facilities of the Institute of Space Science.