Changes in the 11 minute period of 4U 1820 - 30

Tan, J.; Morgan, E.; Lewin, W. H. G.; Penninx, W.; Klis, M. van der; Paradijs, J. van; Makishima, K.; Inoue, H.; Dotani, Tadayasu; Mitsuda, K.

doi:10.1086/170118

Cited by 25 publications

(43 citation statements)

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“…The extremely short orbital period implies that the secondary star is a low-mass helium-rich degenerate star (see Rappaport et al 1987). Subsequent observations with Ginga showed that the 685-s period is decreasing on a time scale of ~ 107 years (Sansom et al 1989;Tan et al 1991b; Van der Klis et al 1992), likely caused by gravitational acceleration in the cluster potential or by a distant third companion in a hierarchical triple see also Tavani 1991).…”

Section: -12mentioning

confidence: 99%

X-ray bursts

1993

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Section: -12mentioning

confidence: 99%

X-ray bursts

1993

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“…In this table we also list the timescales for the orbital period changes for the three compact systems based on the sequences shown in Figure 16 as well as on a simple model where the secondary is a fully degenerate He white dwarf and the system is driven by gravitational radiation alone (labeled "" GR ÏÏ). The 11 minute system (4U 1820[30 \ X1820[303) is particularly interesting since its orbital period is decreasing rather than increasing (Tan et al 1991), as would be expected for a fully degenerate secondary. While it had been argued that this apparent orbital period decrease could be caused by gravitational acceleration within the globular cluster (Tan et al 1991), van der Klis et al (1993) subsequently concluded that, using a more realistic mass model for the globular cluster NGC 6624, it was unlikely that the negative could P0 be fully explained by cluster acceleration.…”

Section: Ultracompact X-ray Binariesmentioning

confidence: 99%

“…The 11 minute system (4U 1820[30 \ X1820[303) is particularly interesting since its orbital period is decreasing rather than increasing (Tan et al 1991), as would be expected for a fully degenerate secondary. While it had been argued that this apparent orbital period decrease could be caused by gravitational acceleration within the globular cluster (Tan et al 1991), van der Klis et al (1993) subsequently concluded that, using a more realistic mass model for the globular cluster NGC 6624, it was unlikely that the negative could P0 be fully explained by cluster acceleration. On the other hand, as Table 1 shows, the theoretical in sequence (c) P/P0 (red) is in excellent agreement with the observed value, and the value in sequence (d) (blue) is in reasonable agreement (Fedorova & Ergma 1989 obtained similar values).…”

Section: Ultracompact X-ray Binariesmentioning

confidence: 99%

Evolutionary Sequences for Low‐ and Intermediate‐Mass X‐Ray Binaries

Podsiadlowski

Rappaport

Pfahl

2002

ApJ

520

623

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We present the results of a systematic study of the evolution of low-and intermediate-mass X-ray binaries (LMXBs and IMXBs). Using a standard Henyey-type stellar evolution code and a standard model for binary interactions, we have calculated 100 binary evolution sequences containing a neutron star and a normal-type companion star, where the initial mass of the secondary ranges from 0.6 to 7 M _ and the initial orbital period from D4 hr to D100 days. This range samples the entire range of parameters one is likely to encounter for LMXBs and IMXBs. The sequences show an enormous variety of evolutionary histories and outcomes, where di †erent mass transfer mechanisms dominate in di †erent phases. Very few sequences resemble the classical evolution of cataclysmic variables, where the evolution is driven by magnetic braking and gravitational radiation alone. Many systems experience a phase of mass transfer on a thermal timescale and may brieÑy become detached immediately after this phase (for the more massive secondaries). In agreement with previous results (Tauris & Savonije 1999), we Ðnd that all sequences with (sub)giant donors up to D2 are stable against dynamical mass transfer. Sequences M _ where the secondary has a radiative envelope are stable against dynamical mass transfer for initial masses up to D4 For higher initial masses, they experience a delayed dynamical instability after a M _ . stable phase of mass transfer lasting up to D106 yr. Systems where the initial orbital period is just below the bifurcation period of D18 hr evolve toward extremely short orbital periods (as short as D10 minutes). For a 1 secondary, the initial period range that leads to the formation of ultracompact M _ systems (with minimum periods less than D40 minutes) is 13È18 hr. Since systems that start mass transfer in this period range are naturally produced as a result of tidal capture, this may explain the large fraction of ultracompact LMXBs observed in globular clusters. The implications of this study for our understanding of the population of X-ray binaries and the formation of millisecond pulsars are also discussed.

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“…Following Chou & Grindlay (2001), we chose 32 phase bins, as varying this value did not give any improvements. Afterwards, these light curves were finally folded with the ephemeris by Tan et al (1991):…”

Section: Data Reductionmentioning

confidence: 99%

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

Peuten

Brockamp

Küpper

et al. 2014

ApJ

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4U 1820-30 is a low-mass X-ray binary near the center of the globular cluster NGC 6624 consisting of, at least, one neutron star and one helium white dwarf. Analyzing 16 years of data from the Rossi X-ray Timing Explorer (RXTE) allows us to measure its orbital period and its time derivative with unprecedented accuracy to be P = 685.01197 ± 0.00003 s andṖ /P = −5.3 ± 0.3 × 10 −8 yr −1 . Hence, we confirm that the period derivative is significantly negative at the > 17σ level, contrary to theoretical expectations for an isolated X-ray binary. We discuss possible scenarios that could explain this discrepancy, and conclude that the center of NGC 6624 most likely contains large amounts of non-luminous matter such as dark remnants. We also discuss the possibility of an IMBH inside NGC 6624, or that a dark remnant close to 4U 1820-30 causes the observed shift.

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Changes in the 11 minute period of 4U 1820 - 30

Cited by 25 publications

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X-ray bursts

X-ray bursts

Evolutionary Sequences for Low‐ and Intermediate‐Mass X‐Ray Binaries

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

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