CCD Spectra Research Articles

The Digitization of Photographic Spectra in the Dominion Astrophysical Observatory Plate Collection with Commercial Scanners: A Pilot Study

Commercial flatbed scanners have the potential to deliver a quick and efficient means of capturing the scientific content of spectra recorded on photographic plates. We discuss the digitization of selected spectra in the Dominion Astrophysical Observatory (DAO) photographic plate collection with commercial scanners. In this pilot study, emphasis is placed on assessing if the information on the plates can be recovered using Epson V800 and 12000XL scanners; the more complicated issues associated with the shortcomings of photographic materials, such as correcting for nonlinearity, are deferred to a future study. Spectra of Vega (α Lyr) that were recorded over ∼4 decades with the DAO 1.8 m telescope are examined. These spectra sample a range of photographic emulsions, plate preparation techniques, calibration information, observing techniques, and spectrograph configuration. A scanning density of 2400 elements per inch recovers information in the spectra. Differences in the modulation transfer function (MTF) of the two scanners are found, with the Epson 12000XL having a superior MTF. Comparisons with a CCD spectrum of Vega confirm that moderately weak features are faithfully recovered in photographic spectra that have been digitized with the 12000XL scanner. The importance of scanning the full plate to cover the light profile of the target and calibration information is emphasized. Lessons learned from these experiments are also presented.

Peculiarities of radial velocity variability of lines in the spectrum of α Cyg supergiant

ABSTRACT We use about 430 CCD spectra obtained in 1998–2001 and in 2007 to study temporal radial velocity variations of the ion, He i, and H β lines in the spectrum of the α Cyg. We found that these variations are caused by pulsation-type motions. In case of the ion and He i lines, fluctuations occur in the fundamental radial mode with the period of about 12.5 ± 1.0 d and the amplitude of 5.0 ± 0.5 km s−1. The oscillation lasts about ∼34 ± 1 d. In the case of the H β line the radial velocity variability was studied separately for the blue and red halves of the line profile. Such a methodical approach allowed to discover three characteristic cases of radial velocity variability for the blue and red halves of the H β line profile. In 1999 and 2001, the period P and amplitude A variability parameters are the same for the blue and red halves, and hence for the line bisector too. In 1998, P and A are the same for the blue and red halves of the profile, however, there is a phase shift between the fluctuations of their radial velocity by 0.6P. In 2000, P and A are different for the two halves of the line profile. Relative to the center of the star’s mass, the average expansion rate for the atmospheric layers, where the H β line is formed, is about −10.0 km s−1. It varies over time with a semi-amplitude of around ±3.3 km s−1.

Gaia EDR3 Data For Three Young Stellar Objects

We present Gaia Early Data Release 3 (Gaia EDR3) high accurate astrometric and photometric data and also Catalina Sky Survey (CSS ) phase-dependent light curves for three Young Stellar Objects (YSO). They are LRL 245, 2MASS J04300424+3533238, and CVSO 592. These tree YSOs are presented as periodic variables in the Catalina Surveys Data Release-1 (CSDR1) data base. CSS phase-dependent curve of LRL 245 shows periodicity with period P=234.66 days and amplitude ∆m≈4.0 mag. For this object high-resolution spectra in H-band (from 1.51 to 1.69 µm) was obtained by the APOGEE instrument. LAMOST telescope moderate-resolution CCD spectra is available for object 2MASS J04300424+3522238 only. The spectra shows clear features of M dwarfs.

Helium absorption in exoplanet atmospheres is connected to stellar coronal abundances

ABSTRACT Transit observations in the helium triplet around 10 830 Angstrom are a successful tool to study exoplanetary atmospheres and their mass loss. Forming those lines requires ionization and recombination of helium in the exoplanetary atmosphere. This ionization is caused by stellar photons at extreme ultraviolet (EUV) wavelengths; however, no currently active telescopes can observe this part of the stellar spectrum. The relevant part of the stellar EUV spectrum consists of individual emission lines, many of them being formed by iron at coronal temperatures. The stellar iron abundance in the corona is often observed to be depleted for high-activity low-mass stars due to the first ionization potential (FIP) effect. I show that stars with high versus low coronal iron abundances follow different scaling laws that tie together their X-ray emission and the narrow-band EUV flux that causes helium ionization. I also show that the stellar iron to oxygen abundance ratio in the corona can be measured reasonably well from X-ray CCD spectra, yielding similar results to high-resolution X-ray observations. Taking coronal iron abundance into account, the currently observed large scatter in the relationship of EUV irradiation with exoplanetary helium transit depths can be reduced, improving the target selection criteria for exoplanet transmission spectroscopy. In particular, previously puzzling non-detections of helium for Neptunic exoplanets are now in line with expectations from the revised scaling laws.

Two configurations of a dielectric barrier discharge enhanced nanoparticle (CexTi1-x)O2 catalyst for the removal of low-concentration SO2

• Reported on NTP enhanced nanoparticle (Ce x Ti 1-x )O 2 catalyst to remove low-concentration SO 2 . • The desulfurization efficiency under the ppc configuration is 30–400% higher than that of the catalyst alone, and the IPC configuration is 100% desulfurization at room temperature and pressure. • NTP increases the specific surface area of the catalyst and generates more unsaturated adsorbed oxygen and oxygen vacancies. • CCD spectrum is used to detect the discharge intermediate, and COMSOL is used to simulate the dynamic change of the intermediate in the discharge area. Removing low-concentration SO 2 present in flue gas is a worldwide problem. Herein, we introduce different technologies for coupling nonthermal plasma (NTP) with mixed CeO 2 -TiO 2 catalysts in a dielectric barrier discharge (DBD) reactor for the degradation of low-concentration SO 2 , including an in-plasma catalysis configuration (IPC) and a post-plasma catalysis configuration (PPC). Thermal catalysis at various Ce:Ti molar ratios and desulfurization efficiencies using different NTP-enhanced catalytic coupling processes were compared. We show that the SO 2 -removal efficiency in the PPC is enhanced by 20–30% by NTP, while 100% SO 2 -removal efficiency in the IPC was recorded at room temperature and atmospheric pressure, with (Ce 0.7 Ti 0.3 )O 2 exhibiting the best catalytic activity. To understand the influence of NTP on the activity of the catalytic reaction, catalytic behavior during (Ce 0.7 Ti 0.3 )O 2 thermal catalysis and during the nonthermal plasma reaction was analyzed by X-ray diffractometry, scanning electron microscopy, X-ray photoelectron spectroscopy, and N 2 physisorption experiments. The results suggest that plasma engraving increases the specific surface area of the catalyst and generates more oxygen vacancies or unsaturated active oxygen sites that promote the catalytic desulfurization reaction. Charged-coupled-device spectroscopy and COMSOL numerical simulations were used to reveal the types and transformations of reactive intermediate free radicals in the dielectric barrier discharge space. The results show that a large number of active N 2 /O 2 free radicals participate in transferring energy in the reactor, and that the first metastable state N 2 A 3 ∑ u + of N 2 is the most important excited state, as it promotes the formation and transformation of other active intermediates.

The Chandra High-resolution X-Ray Spectrum of Quiescent Emission from Sgr A*

Abstract In quiescence, Sgr A* is surprisingly dim, shining 100,000 times less than expected for its environment. This problem has motivated a host of theoretical models to explain radiatively inefficient accretion flows. The Chandra Galactic Center X-ray Visionary Program obtained approximately 3 Ms (1 month) of Chandra high-energy transmission grating (HETG) data, offering the only opportunity to examine the quiescent X-ray emission of Sgr A* with high-resolution spectroscopy. Utilizing custom background regions and filters for removing overlapping point sources, this work provides the first-ever look at stacked HETG spectra of Sgr A*. We model the background data sets with a cubic spline and fit the unbinned Sgr A* spectra with a simple parametric model of a power law plus Gaussian lines under the effects of interstellar extinction. We detect a strong 6.7 keV iron emission line in the HEG spectra and a 3.1 keV emission line in the MEG spectra. In all cases, the line centroids and equivalent widths are consistent with those measured from low-resolution CCD spectra. An examination of the unbinned, stacked HEG ± 1 spectrum reveals fine structure in the iron line complex. In addition to resolving the resonant and forbidden lines from He-like iron, there are apparent emission features arising with higher statistical significance at lower energy, potentially associated with Fe xx–xxiv ions in a ∼1 keV plasma arising near the Bondi radius of Sgr A*. With this work, we release the cleaned and stacked Sgr A* and background HETG spectra to the public as a special legacy data set.

Interstellar Lines and Diffuse Bands in the Spectrum of the Supergiant κ Cas

We have studied the interstellar lines and diffuse bands in the spectrum of the supergiant κ Cas using the CCD spectra obtained with the Echelle spectrograph of the 2 meter telescope at the peak Terskol observatory. A synthetic stellar spectrum was used to correctly reveal the interstellar features, computed for a model atmosphere with Teff = 21 500 K, log g = 2.60, v sin i = 83 kms-1, [M/H] = 0.0, ξ = 15 kms-1 and with partial selection of main chemical element abundances. Eleven interstellar bands and 91 diffuse interstellar bands were identified. A further 14 absorption features were revealed, possibly also diffuse bands. The spectrophotometric diffuse band parameters and their accuracies were tabulated. We present maps of observed and synthetic spectral regions containing interstellar diffuse bands.

On the origin of central abundance drops in the intracluster medium of galaxy groups and clusters

A central drop of ICM Fe abundance has been observed in several cool-core clusters. It has been proposed that this abundance drop may be due, at least partially, to the depletion of Fe into dust grains in the central, high-density regions. According to this scenario, noble gas elements such as Ar and Ne are not expected to be depleted into dust, and therefore should not show any drop, but follow the general increase of metal abundance toward the center. In this work, we test this scenario by measuring with {\sl Chandra} data the radial profiles of Ar and Ne in a sample of 12 groups and clusters where a central drop in Fe abundance has been detected. We confirm the presence of the Fe drop in 10 out of 12 clusters at more than 2$\sigma$ c.l., and 4 Ar drops with similar significance. We also find 4 Ne drops, with the caveat that Ne abundance measurement from CCD spectra suffers from systematics not completely under control. Our results are consistent with an abundance drop common to the three elements. When comparing the profiles, we find that, on average, the abundance profiles of Ar and Ne are significantly higher than Fe and steeper toward the center, while they all gradually become consistent with solar composition at $r\geq 0.05r_{500}$. We also check that Si and S profiles are mostly consistent with Fe. This result confirms a scenario in which some fraction of Fe is depleted into dust grains in the inner regions, although the global central abundance drop is mostly due to mechanical processes, like the displacement of metal-rich ICM from the very center to larger radii by AGN-driven feedback. Finally, we report the detection of an Fe drop in the cluster MACSJ1423.8+2404 at $z=0.543$, showing that this feature appears early on in cool-core clusters.

Constraints on the chemical enrichment history of the Perseus Cluster of galaxies from high-resolution X-ray spectroscopy

High-resolution spectroscopy of the core of the Perseus Cluster of galaxies, using the $Hitomi$ satellite above 2 keV and the $XMM$-$Newton$ Reflection Grating Spectrometer at lower energies, provides reliable constraints on the abundances of O, Ne, Mg, Si, S, Ar, Ca, Cr, Mn, Fe, and Ni. Accounting for all known systematic uncertainties, the Ar/Fe, Ca/Fe, and Ni/Fe ratios are determined with a remarkable precision of less than 10%, while the constraints on Si/Fe, S/Fe, and Cr/Fe are at the 15% level, and Mn/Fe is measured with a 20% uncertainty. The average biases in determining the chemical composition using archival CCD spectra from $XMM$-$Newton$ and $Suzaku$ range typically from 15-40%. A simple model in which the enrichment pattern in the Perseus Cluster core and the proto-solar nebula are identical gives a surprisingly good description of the high-resolution X-ray spectroscopy results, with $\chi^2=10.7$ for 10 d.o.f. However, this pattern is challenging to reproduce with linear combinations of existing supernova nucleosynthesis calculations, particularly given the precise measurements of intermediate $\alpha$-elements enabled by $Hitomi$. We discuss in detail the degeneracies between various supernova progenitor models and explosion mechanisms, and the remaining uncertainties in these theoretical models. We suggest that including neutrino physics in the core-collapse supernova yield calculations may improve the agreement with the observed pattern of $\alpha$-elements in the Perseus Cluster core. Our results provide a complementary benchmark for testing future nucleosynthesis calculations required to understand the origin of chemical elements.

An atlas of cool supergiants from the Magellanic Clouds and typical interlopers

We present an atlas composed of more than 1500 spectra of late-type stars (spectral types from G to M) observed simultaneously in the optical and calcium triplet spectral ranges. These spectra were obtained as part of a survey to search for cool supergiants in the Magellanic Clouds and were taken over four epochs. We provide the spectral and luminosity classification for each spectrum (71% are supergiants, 13% are giants or luminous giants, 4% are carbon or S stars, and the remaining 12% are foreground stars of lesser luminosities). We also provide a detailed guide for the spectral classification of luminous late-type stars, the result of the extensive classification work done for the atlas. Although this guide is based on classical criteria, we have put them together and re-elaborated them for modern CCD-spectra as these criteria were scattered among many different works and mainly conceived for use with photographic plate spectra. The result is a systematic, well-tested process for identifying and classifying luminous late-type stars, illustrated with CCD spectra of standard stars and the classifications of our own catalogue.

New CH Carbon Stars Found in the DFBS

In this paper, we discuss the nature of three new carbon © stars discovered in the Digitized First Byurakan Survey (DFBS). The three stars show early-type spectra in the DFBS. To better characterize these objects, medium-resolution CCD spectra were obtained. These stars show spectral features typical to CH-giants

CHANDRA AND XMM-NEWTON X-RAY OBSERVATIONS OF THE HYPERACTIVE T TAURI STAR RY TAU

ABSTRACT We present results of pointed X-ray observations of the accreting jet-driving T Tauri star RY Tau using Chandra and XMM-Newton. We obtained high-resolution grating spectra and excellent-quality CCD spectra and light curves with the objective of identifying the physical mechanisms underlying RY Tau’s bright X-ray emission. Grating spectra reveal numerous emission lines spanning a broad range of temperature superimposed on a hot continuum. The X-ray emission measure distribution is dominated by very hot plasma at T hot ∼ 50 MK, but higher temperatures were present during flares. A weaker cool plasma component is also present as revealed by low-temperature lines such as O viii. X-ray light curves show complex variability consisting of short-duration (∼hours) superhot flares accompanied by fluorescent Fe emission at 6.4 keV superimposed on a slowly varying (∼one day) component that may be tied to stellar rotation. The hot flaring component is undoubtedly of magnetic (e.g., coronal) origin. Soft- and hard-band light curves undergo similar slow variability implying that at least some of the cool plasma shares a common magnetic origin with the hot plasma. Any contribution to the X-ray emission from cool shocked plasma is small compared to the dominant hot component but production of individual low-temperature lines such as O viii in an accretion shock is not ruled out.

Stars with discrepant v sin i as derived from the Ca II λ3933 Å and Mg II λ4481 Å lines. V. HD 182255 and HD 214923—SPB stars in binary systems

The axial rotation of a star plays an important role in its evolution, the physical conditions in its atmosphere and the appearance of its spectrum.We analyzed the CCD spectra of two stars for which their projected rotational velocity differs remarkably when derived from Ca II λ3933 A and Mg II λ4481 A lines. We estimated the projected rotational velocity of HD182255 to be 15.5 kms−1, although in various spectra of this star the line widths correspond to values as high as 28.5 km s−1. We found the HeI λ4471.498 A line to be shifted to longer wavelengths by 0.046 A, thus indicating a presence of the 3He I isotope in the atmosphere of this star with the 3He : 4He ratio from 0.2 to 0.6.We also found an absorption feature at the position of the forbidden line He I λ4470.02A. We found the lines ofMg II and CII originating from higher excited levels to be missing in the spectra of HD 182255. For HD 214923 we determined the projected rotational velocity v sin i = 165km s−1 from the profiles of the metallic lines and Ca II λ3933A, whereas for helium lines v sin i ≈ 130km s−1 is more appropriate. Radial velocity analysis results in three long periods of ≈ 105, 34, and 15 days, and a short period of ≈ 22 hours, close to the pulsational one mentioned earlier in the literature.

Oxygen-Rich Cool Stars in the Cepheus Region. New Observations. III

We present moderate resolution CCD spectra and R photometry for seven KP2001 stars. We revised the spectral classification of the stars in the range 3900 - 8500 A. On the bases of light curves of the NSVS (Northern Sky Variability Survey) database we classify KP2001-18 as a semi regular and KP2001-176 as Mira type variables. For all observed objects NSVS phase - dependence light curve analysis and variability type classification was performed with the VStar Software. Using period luminosity relation we computed MK magnitudes and the distances to variables.

Diagnosing the accretion flow in ultraluminous X-ray sources using soft X-ray atomic features

The lack of unambiguous detections of atomic features in the X-ray spectra of ultraluminous X-ray sources (ULXs) has proven a hindrance in diagnosing the nature of the accretion flow. The possible association of spectral residuals at soft energies with atomic features seen in absorption and/or emission and potentially broadened by velocity dispersion could therefore hold the key to understanding much about these enigmatic sources. Here we show for the first time that such residuals are seen in several sources and appear extremely similar in shape, implying a common origin. Via simple arguments we assert that emission from extreme colliding winds, absorption in a shell of material associated with the ULX nebula and thermal plasma emission associated with star formation are all highly unlikely to provide an origin. Whilst CCD spectra lack the energy resolution necessary to directly determine the nature of the features (i.e. formed of a complex of narrow lines or intrinsically broad), studying the evolution of the residuals with underlying spectral shape allows for an important, indirect test for their origin. The ULX NGC 1313 X-1 provides the best opportunity to perform such a test due to the dynamic range in spectral hardness provided by archival observations. We show through highly simplified spectral modelling that the strength of the features (in either absorption or emission) appears to anti-correlate with spectral hardness, which would rule out an origin via reflection of a primary continuum and instead supports a picture of atomic transitions in a wind or nearby material associated with such an outflow.

Investigation of Faint Galactic Carbon Stars from the First Byurakan Spectral Sky Survey. II. Early-Type Carbon Stars

In this paper, second in this series, we discuss the nature of 66 faint carbon (C) stars which have been discovered by scrutinizing the plates of the First Byurakan Survey (FBS). These plates display lowresolution spectra of objects located at high Galactic latitudes and have a limiting magnitude of about V = 16. Our sample of 66 objects is part of a total of 120 stars found in the FBS and confirmed spectroscopically to be C stars. These 66 objects are those which show early-type spectra (not N-type). To better characterize these objects, medium-resolution CCD spectra were obtained and are exploited for them all, together with consideration of their 2MASS near-infrared (NIR) colors and their optical variability. First, we establish criteria for getting a spectral classification by using our medium-resolution spectra. Then, 57 objects show spectral features which are typical of CH-giants, while four can be classified as a R-type stars. Five objects in our sample are reported to be probably carbon dwarfs according to previous studies. We derive effective temperatures from photometry. Finally, the optical variability of our objects are studied by using the data of the Catalina Sky Survey (CSS). It is found that the vast majority do not display variability. However, for some of them, the phased light curve may indicate the presence of a secondary component. We estimate the detection range (in kpc) for each class of carbon stars detected in the FBS. Finally, our studies of C stars found at high galactic latitude are discussed in the context of the Gaia mission.

NewXMM-Newtonobservation of the Phoenix cluster: properties of the cool core

(Abridged) We present a spectral analysis of a deep (220 ks) XMM-Newton observation of the Phoenix cluster (SPT-CL J2344-4243), which we also combine with Chandra archival ACIS-I data. We extract CCD and RGS X-ray spectra from the core region to search for the signature of cold gas, and constrain the mass deposition rate in the cooling flow which is thought to be responsible of the massive star formation episode observed in the BCG. We find an average mass deposition rate of $\dot M = 620 (-190 +200)_{stat} (-50 +150)_{syst} M_\odot$/yr in the temperature range 0.3-3.0 keV from MOS data. A temperature-resolved analysis shows that a significant amount of gas is deposited only above 1.8 keV, while upper limits of the order of hundreds of $M_\odot$/yr can be put in the 0.3-1.8 keV temperature range. From pn data we obtain $\dot M = 210 (-80 +85)_{stat} ( -35 +60)_{syst} M_\odot$/yr, and the upper limits from the temperature-resolved analysis are typically a factor of 3 lower than MOS data. In the RGS spectrum, no line emission from ionization states below Fe XXIII is seen above $12 \AA$, and the amount of gas cooling below $\sim 3$ keV has a best-fit value $\dot M = 122_{-122}^{+343}$ $M_{\odot}$/yr. In addition, our analysis of the FIR SED of the BCG based on Herschel data provides $SFR = (530 \pm 50) M_\odot$/yr, significantly lower than previous estimates by a factor 1.5. Current data are able to firmly identify substantial amount of cooling gas only above 1.8 keV in the core of the Phoenix cluster. While MOS data analysis is consistent with values as high as $\dot M \sim 1000$ within $1 \sigma$, pn data provide $\dot M < 500 M_\odot$ yr$^{-1}$ at $3\sigma$ c.l. at temperature below 1.8 keV. At present, this discrepancy cannot be explained on the basis of known calibration uncertainties or other sources of statistical noise.

Asteroid (354) Eleonora: Plucking an odd duck

During a survey of the S-type asteroids, Gaffey et al. (Gaffey, M.J., Bell, J.F., Brown, R.H., Burbine, T.H., Piatek, J., Reed, K.L., Chaky, D.A. [1993]. Icarus 106, 573–602) identified Asteroid (354) Eleonora as anomalous with a 1μm absorption feature ∼2.5 times stronger than any S-asteroid of comparable size. Subsequent investigation revealed significant differences in the 1μm absorption feature between the visible & very near-infrared CCD spectra (λ<∼1.0μm) and other spectral data sets for this asteroid. There were also significant spectral differences among the several CCD survey spectra (SMASS-I, SMASS-II & S3OS2) of Eleonora. These differences could potentially arise from spectral variations across the asteroid surface, from observational phase angle differences, from surface temperature differences, from viewing geometry for a nonspherical body, or from the use of standard stars with deviated to different degrees from a true solar standard.In June 2011 Asteroid (354) Eleonora was observed over two nights using the NASA Infrared Telescope Facility (IRTF) at Mauna Kea Observatory in order to test these possible scenarios and to better understand the nature and history of Eleonora and its relationships to other asteroids and to the meteorites. Analysis of this data set has eliminated the following options as the cause of the differences in the 1μm absorption feature within the CCD data sets and between the CCD data sets and the other spectral data: (1) rotational spectral variations; (2) variation in surface composition with latitude; (3) observation phase; (4) surface temperature variations with differing heliocentric distance in the asteroid’s elliptical orbit; (5) spectral effects of viewing geometry for a nonspherical body; and (6) differences in spectral standard stars. We conclude that none of the CCD spectra of (354) Eleonora are reliable, and that within the limits of their spectral coverage, analyses of the three CCD spectra would produce significantly different – and generally unreliable – indications of surface mineralogy. An effort needs to be made to determine whether “bad” CCD spectra are rare with the case of (354) Eleonora being an uncommon occurrence or whether there is a broader problem with the CCD asteroid survey data sets, and if so, how to identify the “bad” spectra.While CCD survey spectra show apparently irreconcilable differences, the near-infrared spectra of (354) Eleonora from various observers show only minor differences, primarily in the overall spectral slope, most of which can be attributed to slight differences in the standard stars used to calibrate the data.In June 2011, 226 near-infrared (∼0.76–2.5μm) spectra of (354) Eleonora were obtained using the SpeX instrument on the NASA Infrared Telescope Facility at Mauna Kea Observatory. These spectra were consistent with the six sets of NIR spectra obtained for Eleonora by previous observers. The primary variation observed in this new data set was an approximately 10% variation in spectral slope between ∼0.8μm and ∼1.6μm during the rotation period of the asteroid.Mineralogically diagnostic spectral parameters extracted from this new data are most consistent with a surface assemblage of fine-grained intimately mixed olivine (∼60–70%, ∼Fo61–71) and low nickel (<∼7–8% Ni) NiFe metal. The Fo estimate is consistent with previous estimates (Fo66±5) by Sanchez et al. (Sanchez, J.A., Reddy, V., Kelley, M.S., Cloutis, E.A., Bottke, W.F., Nesvorný, D., Lucas, M.P., Hardersen, P.S., Gaffey, M.J., Abell, P.A., Le Corre, L. [2014]. Icarus 228, 288–300), but not with the estimate (∼Fo90) of Sunshine et al. (Sunshine, J.M., Bus, S.J., Corrigan, C.M., McCoy, T.J., Burbine, T.H. [2007]. Meteorit. Planet. Sci. 42, 155–170). The surface assemblage appears to contain a small component (∼8–10%) of igneous pyroxene (weakly constrained at ∼Fs50Wo10). The parent lithology of the surface regolith may be similar to a pallasite assemblage, although none of the three known types of pallasites are good mineralogical matches.

Stars with discrepant v sin i as derived from the Ca II λ3933 Å and Mg II λ4481 Å lines. IV. HD8837—a shell star, HD47964 and HD183986—new binaries

Axial rotation of a star plays an important role in its evolution, physical conditions in its atmosphere, and appearance of its spectrum. We have analyzed CCD spectra of three stars for which their projected rotational velocity remarkably differs when derived from the Ca II λ 3933 A and MgII λ 4481 A lines. We derived effective temperatures and surface gravities using published uvbyβ photometries and computed synthetic spectra. Comparing observed line profiles of the two lines with the computed ones, we estimated values of v sin i. We also derived radial velocities by means of the cross-correlation function. HD8837 is known to be a shell star with pronounced narrow absorption cores in the Balmer lines as well as in the strong metal lines; however, we do not confirm the emission component in the core of Hβ. HD47964 has been discovered by Hipparcos to be a double. However, in our spectra we do not find traces of the other star. Based on the Hipparcos data, we estimated that the other star would be a main sequence A4 star with an extremely high rotational velocity resulting in wiping out any traces of spectral lines of the companion. HD183986 is known to be a triple star. However, we have found a manifestation of a so far not discovered companion of the component HD183986A and estimated it as a main sequence A5 star having v sin i of about 150 km/s.

Hour-timescale profile variations in the broad Balmer lines of the Seyfert galaxy Hour-timescale profile variations in the broad Balmer lines of the Seyfert galaxy Markarian 6

AbstractPart of results of the multi-epoch intranight optical spectroscopic monitoring of the Markarian 6 nucleus carried out at the telescopes of 6-m of the Special Astrophysical Observatory (Russia), 2.6-m of the Byurakan Astrophysical Observatory (Armenia) and 2-m of the Tautenburg Observatory (Germany) is presented.Observations were made in 1979, 1986, 1988-1991 and 2007-2009 during a total of 33 nights with an average sampling rate of 4 spectra per night. TV-scanner and long-slit spectrographs equipped with Image Tube and CCD detector arrays were used. Altogether we analyzed 110 Hβ and 58 Hα region spectra to search for intranight variability in the broad hydrogen emission line profiles. The typical spectral resolutions were 4 Å for scanner spectra, 6 Å for photographic spectra, and 5 Å and 10 Å for CCD spectra. The S/N ratio at the continuum level near the Hβ and Hα lines was in the range 15–50.The purpose of the search was to look for the characteristic variability signatures of different kinematical models of the broad emission-line region. We considered the centering and guiding errors which can result in differences between spectra.We found variations in the broad Balmer line difference profiles on time scale of hour with the level of significance of 3.6 σ to 5.0 σ. Variations take the form of narrow, small bumps located at the blue and red sides or only at the blue side of the lines. In the intermediate level of broad line flux, the Hβ and Hα profiles show fine structure. Detected profile changes occurred at the same radial velocity shifts as the details in the fine structure.The variability is at least 2 orders of magnitude more rapid than any observed for broad Balmer line profiles in AGNs that we are aware of in the literature.Discovered extremely rapid line-profile variability may be associated with reverberation effects. Two-sided profile changes may indicate the response of circularly rotating hydrogen clouds in the BLR to a light pulse from a central source. One-sided profile variations may be attributed to a response of a non-disk component: the subarcsec scale region of the jet.