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1.
We present late-time photometry for two bright type Ⅱ-P supernovae (SNe) 2004dj and 2004et, extending over 400 d after the explosion, which are measured with a set of intermediate-band filters that have the advantage of tracing the strength variations of some spectral features. Although these two SNe Ⅱ-P exhibit similar photometric evolution at earlier times, they diverge during the nebular phase. SN 2004dj shows a slow late-time decline rate with ～0.7±0.1 mag (100d)-1 during the period ranging from t≈200-300 d after the explosion, while SN 2004et shows a much faster decline rate at a comparable phase, e.g., 1.3±0.1 mag (100d)-1. The steeper decay rate seen in SN 2004et is likely due to dust formation in the explosion ejecta. Based on intermediate-band photometry, we derived the evolution of the feature lines [e.g., Hα] of SNe 2004dj and 2004et which are similar in flux at comparable phases but perhaps with significantly different decay rates. The origin of the observed variations in the continuum and the feature lines is briefly discussed.  相似文献   

2.
The optical observations of the type Ic supernova(SN Ic) SN 2012 ap in NGC 1729 are presented. A comparison with other SNe Ic indicates that SN 2012 ap is highly reddened(with E(B- V)host～0.8 mag) and may represent one of the most luminous SNe Ic ever observed, with an absolute V-band peak magnitude of ～-19.3±0.5 mag after extinction correction. The near-maximum-light spectrum shows wide spectral features that are typical of broad-lined SNe Ic. One interesting feature in the spectrum is the appearance of some narrow absorption features that can be attributed to the diffuse interstellar bands, consistent with the large reddening inferred from the photometric method. Based on the light curves and the spectral data, we estimate that SN 2012 ap produced a56 Ni mass of ～ 0.3 ± 0.1M in the explosion, with an ejecta mass of 2.4+0.7-0.7M and a kinetic energy of E5K= 1.1+0.4-0.4× 102 erg. The properties of its progenitor are also briefly discussed.  相似文献   

3.
In recent years a number of double-humped supernovae （SNe） have been discovered. This is a feature predicted by the dual-shock Quark-Nova （QN） model where an SN explosion is followed （a few days to a few weeks later） by a QN explo- sion. SN 2009ip and SN 2010mc are the best observed examples of double-humped SNe. Here, we show that the dual-shock QN model naturally explains their light curves including the late time emission, which we attribute to the interaction between the mixed SN and QN ejecta and the surrounding circumstellar matter. Our model applies to any star （O-stars, luminous blue variables, Wolf-Rayet stars, etc.） provided that the mass involved in the SN explosion is ~ 20 Mo which provides good conditions for forming a QN.  相似文献   

4.
The amount of 56↑Ni produced in Type Ia supernova （SN Ia） explosion is probably the most important physical parameter underlying the observed correlation of SN Ia luminosities with their light curves. Based on an empirical relation between the 56↑Ni mass and the light curve parameter △m15, we obtained rough estimates of the 56↑Ni mass for a large sample of nearby SNe Ia with the aim of exploring the diversity in SN Ia. We found that the derived 56↑Ni masses for different SNe Ia could vary by a factor of ten （e.g., MNi = 0.1 - 1.3 M⊙）, which cannot be explained in terms of the standard Chandrasekhar-mass model （with a 56↑Ni mass production of 0.4 - 0.8 M⊙）. Different explosion and/or progenitor models are clearly required for various SNe Ia, in particular, for those extremely nickel-poor and nickel-rich producers. The nickel-rich （with MNi 〉 0.8 M⊙） SNe Ia are very luminous and may have massive progenitors exceeding the Chandrasekhar-mass limit since extra progenitor fuel is required to produce more 56↑Ni to power the light curve. This is also consistent with the finding that the intrinsically bright SNe Ia prefer to occur in stellar environments of young and massive stars. For example, 75% SNe Ia in spirals have △ml5 〈 1.2 while this ratio is only 18% in E/S0 galaxies. The nickel-poor SNe Ia （with MNi 〈 0.2 M⊙） may invoke the sub- Chandrasekhar model, as most of them were found in early-type E/S0 galaxies dominated by the older and low-mass stellar populations. This indicates that SNe Ia in spiral and E/S0 galaxies have progenitors of different properties.  相似文献   

5.
We present accurate positions and multi-color photometry for 41 star clusters detected by Melnick & D'odorico in the nearby spiral galaxy M33 as a part of the BATC Color Survey of the sky in 13 intermediate-band filters from 3800 to 10 000A. The coordinates of the clusters are found from the HST Guide Star Catalog. By aperture photometry, we obtain the spectral energy distributions of the clusters. Using the relations between the BATC intermediate-band system and UBVRI broadband system, we derive their V magnitudes and B - V colors and find that most of them are blue, which is consistent with previous findings.  相似文献   

6.
The single-degenerate(SD)model is one of the most popular progenitor models of type Ia supernovae(SNe Ia),in which the companion star can survive after an SN Ia explosion and show peculiar properties.Therefore,searching for the surviving companion in type Ia supernova remnants(SNRs)is a potential method to verify the SD model.In the SN 1604 remnant(Kepler’s SNR),although Chandra X-ray observation suggests that the progenitor is most likely a WD+AGB system,the surviving companion has not been found.One possible reason is rapid rotation of the white dwarf(WD),causing explosion of the WD to be delayed for a spin-down timescale,and then the companion evolved into a WD before the supernova explosion,so the companion is too dim to be detected.We aim to verify this possible explanation by carrying out binary evolution calculations.In this paper,we use Eggleton’s stellar evolution code to calculate the evolution of binaries consisting of a WD+red giant(RG).We assume that the rapidly rotating WD can continuously increase its mass when its mass exceeds the Chandrasekhar mass limit(MCh=1.378 M_⊙)until the mass-transfer rate decreases to be lower than a critical value.Eventually,we obtain the final masses of a WD in the range 1.378 M_⊙ to 2.707 M_⊙.We also show that if the spin-down time is less than 10~6 yr,the companion star will be very bright and easily observed;but if the spin-down time is as long as~10~7 yr,the luminosities of the surviving companion would be lower than the detection limit.Our simulation provides guidance in hunting for the surviving companion stars in SNRs,and the fact that no surviving companion has been found in Kepler’s SNR may not be definite evidence disfavoring the SD origin of Kepler’s SN.  相似文献   

7.
The amount of 56Ni produced in Type Ia supernova (SN Ia) explosion is probably the most important physical parameter underlying the observed correlation of SN Ia lumi-nosities with their light curves. Based on an empirical relation between the 56Ni mass and the light curve parameter △m15, we obtained rough estimates of the 56Ni mass for a large sample of nearby SNe Ia with the aim of exploring the diversity in SN Ia. We found that the derived 56Ni masses for different SNe Ia could vary by a factor of ten (e.g., MNi = 0.1 - 1.3 M⊙),which cannot be explained in terms of the standard Chandraseldaar-mass model (with a 56Ni mass production of 0.4 - 0.8 M⊙). Different explosion and/or progenitor models are clearly required for various SNe Ia, in particular, for those extremely nickel-poor and nickel-rich producers. The nickel-rich (with MNi 0.8 M⊙) SNe Ia are very luminous and may have massive progenitors exceeding the Chandrasekhar-mass limit since extra progenitor fuel is required to produce more 56Ni to power the light curve. This is also consistent with the find-ing that the intrinsically bright SNe Ia prefer to occur in stellar environments of young and massive stars. For example, 75% SNe Ia in spirals have △m15 < 1.2 while this ratio is only 18% in E/S0 galaxies. The nickel-poor SNe Ia (with MNi < 0.2 M⊙) may invoke the sub-Chandrasekhar model, as most of them were found in early-type E/S0 galaxies dominated by the older and low-mass stellar populations. This indicates that SNe Ia in spiral and E/S0 galaxies have progenitors of different properties.  相似文献   

8.
In this paper,we study five luminous supernovae(LSNe) Ibc(SN 2009ca,ASASSN-15mj,SN 2019omd,SN 2002ued,and SN 2021bmf) whose peak absolute magnitudes Mpeak are ≈-19.5 to-21 mag by fitting their multi-band light curves(LCs) with different energy source models.We find that SN 2009ca might be powered by the 56Ni model since the required 56Ni mass(0.56 M⊙) is comparable to those of energetic SNe Ic,while the rest four SNe cannot be accounted for the 56...  相似文献   

9.
Type Ia supernovae(SNe Ia) are believed to be thermonuclear explosions of carbon oxygen(CO) white dwarfs(WDs) with masses close to the Chandrasekhar mass limit. How a CO WD accretes matter and grows in mass to this limit is not well understood, hindering our understanding of SN Ia explosions and the reliability of using SNe Ia as a cosmological distance indicator. In this work, we employed the stellar evolution code MESA to simulate the accretion process of hydrogen-rich material onto a 1.0 M_⊙CO WD at a high rate(over the Eddington limit) of 4.3 × 10~(-7) M_⊙yr~(-1). The simulation demonstrates the characteristics of the double shell burning on top of the WD, with a hydrogen shell burning on top of a helium burning shell. The results show that helium shell burning is not steady(i.e.it flashes). Flashes from the helium shell are weaker than those in the case of accretion of helium-rich material onto a CO WD. The carbon to oxygen mass ratio resulting from the helium shell burning is higher than what was previously thought. Interestingly, the CO WD growing due to accretion has an outer part containing a small fraction of helium in addition to carbon and oxygen. The flashes become weaker and weaker as the accretion continues.  相似文献   

10.
It has been suggested that Type Ia supernovae(SNe Ia) could be produced in the conditions of the violent merger scenario of the double-degenerate model, in which a thermonuclear explosion could be produced when a double carbon-oxygen white dwarf(CO WD) merges. It has been recently found that the nucleus of the bipolar planetary nebula Henize 2–428 consists of a double CO WD system that has a total mass of^1.76 M⊙, a mass ratio of^1 and an orbital period of^4.2 h, which is the first and only discovered progenitor candidate for an SN Ia predicted by the violent merger scenario. In this work, we aim to reproduce the evolutionary history of the central double CO WD of Henize 2–428. We find that the planetary nebula Henize 2–428 may originate from a primordial binary that has a^5.4 M⊙primary and a^2.7 M⊙secondary with an initial orbital period of^15.9 d. The double CO WD was formed after the primordial binary experienced two Roche-lobe overflows and two common-envelope ejection processes.According to our calculations, it takes about^840 Myr for the double CO WD to merge and form an SN Ia driven by gravitational wave radiation after their birth. To produce the current status of Henize 2–428,a large common-envelope parameter is needed. We also estimate that the rate of SNe Ia from the violent merger scenario is at most 2.9 × 10-4 yr-1, and that the delay time is in the range of^90 Myr to the Hubble time.  相似文献   

11.
Type II and Ib/c supernovae(SNe II and Ib/c) have made major stellar nucleosynthetic contributions to the inventories of stable nuclides during chemical evolution of the Galaxy. A case study is performed here with the help of recently developed numerical simulations of Galactic chemical evolution in the solar neighborhood to understand the contributions of SNe II and Ib/c by comparing the stellar nucleosynthetic yields obtained by two leading groups in this field. These stellar nucleosynthetic yields differ in terms of their treatment of stellar evolution and nucleosynthesis. The formulation describing Galactic chemical evolution is developed with the recently revised solar metallicity of ～0.014. Furthermore, the recent nucleosynthetic yields of stellar models based on the revised solar metallicity are also used. The analysis suggests that it could be difficult to explain, in a self-consistent manner, the various features associated with the elemental evolutionary trends over Galactic timescales by any single adopted stellar nucleosynthetic model that incorporates SNe II and Ib/c.  相似文献   

12.
Equivalent widths and line widths of Ca II infrared triplet emission lines were measured in the high-resolution optical spectra of 39 young stellar objects.We found that the equivalent widths of the emission lines decrease with stellar evolution.It has often been claimed that strong chromospheric activity is generated by a dynamo process caused by fast rotation of the photosphere.However,we found no clear correlation between the strength of the Ca II lines and the stellar rotation velocity.Instead,we found that the objects with high mass accretion rates had stronger Ca II emission lines.This correlation supports the turbulent chromosphere model or the magnetic accretion theory for classical T Tauri stars.We also noticed that the equivalent widths of Ca II lines in transitional disk objects are one-tenth of those in classical T Tauri stars,even if the masses of the circumstellar disks are comparable.  相似文献   

13.
We test the distance-duality(DD) relation by combining the angular diameter distance DA provided by two galaxy cluster samples compiled by De Filippis et al.(the elliptical β model) and Bonamente et al.(the spherical β model),and the luminosity distance DL from Constitution and Union2 type Ia supernova(SNe Ia) datasets. To obtain DL associated with the observed DA at the same redshift,we smooth the noise of the SNe Ia in a model-independent way,obtain the evolutionary curve of DL and,finally,test the DD rel...  相似文献   

14.
AI Crucis is a short-period semi-detached massive close binary (P = 1.41771d, Sp.=B1.5) in the open cluster NGC 4103. It is a good astrophysical laboratory for investigating the formation and evolution of massive close binary stars via case A mass transfer. Orbital period variations of the system were analyzed based on one newly determined eclipse time and the others compiled from the literature. It is discovered that the orbital period of the binary is continuously increasing at a rate of dP/dt = +1.00(±0....  相似文献   

15.
1 IN~DUCTIONInterest in take la supernovae (SNe la) has risen dramatically with their application to thecosmological problems since Kowal (1968). Their powerful capabilities as distance indicatorson the cosmic scale have pushed them into the limelight of cosmology. They now provide themain route to the current eXPansion rate and the deceleration of the adverse. (see Branch1998; Perlmutter et al. 1999; mess et al. 1998).SNe la are reversally accepted as the result of thermonuclear eXPlo…  相似文献   

16.
The core-degenerate(CD) scenario has been suggested to be a possible progenitor model of type Ia supernovae(SNe Ia),in which a carbon-oxygen white dwarf merges with the hot CO core of a massive asymptotic giant branch star during their common-envelope phase.However,the SN Ia birthrates for this scenario are still uncertain.We conducted a detailed investigation into the CD scenario and then gave the birthrates for this scenario using a detailed Monte Carlo binary population synthesis approach.We found that the delay times of SNe Ia from this scenario are ~70 Myr-1400 Myr,which means that the CD scenario contributes to young SN la populations.The Galactic SN la birthrates for this scenario are in the range of~7.4×10~(-5) yr~(-1)- 3.7 × 10~(-4) yr~(-1),which roughly accounts for ~2%-10%of all SNe Ia.This indicates that,under the assumptions made here,the CD scenario only contributes a small portion of all SNe Ia,which is not consistent with the results of Ilkov Soker.  相似文献   

17.
Type Ia Supernovae(SNe Ia) are widely used as standard candles to probe the Universe. However,how these fierce explosions are produced itself is still a highly debated issue. There are mainly two popular models for SNe Ia: the double-degenerate scenario and the single-degenerate scenario. The doubledegenerate scenario suggests that SNe Ia are produced by the coalescence of two degenerate white dwarfs,while the single-degenerate scenario suggests that the continuous accretion of a single degenerate white dwarf from its normal stellar companion will finally lead to a disastrous explosion when it is over-massive,resulting in an SN Ia. The rapid development of the gravitational wave astronomy sheds new light on the nature of SNe Ia. In this study, we calculate the gravitational wave emissions of double white dwarf coalescences and compare them with the sensitivities of several upcoming detectors. It is found that the gravitational wave emissions from double white dwarf mergers in the local universe are strong enough to be detected by LISA. We argue that LISA-like gravitational wave detectors sensitive in the frequency range of 0.01 — 0.1 Hz will be a powerful tool to test the double-degenerate model of SNe Ia, and also to probe the Universe.  相似文献   

18.
We report a V band photometry of the SU UMa star IR Gem at quiescence in January 2002. The observations were made with two telescopes spaced - 160° apart in longitude. Several photometric modulations have been found. One gives a period of 98.50(13) min, exactly equal to the orbital period determined spectroscopically. Two others occasionally strengthen and seem to be positive and negative superhumps with periods of 103.6(4) and 95.4(4) min, 5.2% longer and 3.1% shorter than the orbital period, respectively. A signal at - 0.6 c/d in the power spectrum is roughly consistent with the expected period of nodal precession of the disk. There is a puzzling peak at 0.21(3) c/d corresponding to the - 4.3 d sine wave seen in the raw light curve. We suspect it to be a beat frequency between the frequencies of apsidal and nodal precessions of the disk. Quasi-periodic cycles with amplitudes 0.15-0.6 mag can be seen in the light curve. The mechanism underlying this modulation is not clear.  相似文献   

19.
We present the results obtained from detailed timing and spectral studies of the Be/X-ray binary pulsar KS 1947+300 during its 2013 giant outburst. We used data from Suzaku observations of the pulsar at two epochs, i.e. on 2013 October 22(close to the peak of the outburst) and 2013 November 22. Xray pulsations at ~18.81 s were clearly detected in the light curves obtained from both observations. Pulse periods estimated during the outburst showed that the pulsar was spinning up. The pulse profile was found to be single-peaked up to ~10 ke V beyond which a sharp peak followed by a dip-like feature appeared at hard X-rays. The dip-like feature has been observed up to ~70 keV. The 1–110 ke V broad-band spectroscopy of both observations revealed that the best-fit model was comprised of a partially absorbed Negative and Positive power law with EXponential cutoff(NPEX) continuum model along with a blackbody component for the soft X-ray excess and two Gaussian functions at 6.4 and 6.7 ke V for emission lines. Both the lines were identified as emission from neutral and He-like iron atoms. To fit the spectra, we included the previously reported cyclotron absorption line at 12.2 keV. From the spin-up rate, the magnetic field of the pulsar was estimated to be ~1.2×10~(12)G and found to be comparable to that obtained from the detection of the cyclotron absorption feature. Pulse-phase resolved spectroscopy revealed the pulsating nature of the soft X-ray excess component in phase with the continuum flux. This confirms that the accretion column and/or accretion stream are the most probable regions of the soft X-ray excess emission in KS1947+300.The presence of the pulsating soft X-ray excess in phase with continuum emission may be the possible reason for not observing the dip at soft X-rays.  相似文献   

20.
Cosmic hydrogen is reionized and maintained in its highly ionized state by the ultraviolet emission attributed to an early generation of stars and quasars. The Lyα opacity observed in absorption spectra of high-redshift quasars permits more stringent constraints on the ionization state of cosmic hydrogen. Based on density perturbation and structure formation theory, we develop an analytic model to trace the evolution of the ionization state in the post-overlap epoch of reionization, in which the bias factor is taken into ac-count. For quasars, we represent an improved luminosity function by utilizing a hybrid approach for the halo formation rate that is in reasonable agreement with the published measurements at 2 z 6. Comparison with the classic Press-Schechter mass function of dark matter halos, we demonstrate that the biased mass distribution indeed enhances star formation efficiency in the overdense environment by more than 25 per cent following the overlap of ionized bubbles. In addition, an alternative way is introduced to derive robust estimates of the mean free path for ionizing photons. In our model, star-forming galax-ies are likely to dominate the ionizing background radiation beyond z = 3, and quasars contribute equally above a redshift of z ～ 2.5. From 5 ≤ z ≤ 6, the lack of evolution in photoionization rate can thus be explained by the relatively flat evolution in star formation efficiency, although the mean free path of ionizing photons increases rapidly. Moreover, in the redshift interval z ～ 2 - 6, the expected mean free path and Gunn-Peterson optical depth obviously evolve by a factor of ～ 500 and ～ 50 respectively. We find that the rel-ative values of critical overdensities for hydrogen ionization and collapse could be 430% at z ≈ 2 and 2% at z ≈ 6, suggesting a rapid overlap process in the overdense regions around instant quasars following reionization. We further illustrate that the absolute esti-mates of the fraction of neutral hydrogen computed from theoretical models may not be important because of comparable uncertainties in the computation.  相似文献   

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