Home     To Survive in the Universe    
    Why to Inhabit     Top Contributors     Astro Photo     The Collection     Forum     Blog New!     FAQ     Login  

α Peg (Markab)



Upload your image

DSS Images   Other Images

Related articles

A High-Resolution Spectral Atlas of α Persei from 3810 to 8100 Å
We present a high-resolution (λ/δλ=90,000) spectralatlas of the F5 Ib star α Per covering the 3810-8100 Åregion. The atlas, based on data obtained with the aid of the echellespectrograph BOES fed by the 1.8 m telescope at Bohyunsan Observatory(Korea), is the result of the co-addition of a few well-exposed spectra.The final signal-to-noise ratio is ~800 at ~6000 Å. The atlas iscompared with a synthetic spectrum computed using a code based on Kuruczsoftware and databases. The adopted model atmosphere parameters areTeff=6240+/-20 K, logg=0.58+/-0.04, andvmicro=3.20+/-0.05 km s-1. We also derived an ironabundance of [Fe/H]=-0.28+/-0.06. The spectral lines of α Per havebeen identified by matching the synthetic spectrum with the observedone. The atlas is presented in figures and available in digital form onthe World Wide Web, along with the synthetic spectrum and spectral lineidentification tables.Based on data collected with the 1.8 m telescope at Bohyunsan OpticalAstronomy Observatory, South Korea.

The First Spatially Resolved Mid-Infrared Spectra of NGC 1068 Obtained at Diffraction-limited Resolution with the Keck I Telescope Long Wavelength Spectrometer
We present spatially resolved mid-infrared (mid-IR) spectra of NGC 1068with a diffraction-limited resolution of 0.25" using the Long WavelengthSpectrometer (LWS) at the Keck I telescope. The mid-IR image of NGC 1068is extended along the north-south direction. Previous imaging studieshave shown that the extended regions are located inside the ionizationcones, indicating that the mid-IR emission arises perhaps from the innerregions of the narrow-line clouds instead of the proposed dusty torusitself. The spatially resolved mid-IR spectra were obtained at twodifferent slit position angles, +8.0d and -13.0d across the elongatedregions in the mid-IR. From these spectra, we found only weak silicateabsorption toward the northern extended regions but strong absorption inthe nucleus and the southern extended regions. This is consistent with amodel of a slightly inclined cold obscuring torus that covers much ofthe southern regions but is behind the northern extension. While adetailed analysis of the spectra requires a radiative transfer model,the lack of silicate emission from the northern extended regions promptsus to consider a dual dust population model as one of the possibleexplanations in which a different dust population exists in theionization cones compared to that in the dusty torus. Dust inside theionization cones may lack small silicate grains, giving rise to only afeatureless continuum in the northern extended regions, while dust inthe dusty torus has plenty of small silicate grains to produce thestrong silicate absorption lines toward the nucleus and the southernextended regions.

Computed Hβ indices from ATLAS9 model atmospheres
Aims.Grids of Hβ indices based on updated (new-ODF) ATLAS9 modelatmospheres were computed for solar and scaled solar metallicities[+0.5], [+0.2], [0.0], [ -0.5] , [ -1.0] , [ -1.5] , [ -2.0] , [ -2.5]and for α enhanced compositions [+0.5a], [0.0a], [ -0.5a] , [-1.0a] , [ -1.5a] , [ -2.0a] , [ -2.5a] , and [ -4.0a] . Methods:.Indices for T_eff > 5000 K were computed with the same methods asdescribed by Lester et al. (1986, LGK86) except for a differentnormalization of the computed natural system to the standard system.LGK86 used special ODFs to compute the fluxes. For T_eff ≤ 5000 K wecomputed the fluxes using the synthetic spectrum method. In order toassess the accuracy of the computed indices comparisons were made withthe indices computed by Smalley & Dworetsky (1995, A&A, 293,446, MD95) and with the empirical relations T_eff-Hβ given byAlonso et al. (1996, A&A, 313, 873) for several metallicities.Furthermore, for cool stars, temperatures inferred from the computedindices were compared with those of the fundamental stars listed byMD95. The same kind of comparison was made between gravities for B-typestars. Results: .The temperatures from the computed indices are ingood agreement, within the error limits, with the literature values for4750 K ≤ T_eff ≤ 8000 K, while the gravities agree for T_eff> 9000 K. The computed Hβ indices for the Sun and for Procyonare very close to the observed values. The comparison between theobserved and computed Hβ indices as function of the observedHβ has shown a very small trend which almost completely disappearswhen only stars hotter than 10 000 K are considered. The trend due tothe cool stars is probably related with the low accuracy of thefundamental T_eff which are affected by large errors for most of thestars.

A search for fine structure inside high resolution profiles of weak diffuse interstellar bands
This paper presents a survey of the high-resolution profiles ofselected, moderately weak diffuse interstellar bands (DIBs) between 4725and 6730 Å. In very high signal-to-noise spectra, obtained as aresult of averaging several individual exposures of reddened, early-typestars that show Doppler splitting of <2 km s-1 ininterstellar gas lines, the profiles seem to have a substructure. Thissupports the molecular origin hypothesis for DIBs. We studied theprofiles of the diffuse interstellar bands at wavelengths of 4726.33,4963.85, 5418.89, 5541.74, 5544.95, 5546.46, 5762.73, 5766.05, 5769.09,6439.41, 6445.53, 6449.16, 6729.28 Å.

An Improved Infrared Passband System for Ground-based Photometry: Realization
We describe new simulations and field trials of the new infraredpassband system developed and discussed by Young, Milone, & Stagg,who discussed and illustrated the state of infrared photometry andsuggested ways in which it could be improved. In particular, theypresented a new set of passbands that minimize the dependence of thephotometry on the water vapor bands of the atmospheric windows, whichdefined the edges of many previous infrared passbands, especially whenused at sites and under conditions for which they were not designed. Inthis paper, we present numerical simulations for three atmosphericmodels, demonstrate a measure of the signal-to-noise ratio in the newpassbands for these models, and present observational data obtained at arelatively low-elevation site. The latter demonstrate the utility ofthis system for most astronomical sites where photometry can beperformed, and permit the transformation of observations to this system.Publications of the Rothney Astrophysical Observatory, No. 74.

Variability of Stars in the Pulkovo Spectrophotometric Catalog
We present the results of a statistical study of brightness variabilityfor 693 stars of the Pulkovo spectrophotometric database in fivespectral bands in the range λλ 320 1080 nm. Significantbrightness variations were detected in at least one spectral bandagainst the background of the random noise for one-third of the starsnot earlier believed to be variable. A comparison of the distributionsof these variations in amplitude and spectral band for the normal andvariable stars shows that variability is inherent to most stars to someextent and is often wavelength dependent.

Profiles of Very Weak Diffuse Interstellar Bands around 6440 Å
Profiles of very weak diffuse interstellar bands (DIBs) between 6400 and6470 Å observed with high resolution and very high S/N aredemonstrated. We show that with the increasing quality of reddenedstellar spectra, the whole spectral range is covered with weak or veryweak DIBs-at least one every 2-3 Å. We also present the details ofthe profiles of a few stronger features; the presence of substructuresresembles the profiles of strong DIBs observed in high resolution duringthe last decade and supports the hypothesis of a molecular origin of atleast a majority of DIBs.

Determining the Physical Properties of the B Stars. II. Calibration of Synthetic Photometry
We present a new calibration of optical (UBV, Strömgren uvbyβ,and Geneva) and near-IR (Johnson RIJHK and Two Micron All Sky Survey)photometry for B and early A stars derived from Kurucz ATLAS9 modelatmospheres. Our sample of stars consists of 45 normal nearby B andearly A stars that have high-quality, low-resolution IUE spectra andaccurate Hipparcos parallaxes. The calibration is unique because itrelies only on the UV spectral energy distributions, the absolute fluxcalibration of the V filter, and the Hipparcos distances to determinethe appropriate model atmospheres for the program stars. These modelsare then used to calibrate the synthetic photometry. We compare ourresults with previous well-accepted results and provide a thoroughdiscussion of the random errors and systematic effects affecting thecalibration. In particular, we demonstrate the influence of vsini onsurface gravities derived from fitting model atmospheres. Finally, wediscuss some of our intended applications of this new calibration.

Excess mid-infrared emission in cataclysmic variables
We present a search for excess mid-infrared emission due tocircumbinary (CB) material in the orbital plane of cataclysmic variables(CVs). Our motivation stems from the fact that the strong brakingexerted by a CB disc on the binary system could explain several puzzlesin our current understanding of CV evolution. Since theoreticalestimates predict that the emission from a CB disc can dominate thespectral energy distribution (SED) of the system at λ > 5μm, we obtained simultaneous visible to mid-infrared (mid-IR) SEDsfor eight systems. We report detections of SS Cyg at 11.7 μm and AEAqr at 17.6 μm, both in excess of the contribution from the secondarystar. In AE Aqr, the IR likely originates from synchrotron-emittingclouds propelled by the white dwarf. In SS Cyg, we argue that theobserved mid-IR variability is difficult to reconcile with simple modelsof CB discs and we consider free-free emission from a wind. In the othersystems, our mid-IR upper limits place strong constraints on the maximumtemperature of a putative CB disc. The results show that if any sizeableCB discs are present in these systems, they must be self-shadowed orperhaps dust-free, with the peak thermal emission shifted to far-IRwavelengths.

Testing the Reality of Strong Magnetic Fields on T Tauri Stars: The Naked T Tauri Star Hubble 4
High-resolution optical and infrared (IR) echelle spectra of the naked(diskless) T Tauri star Hubble 4 are presented. The K-band IR spectrainclude four Zeeman-sensitive Ti I lines along with several magneticallyinsensitive CO lines. Detailed spectrum synthesis combined with modernatmospheric models is used to fit the optical spectra of Hubble 4 inorder to determine its key stellar parameters: Teff=4158+/-56K; logg=3.61+/-0.50 [M/H]=-0.08+/-0.05 vsini=14.6+/-1.7 kms-1. These stellar parameters are used to synthesize K-bandspectra to compare with the observations. The magnetically sensitive TiI lines are all significantly broadened relative to the lines producedin the nonmagnetic model, while the magnetically insensitive CO linesare well matched by the basic nonmagnetic model. Models with magneticfields are synthesized and fitted to the Ti I lines. The best-fit modelsindicate a distribution of magnetic field strengths on the stellarsurface characterized by a mean magnetic field strength of 2.51+/-0.18kG. The mean field is a factor of 2.0 greater than the maximum fieldstrength predicted by pressure equipartition arguments. To confirm thereality of such strong fields, we attempt to refit the observed profilesusing a two-component magnetic model in which the field strength isconfined to the equipartition value representing plagelike regions inone component and the field is allowed to vary in a cooler componentrepresenting spots. It is shown that such a model is inconsistent withthe optical spectrum of the TiO bandhead at 7055 Å.

Near-Infrared Molecular Hydrogen Emission from the Central Regions of Galaxies: Regulated Physical Conditions in the Interstellar Medium
The central regions of many interacting and early-type spiral galaxiesare actively forming stars. This process affects the physical andchemical properties of the local interstellar medium, as well as theevolution of the galaxies. We observed near-infrared H2emission lines: v=1-0 S(1), 3-2 S(3), 1-0 S(0), and 2-1 S(1) from thecentral ~1 kpc regions of the archetypical starburst galaxies M82 andNGC 253 and the less dramatic but still vigorously star-forming galaxiesNGC 6946 and IC 342. Like the far-infrared continuum luminosity, thenear-infrared H2 emission luminosity can directly trace theamount of star formation activity because the H2 emissionlines arise from the interaction between hot and young stars and nearbyneutral clouds. The observed H2 line ratios show that boththermal excitation and nonthermal excitation are responsible for theemission lines but that the great majority of the near-infraredH2 line emission in these galaxies arises from energy statesexcited by ultraviolet fluorescence. The derived physical conditions,e.g., far-ultraviolet radiation field and gas density, from [C II] and[O I] lines and far-infrared continuum observations when used as inputsto photodissociation models also explain the luminosity of the observedH2 1-0 S(1) line. The ratio of the H2 1-0 S(1)line to far-IR continuum luminosity is remarkably constant over a broadrange of galaxy luminosities:LH2/LFIR~=10-5, in normallate-type galaxies (including the Galactic center), in nearby starburstgalaxies, and in luminous IR galaxies (LIRGs:LFIR>1011 Lsolar). Examining thisconstant ratio in the context of photodissociation region models, weconclude that it implies that the strength of the incident UV field ontypical molecular clouds follows the gas density at the cloud surface.

Very high resolution profiles of four diffuse interstellar bands
Ultra-high-resolution (R~ 300000) profiles of four diffuse interstellarbands (DIBs) are presented. The λλ 5797-, 5850-, 6196- and6379-Å DIBs were observed towards the reddened supergiant HD24398, a line of sight free of Doppler splitting; thus the observedprofiles can be considered as intrinsic to the DIB carriers. Three ofthe profiles show substructure which supports the hypothesis of amolecular origin for these DIBs.

Local Interstellar Matter: The Apex Cloud
Several nearby individual low column density interstellar cloudlets havebeen identified previously on the basis of kinematical features evidentin high-resolution Ca+ observations near the Sun. One ofthese cloudlets, the ``Apex Cloud'' (AC), is within 5 pc of the Sun inthe solar apex direction. The question of which interstellar cloud willconstitute the next Galactic environment of the Sun can, in principle,be determined from cloudlet velocities. The interstellar absorptionlines toward α Cen (the nearest star) are consistent withinmeasurement uncertainties with the projected ``G'' cloud (GC) and ACvelocities, and also with the velocity of the cloud inside of the solarsystem (the local interstellar cloud [LIC]), provided a small velocitygradient is present in the LIC. The high GC column density towardα Oph compared to α Aql suggests that α Aql may beembedded in the GC so that the AC would be closer to the Sun than theGC. This scenario favors the AC as the next cloud to be encountered bythe Sun, and the AC would have a supersonic velocity with respect to theLIC. The weak feature at the AC velocity toward 36 Oph suggests that theAC cloud is either patchy or does not extend to this direction.Alternatively, if the GC is the cloud that is foreground to α Cen,the similar values for N(H0) in the GC components towardα Cen and 36 Oph indicate this cloud is entirely contained withinthe nearest ~1.3 pc, and the Ca+ GC data toward α Ophwould then imply a cloud volume density of ~5 cm-3, withdramatic consequences for the heliosphere in the near future.

Abundance analysis of late B stars. Evidence for diffusion and against weak stellar winds
Based on high S/N spectra obtained at La Silla, Chile, and the SpecialAstrophysical Observatory, Russia, the abundances of He, C, O, Ne, Mg,Si, Ca, Fe, Sr, and Ba in 27 optically bright B5-B9 main-sequence starswere determined. NLTE effects were taken into account. A variety ofabundance patterns is present in late B stars. Accurate surfaceabundances of the diffusion indicators O, Mg, Ca, Sr and Ba suggest thatelement stratification due to diffusion is common in the program stars.Models of stellar atmospheres which include meridional mixing canexplain the observed anomalies. Although the program stars representonly a volume-limited sample of the solar neighbourhood this result isimportant for the cosmochemical evolution of the Galaxy: the surfaceabundances of the stars investigated do not necessarily reflect thechemical composition of the interstellar cloud they originated from.Furthermore, five program stars show narrow absorption lines in Ca II Kwhich can be attributed to circumstellar gas. Neon serves as a traceelement for the occurrence of weak stellar winds. Neon overabundances ofsome stars derived under the assumption of LTE suggest that such windshave been detected. In sharp contrast, the more realistic treatment ofNLTE leads to solar neon abundances and thus reveals that weak stellarwinds are absent in the program stars.Based on observations collected at the European Southern Observatory, LaSilla, Chile and at the Special Astrophysical Observatory, NizhnijArkhyz, Russia.

Doppler images of the RS CVn binary HR 1099 (V711 Tau) from the MUSICOS 1998 campaign
We present Doppler Images of the RS CVn binary system HR 1099 (V711 Tau)from spectra taken in two different sites, KPNO and MSO, during theMUSICOS 1998 campaign. Contemporaneous APT photometry is used toconstrain the Doppler Images. The resulting maximum entropyreconstructions based on the least-squares deconvolved profiles, derivedfrom ~ 2000 photospheric absorption lines, reveal the presence ofstarspots at medium-high latitudes. We have obtained maps for bothcomponents of the binary system for the first time. The predominantstructure in the primary component is an off-centered polar spot,confirming previous works on the same target by using independent codes.The result is verified by using both data sets independently. The lowerspectral resolution data set gives a less detailed map for the MSO dataset. The images obtained for the secondary component show a low latitudespot around orbital phase 0.7. This spot seems to mirror the structureseen on the primary. It might suggest that tidal forces may influencethe spot distribution on this binary system.Based on observations obtained during the MUSICOS 98 MUlti-SIteCOntinuous Spectroscopic campaign from Kitt Peak National Observatory,USA, and Mt. Stromlo Observatory, Australia.

The latitude and epoch for the formation of the southern Greek constellations
Not Available

JHK Standards for Small Telescopes
The AAVSO Futures meeting, held in Madison, WI, in May 2001, proposedthat the AAVSO support near-infrared research with small telescopes. Aphotometer, the SSP-4, has been developed to provide J- and H-bandcapability for a reasonable cost. However, proper calibrated photometryrequires a set of standard stars. This paper describes such a set ofstars, suitable for small telescopes, and with accurate coordinates,proper motions, and high-quality magnitudes.

Spectrophotometric observations on asteroids at the Crimean Astrophysical Observatory.
Not Available

The Velocity Distribution of the Nearest Interstellar Gas
The bulk flow velocity for the cluster of interstellar cloudlets within~30 pc of the Sun is determined from optical and ultraviolet absorptionline data, after omitting from the sample stars with circumstellar disksor variable emission lines and the active variable HR 1099. A total of96 velocity components toward the remaining 60 stars yield a streamingvelocity through the local standard of rest of -17.0+/-4.6 kms-1, with an upstream direction of l=2.3d, b=-5.2d (usingHipparcos values for the solar apex motion). The velocity dispersion ofthe interstellar matter (ISM) within 30 pc is consistent with that ofnearby diffuse clouds, but present statistics are inadequate todistinguish between a Gaussian or exponential distribution about thebulk flow velocity. The upstream direction of the bulk flow vectorsuggests an origin associated with the Loop I supernova remnant.Groupings of component velocities by region are seen, indicatingregional departures from the bulk flow velocity or possibly separateclouds. The absorption components from the cloudlet feeding ISM into thesolar system form one of the regional features. The nominal gradientbetween the velocities of upstream and downstream gas may be an artifactof the Sun's location near the edge of the local cloud complex. The Sunmay emerge from the surrounding gas patch within several thousand years.

Rotational Velocities of B Stars
We measured the projected rotational velocities of 1092 northern B starslisted in the Bright Star Catalogue (BSC) and calibrated them againstthe 1975 Slettebak et al. system. We found that the published values ofB dwarfs in the BSC average 27% higher than those standards. Only 0.3%of the stars have rotational velocities in excess of two-thirds of thebreakup velocities, and the mean velocity is only 25% of breakup,implying that impending breakup is not a significant factor in reducingrotational velocities. For the B8-B9.5 III-V stars the bimodaldistribution in V can be explained by a set of slowly rotating Ap starsand a set of rapidly rotating normal stars. For the B0-B5 III-V starsthat include very few peculiar stars, the distributions in V are notbimodal. Are the low rotational velocities of B stars due to theoccurrence of frequent low-mass companions, planets, or disks? Therotational velocities of giants originating from late B dwarfs areconsistent with their conservation of angular momentum in shells.However, we are puzzled by why the giants that originate from the earlyB dwarfs, despite having 3 times greater radii, have nearly the samerotational velocities. We find that all B-type primaries in binarieswith periods less than 2.4 days have synchronized rotational and orbitalmotions; those with periods between 2.4 and 5.0 days are rotating withina factor 2 of synchronization or are ``nearly synchronized.'' Thecorresponding period ranges for A-type stars are 4.9 and 10.5 days, ortwice as large. We found that the rotational velocities of the primariesare synchronized earlier than their orbits are circularized. The maximumorbital period for circularized B binaries is 1.5 days and for Abinaries is 2.5 days. For stars of various ages from 107.5 to1010.2 yr the maximum circularized periods are a smoothexponential function of age.

Magnetic survey of bright northern main sequence stars
The first results of a systematic search for magnetic fields in thebrightest upper main sequence (MS) stars are presented. The main goal isto survey the stars with about the same detection limit and to improveexisting statistics of their magnetism. The target list contains 57upper MS stars and represents well B0.5-F9 stars. High-resolution Zeemanspectra were obtained for 30 stars of the list. The accuracy of themagnetic field measurements ranges from 20 to 300 G depending mainly onspectral class. In the majority of studied stars we did not detectmagnetic fields. In some stars we suspect the presence of a weakmagnetic field. These are the best candidates for more extensivestudies. A particular case is the star chi Dra where we probablydetected the global magnetic field. The longitudinal field strength isB_l= -54+/-12 G. Further observations of this star are needed to confirmthe detection and to ascertain if the magnetic field is variable withthe period of rotation. Based on observations collected at the 1 mtelescope of the Special Astrophysical Observatory (Nizhnij Arkhyz,Russia).

Rotational velocities of A-type stars in the northern hemisphere. II. Measurement of v sin i
This work is the second part of the set of measurements of v sin i forA-type stars, begun by Royer et al. (\cite{Ror_02a}). Spectra of 249 B8to F2-type stars brighter than V=7 have been collected at Observatoirede Haute-Provence (OHP). Fourier transforms of several line profiles inthe range 4200-4600 Å are used to derive v sin i from thefrequency of the first zero. Statistical analysis of the sampleindicates that measurement error mainly depends on v sin i and thisrelative error of the rotational velocity is found to be about 5% onaverage. The systematic shift with respect to standard values fromSlettebak et al. (\cite{Slk_75}), previously found in the first paper,is here confirmed. Comparisons with data from the literature agree withour findings: v sin i values from Slettebak et al. are underestimatedand the relation between both scales follows a linear law ensuremath vsin inew = 1.03 v sin iold+7.7. Finally, thesedata are combined with those from the previous paper (Royer et al.\cite{Ror_02a}), together with the catalogue of Abt & Morrell(\cite{AbtMol95}). The resulting sample includes some 2150 stars withhomogenized rotational velocities. Based on observations made atObservatoire de Haute Provence (CNRS), France. Tables \ref{results} and\ref{merging} are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr ( or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/393/897

On the effective temperatures and surface gravities of superficially normal main sequence band B and A stars
Effective temperatures and surface gravities for 48 main sequence band Band A stars were found by matching optical region spectrophotometry andHγ profiles with the predictions of ATLAS9 solar composition modelatmospheres. When these values were compared with those found usingStrömgren uvbybeta photometry based on ATLAS6 model atmospheres, wefound a difference (photometry-spectrophotometry) of 25+/- 118 K for 29stars with 8000 K le Teff <= 10 050 K compared to 76 +/-105 K for 14 stars with 10 050 K <= Teff <= 17 000 K.The surface gravity scales are in agreement. These stars aresufficiently hot that their effective temperatures and surface gravitydeterminations are unaffected by discrepancies due to the choice ofMixing-Length or Canuto-Mazzitelli convection theories.

Non-radial pulsation, rotation and outburst in the Be star omega Orionis from the MuSiCoS 1998 campaign
omega Ori (HD 37490, HR1934) is a Be star known to have presented variations. Inorder to investigate the nature and origin of its short-term andmid-term variability, a study is performed of several spectral lines(Hα , Hdelta , ion {He}i 4471, 4713, 4921, 5876, 6678, ion {C}{ii}4267, 6578, 6583, ion {Mg}{ii} 4481, ion {Si}{iii} 4553 and ion {Si}{ii}6347), based on 249 high signal-to-noise high-resolution spectra takenwith 8 telescopes over 22 consecutive nights during the MuSiCoS (MultiSIte COntinuous Spectroscopy) campaign in November-December 1998. Thestellar parameters are revisited and the projected rotational velocity(vsin i = 179 km s-1) is redetermined using several methods.With the MuSiCoS 98 dataset, a time series analysis of line-profilevariations (LPVs) is performed using the Restricted Local Cleanest (RLC)algorithm and a least squares method. The behaviour of the velocity ofthe centroid of the lines, the equivalent widths and the apparent vsinifor several lines, as well as Violet and Red components of photosphericlines affected by emission (red ion {He}i lines, ion {Si}{ii} 6347, ion{C}{ii} 6578, 6583) are analyzed. The non-radial pulsation (NRP) modelis examined using phase diagrams and the Fourier-Doppler Imaging (FDI)method. The LPVs are consistent with a NRP mode with l = 2 or 3, |m| = 2with frequency 1.03 c d-1. It is shown that an emission lineoutburst occurred in the middle of the campaign. Two scenarios areproposed to explain the behaviour of a dense cloud, temporarily orbitingaround the star with a frequency 0.46 c d-1, in relation tothe outburst. Based on observations taken during the MuSiCoS 98 campaignat OHP (France), La Silla (ESO, Chile, ID 62.H-0270), Mount Stromlo(Australia), Xinglong Station (China), Kitt Peak (USA), MCT/LNA (Brazil)and INT (Isaac Newton Group, La Palma Island).

The Local Interstellar Medium in the Direction of the Galactic Anticentre
High resolution observations of interstellar Na I absorptions in thespectra of early-type stars in the second Galactic quadrant have beenused to derive the spatial distribution of the nearby interstellar gasin the Galactic anticentre hemisphere. The data show the presence,within the region explored and within the nearest 150 pc, of eightdiffuse interstellar clouds with LSR velocities in the range 15-55 kms^-1. Molecular gas previously identified close to the Sun by Trapero etal. (1995) and Trapero et al. (1996) is embedded in one of the clouds.The motion of these clouds does not reflect any motion of the gas awayfrom the Scorpio-Centaurus association, showing that the kinematicsobserved in the neighbourhood of the Sun by Lallement and Bertin (1992)is restricted, in the second Galactic quadrant, to the nearest ~ 50 pc.

The problem of C7- as source of diffuse interstellar bands revisited
We used spectra of several bright, reddened stars, most of them likelyto be obscured by individual interstellar clouds, to examine theproposition that C7- may carry several diffuseinterstellar bands (DIBs) (Tulej et al. 1998). To search for the broadfeatures of the C7- B <- X system we used lowresolution, very high S/N spectra, but even in heavily reddened objectsthe predicted bands remain undetectable. High resolution (R=80 000)spectra prove that the diffuse bands, found in close vicinity of narrowlines belonging to the A <- X system, show variable strength ratiosfrom object to object which proves that they are not of the same origin.The paper brings thus evidence that the C7-molecule does not cause any of the detected DIBs.

Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics
The Catalogue, available at the Centre de Données Stellaires deStrasbourg, consists of 13 573 records concerning the results obtainedfrom different methods for 7778 stars, reported in the literature. Thefollowing data are listed for each star: identifications, apparentmagnitude, spectral type, apparent diameter in arcsec, absolute radiusin solar units, method of determination, reference, remarks. Commentsand statistics obtained from CADARS are given. The Catalogue isavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr ( or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcar?J/A+A/367/521

Research Note Hipparcos photometry: The least variable stars
The data known as the Hipparcos Photometry obtained with the Hipparcossatellite have been investigated to find those stars which are leastvariable. Such stars are excellent candidates to serve as standards forphotometric systems. Their spectral types suggest in which parts of theHR diagrams stars are most constant. In some cases these values stronglyindicate that previous ground based studies claiming photometricvariability are incorrect or that the level of stellar activity haschanged. Table 2 is only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr ( or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/367/297

The proper motions of fundamental stars. I. 1535 stars from the Basic FK5
A direct combination of the positions given in the HIPPARCOS cataloguewith astrometric ground-based catalogues having epochs later than 1939allows us to obtain new proper motions for the 1535 stars of the BasicFK5. The results are presented as the catalogue Proper Motions ofFundamental Stars (PMFS), Part I. The median precision of the propermotions is 0.5 mas/year for mu alpha cos delta and 0.7mas/year for mu delta . The non-linear motions of thephotocentres of a few hundred astrometric binaries are separated intotheir linear and elliptic motions. Since the PMFS proper motions do notinclude the information given by the proper motions from othercatalogues (HIPPARCOS, FK5, FK6, etc.) this catalogue can be used as anindependent source of the proper motions of the fundamental stars.Catalogue (Table 3) is only available at the CDS via anonymous ftp tocdsarc.u-strasbg.fr ( or viahttp://cdsweb.u-strastg.fr/cgi-bin/qcat?J/A+A/365/222

Narrow Diffuse Interstellar Bands: A Survey with Precise Wavelengths
We present an atlas of 271 diffuse interstellar bands (DIBs) between4460 and 8800 Å based on echelle spectra (R=45,000), of which morethan 100 are new DIBs discovered in this survey. The atlas is restrictedmostly to narrow features, and we describe the tests for an interstellarorigin. The rest wavelength of each DIB was determined in a high-qualitycomposite spectrum of the star HD 23180 using the interstellar Na I (D1and D2) lines to establish the radial velocity of the single interveningcloud. DIB wavelengths are quoted to 0.01 Å and are probablyaccurate to ~0.1 Å. Other, weak DIBs found in the spectra ofheavily reddened stars are included with a lower wavelength precision.

Submit a new article

Related links

  • - No Links Found -
Submit a new link

Member of following groups:

Observation and Astrometry data

Right ascension:23h04m45.70s
Apparent magnitude:2.49
Distance:42.808 parsecs
Proper motion RA:0
Proper motion Dec:0
B-T magnitude:2.456
V-T magnitude:2.452

Catalogs and designations:
Proper NamesMarkab
Matn al Faras, Genubi al Mukdim, Yed Alpheras, Shih, Keawe, Marchab
Bayerα Peg
Flamsteed54 Peg
HD 1989HD 218045
TYCHO-2 2000TYC 1711-2475-1
USNO-A2.0USNO-A2 1050-20553148
BSC 1991HR 8781
HIPHIP 113963

→ Request more catalogs and designations from VizieR