Probing dark contents in globular clusters with timing effects of pulsar acceleration

Abstract We investigate pulsar timing residuals due to the coupling effect of the pulsar transverse acceleration and the Römer delay. The effect is relatively small and usually negligible. Only for pulsars in globular clusters, it is possibly important. The maximum residual amplitude, which is from the pulsar near the surface of the core of the cluster, is about tens of nanoseconds, and may hardly be identified for most globular clusters currently. However, an intermediate-mass black hole in the center of a cluster can apparently increase the timing residual magnitudes. Particularly for pulsars in the innermost core region, their residual magnitudes may be significant. The high-magnitude residuals, which are above critical lines of each cluster, are strong evidence for the presence of a black hole or dark remnants of comparable total mass in the center of the cluster. We also explored the timing effects of line-of-sight accelerations for the pulsars. The distribution of measured line-of-sight accelerations are simulated with a Monte Carlo method. Two-dimensional Kolmogorov-Smirnov tests are performed to reexamine the consistency of distributions of the simulated and reported data for various values of parameters of the clusters. It is shown that the structure parameters of Terzan 5 can be constrained well by comparing the distribution of measured line-of-sight accelerations with the distributions from Monte Carlo simulations. We find that the cluster has an upper limit on the central black hole/dark remnant mass of ∼ 6000 M ⊙.

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Glimpses of the past activity of Sgr A★ inferred from X-ray echoes in Sgr C

Astronomy and Astrophysics ◽

10.1051/0004-6361/201731864 ◽

2018 ◽

Vol 610 ◽

pp. A34 ◽

Cited By ~ 6

Author(s):

D. Chuard ◽

R. Terrier ◽

A. Goldwurm ◽

M. Clavel ◽

S. Soldi ◽

...

Keyword(s):

Monte Carlo ◽

Black Hole ◽

Monte Carlo Model ◽

Line Of Sight ◽

X Rays ◽

X Ray ◽

Supermassive Black Hole ◽

The Past ◽

Sgr A ◽

Past Activity

Context. For a decade now, evidence has accumulated that giant molecular clouds located within the central molecular zone of our Galaxy reflect X-rays coming from past outbursts of the Galactic supermassive black hole. However, the number of illuminating events as well as their ages and durations are still unresolved questions. Aims. We aim to reconstruct parts of the history of the supermassive black hole Sgr A★ by studying this reflection phenomenon in the molecular complex Sgr C and by determining the line-of-sight positions of its main bright substructures. Methods. Using observations made with the X-ray observatories XMM-Newton and Chandra and between 2000 and 2014, we investigated the variability of the reflected emission, which consists of a Fe Kα line at 6.4 keV and a Compton continuum. We carried out an imaging and a spectral analysis. We also used a Monte Carlo model of the reflected spectra to constrain the line-of-sight positions of the brightest clumps, and hence to assign an approximate date to the associated illuminating events. Results. We show that the Fe Kα emission from Sgr C exhibits significant variability in both space and time, which confirms its reflection origin. The most likely illuminating source is Sgr A★. On the one hand, we report two distinct variability timescales, as one clump undergoes a sudden rise and fall in about 2005, while two others vary smoothly throughout the whole 2000–2014 period. On the other hand, by fitting the Monte Carlo model to the data, we are able to place tight constraints on the 3D positions of the clumps. These two independent approaches provide a consistent picture of the past activity of Sgr A★, since the two slowly varying clumps are located on the same wavefront, while the third (rapidly varying) clump corresponds to a different wavefront, that is, to a different illuminating event. Conclusions. This work shows that Sgr A★ experienced at least two powerful outbursts in the past 300 yrs, and for the first time, we provide an estimation of their age. Extending this approach to other molecular complexes, such as Sgr A, will allow this two-event scenario to be tested further.

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Pulsar Timing and the Detection of Black Hole Binary Systems in Globular Clusters

The Astrophysical Journal ◽

10.1086/431949 ◽

2005 ◽

Vol 627 (2) ◽

pp. L125-L128 ◽

Cited By ~ 9

Author(s):

Fredrick A. Jenet ◽

Teviet Creighton ◽

Andrea Lommen

Keyword(s):

Black Hole ◽

Globular Clusters ◽

Binary Systems ◽

Pulsar Timing ◽

Black Hole Binary

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The Imprints of IMBHs on the Structure of Globular Clusters: Monte-Carlo Simulations

Proceedings of the International Astronomical Union ◽

10.1017/s1743921308015913 ◽

2007 ◽

Vol 3 (S246) ◽

pp. 351-355 ◽

Cited By ~ 1

Author(s):

Stefan Umbreit ◽

John M. Fregeau ◽

Frederic A. Rasio

Keyword(s):

Monte Carlo ◽

Black Hole ◽

Mass Spectrum ◽

Monte Carlo Simulations ◽

Stellar Evolution ◽

Globular Clusters ◽

Three Dimensional ◽

Central Black Hole ◽

The Core ◽

First Results

AbstractWe present the first results of a series of Monte-Carlo simulations investigating the imprints of a central black hole on the core structure of globular clusters. We investigate the three-dimensional and the projected density profile of the inner regions of idealized as well as more realistic globular cluster models, taking into account a stellar mass spectrum, stellar evolution and allowing for a larger, more realistic, number of stars than was previously possible with direct N-body methods. We compare our results to other N-body simulations published previously in the literature.

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Gravitational Waves

10.1093/oso/9780198570899.001.0001 ◽

2018 ◽

Cited By ~ 33

Author(s):

Michele Maggiore

Keyword(s):

Black Hole ◽

Perturbation Theory ◽

Gravitational Waves ◽

Transfer Functions ◽

Normal Modes ◽

Cosmological Perturbation ◽

Tests Of General Relativity ◽

Pulsar Timing ◽

Tensor Perturbations ◽

Stochastic Backgrounds

A comprehensive and detailed account of the physics of gravitational waves and their role in astrophysics and cosmology. The part on astrophysical sources of gravitational waves includes chapters on GWs from supernovae, neutron stars (neutron star normal modes, CFS instability, r-modes), black-hole perturbation theory (Regge-Wheeler and Zerilli equations, Teukoslky equation for rotating BHs, quasi-normal modes) coalescing compact binaries (effective one-body formalism, numerical relativity), discovery of gravitational waves at the advanced LIGO interferometers (discoveries of GW150914, GW151226, tests of general relativity, astrophysical implications), supermassive black holes (supermassive black-hole binaries, EMRI, relevance for LISA and pulsar timing arrays). The part on gravitational waves and cosmology include discussions of FRW cosmology, cosmological perturbation theory (helicity decomposition, scalar and tensor perturbations, Bardeen variables, power spectra, transfer functions for scalar and tensor modes), the effects of GWs on the Cosmic Microwave Background (ISW effect, CMB polarization, E and B modes), inflation (amplification of vacuum fluctuations, quantum fields in curved space, generation of scalar and tensor perturbations, Mukhanov-Sasaki equation,reheating, preheating), stochastic backgrounds of cosmological origin (phase transitions, cosmic strings, alternatives to inflation, bounds on primordial GWs) and search of stochastic backgrounds with Pulsar Timing Arrays (PTA).

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Intermediate-mass black holes in globular clusters: observations and simulations - Update

Proceedings of the International Astronomical Union ◽

10.1017/s1743921315010601 ◽

2015 ◽

Vol 12 (S316) ◽

pp. 240-245

Author(s):

Nora Lützgendorf ◽

Markus Kissler-Patig ◽

Karl Gebhardt ◽

Holger Baumgardt ◽

Diederik Kruijssen ◽

...

Keyword(s):

Black Holes ◽

Black Hole ◽

Globular Clusters ◽

Galactic Center ◽

Early Stage ◽

Life Time ◽

Intermediate Mass ◽

Software Environment ◽

Integral Field ◽

Intermediate Mass Black Holes

AbstractThe study of intermediate-mass black holes (IMBHs) is a young and promising field of research. If IMBH exist, they could explain the rapid growth of supermassive black holes by acting as seeds in the early stage of galaxy formation. Formed by runaway collisions of massive stars in young and dense stellar clusters, intermediate-mass black holes could still be present in the centers of globular clusters, today. We measured the inner kinematic profiles with integral-field spectroscopy for 10 Galactic globular cluster and determined masses or upper limits of central black holes. In combination with literature data we further studied the positions of our results on known black-hole scaling relations (such as M• − σ) and found a similar but flatter correlation for IMBHs. Applying cluster evolution codes, the change in the slope could be explained with the stellar mass loss occurring in clusters in a tidal field over its life time. Furthermore, we present results from several numerical simulations on the topic of IMBHs and integral field units (IFUs). N-body simulations were used to simulate IFU data cubes. For the specific case of NGC 6388 we simulated two different IFU techniques and found that velocity dispersion measurements from individual velocities are strongly biased towards lower values due to blends of neighbouring stars and background light. In addition, we use the Astrophysical Multipurpose Software Environment (AMUSE) to combine gravitational physics, stellar evolution and hydrodynamics to simulate the accretion of stellar winds onto a black hole. We find that the S-stars need to provide very strong winds in order to explain the accretion rate in the galactic center.

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MOCCA-Survey Database – I. Unravelling black hole subsystems in globular clusters

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/sty1859 ◽

2018 ◽

Vol 479 (4) ◽

pp. 4652-4664 ◽

Cited By ~ 38

Author(s):

Manuel Arca Sedda ◽

Abbas Askar ◽

Mirek Giersz

Keyword(s):

Black Hole ◽

Globular Clusters

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Central Dynamics of Globular Clusters: the Case for a Black Hole in ω Centauri

Proceedings of the International Astronomical Union ◽

10.1017/s1743921308015895 ◽

2007 ◽

Vol 3 (S246) ◽

pp. 341-345

Author(s):

Eva Noyola ◽

Karl Gebhardt ◽

Marcel Bergmann

Keyword(s):

Black Hole ◽

Relaxation Time ◽

Globular Cluster ◽

Globular Clusters ◽

Dwarf Galaxy ◽

Kinematic Data ◽

The Core ◽

Galactic System ◽

Interesting Candidate ◽

Radial Anisotropy

AbstractThe globular cluster ω Centauri is one of the largest and most massive members of the Galactic system. Its classification as a globular cluster has been challenged making it a candidate for being the stripped core of an accreted dwarf galaxy; this and the fact that it has one of the largest velocity dispersions for star clusters in our galaxy makes it an interesting candidate for harboring an intermediate mass black hole. We measure the surface brightness profile from integrated light on an HST/ACS image, and find a central power-law cusp of logarithmic slope -0.08. We also analyze Gemini GMOS-IFU kinematic data for a 5”x5” field centered on the nucleus of the cluster, as well as for a field 14″ away. We detect a clear rise in the velocity dispersion from 18.6 kms−1 at 14″ to 23 kms−1 in the center. Given the very large core in ω Cen (2.58'), an increase in the dispersion in the central 10″ is difficult to attribute to stellar remnants, since it requires too many dark remnants and the implied configuration would dissolve quickly given the relaxation time in the core. However, the increase could be consistent with the existence of a central black hole. Assuming a constant M/L for the stars within the core, the dispersion profile from these data and data at larger radii implies a black hole mass of 4.0+0.75−1.0×104M⊙. We have also run flattened, orbit-based models and find a similar mass. In addition, the no black hole case for the orbit model requires an extreme amount of radial anisotropy, which is difficult to preserve given the short relaxation time of the cluster.

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