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1.
We present the results of our photometric UBV JHKLM observations in 2008?C2011 for the classical symbiotic star V1413 Aql. At the end of 2008, the hot component of V1413 Aql experienced the next strong outburst (??V > 2 · m 5). According to the photometric criterion (B-V ?? 0 · m 9 ± 0 · m 2), the star was in an active state even in the period preceding the strong 2008 outburst. Two eclipsing minima of the same amplitude were observed for V1413 Aql in 2010 and 2011. Our analysis of the 2011 eclipse has allowed us to estimate the sizes of the components with respect to the orbital semimajor axis if the system is seen edge-on: the radius of the cool component is R g/a = 0.28 and the radius of the hot component is R h/a = 0.17. However, judging by the B-V color index, the eclipse may be noncentral.  相似文献   

2.
We present the results of our spectroscopic observations for the classical symbiotic star V1413 Aql performed in 2008–2011. Various states of the hot component are considered: almost quiescence in 2008, very slow outburst onset in 2009, outburst maximum in 2010, and gradual brightness decline in the erupted hot component in 2011. We have established that, according to a spectroscopic criterion, in 2008 the system was in quiescence. We have shown that the parameters of the hot component during its outburst can be determined only by modeling the differences of the spectra taken at different eclipse phases. The active hot component of V1413 Aql at the outburst maximum is shown to have had the record late (for a symbiotic star) spectral type K2. At various stages of the new activity cycle, we have modeled the continuumenergy distribution based on a standard three-componentmodel, a model including a standard accretion disk and a red giant, and amodel including a supergiant (of various spectral types) and a red giant. The parameters of the system’s components have been determined.  相似文献   

3.
We present the results of our spectroscopic observations for the classical symbiotic star V1413 Aql in 20122017. In this period the system was in both active and rare (for it) quiescent states. In 2012 the optical spectrum was dominated by the radiation from the erupted hot component of spectral type F47 III. In 2017 the system passed to a quiescent state that lasted at least three months. In this period lines of ions with high ionization potentials, such as He II 4686 Å and CIV 5802 Å, appeared in the spectrum. The temperature and luminosity of the hot component in this period were $$T_{\textrm{hot}}\approx 90\,000$$ K and $$L_{\textrm{hot}}\approx 1800L_{\odot}$$. We show that the quiescent state in 2017 differs little in its time and energy characteristics from the previous active state observed in 1993.  相似文献   

4.
We present recent results from optical photometric and spectroscopic observations of the pre‐main sequence star V1184 Tau (CB 34V). The star is associated with the Bok globule CB 34 and was considered as a FUOR candidate in previous studies. Our photometric data obtained from October 2000 to April 2003 show that the stellar brightness varies with an amplitude of about 0.m 5 (I ), but from August 2003 the photometric behavior of the star has changed dramatically. Three deep brightness minima (ΔI ∼ 4m.2) were observed during the past two years. The analysis of available photometric data suggests that V1184 Tau shows two types of variability produced (1) by rotation of large cool spotted surface and (2) by occultation from circumstellar clouds of dust or from features of a circumstellar disk. The behavior of the V – I index indicates that the star becomes redder towards minimum light, but from a certain turning point (V ∼ 18m.2) it gets bluer and is fading further. Five medium dispersion optical spectra of V1184 Tau were obtained in the period 2001–2004. Signi.cant changes in the profile and strength of the emission lines in the spectrum of V1184 Tau were found. During minimum light the equivalent width of the Hα emission line increases from 4 Å to 9 Å. The [O I] lines (λλ 6003, 6363 Å) are also seen in emission while the sodium doublet keeps its absorption strength and equivalent width. The possibility to reconstruct the historical light curve of V1184 Tau using photographical plate archives is brie.y discussed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

5.
We present new photometric UBVRI and spectroscopic observations of the symbiotic star YY Her during its return to quiescence after a strong outburst in 1993. High-resolution spectra of YY Her at similar phases at outburst maximum ?=0.48) and in quiescence ?=0.37) are presented for the first time. The ephemeris of YY Her has been refined P=586d). The last two observed minima (in 1999 and 2000) differed radically in shape from the 1997 minimum described previously. Both were sharp and deep $(\Delta U \sim 1\mathop .\limits^m 6, \Delta V \sim 0\mathop .\limits^m 9)$ . To explain this shape of the V light curve, which is only slightly affected by nebular emission, it should be assumed that the cool component of YY Her fills much of its Roche lobe and has a hot spot on the hemisphere facing the hot component. The emission spectrum rich in Fe II lines, which is characteristic of symbiotic stars, was observed during the outburst, but high-ionization lines (He II λ4686) were also observed. The He I λλ5876, 7065 lines exhibit distinct P Cyg profiles; the centers of the absorption components are shifted from the emission ones by V r≈100 km s?1, suggesting moderate outflow velocities.  相似文献   

6.
We determine abundances from the absorption spectrum of the magnetic Herbig Ae star HD 190073 (V1295 Aql). The observations are primarily from HARPS spectra obtained at a single epoch. We accept arguments that the presence of numerous emission lines does not vitiate a classical abundance analysis, though it likely reduces the achievable accuracy. Most abundances are closely solar, but several elements show departures of a factor of two to three, as an earlier study has also shown. We present quantitative measurements of more than 60 emission lines, peak intensities, equivalent widths, and FWHM's. The latter range from over 200 km s–1(Hα, He D3) down to 10–20 km s–1(forbidden lines). Metallic emission lines have intermediate widths. We eschew modeling, and content ourselves with a presentation of the observations a successful model must explain. Low‐excitation features such as the Na I D‐lines and [O I] appear with He I D3, suggesting proximate regions with widely differing Te and Ne as found in the solar chromosphere. The [O I] and [Ca II] lines show sharp, violet‐shifted features. Additionally, [Fe II] lines appear tobe weakly present in emission (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

7.
We have constructed the light curves of the symbiotic nova V1016 Cyg for the period 1971–2007 in a homogeneous photometric system close to UBV using our observations with the Zeiss-600 SAI telescope. Based on the observational data obtained with the 125-cm SAI telescope in 2000–2007, we have performed absolute spectrophotometry of the star in the range λ3700–9300 Å. The derived line intensities are compared with the data of other authors in the preceding years (1965–1988). The behavior of nebular lines showed the variations in electron density and, probably, electron temperature in the [OIII] emission region caused by a variable stellar wind from the hot component. All the available observations of the star confirm the theoretical conclusion that the nova-like outburst of V1016 Cyg was produced by a thermonuclear flash in the accreted envelope of a white dwarf.  相似文献   

8.
New BVR light curves and a photometric analysis of the eclipsing binary star V1430 Aql are presented. The light curves were obtained at the Çanakkale Onsekiz Mart University Observatory in 2004. The light curves are generally those of detached eclipsing binaries, but there are large asymmetries between maxima. New BVR light curves were analysed with an ILOT procedure. Light curve asymmetries of the system were explained in terms of large dark starspots on the primary component. The primary star shows a long‐lived and quasi‐poloidal spot distribution with active longitudes in opposite hemispheres. Absolute parameters of the system were derived.We also discuss the evolution of the system: the components are likely to be pre‐main sequence stars, but a post‐main sequence stage cannot be ruled out. More observations are needed to decide this point. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

9.
We present the results of our photometric UBV JHKL observations for the symbiotic star V1413 Aql obtained in 2012–2018. An analysis of the data has shown that inMay 2017 the system passed to a quiescent state with B ? V ≈ 0? 6 for the first time since 1993. It lasted no more than five months. The J ? K color at the primary minimum of 2012 reached 1? 5, which, given the interstellar reddening, corresponds to spectral type M5-M6 III of the cool component. A secondary minimum has been detected at φ ≈ 0.5 on the JK phase light curves constructed for the dates of observations with B ≥ 13.  相似文献   

10.
Orbital period variations of two neglected Algol type binaries, CC Her and XZ Aql, are studied based on all available times of minima. In the case of CC Her, it is found that the O –C curve displays a tilted sinusoidal variation with an eccentricity of 0.54 ± 0.03 and a period of 52.4 ± 0.4 yr, which can be explained by the light‐time effect due to the presence of an unseen component. The course of the orbital period change in XZ Aql appears less reliable but its O –C curve can be represented by a periodic variation with a period of 36.7 ± 0.6 yr superimposed on an upward parabola. The parabolic variation indicates a secular period increase with a rate of dP /dt = 7.1 s per century. The corresponding conservative mass transfer from less massive component to the more massive one is about 3.26 × 10–7 M⊙ yr–1. It is interesting to see that the O –C variation of CC Her displays no evidence (as upward parabola) on the mass transfer characteristic for Algols. The periodic change of the orbital period of XZ Aql, like CC Her, may be caused by the presence of the thirdbody. The lower limits of the masses of the hypothetical unseen components for CC Her and XZ Aql are found to be 2.69 M⊙ and 0.47 M⊙, respectively. The third body of CC Her should be detectable not only spectroscopically but also photoelectrically, if it exists. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

11.
We report the first survey of chemical abundances in M and K dwarf stars using atomic absorption lines in high-resolution spectra. We have measured Fe and Ti abundances in 35 M and K dwarf stars using equivalent widths measured from  λ/Δλ≈ 33 000  spectra. Our analysis takes advantage of recent improvements in model atmospheres of low-temperature dwarf stars. The stars have temperatures between 3300 and 4700 K, with most cooler than 4100 K. They cover an iron abundance range of  −2.44 < [Fe/H] < +0.16  . Our measurements show [Ti/Fe] decreasing with increasing [Fe/H], a trend similar to that measured for warmer stars, where abundance analysis techniques have been tested more thoroughly. This study is a step towards the observational calibration of procedures to estimate the metallicity of low-mass dwarf stars using photometric and low-resolution spectral indices.  相似文献   

12.
Spectroscopic observations of the recurrent Nova CI Aql in the wavelength range 4000–11000 Å are presented. Its evolution is traced from maximum light to the disappearance of nebular lines. 〈E B-V 〉 = 0.91 ± 0.11, as inferred from the Balmer decrement. The mean expansion velocity of the envelope measured near maximum light is 2800 km s?1. The helium abundance in the Nova envelope has been found to be enhanced, ?He/H?=0.22. CI Aql is similar in spectral evolution, in change of the envelope expansion velocity, and in helium abundance to other recurrent novae.  相似文献   

13.
We present the results of our analysis of magnetic-field configuration and abundance anomalies on the surface of the rapidly rotating, chemically peculiar helium-strong variable B2 V star HD 37776 with unresolved Zeeman components of spectral lines. Simultaneous inversion of the observed Stokes I and V profiles, which realizes the method of Doppler-Zeeman mapping [1], has been applied for the first time. Spectroscopic observations were carried out with the Main stellar spectrograph of the 6-m Special Astrophysical Observatory telescope equipped with a Zeeman analyzer and a CCD array, which allowed spectra in right-and left-hand circularly polarized light to be taken simultaneously at a signal-to-noise ratio S/N≥200 [2]. The profile width of winged spectral lines (reaching 5 Å) is determined by Zeeman line splitting; however, the observed Zeeman components are blurred and unresolved because of the rapid stellar rotation. When solving the inverse problem, we sought for the magnetic-field configuration in the form of a combination of arbitrarily oriented dipole, quadrupole, and octupole placed at the stellar center. The observed Stokes I and V profiles for eight spectral lines of He, O II, Al III, Si III, and Fe III averaged over the visible stellar surface were used as input data. We constructed a model of the magnetic field from the condition of coincidence of magnetic maps obtained from different lines of different chemical elements and from the condition of a minimum profile residual. This model is a combination of centered coaxial dipole and quadrupole with the dominant quadrupole component at 30°<i<50°, β=40°, and a maximum surface field strength H s=60 kG. A comparison of our abundance maps with the field configuration shows that the He concentration is at a maximum in the regions of maximum radial field, while the maximum concentrations of O, Al, Si, and Fe coincide with the regions of maximum tangential field.  相似文献   

14.
We present differential Hα and Hβ photometry of the very bright RS CVn‐binary α Aurigae (Capella)obtained with theVienna automatic photoelectric telescope in the years 1996 through 2000. Low‐level photometric variations of up to 0m.04 are detected in Hα. A multifrequency analysis suggests two real periods of 106 ± 3 days and 8.64 ± 0.09 days, that we interpret to be the rotation periods of the cool and the hot component of the Capella binary, respectively. These periods confirm that the hotter component of Capella rotates asynchronously, while the cooler component appears to be synchronized with the binary motion. The combined Hα data possibly contains an additional period of 80.4 days that we, however, believe is either spurious and was introduced due to seasonal amplitude variations or stems from a time‐variable circumbinary mass flow. The rotational periods result in stellar radii of 14.3 ± 4.6 R⊙ and 8.5 ± 0.5 R⊙ for the cool and hot component, respectively, and are in good agreement with previously published radii based on radiometric and interferometric techniques. The long‐period eclipsing binary Aurigae served as our check star, and we detected complex light variations outside of eclipse of up to 0m.15 in H α and 0m.20 in Hβ. Our frequency analysis suggests the existence of at least three significant periods of 132, 89, and 73 days. One of our comparison stars (HD 33167, F5V) was discovered to be a very‐low amplitude variable with a period of 2.6360 ± 0.0055 days.  相似文献   

15.
The photometric UBV observations of AS 338 that we began after its outburst in 1983 are presented. They were accompanied by yearly spectroscopic observations and by occasional estimations of the star’s infrared JHKL magnitudes. In June 1993, the star’s optical spectrum was extended to the ultraviolet via IUE observations of AS 338. Collectively, the above observations make it possible to trace the evolution of stellar activity over a period of 15 years in various spectral ranges. In particular, a short-time return of the hot component of AS 338 to the state when He II lines reappeared in the star’s spectrum was noted in 1993. At this time, a blend of the C IV λλ5802 and 5812 lines, which is typical of Wolf-Rayet spectra, was detected in it. In June 1993, the temperature of the hot component was T h ≈ 8.8 × 104 K, and the ratio of its bolometric flux to that of the red giant was F h, bol/F g, bol ≈ 1.0. In August, its temperature increased to ～1.0×105 K, while the bolometric flux dropped by a factor of ～1.5(F h, bol/F g, bol ≈ 0.7). In the B-V, U diagram, the points referring to this so-called quiescent state form a separate group shifted in B-V from all the remaining ones located in a horizontal strip with $\Delta U \approx 3\mathop .\limits^m 5$ and $\Delta (B - V) \approx 0\mathop .\limits^m 4$ . This allows us to diagnose the state of the hot component without spectroscopic observations of the star. In October 1993, the hot component flared up again. The main brightness rise took no more than 19 days. The outburst occurred shortly before eclipse egress of the hot component, whose duration was ～0.01P orb. In December 1993, F h, bol/F g, bol≤1.5 at maximum light. During the recurrent, even stronger outburst in April 1995, F h, bol/F g, bol≤3.4. The Hαline during outbursts has a P Cyg profile and broad wings stretching to velocities of ±1500 km s?1. The color temperature of the active hot component at short optical wavelengths and in the ultraviolet lies in the range of effective temperatures for hot supergiants. Nevertheless, it always produces an H II region in the circumstellar envelope that is larger in size than this binary system.  相似文献   

16.
We present our photoelectric observations of the binary star VV8=V471 Per over the period 1971–2007. A long-term photometric variability with a period of about 17 yr in the V and B bands has been confirmed. A systematic rise in brightness was recorded in the U band, suggesting that the gas ionization increases in the binary system. Our spectroscopic observations from 1995 to 2007 have shown that the emission line fluxes, on average, did not change compared to the data of other authors obtained in the previous decades. We have shown that the cool giant is a G5III star and is probably enriched with nucleosynthesis products from the evolved former primary component of the binary. We provide arguments for the hypothesis that the hot component in V471 Per is the massive nucleus of a young planetary nebula that rapidly evolved to a temperature of 65 000–75 000 K, while the surrounding nebula is very dense and optically thick and has not yet been entirely ionized.  相似文献   

17.
We present our spectroscopic observations of the novae V1425, V1493, and V1494 Aql carried out with the 125-cm telescope at the Crimean Station of the Sternberg Astronomical Institute in the wavelength range 4000–11000 Å. We measured the emission-line intensities, determined the nova shell expansion velocities from the line profile FWHMs and components, and estimated the interstellar reddening from the first members of the Balmer series. The chemical composition of the nova shells is analyzed. Nitrogen and oxygen were found to be overabundant in V1425 and V1494 Aql; the helium abundance turned out to be normal in the two stars.  相似文献   

18.
We present the first ever study of the bright star HD 1. The star was chosen arbitrarily just because of its outstanding Henry Draper number. Surprisingly, almost nothing is known about this bright 7.m4 star. Our observations were performed as part of the commissioning of the robotic telescope facility STELLA and its fiber‐fed high‐resolution optical echelle spectrograph SES in the years 2007–2010. We found long‐term radial velocity variations with a full amplitude of 9 km s–1 with an average velocity of –29.8 km s–1 and suggest the star to be a hitherto unknown single‐lined spectroscopic binary. A preliminary orbit with a period of 6.2 years (2279±69 days) and an eccentricity of 0.50±0.01 is given. Its rms uncertainty is just 73 m s–1. HD 1 appears to be a G9‐K0 giant of luminosity class IIIa with Teff = 4850±100 K, logg = 2.0±0.2, L ≈ 155 L⊙, a mass of 3.0±0.3 M⊙, a radius of 17.7 R⊙, and an age of ≈350 Myr. A relative abundance analysis led to a metallicity of [Fe/H] = –0.12 ± 0.09. The α ‐element silicon may indicate an overabundance of +0.13 though. The low strengths of some s‐process lines and a lower limit for the 12C/13C isotope ratio of ≥16 indicate that HD 1 is on the first ascend of the RGB. The absorption spectral lines appear rotationally broadened with a v sin i of 5.5±1.2 km s–1 but no chromospheric activity is evident. We also present photometric monitoring BV (RI)C data taken in parallel with STELLA. The star is likely a small‐amplitude (<10 mmag) photometric variable although no periodicity was found (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

19.
We present new results of our UBV photometry for HD 179821=V1427 Aql, an F supergiant with an infrared excess, from 2000 to 2008. The semiregular low-amplitude (ΔV = 0. m 05−0. m 20) photometric variability of the star with a cycle period from 130 to 200 days is caused by pulsations, along with the instability of a variable stellar wind. V1427 Aql also exhibits a long-term trend in the brightness and colors that is probably attributable to a change in the stellar temperature as a result of mass loss episodes, which cause variations in the continuum formation level. We present the results of our JHKLM photometry for V1427 Aql in 1992–2008. We trace the trend in the near-infrared brightness, which agrees with the long-term variability in the V band. Based on broadband photometry, we have determined the color excess for V1427 Aql: E(B−V) = 0.7. Based on low-resolution spectroscopy, we have estimated the stellar temperature and revealed variability of the Hα line caused by a change in the contribution from the emission component. The hypotheses of whether the star belongs to post-AGB objects or to massive yellow hypergiants are discussed.  相似文献   

20.
The UBVRI photometry of the eclipsing symbiotic star CI Cyg in 1996–1999 is presented. The system continued to be in quiescence during this period. The shape of the minima in its light curves attributable to eclipses of the compact star with an accretion disk by the red giant is the same as that in 1988–1995. An analysis of our observations and those of other researchers, which span a total of 27 years, has revealed a cyclic variability of the out-of-eclipse photometric properties of CI Cyg on a time scale of about 10.7±0.6 years with the clearest manifestation in the U-B color. The fact that the system’s out-of-eclipse light variations in U, on the one hand, and in BVRI, on the other, occur in antiphase suggests that the titanium red giant plays a significant role in this cyclic process. However, with its contribution to the total U flux being no larger than 10%, the observed light fluctuations of CI Cyg in this band must be caused not only by variability of the giant but also by light variations of the hot component. The presence of a 10.7-year cycle in the system’s active and quiescent states suggests that some precession phenomenon is responsible for it. Precession of the accretion disk, which would cause both the observed brightness of the primary component and the effect of its radiation on the titanium red giant to vary, can serve as an example of such a phenomenon.  相似文献   

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