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Classification study of WISE infrared sources:identification of candidate asymptotic giant branch stars

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Research in Astronomy and Astrophysics 2013年第3期13卷 323-333页

作者： Xun Tu zhong-xiang wang Key Laboratory for Research in Galaxies and Cosmology and Shanghai Astronomical Observatory Chinese Academy of Sciences Graduate University of Chinese Academy of Sciences

In the Wide-field Infrared Survey Explorer （WISE） all-sky source catalog there are 76 million mid-infrared point sources that were detected in the first three WISE bands and have association with only one 2MASS near-IR source within 3. We search for their identifications in the SIMBAD database and find 3.2 million identified sources. Based on these known sources, we establish three criteria for selecting candidate asymptotic giant branch （AGB） stars in the Galaxy, which are three defined zones in a color-color diagram, Galactic latitude ｜b｜〈 20°, and ＂corrected＂ WISE third-band W3c≤ 11. Applying these criteria to the WISE＋2MASS sources, 1.37 million of them are selected. We analyze the WISE third-band W3 distribution of the selected sources, and further establish that W3〈8 is required in order to exclude a large fraction of normal stars from them. We therefore find 0.47 million candidate AGB stars in our Galaxy from the WISE source catalog. Using W3c, we estimate their distances and derive their Galactic distributions. The candidates are generally distributed around the Galactic center uniformly, with 68% （1-σ） of them within approximately 8 kpc. We discuss the idea that optical spectroscopy can be used to verify the C-rich AGB stars in our candidates, and thus a fraction of them （-10%） will be good targets for the Large Sky Area Multi-Object Fiber Spectroscopic Telescope （LAMOST） survey that is planned to start in fall of 2012.

关键词： stars: AGB and post-AGB -- infrared: stars -- stars: carbon

Dynamics of neutrino-driven winds:inclusion of accurate weak interaction rates in strong magnetic fields

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Research in Astronomy and Astrophysics 2013年第2期13卷 207-214页

作者： Men-Quan Liu zhong-xiang wang Shanghai Astronomical Observatory Chinese Academy of Sciences Institute of Theoretical Physics China West Normal University

Solving Newtonian steady-state wind equations while considering the ac- curate weak interaction rates and magnetic fields （MFs） of young neutron stars, we study the dynamics and nucleosynthesis of neutrino-driven winds （NDWs） from proto neutron stars （PNSs）. For a typical 1.4 Mo PNS model, we find that the nucleosyn- thesis products are closely related to the luminosity of neutrinos and anti-neutrinos. The lower the luminosity is, the larger is the effect on the NDWs caused by weak in- teractions and MFs. At a high anti-neutrino luminosity of typically 8 × 1051 erg s-1, neutrinos and anti-neutrinos dominate the processes in an NDW and the MFs hardly change the wind＇s properties. But at a low anti-neutrino luminosity of 1051 erg s-1 at the late stage of an NDW the mass of the product and process of nucleosynthesis are changed significantly in strong MFs. Therefore, in most of the models considered for the NDWs from PNSs, based on our calculations, the influences of MFs and the net weak interactions on the nucleosynthesis are not significant.

关键词： nuclear reactions, nucleosynthesis, abundances -- hydrodynamics --stars neutrons

A new estimation of manganese distribution for local dwarf spheroidal galaxies

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Research in Astronomy and Astrophysics 2016年第9期16卷 137-144页

作者： Men-Quan Liu zhong-xiang wang School of Physics and Space Science China West Normal University Shanghai Astronomical Observatory Chinese Academy of Sciences

The distribution of abundance for iron-peak elements in dwarf spheroidal galaxies （dSphs） is important for galaxy evolution and supernova （SN） nucleosynthesis. Nowadays, manganese （Mn） is one of the most observed iron-peak elements in local dSphs. Studies of its distributions allow us to derive and understand the evolution history of these dSphs. We improve a phenomenological model by a two-curve model including a new initial condition, that includes detailed calculations of SN explosion rates and yields. We compare the results with the observed Mn distribution data for three dSphs： Fornax, Sculpture and Sextans. We find that the model can describe the observed Fe and Mn distributions well simultaneously for the three dSphs. The results also indicate that the initial conditions should be determined by the low metallicity sam- ples in the beginning time of the galaxies and the previous assumption of metellicity-dependant Mn yield of SNIa is not needed when a wide mass range of core-collapse SNe is included. Our method is applicable to the chemical evolution of other iron-peak elements in dSphs and can be modified to provide more detailed processes for the evolution of dSphs.

关键词： galaxies dwarf-- galaxies individual (Fornax, Sculptor, Sextans) -- galaxies evolution --supernovae general

Possible modulated γ-ray emission from the transitional millisecond pulsar binary PSR J1023+0038

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Research in Astronomy and Astrophysics 2018年第10期18卷 109-116页

作者： Yi Xing zhong-xiang wang Jumpei Takata Key Laboratory for Research in Galaxies and Cosmology Shanghai Astronomical Observatory Chinese Academy of Sciences School of Physics Huazhong University of Science and Technology

We report the results from our analysis of Fermi Large Area Telescope （LAT） data for the transitional millisecond pulsar binary PSR J1023＋0038. The time period of the data is nearly 9 yr, and that after the source＇s transition, in June 2013 from the disk-free state to the active state of having an accretion disk, is approximately 4 yr. We identify a high-energy 〉5.5 GeV component in the source＇s spectrum in the active state, and find this component is only significantly detected in half of the orbital phase centered at the descending node （when the pulsar is moving towards the Earth）. Considering the pulsar scenario proposed for multi-frequency emission from the source, in which the pulsar is still active and a cold-relativistic pulsar wind inverse-Compton scatters the photons from the accretion disk, we discuss the origin of the high-energy component. In order to explain the observed spectrum, a power-law distribution of particles, with an index of ~3, in the pulsar wind is required, while the orbital variations are possibly due to changes in power-law index as a function of orbital phase.

关键词： gamma rays stars - binaries eclipsing - stars neutron

Fermi Blazars in the Zwicky Transient Facility Survey:A Correlation Study

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Research in Astronomy and Astrophysics 2023年第7期23卷 64-79页

作者： Si-Si Sun zhong-xiang wang Yi Xing Department of Astronomy School of Physics and AstronomyYunnan UniversityKunming 650091China Shanghai Astronomical Observatory Chinese Academy of SciencesShanghai 200030China

We report on our correlation analysis for theγ-ray blazars detected with the Large Area Telescope(LAT)onboard the Fermi Gamma-ray Space Telescope(Fermi),for which we use the Fermi-LAT data and the optical zr and zg band data from the Zwicky Transient Facility survey in the time period approximately from 2018 July to *** start from the full sample of the Fermi-LAT blazars and find~38%of them as significant variables in bothγ-ray and optical *** the variables,which are 705 blazars,95 are selected as our targets based on the requirement for theγ-ray *** 15 out of the 95 blazars are found to show theγ-ray-optical correlations in the~3.7 yr time *** of the 15 blazars are classified as low synchrotron peaked(LSP)ones with the time lags between theγ-ray and optical bands in a range from-19 to+25 *** results generally fit the often-considered emission scenario for the LSP *** cases of showing~-100 days time lags are discussed,which require farther studies for *** analysis results suggest that among the detected significant variables,~23%LSPs can showγ-ray and optical correlations,while their averageγ-ray fluxes are above~4×10^(-8)photon cm^(-2)s^(-1).

关键词： gamma-rays:galaxies (galaxies:)quasars:general (galaxies:)BL Lacertae objects:general

X-Ray and Radio Studies of the Candidate Millisecond Pulsar Binary 4FGL J0935.3+0901

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Research in Astronomy and Astrophysics 2022年第2期22卷 128-134页

作者： Dong Zheng zhong-xiang wang Yi Xing Jithesh Vadakkumthani Department of Astronomy School of Physics and AstronomyYunnan UniversityKunming 650091China Key Laboratory of Astroparticle Physics of Yunnan Province Yunnan UniversityKunming 650091China Shanghai Astronomical Observatory Chinese Academy of Sciences80 Nandan RoadShanghai 200030China Inter-University Centre for Astronomy and Astrophysics PB No.4GaneshkhindPune-411007India Department of Physics University of CalicutMalappuram-673635KeralaIndia

4 FGL J0935.5+0901, a γ-ray source recently identified as a candidate redback-type millisecond pulsar(MSP)binary, shows an interesting feature of having double-peaked emission lines in its optical spectrum. This feature would further suggest the source is a transitional MSP system in the sub-luminous disk state. We have observed the source with XMM-Newton and Five-hundred-meter Aperture Spherical radio Telescope(FAST) at X-ray and radio frequencies respectively for further studies. From the X-ray observation, a bimodal count-rate distribution, which is a distinctive feature of the transitional MSP systems, is not detected, but the properties of X-ray variability and power-law spectrum are determined for the source. These results help establish the consistency of it being a redback in the radio pulsar state. However no radio pulsation signals are found in the FAST observation, resulting in an upper limit on the flux density of ~4 μJy. Implications of these results are discussed.

关键词： (stars:)binaries(including multiple):close (stars:)pulsars:general gamma-rays:stars

Fermi Blazars in the Zwicky Transient Facility Survey:Properties of Large Optical Variations

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Research in Astronomy and Astrophysics 2024年第10期24卷 104-115页

作者： Si-Si Sun zhong-xiang wang Shun-Hao Ji Department of Astronomy School of Physics and AstronomyYunnan UniversityKunming 650091China Shanghai Astronomical Observatory Chinese Academy of SciencesShanghai 200030China

We analyze the optical light curve data,obtained with the Zwicky Transient Facility(ZTF)survey,for 47 γ-ray blazars monitored by the Large Area Telescope onboard the Fermi Gamma-ray Space Telescope(Fermi).These 47sources are selected because they are among the Fermi blazars with the largest optical variations in the ZTF *** color-magnitude variation patterns are seen in them,with one being redder-to-stable-when-brighter(RSWB;in 31 sources)and the other being stable when brighter(in 16 sources).The patterns fit with the results recently reported in several similar studies with different ***,we find that the colors in the stable state of the sources share similar values,for which(after being corrected for the Galactic extinction)most sources are in a range of 0.4–*** feature could be intrinsic and may be applied in,for example,study of the intragalactic *** also determine the turning points for the sources showing the RSWB pattern,after which the color changes saturate and become *** find a correlation between optical fluxes and γ-ray fluxes at the turning *** physical implications of the correlation remain to be investigated,probably better with a sample of high-qualityγ-ray flux measurements.

关键词： (galaxies:)BL Lacertae objects:general (galaxies:)quasars:general gamma-rays:galaxies

Identification of candidate millisecond pulsars from Fermi LAT observations Ⅱ

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Research in Astronomy and Astrophysics 2017年第7期17卷 89-98页

作者： Xue-Jie Dai zhong-xiang wang Jithesh Vadakkumthani Yi Xing Shanghai Astronomical Observatory Chinese Academy of Sciences University of Chinese Academy of Sciences

On the basis of the properties of known γ-ray millisecond pulsars（MSPs）, we have selected 77un-associated sources from the Fermi Large Area Telescope（LAT） third source catalog for the purpose of finding likely candidate MSPs. Previously, detailed LAT data analysis for 39 of them was reported,and here we report the analysis for the remaining 38 sources. We identify that among the 38 sources, 28 of them are single point-like sources with clean background and their spectra show significant *** also conduct an analysis of archival X-ray data available for 24 of the 28 sources. In the fields of10 sources, there is at least one X-ray object, and in those of the other 14 sources, no X-ray object is detected but this is probably due to the X-ray observations being short. We discuss the possible MSP nature for these sources. Six of them（J0514.6-4406, J1035.7-6720, J1624.2-4041, J1744.1-7619,J1946.4-5403 and J2039.6-5618） are most likely associated with pulsars because of multi-wavelength identifications including direct radio or γ-ray detection of pulsations. To firmly establish the associations or verify the MSP nature for other sources, deep X-ray and/or optical observations are needed.

关键词： stars pulsars - stars binaries - gamma rays stars

Identification of candidate millisecond pulsars from Fermi LAT observations

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Research in Astronomy and Astrophysics 2016年第6期16卷 113-122页

作者： Xue-Jie Dai zhong-xiang wang Jithesh Vadakkumthani Yi Xing Shanghai Astronomical Observatory Chinese Academy of SciencesShanghai 200030China University of Chinese Academy of Sciences Beijing 100049China

We report our detailed data analysis of 39 γ-ray sources selected from the 992 unassociated sources in the third Fermi Large Area Telescope Third Source Catalog. The selection criteria, which were set for finding candidate millisecond pulsars （MSPs）, are non-variables with curved spectra and 〉5° Galactic latitudes. From our analysis, 24 sources were found to be point-like sources not contaminated by back- ground or nearby unknown sources. Three of them, Jl544.6-1125, J1625.1-0021 and J1653.6-0158, have been previously studied, indicating that they are likely MSPs. The spectra of J0318.1＋0252 and J2053.9＋2922 do not have properties similar to known γ-ray MSPs, and we thus suggest that they are not MSPs. Analysis of archival X-ray data for most of the 24 sources was also conducted. Four sources were found with X-ray objects in their error circles, and 16 with no detection. The ratios between the γ-ray fluxes and X-ray fluxes or flux upper limits are generally lower than those of known γ-ray MSPs, suggesting that if the γ-ray sources are MSPs, none of the X-ray objects are their counterparts. Deep X-ray or radio observations of these sources are needed in order to identify their MSP nature.

关键词： stars pulsars -- stars binaries -- gamma rays stars