Atmospheric and water loss from early Venus     

《Planetary and Space Science》2006,54(13-14):1425-1444

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Loss of hydrogen and oxygen from the upper atmosphere of Venus     

《Planetary and Space Science》2006,54(13-14):1445-1456

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A revisit to the regions of some van den Bergh open clusters using photometric and astrometric parameters     

《New Astronomy》2015

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Young eccentric binary KL CMa revisited in the light of spectroscopy     

《New Astronomy》2015

The absolute dimensions of the components of the eccentric eclipsing binary KL CMa have been determined. The solution of light and radial velocity curves of high ($\mathrm{\Delta }\lambda =0.14$ Å) and intermediate ($\mathrm{\Delta }\lambda =1.1$ Å) resolution spectra yielded masses M₁ = 3.55 ± 0.27 M_⊙, M₂ = 2.95 ± 0.24 M_⊙ and radii R₁ = 2.37 ± 0.09 R_⊙, R₂ = 1.70 ± 0.1 R_⊙ for primary and secondary components, respectively. The system consists of two late B-type components at a distance of 220 ± 20 pc for an estimated reddening of $E(B-V)=0.127$.The present study provides an illustration of spectroscopy’s crucial role in the analysis of binary systems in eccentric orbits. The eccentricity of the orbit ($e=0.20$) of KL CMa is found to be bigger than the value given in the literature ($e=0.14$). The apsidal motion rate of the system has been updated to a new value of $\dot{w}=0°.0199\pm 0.0002{\text{cycle}}^{-1}$, which indicates an apsidal motion period of $U=87\pm 1$ yrs, two times slower than given in the literature. Using the absolute dimensions of the components yielded a relatively weak relativistic contribution of ${\dot{w}}_{\mathit{rel}}=0°.0013{\text{cycle}}^{-1}$. The observed internal-structure component ($\log k_{2\text{,}\mathit{obs}}=-2.22\pm 0.01$) is found to be in agreement with its theoretical value ($\log k_{2\text{,}\mathit{theo}}=-2.23$).Both components of the system are found very close to the zero-age main-sequence and theoretical isochrones indicate a young age ($\tau =50$ Myr) for the system. Analysis of the spectral lines yields a faster rotation ($V_{\mathit{rot}1\text{,}2}=100$ km s⁻¹) for the components than their synchronization velocities ($V_{\mathit{rot}\text{,}\mathit{syn}1}=68$ km s⁻¹, $V_{\mathit{rot}\text{,}\mathit{syn}1}=49$ km s⁻¹).  相似文献   

Mapping Titan's surface features within the visible spectrum via Cassini VIMS     

Graham Vixie  Jason W. Barnes  Jacob Bow  Stéphane Le Mouélic  Sébastien Rodriguez  Robert H. Brown  Priscilla Cerroni  Federico Tosi  Bonnie Buratti  Christophe Sotin  Gianrico Filacchione  Fabrizio Capaccioni  Angioletta Coradini 《Planetary and Space Science》2012,60(1):52-61

Titan shows its surface through many methane windows in the 1–5 $\mathrm{\mu }\mathrm{m}$ region. Windows at shorter wavelengths also exist, polluted by scattering off of atmospheric haze that reduces the surface contrast. At visible wavelengths, the surface of Titan has been observed by Voyager I, the Hubble Space Telescope, and ground-based telescopes. We present here global surface mapping of Titan using the visible wavelength channels from Cassini's Visual and Infrared Mapping Spectrometer (VIMS). We show global maps in each of the VIMS-V channels extending from 0.35 to 1.05 $\mathrm{\mu }\mathrm{m}$. We find methane windows at 0.637, 0.681, 0.754, 0.827, 0.937, and $1.046\mathrm{\mu }\mathrm{m}$ and apply an RGB color scheme to the 0.754, 0.827 and $0.937\mathrm{\mu }\mathrm{m}$ windows to search for surface albedo variations. Our results show that Titan appears gray at visible wavelengths; hence scattering albedo is a good approximation of the Bond albedo. Maps of this genre have already been made and published using the infrared channels of VIMS. Ours are the first global maps of Titan shortward of $0.938\mathrm{\mu }\mathrm{m}$. We compare the older IR maps to the new VIMS-V maps to constrain surface composition. For instance Tui Regio and Hotei Regio, referred to as $5\text{‐}\mathrm{\mu }\mathrm{m}$ bright spots in previous papers, do not distinguish themselves at all visible wavelengths. The distinction between the dune areas and the bright albedo spots, however, such as the difference between Xanadu and Senkyo, is easily discernible. We employ an empirically derived algorithm to remove haze layers from Titan, revealing a better look at the surface contrast.  相似文献   

A period study and revised photometric model for the eclipsing binary ZZ Cyg     

《New Astronomy》2015

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Absolute parameters of the newly-identified contact binary star IS Canis Major     

B. Özkardeş  A. Erdem 《New Astronomy》2010,15(2):247-253

This paper presents the results of the first high-resolution spectroscopic observations of the Southern W UMa type system IS CMa. Spectroscopic observations of the system were made at Mt. John University Observatory using a HERCULES fibre-fed échelle spectrograph in September 2007. The first radial velocities of the component stars of the system were determined by using the spectral disentangling technique. The resulting orbital elements of IS CMa are: $a_1\sin i=0.0041\pm 0.0001$ AU, $a_2\sin i=0.0135\pm 0.0001$ AU, $M_1{\sin }^{3}i=1.48\pm 0.01{\mathrm{M}}_{\odot }$, and $M_2{\sin }^{3}i=0.44\pm 0.01{\mathrm{M}}_{\odot }$. The components were found to be in synchronous rotation taking into account the disentangled ${\mathrm{H}}_{\delta }$ line profiles of both components of the system. The Hipparcos light curve was solved by means of the Wilson–Devinney method supplemented with a Monte Carlo type algorithm. The radial velocity curve solutions including the proximity effects give the mass ratio of the system as 0.297 ± 0.001. The combination of the Hipparcos light and radial velocity curve solutions give the following absolute parameters of the components: $M_1=1.68\pm 0.04{\mathrm{M}}_{\odot }\text{,}{\mathrm{M}}_2=0.50\pm 0.02{\mathrm{M}}_{\odot }\text{,}{R}_1=2.00\pm 0.02{\mathrm{R}}_{\odot }\text{,}{R}_2=1.18\pm 0.03R_{\odot }\text{,}{L}_1=7.65\pm 0.60$ ${\mathrm{L}}_{\odot }$ and $L_2=1.99\pm 0.80{\mathrm{L}}_{\odot }$. The distance to IS CMa was calculated as $87\pm 5$ pc using the distance modulus with corrections for interstellar extinction. The position of the components of IS CMa in the HR diagram are also discussed: the system seems to have an age of 1.6 Gyr.  相似文献   

New orbital solutions and absolute elements of the eclipsing binary TV Cet     

Z. Bozkurt  Ö.L. Değirmenci 《New Astronomy》2010,15(4):356-361

We present new differential, four-color photoelectric photometry for the eclipsing binary TV Cet. UBVR light curves and radial velocities published previously are solved simultaneously using the Wilson–Devinney computer program. Our solutions indicate that TV Cet includes a third light contribution with 2.3% in U, 1.9% in B, 1.3% in V and 1.6% in R. The masses of the component stars are $1.34\pm 0.05$ and $1.23\pm 0.05M\odot$, while the radii are $1.47\pm 0.02$ and $1.21\pm 0.01R\odot$ for the primary and secondary components, respectively. Using new absolute properties and our previous results from period analysis, we calculated the observational and theoretical internal structure constants to be ${\overline{k}}_{2\text{,}\mathit{obs}}=-1.66$ and ${\overline{k}}_{2\text{,}\mathit{theo}}=-2.25$, respectively. Taking into account the third light contribution from the Wilson–Devinney solution and properties of the third body orbit from period analysis, the mass of the third body is obtained as $0.56M\odot$, corresponding to the inclination value $i_3=20°$. Evolutionary status of the component stars is also studied. We present the position of the stars in an H–R diagram for solar compositions.  相似文献   

Six observations consistent with the electron neutrino being a m2=-0.11±0.02eV2 tachyon     

《Astroparticle Physics》2015

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Dynamics of the Venus upper atmosphere: Outstanding problems and new constraints expected from Venus Express     

《Planetary and Space Science》2006,54(13-14):1371-1380

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An application of the tensor virial theorem to hole + vortex + bulge systems     

R. Caimmi 《New Astronomy》2009,14(3):254-263

The tensor virial theorem for subsystems is formulated for three-component systems and further effort is devoted to a special case where the inner subsystems and the central region of the outer one are homogeneous, the last surrounded by an isothermal homeoid. The virial equations are explicitly written under the additional restrictions: (i) similar and similarly placed inner subsystems, and (ii) spherical outer subsystem. An application is made to hole + vortex + bulge systems, in the limit of flattened inner subsystems, which implies three virial equations in three unknowns. Using the Faber-Jackson relation, $R_{\text{e}}\propto {\sigma }_0^2$, the standard $M_{\text{H}}$-${\sigma }_0$ form $(M_{\text{H}}\propto {\sigma }_0^4)$ is deduced from qualitative considerations. The projected bulge velocity dispersion to projected vortex velocity ratio, $\eta =({\sigma }_{\text{B}}{)}_{33}/\{[(v_{\text{V}}{)}_{\mathit{qq}}{]}^2+[({\sigma }_{\text{V}}{)}_{\mathit{qq}}{]}^2{\}}^{1/2}$, as a function of the fractional radius, $y_{\text{BV}}=R_{\text{B}}/R_{\text{V}}$, and the fractional masses, $m_{\text{BH}}=M_{\text{B}}/M_{\text{H}}$ and $m_{\text{BV}}=M_{\text{B}}/M_{\text{V}}$, is studied in the range of interest, $0?m_{\text{VH}}=M_{\text{V}}/M_{\text{H}}?5$ [Escala, A., 2006. ApJ, 648, L13] and $229?m_{\text{BH}}?795$ [Marconi, A., Hunt, L.H., 2003. ApJ 589, L21], consistent with observations. The related curves appear to be similar to Maxwell velocity distributions, which implies a fixed value of $\eta$ below the maximum corresponds to two different configurations: a compact bulge on the left of the maximum, and an extended bulge on the right. All curves lie very close one to the other on the left of the maximum, and parallel one to the other on the right. On the other hand, fixed $m_{\text{BH}}$ or $m_{\text{BV}}$, and $y_{\text{BV}}$, are found to imply more massive bulges passing from bottom to top along a vertical line on the $(\mathsf{O}{y}_{\text{BV}}\eta )$ plane, and vice versa. The model is applied to NGC 4374 and NGC 4486, taking the fractional mass,$m_{\text{BH}}$, and the fractional radius, $y_{\text{BV}}$, as unknowns, and the bulge mass is inferred from the knowledge of the hole mass, and compared with results from different methods. In presence of a massive vortex $(m_{\text{VH}}=5)$, the hole mass has to be reduced by a factor 2–3 with respect to the case of a massless vortex, to get the fit. Finally, the assumptions of homogeneous inner bulge and isotropic stress tensor are discussed.  相似文献   

Signature of slow acoustic oscillations in a non-flaring loop observed by EIS/Hinode     

A.K. Srivastava  B.N. Dwivedi 《New Astronomy》2010,15(1):8-15

We study intensity oscillations near the apex of a coronal loop to find the signature of MHD oscillations. We analyse the time series of the strongest Fe XII 195.12 Å image data, observed by 40″ SLOT of the EUV Imaging Spectrometer (EIS) onboard the Hinode spacecraft. Using a standard wavelet tool, we produce power spectra of intensity oscillations at location ‘${\mathrm{L}}_3$’ near the apex of a clearly visible coronal loop. We detect intensity oscillations of a period of ≈322 s with a probability of 96%. This oscillation period of ≈322 s is found to be in good agreement with theory of the (second) harmonics of standing slow acoustic oscillations of $P_{2\mathit{nd}\mathit{slow}}\approx 313\pm 31\text{s}$. We detect, for the first time, the observational signature of multiple (first and second) harmonics of slow acoustic oscillations in the non-flaring coronal loop. Such oscillations have been observed in the past in hot and flaring coronal loops only, but have been predicted recently to exist in comparatively cooler and non-flaring coronal loops as well. We find the periodicities ～497 s and ～592 s with the probability 99–100% at the ‘L₁’ and ‘L₂’ locations, respectively, near the clearly visible western footpoint of the loop. We interpret these oscillations to be likely associated with the first harmonics (fundamental mode) of slow acoustic oscillations. Using the period ratios $P_1/P_2=1.54\text{and}1.84$, we estimate the density scale heights in the EUV loop as ～10 Mm and 21 Mm, respectively, in which the latter value (～21 Mm) is compared well with the loop half length. We also find an evidence of propagating bright blob at its lower bound sub-sonic speed of ≈6.4 km/s, suggesting that they are caused by the mass flow from one end to the other in the coronal loop. We also suggest that standing oscillations, and propagating bright blobs caused probably by the pulse of plasma flow, co-exist in comparatively cooler and non-flaring coronal loop.  相似文献   

Galileo dust data from the jovian system: 1997–1999     

《Planetary and Space Science》2006,54(9-10):879-910

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The effect of a thin weak layer covering a basalt block on the impact cratering process     

Koji Dohi  Masahiko Arakawa  Chisato Okamoto  Sunao Hasegawa  Minami Yasui 《Icarus》2012,218(2):751-759

To clarify the effect of a surface regolith layer on the formation of craters in bedrock, we conducted impact-cratering experiments on two-layered targets composed of a basalt block covered with a mortar layer. A nylon projectile was impacted on the targets at velocities of 2 and 4 km s^?1, and we investigated the crater size formed on the basalt. The crater size decreased with increased mortar thickness and decreased projectile mass and impact velocity. The normalized crater volume, π_V, of all the data was successfully scaled by the following exponential equation with a reduction length λ₀: ${\pi }_{\text{V}}=b_0{\pi }_{\text{Y}}^{-b_1}\exp (-\lambda /{\lambda }_0)$, where λ is the normalized thickness T/L_p, T and L_p are the mortar thickness and the projectile length, respectively, b₀ and b₁ are fitted parameters obtained for a homogeneous basalt target, 10^?2.7±0.7 and ?1.4 ± 0.3, respectively, and λ₀ is obtained to be 0.38 ± 0.03. This empirical equation showing the effect of the mortar layer was physically explained by an improved non-dimensional scaling parameter, ${\pi }_{\text{Y}}^1$, defined by ${\pi }_{\text{Y}}^1=Y/({\rho }_{\text{t}}{u}_{\text{p}}^2)$, where u_p was the particle velocity of the mortar layer at the boundary between the mortar and the basalt. We performed the impact experiments to obtain the attenuation rate of the particle velocity in the mortar layer and derived the empirical equation of $\frac{u_{\text{p}}}{v_{\text{i}}}=0.50\exp \left(-\frac{\lambda }{1.03}\right)$, where v_i is the impact velocity of the projectile. We propose a simple model for the crater formation on the basalt block that the surface mortar layer with the impact velocity of u_p collides on the surface of the basalt block, and we confirmed that this model could reproduce our empirical equation showing the effect of the surface layer on the crater volume of basalt.  相似文献   

New intrinsic-colour calibration for uvby-β photometry     

Yüksel Karataş  William J. Schuster 《New Astronomy》2010,15(5):444-449

A new intrinsic-colour calibration $((b-y{)}_o-\beta )$ is presented for the uvby-β photometric system, making use of re-calibrated Hipparcos parallaxes and published reddening maps. This new calibration for $(b-y{)}_o-\beta$, our Eq. (1), has been based upon stars with $d_{\mathit{Hip}}<70\text{pc}$ in the photometric catalogues of Schuster and Nissen (1988), Schuster et al., 2004, Schuster et al., 2006, provides a small dispersion, $\pm 0.009$, and has a positive “standard” $+2.239\mathrm{\Delta }\beta$ coefficient, which is not too different from the coefficients of Crawford (1975a, +1.11) and of Olsen (1988, +1.34). For 61 stars with spectra from CASPEC, UVES/VLT, and FIES/NOT databases, without detectable Na I lines, the average reddening value $〈E(b-y)〉=-0.001\pm 0.002$ shows that any zero-point correction to our intrinsic-colour equation must be minuscule.  相似文献   

KIC 9851142: A binary star with total eclipses and γ Dor pulsations     

《New Astronomy》2015

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Multiwavelength modeling the SED of supersoft X-ray sources III. RS Ophiuchi: The supersoft X-ray phase and beyond     

《New Astronomy》2015

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Long-term optical and radio variability of BL Lacertae     

《New Astronomy》2015

Well-sampled optical and radio light curves of BL Lacertae in $B\text{,}V\text{,}R\text{,}I$ bands and 4.8, 8.0, 14.5 GHz from 1968 to 2014 were presented in this paper. A possible $1.26\pm 0.05$ yr period in optical bands and a $7.50\pm 0.15$ yr period in radio bands were detected based on discrete correlation function, structure function as well as Jurkevich method. Correlations among different bands were also analyzed and no reliable time delay was found between optical bands. Very weak correlations were detected between V band and radio bands. However, in radio bands the variation at low frequency lagged that at high frequency obviously. The spectrum of BL Lacertae turned mildly bluer when the object turned brighter, and stronger bluer-when-brighter trends were found for short flares. A scenario including a precessing helical jet and periodic shocks was put forward to interpret the variation characteristics of BL Lacertae.  相似文献   

Inductive acceleration of UHECRs in sheared relativistic jets     

《Astroparticle Physics》2008,28(6):473-489

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Molecular Lines of CO Isotopes of the High Galactic Latitude Cloud HSVMT27     

Zhi-hong He  Ye Xu  Ji Yang  Deng-rong Lu  Xin-yu Du  Fa-cheng Li  Qing-zeng Yan 《Chinese Astronomy and Astrophysics》2018,42(2):188-201

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