Beta decay of nuclides ~(56)Fe,~(62)Ni,~(64)Ni and ~(68)Ni in the crust of magnetars

By introducing the Dirac δ-function and Pauli exclusion principle in the presence of superstrong magnetic fields(SMFs), we investigate the influence of SMFs on beta decay and the change rates of electron fraction(CREF) of nuclides~(56)Fe,~(62)Ni,~(64)Ni and~(68)Ni in magnetars, which are powered by magnetic field energy. We find that the magnetic fields have a great influence on the beta decay rates, and the beta decay rates can decrease by more than six orders of magnitude in the presence of SMFs. The CREF also decreases by more than seven orders of magnitude in the presence of SMFs.     

Supernova β~- decay of nuclides ~(53)Fe,~(54)Fe,~(55)Fe and ~(56)Fe in strongly screened plasma

Electron screening has strong effects on electron energy and threshold energy of the beta decay reaction.In this paper,we study β~-decay rates of some iron isotopes.The beta decay rates increase by about two orders of magnitude due to electron screening.Strongly screened beta decay rates due to Q-value correction are more than one order of magnitude higher than those without Q-value correction.     

R-band host galaxy contamination of TeV γ-ray blazar Mrk 501: effects of aperture size and seeing

We simulated the R-band contribution of the host galaxy of TeV γ-ray BL Lac object Mrk 501 in different aperture sizes and seeing conditions. An intensive set of observations was acquired with the 1.02 m optical telescope, managed by Yunnan Observatories, from 2010 May 15 to 18. Based on the host subtraction data usually used in the literature, the subtraction of host galaxy contamination results in significant seeing-brightness correlations. These correlations would lead to illusive large amplitude variations at short timescales, which will mask the intrinsic microvariability, thus giving rise to difficulty in detecting the intrinsic microvariability. Both aperture size and seeing condition influence the flux measurements, but the aperture size impacts the result more significantly. Based on the parameters of an elliptical galaxy provided in the literature, we simulated the host contributions of Mrk 501 in different aperture sizes and seeing conditions. Our simulation data of the host galaxy obviously weaken these significant seeing-brightness correlations for the host-subtracted brightness of Mrk 501, and can help us discover the intrinsic short timescale microvariability. The pure nuclear flux is ~8.0 m Jy in the R band,i.e., the AGN has a magnitude of R ~13.96 mag.     

Observational evidence for the evolution of nuclear metallicity and star formation rate with the merger stage

We investigate the evolution of nuclear gas-phase oxygen abundance and star formation rate(SFR) of local far-infrared selected star-forming galaxies along the merger sequence, as traced by their optical morphologies. The sample was drawn from a cross-correlation analysis of the IRAS Point Source Catalog Redshift Survey and 1 Jy ultraluminous infrared galaxy sample with the Sloan Digital Sky Survey Data Release 7 database. The investigation is done by comparing our sample to a control sample matched in the normalized redshift distribution in two diagnostics, which are the nuclear gas-phase metallicity vs.stellar mass and the nuclear SFR vs. stellar mass diagrams. Galaxies with different morphological types show different mass-metallicity relations(MZRs). Compared to the MZR defined by the control sample,isolated spirals have comparable metallicities with the control sample at a given stellar mass. Spirals in pairs and interacting galaxies with projected separations of rp 20 kpc show a mild metallicity dilution of0.02–0.03 dex. Interacting galaxies with rp 20 kpc, pre-mergers and advanced mergers are underabundant by～0.06,～0.05 and～0.04 dex, respectively. This shows an evolutionary trend that the metallicity is increasingly depressed as the merging proceeds and it is diluted most dramatically when two galaxies are closely interacting. Afterwards, the interstellar medium(ISM) is enriched when the galaxies coalesce.This is the first time that such ISM enrichment at the final coalescence stage has been observed, which demonstrates the importance of supernova explosions in affecting the nuclear metallicity. Moreover, the central SFR enhancement relative to the control sample evolves simultaneously with the nuclear gas-phase oxygen abundance. Our results support the predictions from numerical simulations.     

Morphology of the ~(13)CO(3–2) millimetre emission across the gas disc surrounding the triple protostar GG Tau A using ALMA observations

Observations by the Atacama Large Millimetre/sub-millimetre Array of the dust continuum and13 CO(3–2) millimetre emissions of the triple stellar system GG Tau A are analysed,giving evidence for a rotating gas disc and a concentric and coplanar dust ring. The present work complements an earlier analysis(Tang et al.) by exploring detailed properties of the gas disc. A 95% confidence level upper limit of 0.24′′(34 au) is placed on the disc scale height at a distance of 1′′(140 au) from the central stars. Evidence for Keplerian rotation of the gas disc is presented,with the rotation velocity reaching~3.1 km s~(-1) at 1′′ from the central stars,and a 99% confidence level upper limit of 9% is placed on relative contribution from a possible in-fall velocity. Variations of the intensity across the disc area are studied in detail and confirm the presence of a hot spot in the south-eastern quadrant. However several other significant intensity variations,in particular a depression in the northern direction,are also revealed. Variations of the intensity are found to be positively correlated to variations of the line width. Possible contributions to the measured line width are reviewed,suggesting an increase of the disc temperature and opacity with decreasing distance from the stars.     

Strict Limits on the Ionizing Luminosity in NGC 1068 from Jet-Axis Molecular Clouds

The radio jet axis of NGC 1068 is characterised by energetic activity from x-ray to radio wavelengths. Detailed kinematic and polarization studies have shown that this activity is confined to bipolar cones centered on the AGN which intersect the plane of the disk. Thus, molecular clouds at 1 kpc distance along this axis are an important probe of the nuclear ionizing luminosity and spectrum. Extended 10.8μm emission coincident with the clouds is reasonably understood by dust heated to high temperatures by the nuclear radiation field. This model predicts that the nuclear spectrum is quasar-like (power law + blue excess) with a luminosity 2-5 times higher than inferred by Pier et al. (1994). Consequently, there is little or no polyaromatic hydrocarbon (PAH) emission associated with the radio-axis molecular clouds. We review this model in the light of new observations. A multi-waveband collage is included to illustrate the possible orientations of the double cones to our line of sight and the galaxian plane. This revised version was published online in July 2006 with corrections to the Cover Date.     

Study of temporal evolution of emission spectrum in a steeply rising submillimeter burst

The temporal evolution of a spectrum during a steeply rising submillimeter(THz) burst that occurred on 2003 November 2 was investigated in detail for the first time.Observations show that the flux density of the THz spectrum increased steeply with frequency above 200 GHz.Their average rising rates reached a value of 235 sfu GHz~(-1)(corresponding to spectral index α of 4.8) during the burst.The flux densities reached about 4 000 and 70 000 sfu at 212 and 405 GHz at the maximum phase,respectively.The emissions at 405 GHz maintained such a continuous high level that they largely exceeded the peak values of the microwave(MW) spectra during the main phase.Our studies suggest that only energetic electrons with a low-energy cutoff of~ 1 MeV and number density of ~ 10~6-10~8 cm~(-3) can produce such a strong and steeply rising THz component via gyrosynchrotron radiation based on numerical simulations of burst spectra in the case of a nonuniform magnetic field.The electron number density N,derived from our numerical fits to the THz temporal evolution spectra,increased substantially from 8 ×10~6 to 4 × 10~8 cm~(-3),i.e.,the N value increased 50 times during the rise phase.During the decay phase it decreased to 7 ×10~7 cm~(-3),i.e.,it decreased by about five times from the maximum phase.The total electron number decreased an order of magnitude from the maximum phase to the decay phase.Nevertheless,the variation in amplitude of N is only about one time in the MW emission source during this burst,and the total electron number did not decrease but increased by about 20%during the decay phase.Interestingly,we find that the THz source radius decreased by about 24%while the MW source radius,on the contrary,increased by 28%during the decay phase.     

The formation and evolution of massive galaxies

The discovery of massive galaxies at high redshifts,especially the passive ones,poses a big challenge for the current standard galaxy formation models.Here we use the semi-analytic galaxy formation model developed by Henriques et al.to explore the formation and evolution of massive galaxies(MGs,stellar-mass M_* 10~(11) M_⊙).Different from previous works,we focus on the ones just formed(e.g.just reach?10~(11) M_⊙).We find that most of the MGs are formed around z=0.6,with the earliest formation at z 4.Interestingly,although most of the MGs in the local Universe are passive,we find that only 13% of the MGs are quenched at the formation time.Most of the quenched MGs at formation already host a very massive supermassive black hole(SMBH) which could power the very effective AGN feedback.For the star-forming MGs,the ones with more massive SMBH prefer to quench in shorter timescales;in particular,those with M_(SMBH) 10~(7.5) M_⊙ have a quenching timescale of～0.5 Gyr and the characteristic MSMBH depends on the chosen stellar mass threshold in the definition of MGs as a result of their co-evolution.We also find that the "in-situ" star formation dominates the stellar mass growth of MGs until they are formed.Over the whole redshift range,we find the quiescent MGs prefer to stay in more massive dark matter halos,and have more massive SMBH and less cold gas masses.Our results provide a new angle on the whole life of the growth of MGs in the Universe.     

Are collisions with electrons important for modeling the polarization of the lines of the C_2 solar molecule?

Observations of the second solar spectrum(SSS) revealed the existence of prominent linear polarization signals due to lines of the C_2 molecule.Interpretation of the SSS is the only tool to obtain the weak and turbulent magnetic field which is widespread in the Quiet Sun.However,this interpretation is conditioned by the determination of accurate collisional data.In this context,we present a formulation of the problem of the calculation of the polarization transfer rates by collisions of polarized C_2 states with electrons.The obtained formulae are applied to determine,for the first time,the polarization transfer rates between the C_2 states of the Swan band electronic system(a ~3Π_u d ~3Π_q) and electrons for temperatures going up from 1000 to 10000 K.However,due to the closeness of the electronic states of the C_2 molecule,the two electronic d ~3Π_g and a ~3Π_u cannot be disconnected from the other electronic levels and,thus,a model based on only two states is not sufficient to describe the formation of the lines in the Swan band.Consequently,we also calculated the collisional polarization transfer rates in the case where the first eight electronic states of C_2 are taken into account.All rates are given as functions of the temperature by power laws.Our results should be useful for future solar applications.     

Space Observation and Study of the Sun.

The ejection of energetic electrons and protons,and γ-ray burst are revealed by solar space observations,which have confirmed some related theories of solar radio emission and uncovered the nuclear reaction in flares.The difference and relationship between CME and plasma cloud in flares are shown by space observations.The hot and cold regions of flares are known.The theory of nonlinear magnetohydrodynamics is developed by solar and heliospheric magnetic field observations.     

The first detection of the solar U+Ⅲ association with an antenna prototype for the future lunar observatory

We report about observations of solar U+Ⅲ bursts on 2020 June 5 by means of a new active antenna designed to receive radiation in 4–70 MHz. This instrument can serve as a prototype of the ultralong-wavelength radio telescope for observations on the farside of the Moon. Our analysis of experimental data is based on simultaneous records obtained with the antenna arrays GURT and NDA in high frequency and time resolution, e-Callisto network as well as by using the space-based observatories STEREO and WIND. The results from this observational study confirm the model of Reid and Kontar.     

A very bright (i=16.44) quasar in the ‘redshift desert’ discovered by the Guoshoujing Telescope (LAMOST)

The redshift range from 2.2 to 3 is known as the 'redshift desert' of quasars because quasars with redshifts in this range have similar optical colors as normal stars and are thus difficult to find in optical sky surveys.A quasar candidate, SDSS J085543.40001517.7, which was selected by a recently proposed criterion involving near-IR Y-K and optical g-z colors, was identified spectroscopically as a new quasar with a redshift of 2.427 by the Guoshoujing Telescope (LAMOST) commissioning observation in 2009 December and confirmed by the observation made with the NAOC/Xinglong 2.16 m telescope in 2010 March.This quasar was not identified in the SDSS spectroscopic survey.Comparing with other SDSS quasars, we found that this new quasar, with an i magnitude of 16.44, is apparently the brightest one in the redshift range from 2.3 to 2.7.From its spectral properties, we derived its central black hole mass to be (1.4～3.9)×1010 M and its bolometric luminosity to be 3.7×1048 erg s?1, which indicates that this new quasar is intrinsically very bright and belongs to the class of the most luminous quasars in the universe.Our identification supports the notion that quasars in the redshift desert can be found by the quasar selection criterion involving the near-IR colors.More missing quasars are expected to be uncovered by future LAMOST spectroscopic surveys, which is important to the study of the cosmological evolution of quasars at redshifts higher than 2.2.     

Hydrodynamical simulations of the triggering of nuclear activities by minor mergers of galaxies

Major mergers of galaxies are considered to be an efficient way to trigger Active Galactic Nuclei and are thought to be responsible for the phenomenon of quasars. This has however recently been challenged by observations of a large number of low luminosity Active Galactic Nuclei at low redshift(z■1) without obvious major merger signatures. Minor mergers are frequently proposed to explain the existence of these Active Galactic Nuclei. In this paper, we perform nine high resolution hydrodynamical simulations of minor galaxy mergers, and investigate whether nuclear activities can be efficiently triggered by minor mergers, by setting various properties for the progenitor galaxies of those mergers. We find that minor galaxy mergers can activate the massive black hole in the primary galaxy with an Eddington ratio of f Edd 0.01 and 0.05(or a bolometric luminosity 10~(43) and 10~(44) erg s~(-1)) with a duration of 2.71 and 0.49 Gyr(or 2.69 and 0.19 Gyr), respectively. The nuclear activity of the primary galaxy strongly depends on the nucleus separation, such that the nucleus is more active as the two nuclei approach each other. Dual Active Galactic Nuclei systems can still possibly be formed by minor mergers of galaxies, though the time duration for dual Active Galactic Nuclei is only ～ 0.011 Gyr and ～ 0.017 Gyr with Eddington ratio of f Edd 0.05 and bolometric luminosity 10~(44) erg s~(-1). This time period is typically shorter than that of dual Active Galactic Nuclei induced by major galaxy mergers.     

Chinese sunspot drawings and their digitization –(Ⅱ) accuracy analysis for digitized sunspot hand-drawing records of Yunnan Observatories

Sunspots are the most striking and easily observed magnetic structures of the Sun, and statistical analysis of solar historical data could reveal a wealth of information on the long-term variation of solar activity cycle. The hand-drawn sunspot records of Yunnan Observatories, Chinese Academy of Sciences have been accumulating for more than 60 years, and nearly 16 000 images have been preserved. In the future, the observation mode of recording sunspots by hand-drawing will be replaced inevitably by digital images observed either at ground or in space. To connect the hand-drawn sunspot data and the purely digital sunspot data in future, it is necessary to analyze the systematic errors of the data which are observed by the two observation modes in the period of transition. In this paper, we choose 268 round sunspots(Htype in modified Zurich sunspot classification) from the drawing of Yunnan Observatories to compare their positions and areas with the CCD observations made by Helioseismic and Magnetic Imager(HMI) on board Solar Dynamic Observatory(SDO) and Global Oscillation Network Group(GONG). We find that the latitude and longitude accuracy of hand-drawn sunspot are within-0.127 and 2.29 degree respectively,and the area accuracy is about 16.36 sunspot unit(μHem). Systematic errors apparently decrease with large sunspot.     

The non-Gaussian distribution of galaxy gravitational fields

We perform a theoretical analysis of the observational dependence between angular momentum of galaxy clusters and their mass(richness), based on the method introduced in our previous paper.For that we obtain the distribution function of gravitational fields for astronomical objects(like galaxies and/or smooth halos of different kinds) due to their tidal interaction. By applying the statistical method of Chandrasekhar, we are able to show that the distribution function is determined by the form of interaction between objects and for multipole(tidal) interaction it is never Gaussian. Our calculation permits demonstrating how the alignment of galaxy angular momenta depends on cluster richness. The specific form of the corresponding dependence is due to assumptions made about cluster morphology. Our approach also predicts the time evolution of stellar object angular momenta within CDM and ΛCDM models. Namely, we have shown that angular momentum of galaxies increases with time.     

1SWASP J034439.97+030425.5: a short-period eclipsing binary system with a close-in stellar companion

First multi-wavelength photometric light curves(LCs) of the short-period eclipsing binary(EB)1 SWASP J034439.97+030425.5(hereafter J0344) are presented and analyzed by using the 2013 version of the Wilson-Devinney(W-D) code. To explain the asymmetric LCs of J0344, a cool star-spot on the less massive component was employed. The photometric solutions suggest that J0344 is a W-subtype shallow contact EB with a contact degree of f = 4.9% ± 3.0% and a mass ratio of q = 2.456 ± 0.013. Moreover,an obvious third light was detected in our analysis. We calculated the average luminosity contribution of the third light to the total light, and that value reaches up to 49.78%. Based on the O-C method,the variations of the orbital period were studied for the first time. Our O-C diagram reveals a secular decrease superimposed on a cyclic oscillation. The orbital period decreases at a rate of d P/dt =-6.07 ×10~(-7) d yr~(-1), which can be explained by the mass transfer from the more massive component to the less massive one. Besides, its O-C diagram also shows a cyclic oscillation with an amplitude of 0.0030 d and a period about 7.08 yr, which can be explained by the presence of a third body with a minimum mass of M3 min= 0.15 ± 0.02 M_⊙. The third component may play an important role in the formation and evolution of J0344 by drawing angular momentum from the central system.     

A New Approach for Estimating Kinetic Luminosity of Jet in AGNs

The Konigl inhomogeneous jet model can successfully reproduce most observa-tional features of jets in active galactic nuclei (AGN), when suitable physical parameters are adopted. We improve Konigl's calculations on the core emission from the jet with a small viewing angle θ0～ψ (ψ is half opening angle of the conical jet). The proper motion of the jet component provides a constraint on the jet kinematics. Based on the inhomogeneous jet model, we use the proper motion data of the jet component to calculate the minimal kinetic luminosity of the jet required to reproduce the core emission measured by the very-long-baseline intefferometry (VLBI) for a sample of BL Lac objects. Our results show that the minimal kinetic luminosity is slightly higher than the bolometric luminosity for most sources in the sample, which implies that radiatively inefficient accretion flows (RIAFs) may be in those BL Lac objects, or/and the properties of their broad-line regions (BLRs) are signifi-cantly different from flat-spectrum radio-loud quasars.     

Correlation between excitation index and Eddington ratio in radio galaxies

We use a sample of 111 radio galaxies with redshift z 0.3 to investigate their nuclear properties.The black hole masses of the sources in this sample are estimated with the velocity dispersion/luminosity of the galaxies, or the width of the broad-lines. We find that the excitation index, the relative intensity of low and high excitation lines, is correlated with the Eddington ratio for this sample. The size of the narrow-line region(NLR) was found to vary with ionizing luminosity as RNLR∝L_(ion)~(0.25)(Liu et al. 2013). Using this empirical relation, we find that the correlation between the excitation index and the Eddington ratio can be reproduced by photoionization models. We adopt two sets of spectral energy distributions(SEDs), with or without a big blue bump in ultraviolet as the ionizing continuum, and infer that the modeled correlation between the excitation index and the Eddington ratio is insensitive to the applied SED. This means that the difference between high excitation galaxies and low excitation galaxies is not caused by the different accretion modes in these sources. Instead, it may be caused by the size of the NLR.     

Reduced spin-down rate of PSR J0738–4042 explained as due to an asteroid disruption event

Long term observations by Brook et al. reveal that the derivative of rotational frequency of PSR J0738–4042 changed abruptly in 2005. Originally, the spin-down rate was relatively stable, with the rotational frequency derivative being-1.14×10~(-14)s~(-2). After September 2005, the derivative began to rise.About 1000 days later, it arrived at another relatively stable value of about-0.98 × 10~(-14)s~(-2), indicating that the pulsar is spinning-down relatively slowly. To explain the observed change in spin-down rate, we resort to an asteroid disrupted by PSR J0738–4042. In our model, the orbital angular momentum of the asteroid is assumed to be parallel to that of the rotating pulsar, so that the pronounced reduction in the spin-down rate can be naturally explained as due to the transfer of angular momentum from the disrupted material to the central pulsar. The derived magnetospheric radius is about 7.0 × 10~9 cm, which is smaller than the tidal disruption radius(8.7 × 10~(10)cm). Our model is self-consistent. It is shown that the variability in the spin-down rate of PSR J0738–4042 can be quantitatively accounted for by accretion from the asteroid disrupted by the central pulsar.     

The Early X-ray Afterglows of Optically Bright and Dark Gamma-Ray Bursts

A systematic study on the early X-ray afterglows of both optically bright and dark gamma-ray bursts (B-GRBs and D-GRBs) observed by Swift is presented. Our sample includes 25 GRBs of which 13 are B-GRBs and 12 are D-GRBs. Our results show that the distributions of the X-ray afterglow fluxes (Fx), the gamma-ray fluxes (5r), and the ratio (Rr,x.) are similar for the two kinds of GRBs, that any observed differences should be simply statistical fluctuation. These results indicate that the progenitors of the two kinds of GRBs are of the same population with comparable total energies of explosion. The suppression of optical emission in the D-GRBs should result from circumburst but not from their central engine.