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1.
Multi-color light curves of V1197 Her were obtained with the 2.4 meter optical telescope at the Thai National Observatory and the Wilson-Devinney(W-D) program was used to model the observational light curves. The photometric solutions reveal that V1197 Her is a W-subtype shallow contact binary system with a mass ratio of q = 2.61 and a fill-out factor of f = 15.7%. The temperature difference between the primary star and secondary star is only 140 K in spite of the low degree of contact, which means that V1197 Her is not only in geometrical contact configuration but is also already under thermal contact status.The orbital inclination of V1197 Her is as high as i = 82.7?, and the primary star is completely eclipsed at the primary minimum. The totally eclipsing characteristic implies that the determined physical parameters are highly reliable. The masses, radii and luminosities of the primary star(star 1) and secondary star(star2) are estimated to be M1 = 0.30(1) M_⊙, M2 = 0.77(2) M_⊙, R1 = 0.54(1) R_⊙, R2 = 0.83(1) R_⊙,L1 = 0.18(1) L_⊙and L2 = 0.38(1) L_⊙. The evolutionary statuses of the two component stars are drawn in the Hertzsprung-Russell diagram, showing that the less massive but hotter primary star is more evolved than the secondary star. The period of V1197 Her is decreasing continuously at a rate of d P/dt =-2.58 ×10-7 day · year-1, which can be explained by mass transfer from the more massive star to the less massive one at a rate of dM_2/dt=-1.61 × 10~(-7) M_⊙year~(-1). The light curves of V1197 Her are reported to show the O'Connell effect. Thus, a cool spot is added to the more massive star to model the asymmetry in the light curves.  相似文献   

2.
We present an exact analytical solution of the gravitational field equations describing a static spherically symmetric anisotropic quark matter distribution. The radial pressure inside the star is assumed to obey a linear equation of state, while the tangential pressure is a complicated function of the radial coordinate. In order to obtain the general solution of the field equations a particular density profile inside the star is also assumed. The anisotropic pressure distribution leads to an increase in the maximum radius and mass of the quark star, which in the present model is around three solar masses.  相似文献   

3.
The properties and classification of IRAS 19111 2555 have so far not been well determined. We collect all the available information and data of this star, and take the data obtained by IRAS LRS and ISO SWS to discuss its properties and classification. The star is found to have a 3.1μm feature in absorption and a 10μm feature in emission, so it is possibly a new silicate carbon star.  相似文献   

4.
We put forth three modes of black hole formation, i.e. (1) A black hole kern forms initially inside the collapsing star. (2) The different mass shells of the collapsing star fulfils the Schwarzschild condition simultaneously. (3) Only the outmost mass shell of the collapsing star fulfils the Schwarzschild condition. We then calculate the entropy of the collapsing star for modes (1) and (3) and find that they are only 10-19 times the entropy of black hole. Modes (1) may be occure during the supernova explosions or galaxy explosions. Mode (3) may be occur in the formation of galactic black hole.  相似文献   

5.
The star 1-1-42 （=vZ1390）, a cluster member in M3, located near the red edge of the instability strip of the horizontal branch, was discovered by Roberts and Sandage as a low amplitude variable, it was designated as V204 in the ＂second catalogue of variable stars in globular clusters＂, but its coordinates given in all versions of this catalogue are wrong since 1955. We argue that V204 is indeed a low amplitude HB variable star, located near to the red edge of the instability strip, with a period of 0.74785d and an amplitude of about 0.04 mag in V. We also find that the red cluster member star 1-1-39 is a low amplitude variable with a period of 1.16^d and amplitude of about 0.03 mag in V which might be pulsating at the second overtone.  相似文献   

6.
The massive star forming region S 233 IR is observed in the molecular lines CO J = 2-1, 3-2, NH3 (1,1), (2,2) and the 870#m dust continuum. Four submillimeter continuum sources, labelled SMM 1-4, are revealed in the 870μm dust emission. The main core, SMM1, is found to be associated with a deeply embedded near infrared cluster in the northeast; while the weaker source SMM2 coincides with a more evolved cluster in the southwest. The best fit spectral energy distribution of SMM1 gives an emissivity of β = 1.6, and temperatures of 32 K and 92 K for the cold- and hot-dust components. An SMM1 core mass of 246 M⊙ and a total mass of 445 M⊙ are estimated from the 870μm dust continuum emission.SMM1 is found to have a temperature gradient decreasing from inside out, indicative of the presence of interior heating sources. The total outflow gas mass as traced by the CO J = 3-2 emission is estimated to be 35 M⊙. Low velocity outflows are also found in the NH3 (1,1) emission. The non-thermal dominant NH3 line width as well as the substantial core mass suggest that the SMM1 core is a “turbulent,massive dense core”, in the process of forming a group or a cluster of stars. The much higher star formation efficiency found in the southwest cluster supports the suggestion that this cluster is more evolved than the northeast one. Large near infrared photometric variations found in the source PCS-IR93, a previously found highly polarized nebulosity, indicate an underlying star showing the FU Orionis type of behavior.  相似文献   

7.
The property of the H-burning shell and the mecanism of the mass ejection of the AGB star are investigated by means of detailed computations carried out for the evolution of a star with its initial mass of 7. The energe generation rate εH of the H-burning shell changes periodically and has a phase-shifting with respect to that of the He-burning shell which undergoes thermonuclear runaway. For the most time of a period the value of εH is about one to three order of magnitude larger than that of the He-burning shell εHe . So the dominative energy supply of the star in the AGB phase comes from the H-burning shell. The luminosity of the star changes periodically and cynchronizes with the variation of εH . The upper limit of the luminosity of an AGB star can be obtained by the condition that the inward gravitational acceleration is balanced by the outward acceleration owing to the radiations, rotation and turbulent forces. Comparing the luminosity of the star with its upper limit, we can find that the lu  相似文献   

8.
A new method of light curve inversion with bipartite regularization(LIBR),which is complementary to the previous treatments by Bonomo and Lanza and Estrela and Valio,is used to reconstruct the physical properties of star spots on the solar-type star Kepler-17 by using the full Q1-Q17 data set.The Markov Chain Monte Carlo(MCMC) method was applied to find the best profile of the reconstructed surface.The known value of the rotation inclination of Kepler-17 allows the generation of a star spot model in a sequence of stellar rotation with a period of 12.26 d.Because of the nature of the light curve inversion,the spot model is limited to the equatorial region.We also investigated the starspot lifetimes of Kepler-17 utilizing the MCMC method.Combined with the LIBR inversion results,it was found that the star spots typically last from one to several stellar rotations.From the time evolution of the spot size,a magnetic cycle period of 437 d can be derived.This value is comparatively shorter than the solar cycle which might be a consequence of the younger age(～1.78 Gyr) of Kepler-17.The light curve of Kepler-17 is characterized by the presence of large-amplitude variation caused by star spots but no superflare activity.An interesting possibility is that the magnetic energy stored in the star spot regions could have been constantly dissipated by electrodynamic interaction between the central star and the hot Jupiter,Kepler-17 b,via a lower-level energy release process.  相似文献   

9.
1 INTRODUCTION The globular cluster (GC hereafter), as the oldest star group in the universe, has been a target that astro- physics has paid close attention to all the time. The near-field (Galaxy) cosmology makes contacts with the far-field cosmology by …  相似文献   

10.
New V-band CCD observations of variable star V2455 Cyg were performed during two nights in September 2017. According to all times of maximum light and new maxima, the O-C curve was analyzed.The period changes of V2455 Cyg were investigated and the rate of increasing period was obtained to be(1/P) d P/dt = 1.99 × 10~(-7) yr~(-1). Frequency analysis indicated that V2455 Cyg pulsates with the radial p mode and the fundamental frequency is 10.61574 d-1. Physical parameters of V2455 Cyg at mean temperature were determined(e.g., R = 2.52 R_⊙and M = 1.92 M_⊙). The position of this star in the H-R diagram confirms that V2455 Cyg is a high amplitude δ Scuti star.  相似文献   

11.
In this second paper of our series, we estimate the age of 41 star clusters, which were detected by Melnick & D'odorico in the nearby spiral galaxy M33, by comparing the integrated photometric measurements with theoretical stellar population synthesis models of Bruzual & Chariot. Also, we calculate the mass of these star clusters using the theoretical M/Lv ratio. The results show that, these star clusters formed continuously in M33 from ~ 7×106 - 1010 years and have masses between ~ 103 and 2×106 M⊙. M33 frames were observed as a part of the BATC Multicolor Survey of the sky in 13 intermediate-band niters from 3800 to 10 OOOA. The relation between age and mass confirms that the sample star cluster masses systematically decrease from the oldest to the youngest.  相似文献   

12.
High-resolution optical spectra of the zero age star HD77407 are analysed and its Li, C, O, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Co, Ni and Ba contents are determined using spectral synthesis method. The temperature of the star is determined by fitting the H α line wings. The parameters derived for this star are Teff=5900K, log g=4.47 and [Fe/H] = 0.07. It is found that the derived iron content is slightly higher than what is given in the published literature. This star shows a relative overabundances of Ca and Ba, and underabundances of Na, V and Ni with respect to the solar mix. Activity of the star is indicated by the filled in Hα and Ca II triplet line cores. It has been confirmed that our spectroscopic approach yields fairly reliable and consistent results for active stars.  相似文献   

13.
Data representing 864 times of light maxima of the high-amplitude δ Scuti star CY Aqr were collected from the literature,based on which,long-term period changes of the variable star were investigated.A revised period and new ephemerides were given for the pulsating star.Remarkable cyclic variations were found in the O-C residuals which can be attributed to the light-time effects due to probable unseen components of the object.By using Kopal's method,the orbital parameters of the supposed component stars were derived.The solution suggests that CY Aqr is very probably in a triple system orbited eccentrically by two low-mass companions with periods of 54.2 and 47.3 yr.The lower limits on masses were estimated as0.04 M_⊙and 0.02 M_⊙,respectively,for the two hidden companions.  相似文献   

14.
In this paper, we study the age and spatial distributions of Cepheids in the Small Magellanic Cloud(SMC) as a function of their ages using data from the OGLE III photometric catalogue. A period- age relation derived for Classical Cepheids in the Large Magellanic Cloud(LMC) has been used to find the ages of Cepheids. The age distribution of the SMC Classical Cepheids is found to have a peak at log(Age) = 8.40 ± 0.10 which suggests that a major star formation event might have occurred in the SMC about 250 ± 50 Myr ago. It is believed that this star forming burst had been triggered by close interactions of the SMC with the LMC and/or the Milky Way. A comparison of the observed spatial distributions of the Cepheids and open star clusters has also been carried out to study the star formation scenario in the SMC.  相似文献   

15.
PSR B1259–63 is a γ-ray emitting high mass X-ray binary system, in which the compact object is a millisecond pulsar.The system has an orbital period of 1236.7 d and shows peculiar γ-ray flares when the neutron star moves out of the stellar disk of the companion star.The γ-ray flare events were firstly discovered by using Fermi-LAT around the 2010 periastron passage, which was repeated for the 2014 and 2017 periastron passages.We analyze the Fermi-LAT data for all the three periastron passages and found that in each flare the energy spectrum can be represented well by a simple power law.The γ-ray light curves show that in 2010 and 2014 after each periastron there are two main flares,but in 2017 there are four flares including one precursor about 10 d after the periastron passage.The first main flares in 2010 and 2014 are located at around 35 d after the periastron passage, and the main flare in 2014 is delayed by roughly 1.7 d with respect to that in 2010.In the 2017 flare, the source shows a precursor about 10 d after the periastron passage, but the following two flares become weaker and lag behind those in 2010 by roughly 5 d.The strongest flares in 2017 occurred 58 d and 70 d after the periastron passage.These results challenge the previous models.  相似文献   

16.
The continuum energy distributions of the luminous blue variables R127 and R110 in the outburst phase are fitted with a circumstellar envelope model.Both stars show two peaks in their continuum, one near 1250A and the other in the optical band. We suggest that their UV and optical fluxes may have different origins: the UV flux comes from the central star while the optical flux comes from an expanding circumstellar envelope. We construct a model for LBVs consisting of two LTE atmosphere models with different temperatures, and find it to be in agreement with the observed spectral energy distributions of R127 and R110.According to our numerical experiments, R127‘s continuum is composed of fluxes from a circumstellar envelope of Teff = 8000K, R = 485R⊙, and log g = 1,and from a central star of Tef = 17000K, R = 135R⊙, and log g = 2.5 with a permeating factor f = 0.5; while R110‘s continuum can be fitted by a circumstellar envelope of Teff =7000K, R = 350R⊙, and logg = 0.5, and a central star of Teff =25 000 K, R = 27R⊙, and log g 3.0 with a permeating factor f = 0.65.Both models show that the non-spherically symmetric, optically thick regions are formed surrounding the central star in the outburst phase. The light of the central star is shielded by the circumstellar envelope so that the visual brightness increases with the decrease/increase of the temperature/radius of the optically thick regions.  相似文献   

17.
Using the 13.7m radio telescope at Delingha, the millimeter-wave radio observatory of Purple Mountain Observatory, we made mapping observations in 12CO J = 1 - 0 line towards IRAS 05417+0907, located in the bright-rimmed cloud (BRC) BRC18. We used a 7 × 7 grid with 1' spacing, a finer and larger grid than the one used by Myers et al. Our results show that there is a bipolar outflow near IRAS 05417+0907. Combining with the observations at other wave bands, we find that the star formation process in this region is triggered by radiation-driven implosion. The significant difference between the masses of BRC18 and the cores and the relatively large ratio of associated source bolometric luminosity to the mass show that the star formation in BRC18 may be taking place in a sequence.  相似文献   

18.
The discovery of silicate carbon star poses a challenge to the theory of stellar evolution in the late stage, hence it is important to look for more silicate carbon stars. To this end we have carried out cross-identifications between the new IRAS Low-Resolution Spectrum (LRS) database and the new carbon star catalog, CGCS3. We have found nine new silicate carbon stars with silicate features around 10μm and/or 18μm. These newly identified stars are located in the Regions IIIa and VII in the IRAS two-color diagram, which means they indeed have typical far infrared colors of silicate carbon stars. The infrared properties of each of these sources are discussed.  相似文献   

19.
1. The Circumstellar Disk as a Byproduct of Star Formation The fundamental theory of star formation predicts the wide existence of circumstellar disks around the young stellar objects. Restricted by the conservation law of angular momentum, the protostellar core deviates more significantly as the contraction proceeds. As a consequence, a star-disk system develops and, at an early stage of its dvolution, can be observed in molecular lines.  相似文献   

20.
The spin period variations and hard X-ray spectral properties of the Be/Xray pulsar GRO J1008–57 are studied with INTEGRAL observations during two outbursts in 2004 June and 2009 March.The pulsation periods of～93.66 s in 2004and～93.73 s in 2009 are determined.Pulse profiles of GRO J1008–57 during outbursts are strongly energy dependent with a double-peaked profile from 3–7 keV and a single-peaked profile in hard X-rays above 7 keV.Combined with previous measurements,we find that GRO J1008–57 has undergone a spin-down trend from 1993–2009 with a rate of～4.1×10-5s d-1,and could have changed into a spin-up trend after 2009.We find a relatively soft spectrum in the early phase of the 2009 outburst with cutoff energy～13 keV.Above a hard X-ray flux of～10-9erg cm-2s-1,the spectra of GRO J1008–57 during outbursts need an enhanced hydrogen absorption with column density～6×1022cm-2.The observed dip-like pulse profile of GRO J1008–57 in soft X-ray bands could be caused by this intrinsic absorption.Around the outburst peaks,a possible cyclotron resonance scattering feature at～74 keV is detected in the spectra of GRO J1008–57 which is consistent with the feature that was reported in MAXI/GSC observations,making the source a neutron star with the highest known magnetic field(～6.6×1012G)among accreting X-ray pulsars.This marginal feature is supported by the present detections in GRO J1008–57 following the correlation between the fundamental line energies and cutoff energies in accreting X-ray pulsars.Finally we discovered two modulation periods at～124.38 d and～248.78 d using RXTE/ASM light curves of GRO J1008–57.Two flare peaks appearing in the folded light curve had different spectral properties.The normal outburst lasting 0.1 of an orbital phase had a hard spectrum and could not be significantly detected below 3 keV.The second flare lasting ten days showed a very soft spectrum without significant detections above 5 keV.GRO J1008–57 is a good candidate of an accreting system with an equatorial circumstellar disk around the companion star.The neutron star passing the disk of the Be star near periastron and apastron produces two X-ray flares.The soft spectral properties in the secondary flares still need further detailed studies with soft X-ray spectroscopy.  相似文献   

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