Synchronous <Emphasis Type="Italic">UBVR</Emphasis> photometry and spectroscopy of DI Cephei

We present our synchronous spectroscopy and photometry of DI Cep, a classical T Tauri star. The equivalent widths and radial velocities of the individual components and Hα, Hβ, D1 and D2 Na I, and HeI λ5876 Å emission line profiles exhibit variability. We have found a clear positive correlation between the brightness and equivalent width for the Hα and Hβ emission lines. The photometric and spectroscopic data are satisfactorily described in phases of a 9-day period. The expected magnetic field of the star has been estimated using existing magnetospheric models to be 655–1000 G. The star is suspected to be a binary.     

Swift ultraviolet photometry of the Deep Impact encounter with Comet 9P/Tempel 1

We report time-resolved imaging UV photometry of Comet 9P/Tempel 1 during the interval 2005 June 29-2005 July 21, including intensive coverage of the collision with the Deep Impact probe and its immediate aftermath. The nuclear flux of the comet begins to rise within minutes of the collision, and peaks about 3 h after impact. There is no evidence for a prompt flash at the time of impact. The comet exhibits a significant re-brightening about 40 h after the initial outburst, consistent with the rotation period of the comet, with evidence for further periodic re-brightenings on subsequent rotations. Modelling of the brightness profile of the coma as a function of time suggests two distinct velocity systems in the ejecta, at de-projected expansion speeds of 190 and 550 m/s, which we suggest are due to dust and gas, respectively. There is a distinct asymmetry in the slower-moving (dust) component as a function of position angle on the sky. This is confirmed by direct imaging analysis, which reveals an expanding plume of material concentrated in the impact hemisphere. The projected expansion velocity of the leading edge of this plume, measured directly from the imaging data, is 190 m/s, consistent with the velocity of the dust component determined from the photometric analysis. From our data we determine that a total of (1.4±0.2)×¹⁰³² water molecules were ejected in the impact, together with a total scattering area of dust at 300 nm of 190±20 km².     

X-ray intensity-hardness correlation and deep IR observations of the anomalous X-ray pulsar 1RXS J170849-400910

We report here on X-ray and IR observations of the Anomalous X-ray Pulsar (AXP) 1RXS J170849-400910. First, we report on new XMM-Newton, Swift-XRT and Chandra observations of this AXP, which confirm the intensity–hardness correlation observed in the long term X-ray monitoring of this source. These new X-ray observations show that the AXP flux is rising again, and the spectrum hardening. If the increase of the source intensity is indeed connected with the glitches and a possible bursting activity, we expect this source to enter in a bursting active phase around 2006–2007. Second, we report on deep IR observations of 1RXS J170849-400910, taken with the VLT-NACO adaptive optics, showing that there are many weak sources consistent with the AXP position. Neither star A or B, as previously proposed by different authors, might yet be conclusively recognised as the IR counterpart of 1RXS J170849-400910. Third, using Monte Carlo simulations, we re-address the calculation of the significance of the absorption line found in a phase-resolved spectrum of this source, and interpreted as a resonant scattering cyclotron feature.     

Characterization of the lithological contact in the shergottite EETA79001—A record of igneous differentiation processes on Mars

Abstract— Elephant Moraine (EET) A79001 is the only Martian meteorite that consists of both an olivine‐phyric shergottite (lithology A) and a basaltic shergottite (lithology B). The presence of these lithologies in one rock has previously been ascribed to mixing processes (either magmatic or impact‐induced). Here we present data regarding phase changes across the contact between the lithologies. These data show that the contact is gradational and suggest that it is a primary igneous feature consistent with crystallization of a single cooling magma. We present a model to establish a petrogenetic connection between an olivine‐phyric and a basaltic shergottite through differentiation. The model involves the shallow or surface emplacement of a magma that contained pre‐eruptive solids (phenocrysts and minor xenocrysts). Subsequent differentiation via crystal settling and in situ crystallization (Langmuir 1989) resulted in a layered sequence of lithology A overlain by lithology B, with gradations in modal abundance of maskelynite (increasing from A to B) and pigeonite/maskelynite (decreasing from A to B), and a gradational change in pattern of pyroxene zonation (zones of magnesian augite separating magnesian and ferroan pigeonite appear and thicken into B) across the contact. A pigeonite phenocryst‐bearing zone near the contact in lithology B appears to be intermediate between lithology A and the bulk of lithology B (which resembles basaltic shergottite Queen Alexandra Range [QUE] 94201). Re‐examination of Sr isotopic compositions in lithology A and across the contact is required to test and constrain the model.     

Mass‐dependent fractionation of nickel isotopes in meteoritic metal

Abstract— We measured nickel isotopes via multicollector inductively coupled plasma mass spectrometry (MC‐ICPMS) in the bulk metal from 36 meteorites, including chondrites, pallasites, and irons (magmatic and non‐magmatic). The Ni isotopes in these meteorites are mass fractionated; the fractionation spans an overall range of ～0.4‰ amu^?1. The ranges of Ni isotopic compositions (relative to the SRM 986 Ni isotopic standard) in metal from iron meteorites (～0.0 to ～0.3‰ amu^?1) and chondrites (～0.0 to ～0.2‰ amu^?1) are similar, whereas the range in pallasite metal (～–0.1 to 0.0‰ amu^?1) appears distinct. The fractionation of Ni isotopes within a suite of fourteen IIIAB irons (～0.0 to ～0.3‰ amu^?1) spans the entire range measured in all magmatic irons. However, the degree of Ni isotopic fractionation in these samples does not correlate with their Ni content, suggesting that core crystallization did not fractionate Ni isotopes in a systematic way. We also measured the Ni and Fe isotopes in adjacent kamacite and taenite from the Toluca IAB iron meteorite. Nickel isotopes show clearly resolvable fractionation between these two phases; kamacite is heavier relative to taenite by ～0.4‰ amu^?1. In contrast, the Fe isotopes do not show a resolvable fractionation between kamacite and taenite. The observed isotopic compositions of kamacite and taenite can be understood in terms of kinetic fractionation due to diffusion of Ni during cooling of the Fe‐Ni alloy and the development of the Widmanstätten pattern.     

J1128+592: a highly variable IDV source

Short time‐scale radio variations of compact extragalactic radio quasars and blazars known as IntraDay Variability (IDV) can be explained in at least some sources as a propagation effect; the variations are interpreted as scintillation of radio waves in the turbulent interstellar medium of the Milky Way. One of the most convincing observational arguments in favor of a propagation‐induced variability scenario is the observed annual modulation in the characteristic time scale of the variation due to the Earth's orbital motion. So far there are only two sources known with a well‐constrained seasonal cycle. Annual modulation has been proposed for a few other less well‐documented objects. However, for some other IDV sources source‐intrinsic structural variations which cause drastic changes in the variability time scale were also suggested. J1128+592 is a recently discovered, highly variable IDV source. Previous, densely time‐sampled flux‐density measurements with the Effelsberg 100‐m radio telescope (Germany) and the Urumqi 25‐m radio telescope (China), strongly indicate an annual modulation of the time scale. The most recent 4 observations in 2006/7, however, do not fit well to the annual modulation model proposed before. In this paper, we investigate a possible explanation of this discrepancy. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Tidal torque constants as a critical test for an evolution of close eclipsing binaries

Individual tidal torque λ ₂,E ₂ and apsidal-motion k ₂ constants were calculated for 112 close eclipsing binaries (CEBs) with Detached components belonging to the Main Sequence (DMS-type) from the catalogue by Svechnikov and Perevozkina (Catalogue of orbital elements, masses and luminosities of variable stars of DMS-type and some results of its statistical treatment, Ural State University Press, Yekaterinburg, pp. 1–5, 1999) and for 95 detached binaries taken from the catalogue by Torres et al. (Astron. Astrophys. Rev. 18:67, 2010) on the base of theoretical evolutionary stellar models including tidal torque constants by Claret (Astron. Astrophys. 424:919, 2004). A method of the inversion of model track grid into isochrones was formulated as a complex interpolation procedure for DMS-binaries data. Sets of isochrones were computed in k ₂–M, k ₂–R, λ ₂–M, λ ₂–R, E ₂–M, and E ₂–R planes. Calculated tidal torque constants allow to test stellar structure theory by comparing observed and estimated values of apsidal motion period and analyzing the correlation between timescales of synchronization, circularization, magnetic braking, as well as nuclear burning of DMS-components.     

Investigation of the open star cluster NGC 2323 (M50) based on the proper motions and photometry of its constituent stars

The results of a comprehensive study of the Galactic open cluster NGC 2323 (M50) are presented. The positions of stars to a limiting magnitude {ie74-1} in a {ie74-2} area centered on the cluster were measured on six plates from the Pulkovo normal astrograph with a maximum epoch difference of 60 yr. The measurements were performed with the Pulkovo “Fantasy” automated measuring system upgraded in 2010. The corresponding areas from the USNO-A2.0, USNO-B1, and 2MASS catalogues were used as additional plates. As a result, the relative proper motions of stars were obtained with a root-mean-square error of 5.85 mas yr⁻¹. A catalogue of UBV and JHK magnitudes for objects in the investigated area was compiled from available published resources. The astrometric selection of cluster members was made by the maximum likelihood method. A high individual cluster membership probability of a star (P ≥ 80%) served as the first selection criterion. The position of a star on the photometric color-magnitude (V ∝ (B-V), J ∝ (J-K)) diagrams of the cluster was considered as the second criterion. The position of an object on the color-color ((U-B)-(B-V), (J-H)-(J-K)) diagrams served as the third criterion. On the basis of these criteria, it was established that 508 stars are members of NGC 2323. These data were used to refine the physical parameters of the cluster: the mean reddening {ie74-3}, the true distance modulus {ie74-4}, and the cluster age of about 140 Myr from the grid of isochrones computed by the Padova group for solar chemical composition. Two tables contain the catalogues of proper motions and photometry for stars in the area. The luminosity and mass functions were constructed. The cluster membership of red and blue giants, variable, double, and multiple stars was considered. The position of the cluster center was improved: {ie74-5}, δ = −08°20′16″(2000.0).     

Non-LTE effects in Al I lines

We present the theoretical analysis of the Al I line formation in the spectra of late-type stars ignoring the assumption of local thermodynamic equilibrium (LTE). The calculations were based on the 39-level aluminum atom model for one-dimensional hydrostatic stellar atmosphere models with the parameters: T _eff from 4000 to 9000 K, log g = 0.0–4.5, and metallicity [A] = 0.0;–1.0;–2.0;–3.0;–4.0. The aluminum atom model and the method of calculations were tested by the study of line profiles in the solar spectrum. We refined the oscillator strengths and Van-der-Vaals broadening constants C ₆ of the investigated transitions. We conclude that the Al I atom is in the overionization state: the 3p level is underpopulated in the line formation region. This leads to the line weakening, as compared with the LTE results. The overionization effect becomes more pronounced with increasing temperature and decreasing metallicity. We show that the use of various atomic data (ionization cross-sections) for the low levels of Al I does not change the behavior of non-LTE deviations, whereas the value of these deviations varies essentially. For nine selected Al I lines we calculated the grids of theoretical non-LTE corrections (ΔX _NLTE = logɛ _NLTE − log ɛ _LTE) to the Al abundances determinedwith the LTE assumption. The non-LTE corrections are positive and significant for the stars with temperatures T _eff > 6000 K. These corrections weakly depend on log g, and increase with declining stellar metallicity.     

Heliospheric Observations of STEREO-Directed Coronal Mass Ejections in 2008?–?2010: Lessons for Future Observations of Earth-Directed CMEs

We present a study of coronal mass ejections (CMEs) which impacted one of the STEREO spacecraft between January 2008 and early 2010. We focus our study on 20 CMEs which were observed remotely by the Heliospheric Imagers (HIs) onboard the other STEREO spacecraft up to large heliocentric distances. We compare the predictions of the Fixed-?? and Harmonic Mean (HM) fitting methods, which only differ by the assumed geometry of the CME. It is possible to use these techniques to determine from remote-sensing observations the CME direction of propagation, arrival time and final speed which are compared to in-situ measurements. We find evidence that for large viewing angles, the HM fitting method predicts the CME direction better. However, this may be due to the fact that only wide CMEs can be successfully observed when the CME propagates more than 100^° from the observing spacecraft. Overall eight CMEs, originating from behind the limb as seen by one of the STEREO spacecraft can be tracked and their arrival time at the other STEREO spacecraft can be successfully predicted. This includes CMEs, such as the events on 4 December 2009 and 9 April 2010, which were viewed 130^° away from their direction of propagation. Therefore, we predict that some Earth-directed CMEs will be observed by the HIs until early 2013, when the separation between Earth and one of the STEREO spacecraft will be similar to the separation of the two STEREO spacecraft in 2009??C?2010.