The Puzzling Negative Orbit-Period Derivative of the Low-Mass X-Ray Binary 4u 1820-30 in NGC 6624

Peuten, M.; Brockamp, M.; Küpper, Andreas H. W.; Kroupa, Pavel

doi:10.1088/0004-637x/795/2/116

Cited by 26 publications

(56 citation statements)

References 63 publications

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“…We note that the enclosed mass within the radius of the MSP is lower than the inferred IMBH mass of Perera et al (2017a): M(< 0.41 ) = 646 +74 −163 M (and in three dimensions: M(< 0.41 ) = 362 +93 −199 M ). We therefore agree with the conclusion of Peuten et al (2014) that NGC 6624 has a population of centrally concentrated dark remnants. However, these authors did not present dynamical models.…”

Section: Discrete Modelssupporting

confidence: 92%

“…A convincing signal of an IMBH would be a measure of the gravitational acceleration in its vicinity, which can be obtained with timing observations. Peuten et al (2014) analysed the orbital period, P orb , of the low-mass X-ray binary (LMXB) 4U 1820-30 that sits at 1.3 from the centre in projection of the bulge GC NGC 6624. If there are no intrinsic binary processes changing the orbital period, then the period derivate,Ṗ orb , is due to a gravitational acceleration along the line-of-sight (a los ), which contributes toṖ orb asṖ orb /P = a los /c (Blandford et al 1987;Phinney 1993), where c is the speed of light and we assumed that a positive a los implies an acceleration away from the observer.…”

Section: Introductionmentioning

confidence: 99%

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Mass models of NGC 6624 without an intermediate-mass black hole

Gieles

Balbinot

Yaaqib

et al. 2017

Monthly Notices of the Royal Astronomical Society

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An intermediate-mass black hole (IMBH) was recently reported to reside in the centre of the Galactic globular cluster (GC) NGC 6624, based on timing observations of a millisecond pulsar (MSP) located near the cluster centre in projection. We present dynamical models with multiple mass components of NGC 6624 -without an IMBH -which successfully describe the surface brightness profile and proper motion kinematics from the Hubble Space Telescope (HST) and the stellar-mass function at different distances from the cluster centre. The maximum line-of-sight acceleration at the position of the MSP accommodates the inferred acceleration of the MSP, as derived from its first period derivative. With discrete realizations of the models we show that the higher-order period derivatives -which were previously used to derive the IMBH mass -are due to passing stars and stellar remnants, as previously shown analytically in literature. We conclude that there is no need for an IMBH to explain the timing observations of this MSP.

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Section: Discrete Modelssupporting

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Mass models of NGC 6624 without an intermediate-mass black hole

Gieles

Balbinot

Yaaqib

et al. 2017

Monthly Notices of the Royal Astronomical Society

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“…Finally, we cannot exclude the existence of an additional source near the centre of the globular cluster (located at 18:23:40.51, -30:21:39.7 ± 0.1 , Goldsbury et al 2010), which is not resolved within the ALMA or ATCA beams (see, e.g. Peuten et al 2014, for suggestions of a large number of dark remnants in the central region of the cluster). Such potential source could significantly contribute at the ALMA band but not at the radio or X-ray bands, which would remain dominated by the emission from 4U 1820−30.…”

Section: U 1820−30mentioning

confidence: 98%

ALMA observations of 4U 1728−34 and 4U 1820−30: first detection of neutron star X-ray binaries at 300 GHz

Trigo¹,

Migliari

Miller-Jones

et al. 2017

A&A

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We report on the first observations of neutron star low-mass X-ray binaries with the Atacama Large Millimeter/submillimeter Array (ALMA) at ∼300 GHz. Quasi-simultaneous observations of 4U 1728−34 and 4U 1820−30 were performed at radio (ATCA), infrared (VLT) and X-ray (Swift) frequencies, spanning more than eight decades in frequency coverage. Both sources are detected at high significance with ALMA. The spectral energy distribution of 4U 1728−34 is consistent with synchrotron emission from a jet with a break from optically thick to optically thin emission at 1.3-11.0×10 13 Hz. This is the third time a jet spectral break has been reported for a neutron star X-ray binary. The radio to mm spectral energy distribution of 4U 1820−30 has significant detections at 5 and 300 GHz. This confirms the presence of radio emission during a soft state for this neutron star and represents the first detection of mm emission during such a state, unambiguously pointing to the presence of a jet. We also report on three additional unrelated sources -showing mm emission -in the ALMA fields of view of 4U 1728−34 and 4U 1820−30.

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“…We therefore conclude that the mass fraction of stellar-mass black holes that we found from the N-body models is, within the model uncertainties, in agreement with the expected fraction based on recent models for the evolution of massive stars. Peuten et al (2014) analysed 16 yr of timing data of the low-mass X-ray binary (LMXB) 4U 1820-30 that is located close to the centre of NGC 6624 and found that this LMXB has a strongly negative period derivative. They suggested that an acceleration of the star along the line of sight due to either a dark concentration of remnants or an IMBH could be responsible for creating this period change.…”

Section: Implication For the Initial Stellar-mass Black Hole Retentiomentioning

confidence: 99%

No evidence for intermediate-mass black holes in the globular clusters ω Cen and NGC 6624

Baumgardt

Sweet

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We compare the results of a large grid of N-body simulations with the surface brightness and velocity dispersion profiles of the globular clusters ω Cen and NGC 6624. Our models include clusters with varying stellar-mass black hole retention fractions and varying masses of a central intermediate-mass black hole (IMBH). We find that an ∼ 45 000 M IMBH, whose presence has been suggested based on the measured velocity dispersion profile of ω Cen, predicts the existence of about 20 fast-moving, m > 0.5 M , main-sequence stars with a (1D) velocity v > 60 km s −1 in the central 20 arcsec of ω Cen. However, no such star is present in the HST/ACS proper motion catalogue of Bellini et al. (2017), strongly ruling out the presence of a massive IMBH in the core of ω Cen. Instead, we find that all available data can be fitted by a model that contains 4.6 per cent of the mass of ω Cen in a centrally concentrated cluster of stellar-mass black holes. We show that this mass fraction in stellar-mass BHs is compatible with the predictions of stellar evolution models of massive stars. We also compare our grid of N-body simulations with NGC 6624, a cluster recently claimed to harbour a 20 000 M black hole based on timing observations of millisecond pulsars. However, we find that models with M IMBH > 1000 M IMBHs are incompatible with the observed velocity dispersion and surface brightness profile of NGC 6624, ruling out the presence of a massive IMBH in this cluster. Models without an IMBH provide again an excellent fit to NGC 6624.

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The Puzzling Negative Orbit-Period Derivative of the Low-Mass X-Ray Binary 4u 1820-30 in NGC 6624

Cited by 26 publications

References 63 publications

Mass models of NGC 6624 without an intermediate-mass black hole

Mass models of NGC 6624 without an intermediate-mass black hole

ALMA observations of 4U 1728−34 and 4U 1820−30: first detection of neutron star X-ray binaries at 300 GHz

No evidence for intermediate-mass black holes in the globular clusters ω Cen and NGC 6624

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