Since there is a large population of massive O/B stars and putative neutron stars （NSs） located in the vicinity of the Galactic Center （GC）, intermediate-mass X-ray binaries （IMXBs） constituted by an NS and a B-...Since there is a large population of massive O/B stars and putative neutron stars （NSs） located in the vicinity of the Galactic Center （GC）, intermediate-mass X-ray binaries （IMXBs） constituted by an NS and a B-type star probably exist there. We investigate the evolutions of accreting NSs in IMXBs （similar to M82 X-2） with a - 5.2 M companion and orbital period 2.53 d. By adopting a mildly super-Eddington rate M = 6 × 10-8 M yr-1 for the early Case B Roche-lobe overflow （RLOF） accretion, we find that only in accreting NSs with quite elastic crusts （slippage factor s = 0.05） can the toroidal magnetic fields be amplified within 1 Myr, which is assumed to be the longest duration of the RLOF. These IMXBs will evolve into NS＋white dwarf （WD） binaries if they are dynamically stable. However, before the formation of NS＋WD binaries, the high stellar density in the GC will probably lead to frequent encounters between the NS＋evolved star binaries （in post-early Case B mass transfer phase） and NSs or exchange encounters with other stars, which may produce single NSs. These NSs will evolve into magnetars when the amplified poloidal magnetic fields diffuse out to the NS surfaces. Consequently, our results provide a possible expianation for the origin of the GC magnetar SGR 1745-2900. Moreover, the accreting NSs with s 〉 0.05 will evolve into millisecond pulsars （MSPs）. Therefore, our model reveals that the GC magnetars and MSPs could both originate from a special kind of IMXB.展开更多
SGR J1745-2900 is a magnetar near the Galactic center. X-ray observations of this source found a decreasing X-ray luminosity accompanied by an enhanced spindown rate. This negative correlation between X-ray luminosity...SGR J1745-2900 is a magnetar near the Galactic center. X-ray observations of this source found a decreasing X-ray luminosity accompanied by an enhanced spindown rate. This negative correlation between X-ray luminosity and spindown rate is hard to understand. The wind braking model of magnetars is employed to explain this puzzling spindown behavior. During the release of magnetic energy of magnetars, a system of particles may be generated. Some of these particles remain trapped in the magnetosphere and may contribute to the X-ray luminosity. The rest of the particles can flow out and take away the rotational energy of the central neutron star. A smaller polar cap angle will cause the decrease of X-ray luminosity and enhanced spindown rate of SGR J1745-2900. This magnetar is shortly expected to have a maximum spindown rate.展开更多
Recently,the LHCb Collaboration reported their observation of the first two fully open-flavor tetraquark states named X_(0)(2900)and X_(1)(2900)with unknown parity.Inspired by the report,we consider all the possible f...Recently,the LHCb Collaboration reported their observation of the first two fully open-flavor tetraquark states named X_(0)(2900)and X_(1)(2900)with unknown parity.Inspired by the report,we consider all the possible fourquark candidates for X(2900),which include the molecular structure,diquark structure,and their coupling in a chiral quark model via the Gaussian expansion method.To identify the genuine resonances,the real-scaling method(stabilization method)was employed.Our results show that five possible resonances,R_(0)(2914)withΓ=42 MeV,R_(1)(2906)withΓ=29 MeV,R_(1)(2912)withΓ=10 McV,R_(J)(2920)withΓ=9 MeV,and R_(J)(2842)withΓ=24 MeV,originate in the csqq system.Compared with experimental data,R_(0)(2914)withΓ=42 MeV may be an optimal X_(0)(2900)candidate.However,none of the resonances have a similar width for X_(1)(2900).Hence,further study is required.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.11133002 and 11178001)
文摘Since there is a large population of massive O/B stars and putative neutron stars （NSs） located in the vicinity of the Galactic Center （GC）, intermediate-mass X-ray binaries （IMXBs） constituted by an NS and a B-type star probably exist there. We investigate the evolutions of accreting NSs in IMXBs （similar to M82 X-2） with a - 5.2 M companion and orbital period 2.53 d. By adopting a mildly super-Eddington rate M = 6 × 10-8 M yr-1 for the early Case B Roche-lobe overflow （RLOF） accretion, we find that only in accreting NSs with quite elastic crusts （slippage factor s = 0.05） can the toroidal magnetic fields be amplified within 1 Myr, which is assumed to be the longest duration of the RLOF. These IMXBs will evolve into NS＋white dwarf （WD） binaries if they are dynamically stable. However, before the formation of NS＋WD binaries, the high stellar density in the GC will probably lead to frequent encounters between the NS＋evolved star binaries （in post-early Case B mass transfer phase） and NSs or exchange encounters with other stars, which may produce single NSs. These NSs will evolve into magnetars when the amplified poloidal magnetic fields diffuse out to the NS surfaces. Consequently, our results provide a possible expianation for the origin of the GC magnetar SGR 1745-2900. Moreover, the accreting NSs with s 〉 0.05 will evolve into millisecond pulsars （MSPs）. Therefore, our model reveals that the GC magnetars and MSPs could both originate from a special kind of IMXB.
基金supported by the Xinjiang Bairen projectthe National Natural Science Foundation of China (NSFC, 11103021)+2 种基金West Light Foundation of CAS (LHXZ201201)Youth Innovation Promotion Association of CASthe National Basic Research Program of China (973 Program, 2015CB857100)
文摘SGR J1745-2900 is a magnetar near the Galactic center. X-ray observations of this source found a decreasing X-ray luminosity accompanied by an enhanced spindown rate. This negative correlation between X-ray luminosity and spindown rate is hard to understand. The wind braking model of magnetars is employed to explain this puzzling spindown behavior. During the release of magnetic energy of magnetars, a system of particles may be generated. Some of these particles remain trapped in the magnetosphere and may contribute to the X-ray luminosity. The rest of the particles can flow out and take away the rotational energy of the central neutron star. A smaller polar cap angle will cause the decrease of X-ray luminosity and enhanced spindown rate of SGR J1745-2900. This magnetar is shortly expected to have a maximum spindown rate.
基金Supported in part by the National Natural Science Foundation of China(11775118,11535005)。
文摘Recently,the LHCb Collaboration reported their observation of the first two fully open-flavor tetraquark states named X_(0)(2900)and X_(1)(2900)with unknown parity.Inspired by the report,we consider all the possible fourquark candidates for X(2900),which include the molecular structure,diquark structure,and their coupling in a chiral quark model via the Gaussian expansion method.To identify the genuine resonances,the real-scaling method(stabilization method)was employed.Our results show that five possible resonances,R_(0)(2914)withΓ=42 MeV,R_(1)(2906)withΓ=29 MeV,R_(1)(2912)withΓ=10 McV,R_(J)(2920)withΓ=9 MeV,and R_(J)(2842)withΓ=24 MeV,originate in the csqq system.Compared with experimental data,R_(0)(2914)withΓ=42 MeV may be an optimal X_(0)(2900)candidate.However,none of the resonances have a similar width for X_(1)(2900).Hence,further study is required.
