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Research in Astronomy and Astrophysics 2024年第9期24卷 7-27页

作者： Hakim Luthfi Malasan Bakuh Danang Setyo Budi Department of Astronomy Faculty of Mathematics and Natural SciencesInstitut Teknologi BandungBandung 40132Indonesia bosscha observatory Institut Teknologi BandungLembang 40391Indonesia Master Program in Astronomy Faculty of Mathematics and Natural SciencesInstitut Teknologi BandungJl.Ganesha No.10Bandung 40132Indonesia

We present optical spectra of 10 Galactic Wolf-Rayet(WR)stars that consist of five WN and five WC *** optical observation was conducted using a low-resolution spectrograph NEO-R1000(λ/Δλ~1000)at GAO-ITB RTS(27.94 cm,F/10.0),bosscha observatory,*** implemented stellar atmosphere Postdam Wolf-Rayet(PoWR)grid modeling to derive stellar *** normalized optical spectrum can be used to find the best model from the available PoWR grid,then we could derive stellar temperature and transformation *** derive luminosity,stellar radius and color excess,we conducted a Spectral Energy Distribution(SED)analysis with additional data on the near-ultraviolet spectrum from the International Ultraviolet Explorer(IUE)database,and UBV and 2MASS JHK broadband filter *** analysis to derive asymptotic terminal wind velocity was conducted from the P-Cygni profile analysis of the high-resolution IUE ultraviolet *** previously derived parameters,we could determine the mass loss rate of the WR ***,we compared our results with previous work that used PoWR code and the differences are not more than 20%.We conclude that the PoWR spectral grid is sufficient to derive WR stellar parameters quickly and could provide more accurate initial parameter input to the PoWR program code.

关键词： stars:massive stars:mass-loss stars:Wolf-Rayet stars:atmospheres stars:winds outflows

Studying the Equilibrium Points of the Modified Circular Restricted Three-body Problem: The Case of Sun–Haumea System

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Research in Astronomy and Astrophysics 2023年第11期23卷 232-242页

作者： INurul Huda B.Dermawan M.B.Saputra R.Sadikin T.Hidayat Research Center for Computing National Research and Innovation AgencyBogorIndonesia Department of Astronomy and bosscha observatory FMIPAInstitut Teknologi BandungBandungIndonesia

We intend to study a modified version of the planar Circular Restricted Three-Body Problem(CRTBP) by incorporating several perturbing parameters. We consider the bigger primary as an oblate spheroid and emitting radiation while the small primary has an elongated body. We also consider the perturbation from a disk-like structure encompassing this three-body system. First, we develop a mathematical model of this modified *** have found there exist five equilibrium points in this modified CRTBP model, where three of them are collinear and the other two are non-collinear. Second, we apply our modified CRTBP model to the Sun–Haumea system by considering several values of each perturbing parameter. Through our numerical investigation, we have discovered that the incorporation of perturbing parameters has resulted in a shift in the equilibrium point positions of the Sun–Haumea system compared to their positions in the classical CRTBP. The stability of equilibrium points is investigated. We have shown that the collinear equilibrium points are unstable and the stability of non-collinear equilibrium points depends on the mass parameter μ of the system. Unlike the classical case, non-collinear equilibrium points have both a maximum and minimum limit of μ for achieving stability. We remark that the stability range of μ in non-collinear equilibrium points depends on the perturbing parameters. In the context of the Sun–Haumea system, we have found that the non-collinear equilibrium points are stable.

关键词： celestial mechanics Kuiper Belt:general planets and satellites:dynamical evolution and stability

Tidal triggering of seismicity in the region of Palu, Central Sulawesi, Indonesia

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Geodesy and Geodynamics 2023年第4期14卷 377-384页

作者： Ibnu Nurul Huda Sebastien Lambert Jean Souchay Research Center for Computing National Research and Innovation AgencyBogorIndonesia Department of Astronomy and bosscha observatory FMIPAInstitut Teknologi BandungBandungIndonesia SYRTE Observatoire de ParisUniversité PSLCNRSSorbonne UniversitéLNEParisFrance

This paper investigates the correlation between tidal stress and earthquakes for periods ranging from hours to months in the limited zone of the Palu region(Central Sulawesi,Indonesia).Through Schuster and binomial tests,we examined the relation between the seismicity(time density of seismic events)and tidal potential arising from the Moon and Sun,using all tidal components simultaneously and focusing on the estimation of specific *** results show significant correlations between the seismicity and tidal potential for S2(0.5 d)and O1(1.075 d)tidal components in the case of solely isolated earthquake events,particularly for shallow ***,there is a strong relationship between aftershocks and tidal components larger than the Mf period(13.661 d).Finally,the analysis of the temporal variation of the earthquake-tide relation reveals an optimal correlation for about six years before the 2018 great Palu *** correlation becomes insignificant afterwards.

关键词： Tidal triggering Earth tides Palu region Statistical test

Statistical improvement in detection level of gravitational microlensing events from their light curves

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Research in Astronomy and Astrophysics 2018年第4期18卷 43-58页

作者： Ichsan Ibrahim Hakim L.Malasan Chatief Kunjaya Anton Timur Jaelani Gerhana Puannandra Putri Mitra Djamal Department of Astronomy Institute of Technology Bandung Bandung Indonesia Department of Physics Department of Astronomy Institute of Technology Bandung Bandung Indonesia bosscha Astronomical observatory Department of Astronomy Institute of Technology Bandung LembangIndonesia Department of Informatics STMIK-Indonesia Mandiri Bandung Indonesia Universitas Ma Chung Malang Indonesia Faculty of Shariah Institut Agama Islam Ternate Ternate North Molucca Indonesia Astronomical Institute Tohoku University Sendai Japan

In astronomy,the brightness of a source is typically expressed in terms of ***,the magnitude is defined by the logarithm of received *** relationship is known as the Pogson *** received flux with a small signal to noise ratio（S/N）,however,the formula gives a large magnitude *** investigate whether the use of Inverse Hyperbolic Sine function（hereafter referred to as the Asinh magnitude）in the modified formulae could allow for an alternative calculation of magnitudes for small S/N flux,and whether the new approach is better for representing the brightness of that *** study the possibility of increasing the detection level of gravitational microlensing using 40 selected microlensing light curves from the 2013 and 2014 seasons and by using the Asinh *** data of the selected events are obtained from the Optical Gravitational Lensing Experiment（OGLE）.We found that utilization of the Asinh magnitude makes the events brighter compared to using the logarithmic magnitude,with an average of about 3.42×10^（-2）magnitude and an average in the difference of error between the logarithmic and the Asinh magnitude of about 2.21×10（-2）*** microlensing events OB140847 and OB140885 are found to have the largest difference values among the selected *** a Gaussian fit to find the peak for OB140847 and OB140885,we conclude statistically that the Asinh magnitude gives better mean squared values of the regression and narrower residual histograms than the Pogson *** on these results,we also attempt to propose a limit in magnitude value for which use of the Asinh magnitude is optimal with small S/N data.

关键词： gravitational lensing micro — methods data analysis

Fallback in bipolar planetary nebulae?

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Research in Astronomy and Astrophysics 2021年第11期21卷 47-54页

作者： Willem A.Baan Hiroshi Imai Gabor Orosz Netherlands Institute for Radio Astronomy ASTRON 79901 PD DwingelooNetherlands Center for General Education Institute for Comprehensive EducationKagoshima University1-21-30 KorimotoKagoshima 890-0065Japan Xinjiang Astronomical observatory Urumqi 830011China Amanogawa Galaxy Astronomy Research Center Graduate School of Science and EngineeringKagoshima University1-21-35 KorimotoKagoshima 890-0065Japan School of Natural Sciences University of TasmaniaPrivate Bag 37HobartTasmania 7001Australia

The subclass of bipolar Planetary Nebulae(PNe)exhibits well-defined low-power outflows and some shows shock-related equatorial spiderweb structures and hourglass structures surrounding these *** structures are distinctly different from the phenomena associated with spherical and elliptical PNe and suggest a non-standard way to simultaneously energise both kinds of *** paper presents evidence from the published literature on bipolar PN Hb 12 and other sources in support of an alternative scenario for energising these structures by means of accretion from material shells deposited during earlier post-AGB and pre-PNe evolutionary *** addition to energising the bipolar outflow,a sub-Eddington accretion scenario could hydrodynamically explain the spiderweb and outer hourglass structures as oblique shockwaves for guiding the accreting material into the equatorial region of the *** of the accretion rate resulting from fallback-related spherical accretion could indeed help to drive a low-power outflow and contribute to the total luminosity of these sources.

关键词： ISM:planetary nebulae:general ISM:planetary nebulae:individual Hb 12,Hen 2-104,MyCn 18 ISM:jets and outflows stars:evolution