首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 62 毫秒
1.
We present the results of our UBVRI photometry for the type II-P supernova SN 2017eaw in NGC6946 obtained fromMay 14 to December 7, 2017, at several telescopes, including the 2.5-m telescope at the CaucasusHigh-Altitude Observatory of the SAIMSU. The dates andmagnitudes atmaximumlight and the light-curve parameters have been determined. The color evolution, extinction, and peak luminosity of SN 2017eaw are discussed. The results of our preliminary radiation–gasdynamic simulations of its light curves with the STELLA code describe satisfactorily the UBVRI observational data.  相似文献   

2.
The use of Type Ia supernovae (SNe Ia) as cosmological standard candles is a key to solving the mystery of dark energy. Improving the calibration of SNe Ia increases their power as cosmological standard candles. We find tentative evidence for a correlation between the late-time light-curve slope and the peak luminosity of SNe Ia in the B band; brighter SNe Ia seem to have shallower light-curve slopes between 100 and 150 d from maximum light. Using a Markov Chain Monte Carlo (MCMC) analysis in calibrating SNe Ia, we are able to simultaneously take into consideration the effect of dust extinction, the luminosity and light-curve width correlation (parametrized by  Δ m 15  ), and the luminosity and late-time light-curve slope correlation. For the available sample of 11 SNe Ia with well-measured late-time light curves, we find that correcting for the correlation between luminosity and late-time light-curve slope of the SNe Ia leads to an intrinsic dispersion of 0.12 mag in the Hubble diagram. Our results have significant implications for future supernova surveys aimed to illuminate the nature of dark energy.  相似文献   

3.
UBVRIJ photometry and optical spectra of the type Ia SN 1996X obtained at the European Southern Observatory (ESO) during a 1-yr-long observational campaign are presented, and supplemented by late-time Hubble Space Telescope (HST) photometry. Spectroscopically, SN 1996X appears to be a 'normal' SN Ia. The apparent magnitude at maximum was     and the colour     The luminosity decline rate,     is close to average for a SN Ia. The best estimate of the galactic extinction is     and there is evidence that reddening within the parent galaxy is negligible.
Detailed comparison of the light and colour curves of various 'normal' SNe Ia shows that the assumption that multicolour light curves can be described simply as a one-parameter family is not perfect. Together with problems in the calibration of the templates, this may explain the discrepancies in the distance modulus derived adopting different calibrations of the absolute magnitude versus light-curve shape relations. Indeed, we found that M B ranges from −19.08 to −19.48 and μ ranges from 32.02 to 32.48 depending on the method used.
Computations of model light-curve and synthetic spectra for both early and late times confirm that 1996X is a normal type Ia SN and that a satisfactory fit can be obtained using a W7 progenitor structure only if we adopt the short distance. A larger distance would imply too large a Ni mass for this fainter than average SN Ia.  相似文献   

4.
We present the first statistical analysis of 27 Ultraviolet Optical Telescope (UVOT) optical/ultraviolet light curves of gamma-ray burst (GRB) afterglows. We have found, through analysis of the light curves in the observer's frame, that a significant fraction rise in the first 500 s after the GRB trigger, all light curves decay after 500 s, typically as a power law with a relatively narrow distribution of decay indices, and the brightest optical afterglows tend to decay the quickest. We find that the rise could be either produced physically by the start of the forward shock, when the jet begins to plough into the external medium, or geometrically where an off-axis observer sees a rising light curve as an increasing amount of emission enters the observers line of sight, which occurs as the jet slows. We find that at 99.8 per cent confidence, there is a correlation, in the observed frame, between the apparent magnitude of the light curves at 400 s and the rate of decay after 500 s. However, in the rest frame, a Spearman rank test shows only a weak correlation of low statistical significance between luminosity and decay rate. A correlation should be expected if the afterglows were produced by off-axis jets, suggesting that the jet is viewed from within the half-opening angle θ or within a core of a uniform energy density  θc  . We also produced logarithmic luminosity distributions for three rest-frame epochs. We find no evidence for bimodality in any of the distributions. Finally, we compare our sample of UVOT light curves with the X-ray Telescope (XRT) light-curve canonical model. The range in decay indices seen in UVOT light curves at any epoch is most similar to the range in decay of the shallow decay segment of the XRT canonical model. However, in the XRT canonical model, there is no indication of the rising behaviour observed in the UVOT light curves.  相似文献   

5.
Statistical relations between the luminosity L of gamma-ray burster (GRBs) and several of their other observable properties have been discovered. Four of these properties are considered here: the spectral lag; a measure of the light-curve variability; peak energy and the minimum light-curve rise time. Data are taken from a tabulation by Schaefer. Log–log regression of L on various combinations of the four light-curve properties, as well as redshift, is considered, using conventional multiple linear regression, and multiple errors-in-variables regression. Several cases are found in which the regression coefficients of more than one luminosity indicators are significant. In particular, the simultaneous regression of luminosity on peak energy, spectral lag, minimum rise time and redshift is meaningful.  相似文献   

6.
We have determined the absolute magnitude at maximum light of SN 1992A by using the turnover magnitude of the globular cluster luminosity function of its parent galaxy, NGC 1380. A recalibration of the peak of the turnover magnitude of the Milky Way clusters using the latest Hipparcos results has been made with an assessment of the complete random and systematic error budget. The following results emerge: a distance to NGC 1380 of 18.6 ± 1.4 Mpc, corresponding to ( m  −  M )  31.35 ± 0.16, and an absolute magnitude of SN 1992A at maximum of M B (max)  −18.79 ± 0.16. Taken at face value, SN 1992A seems to be more than half a magnitude fainter than the other SNe Ia for which accurate distances exist. We discuss the implications of this result and present possible explanations. We also discuss the Phillips relationship between rate of decline and the absolute magnitude at maximum, on the basis of nine SNe Ia, the individual distances of which have been obtained with Cepheids and the globular cluster luminosity function. The new calibration of this relationship, applied to the most distant SNe of the Calan–Tololo survey, yields H 0 = 62 ± 6 km s−1 Mpc−1.  相似文献   

7.
超新星在宇宙学中的应用   总被引：2，自引：0，他引：2  
对Ｉａ超新星在宇宙学中的应用作了述评。蓝Ｉａ超新星具有相对均匀的光谱、光变曲线及峰值光度,是较好的相对距离指示器。利用峰值光度同光变曲线形状或其它与距离无关的可观测量的关系可进一步将Ｉａ超新星校准成精确的距离指示器。一旦它们的绝对光度得到标定,就可以定出哈勃常数Ｈ０。基于对邻近星系Ｉａ超新星的理解,高红移Ｉａ超新星的数据可对宇宙密度参数ΩＭ、ΩＶ及减速因子ｑ０作出限制,并对膨胀宇宙的最终命运作出判  相似文献   

8.
Extensive photometric and spectroscopic observations of SN 1994aj until 540 d after maximum light have been obtained. The photometry around maximum suggests that the SN belongs to the Type II Linear class, with a peak absolute magnitude of M V∼−17.8 (assuming H 0=75 km s−1 Mpc−1). The spectra of SN 1994aj were unusual, with the presence of a narrow line with a P Cygni profile on top of the broad Balmer line emission. This narrow feature is attributed to the presence of a dense superwind surrounding the SN. At 100–120 d after maximum light the SN ejecta start to interact with this circumstellar material. The SN luminosity decline rates slowed down [γ R =0.46 mag (100 d)−1], becoming less steep than the average late luminosity decline of normal SN II [∼1 mag (100 d)−1]. This dense ( ˙M / u W∼1015 g cm−1) wind was confined to a short distance from the progenitor ( R out=∼5×1016 cm), and results from a very strong mass-loss episode ( ˙M =10−3 M⊙ yr−1), which terminated shortly before explosion (∼5–10 yr).  相似文献   

9.
We present the photometric and spectroscopic evolution of the type IIn SN 1995G in NGC 1643, on the basis of 4 years of optical and infrared observations. This supernova shows very flat optical light curves similar to SN 1988Z, with a slow decline rate at all times. The spectra are characterized by strong Balmer lines with multiple components in emission and with a P Cygni absorption component blueshifted by only 700 km s−1. This feature indicates the presence of a slowly expanding shell above the SN ejecta as in the case of SNe 1994aj and 1996L. As in other SNe IIn, the slow luminosity decline cannot be explained only with a radioactive energy input, and an additional source of energy is required, most likely that produced by the interaction between supernova ejecta and a pre-existent circumstellar medium (CSM). It was estimated that the shell material has a density   n H≫108 cm-3  , consistent with the absence of forbidden lines in the spectra. About 2 years after the burst the low-velocity shell is largely overtaken by the SN ejecta and the luminosity drops at a faster rate.  相似文献   

10.
The BVR photometric light curves of the eclipsing binary BD And were obtained in 2008 and 2009. We estimated the mass ratio of the system as 0.97 and the photometric solutions were derived. The results show that BD And is a detached binary system, whose components have a little temperature difference of about 40 K. By analyzing photometric available light minimum times, we also derived an update ephemeris and found for the first time a possible periodic oscillation with an amplitude of 0.011 days and a period of 9.6 years. The results indicate that the periodic oscillation could be caused by a third component physically attached to the eclipsing binary. After removing the light variations due to the eclipses and proximity effects, the light-curve distortions are further explained by the pulsation of the primary component with a dominant period of ∼1 day. In accordance with the position of the primary component on the Hertzsprung–Russell diagram and its pulsation period, the primary component of BD And could be an excellent γ Doradus candidate. It is rarely phenomenon that a component of the eclipsing binary system is a γ Doradus variable.  相似文献   

11.
超新星SN 1987A的热光度演化──内部中子星的贡献   总被引：1，自引：1，他引：0  
本文介绍了超新星SN1987A爆发六年多来其热光度演化的研究情况．爆发后的前800天，观测的热光度曲线与由超新星爆发时合成的放射性元素的放射衰变加热模型符合得很好．但900天以后，观测的热光度曲线比考虑了所有放射性元素贡献后的理论曲线下降得还要缓慢．这可能表明有新的能源在起作用．我们认为这个新的能源可能是超新星爆发时产生的中子星的吸积．通过吸积超新星爆发时抛射气壳中小于逃逸速度的部分物质而增大SN1987A的热光度．这一模型能很好地解释900天以后的光度曲线的下降变级以及900至1200天之间光度曲线的凸起，这也为内部中子星的存在提供了间接的证据．  相似文献   

12.
We present a new method for determining physical parameters of RRab variables exclusively from multicolour light curves. Our method is an inverse photometric Baade–Wesselink analysis which, using a non-linear least-squares algorithm, searches for the effective temperature ( T eff) and pulsational velocity ( V p) curves and other physical parameters that best fit the observed light curves, utilizing synthetic colours and bolometric corrections from static atmosphere models. The T eff and V p curves are initially derived from empirical relations then they are varied by the fitting algorithm. The method yields the variations and the absolute values of the radius, the effective temperature, the visual brightness and the luminosity of individual objects. Distance and mass are also determined. The method is tested on nine RRab stars subjected to Baade–Wesselink analyses earlier by several authors. The physical parameters derived by our method using only the light-curve data of these stars are well within their possible ranges defined by direct Baade–Wesselink and other techniques. A new empirical relation between the I C magnitude and the pulsational velocity is also presented, which allows to construct the V p curve of an RRab star purely from photometric observations to an accuracy of about 3.5 km s−1.  相似文献   

13.
We present contemporaneous optical and infrared (IR) photometric observations of the Type IIn SN 1998S covering the period between 11 and 146 d after discovery. The IR data constitute the first ever IR light curves of a Type IIn supernova. We use blackbody and spline fits to the photometry to examine the luminosity evolution. During the first 2–3 months, the luminosity is dominated by the release of shock-deposited energy in the ejecta. After ∼100 d the luminosity is powered mostly by the deposition of radioactive decay energy from 0.15±0.05 M⊙ of 56Ni which was produced in the explosion. We also report the discovery of an astonishingly high IR excess, K − L '=2.5, that was present at day 130. We interpret this as being due to thermal emission from dust grains in the vicinity of the supernova. We argue that to produce such a high IR luminosity so soon after the explosion, the dust must be pre-existing and so is located in the circumstellar medium of the progenitor. The dust could be heated either by the UV/optical flash (IR echo) or by the X-rays from the interaction of the ejecta with the circumstellar material.  相似文献   

14.
In this paper, we give theBV photoelectric light curves of the Algol-type eclipsing binary EU Hydrae. We have analysed its period by means of the times of minima determined from this observation and the times of minima which other observers published. The period was found to gradually decrease with a change rate dP/dE = -3 . d 29 × 10–10. The obtained light curves have been solved using Wilson-Devinney's synthetic light-curve program. The results demonstrate that EU Hydrae is a detached system, the secondary component fills the Roche-lobe, its mass ratio is 0.205. EU Hya may evolve to be a semidetached system in which the secondary component fills the Roche-lobe.  相似文献   

15.
The accelerated expansion of the Universe was proposed through the use of Type-Ia supernovae （SNe） as standard candles. The standardization depends on an empirical correlation between the stretch/color and peak luminosity of the light curves. The use of Type-Ia SNe as standard candles rests on the assumption that their properties （and this correlation） do not vary with redshift. We consider the possibility that the majority of Type-Ia SNe are in fact caused by a Quark-Nova detonation in a tight neutron-star-CO-white-dwarf binary system, which forms a Quark-Nova Ia （QN-Ia）. The spin-down energy injected by the Quark-Nova remnant （the quark star） contributes to the post-peak light curve and neatly explains the observed correlation between peak luminosity and light curve shape. We demonstrate that the parameters describing QN-Ia are NOT constant in redshift. Simulated QN-Ia light curves provide a test of the stretch/color correlation by comparing the true distance modulus with that determined using SN light curve fitters. We determine a correction between the true and fitted distance moduli, which when applied to Type-Ia SNe in the Hubble diagram recovers the ΩM = 1 cosmology. We conclude that Type-Ia SNe observations do not necessitate the need for an accelerating expansion of the Universe （if the observed SNe Ia are dominated by QNe Ia） and by association the need for dark energy.  相似文献   

16.
We use semi-analytic modelling on top of the Millennium simulation to study the joint formation of galaxies and their embedded supermassive black holes. Our goal is to test scenarios in which black hole accretion and quasar activity are triggered by galaxy mergers, and to constrain different models for the light curves associated with individual quasar events. In the present work, we focus on studying the spatial distribution of simulated quasars. At all luminosities, we find that the simulated quasar two-point correlation function is fit well by a single power law in the range  0.5 ≲ r ≲ 20  h −1 Mpc  , but its normalization is a strong function of redshift. When we select only quasars with luminosities within the range typically accessible by today's quasar surveys, their clustering strength depends only weakly on luminosity, in agreement with observations. This holds independently of the assumed light-curve model, since bright quasars are black holes accreting close to the Eddington limit, and are hosted by dark matter haloes with a narrow mass range of a few  1012  h −1 M⊙  . Therefore, the clustering of bright quasars cannot be used to disentangle light-curve models, but such a discrimination would become possible if the observational samples can be pushed to significantly fainter limits. Overall, our clustering results for the simulated quasar population agree rather well with observations, lending support to the conjecture that galaxy mergers could be the main physical process responsible for triggering black hole accretion and quasar activity.  相似文献   

17.
A set of well-measured, {low-z}, type Ia supernovae from the Calán/Tololo SNe data sets is used to determine benchmark parameters in our hydrodynamics-based, light-curve model. The light-curve data fit fairly well in B, V, and R passbands but not as well in the I passband. The fitting procedure, extracted best-fit model parameters, and their connection to type Ia SN parameters are presented. Our benchmarked light-curve model represents an alternative to empirical template methods for the analysis of light-curve data.  相似文献   

18.
The new multi-color BVRI photometric light curves of the short-period eclipsing binary GSC 3576-0170 were obtained on two consecutive nights (October 5 and 6, 2009). With the 2003 version of Wilson–Devinney program, the precise photometric solutions are derived for the first time. The result shows that GSC 3576-0170 is a semi-detached binary system with a large temperature difference of approximately 1490 K. The light-curve distortions are further explained by a hot spot on the secondary component through mass transfer via a stream hitting the facing surface of the secondary component. By analyzing all available light minimum times, we also derived an update ephemeris and found for the first time a possible periodic oscillation with an amplitude of 0.0038 days and a period of 4.3 years. The periodic oscillation could be explained either by the light-time effect due to a presumed third component or by magnetic activity cycle of the system.  相似文献   

19.
We report on multi-epoch X-ray observations of the Type IIn (narrow emission line) Supernova (SN) 1995N with the ROSAT and ASCA satellites. The 1998 January ASCA X-ray spectrum is well fitted by a thermal bremsstrahlung         or power-law         model. The X-ray light curve shows evidence for significant flux evolution between 1996 August and 1998 January: the count rate from the source decreased by 30 per cent between our 1996 August and 1997 August ROSAT observations, and the X-ray luminosity most likely increased by a factor of ∼2 between our 1997 August ROSAT and 1998 January ASCA observations, although evolution of the spectral shape over this interval is not ruled out. The high X-ray luminosity,     places SN 1995N in a small group of Type IIn supernovae with strong circumstellar interaction, and the evolving X-ray luminosity suggests that the circumstellar medium is distributed inhomogeneously.  相似文献   

20.
In this paper, we present and discuss the effects of scattered light echoes (LEs) on the luminosity and spectral appearance of Type Ia supernovae (SNe). After introducing the basic concept of LE spectral synthesis by means of LE models and real observations, we investigate the deviations from pure SN spectra, light and colour curves, the signatures that witness the presence of an LE and the possible inferences on the extinction law. The effects on the photometric parameters and spectral features are also discussed. In particular, for the case of circumstellar dust, LEs are found to introduce an apparent relation between the post-maximum decline rate and the absolute luminosity, which is most likely going to affect the well-known Pskowski–Phillips relation.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号