Contents
Images
Upload your image
DSS Images Other Images
Related articles
A new absolute magnitude calibration with 2MASS for cataclysmic variables
Using reliable trigonometric measurements, we find that the absolutemagnitude of cataclysmic variables depends on the orbital period andde-reddened (J ‑ H)0 and (H ‑Ks)0 colours of 2MASS (Two Micron All Sky Survey)photometric system. The calibration equation covers the ranges0.032d < Porb ⩽ 0.454d,‑0.08 < (J ‑ H)0 ⩽ 1.54, ‑0.03 <(H ‑ Ks)0 ⩽ 0.56 and 2.0
| Theoretical Orbital Period Distributions of Cataclysmic Variables above the Period Gap: Effects of Circumbinary Disks
Population synthesis tools are used to investigate the population ofnonmagnetic cataclysmic variables with unevolved main-sequence-likedonors at orbital periods greater than 2.75 hr. In addition to theangular momentum losses associated with gravitational radiation,magnetic braking, and mass loss from the system, we also include theeffects of circumbinary disks on the evolution. For a fractional massinput rate into the disk, corresponding to 3×10-4 ofthe mass transfer rate, the model systems exhibit a bounce at orbitalperiods greater than 2.75 hr. The simulations reveal that (1) somesystems can exist as dwarf novae throughout their lifetime, (2) dwarfnovae can evolve into novalike systems, and (3) novalike systems canevolve back into dwarf novae during their postbounce evolution to longerorbital periods. Among these subclasses, novalike cataclysmic variableswould be the best candidates to search for circumbinary disks atwavelengths >~10 μm. The theoretical orbital period distributionis in reasonable accord with the combined population of dwarf novae andnovalike systems above the period gap, suggesting the possibility thatsystems with unevolved donors need not detach and evolve below theperiod gap as in the disrupted magnetic braking model. The resultingpopulation furthermore reveals the possible presence of systems withsmall mass ratios and a preference of O/Ne/Mg white dwarfs in dwarf novasystems in comparison to novalike systems. The novalike populationfurthermore shows a lack of systems with high-mass white dwarfs. Theimportance of observational bias in accounting for the differingpopulations is examined, and it is shown that an understanding of theseeffects is necessary in order to confront the theoretical distributionswith the observed ones in a meaningful manner.
| Report on CCD activities at the Bronberg Observatory (CBA Pretoria) in 2005.
Not Available
| The Galactic Constants and Rotation Curve from Molecular-Gas Observations
We obtained the photometric distances and radial velocities for themolecular gas for 270 star-forming regions and estimated the distance tothe Galactic center from ten tangent points to be R 0 = 8.01 ±0.44 kpc. Estimates of R 0 derived over the last decade are summarizedand discussed; the average value is R 0 = 7.80 ± 0.33 kpc. Weanalyze deviations from axial symmetry of the gas motion around theGalactic center in the solar neighborhood. Assuming a flat rotationcurve, we obtain Θ0 ˜ 200 km/s for the circular velocity ofthe Sun from regions beyond the Perseus arm. We used these Galacticconstants to construct the Galactic rotation curve. This rotation curveis flat along virtually its total extent from the central bar to theperiphery. The velocity jump in the corotation region of the central barin the first quadrant is 20 km/s. We present analytical formulas for therotation curves of the Northern and Southern hemispheres of the Galaxyfor R 0 = 8.0 kpc and Θ0 = 200 km/s.
| Astrophysics in 2004
In this 14th edition of ApXX,1 we bring you the Sun (§ 2) and Stars(§ 4), the Moon and Planets (§ 3), a truly binary pulsar(§ 5), a kinematic apology (§ 6), the whole universe(§§ 7 and 8), reconsideration of old settled (§ 9) andunsettled (§ 10) issues, and some things that happen only on Earth,some indeed only in these reviews (§§ 10 and 11).
| The extraordinary luminous binary star QU CAR.
Not Available
| Recovery of old novae
In the course of a long-term project investigating classical novae withlarge outburst amplitudes, we have performed multi-wavelength photometryand optical spectroscopy of several old-nova candidates. We hereintroduce the aim of the project, the search for low mass-transfer novaewith short orbital periods, and explain the method to recover these oldnovae via their colour characteristics. Finally we concentrate on firstresults for selected objects in our sample.
| A Preliminary Observational Search for Circumbinary Disks around Cataclysmic Variables
Circumbinary (CB) disks have been proposed as a mechanism to extractorbital angular momentum from cataclysmic variables (CVs) during theirevolution. As proposed by Taam & Spruit, these disks extend outwardto several astronomical units and should be detected observationally viatheir infrared flux or by absorption lines in the ultraviolet spectra ofthe CV. We have made use of archival HST/STIS spectra, as well as ourown near-IR imaging, to search for observational evidence of such CBdisks in seven CVs. Based on the null result, we place an upper limit onthe column density of the disk ofNH~1017cm-2.Based on observations with the NASA/ESA Hubble Space Telescope, obtainedat the Space Telescope Science Institute, which is operated by theAssociation of Universities for Research in Astronomy, Inc., under NASAcontract NAS 5-26555. This work was started while three of the authors(K. E. B., N. S., S. B. H.) were at the Planetary Science Institute,Tucson, AZ.
| Astrophysics in 2003
Five coherent sections appear this year, addressing solar physics,cosmology (with WMAP highlights), gamma-ray bursters (and theirassociation with Type Ia supernovae), extra-solar-system planets, andthe formation and evolution of galaxies (from reionization to assemblageof Local Group galaxies). There are also eight incoherent sections thatdeal with other topics in stellar, galactic, and planetary astronomy andthe people who study them.
| A Carbon-Rich Nova V 840 OPH
We present optical spectroscopy and multicolor photometry of the oldnova V 840 Oph. As part of a long-term project to investigate novae withlarge outburst amplitudes, we identified this nova via its colorcharacteristics and confirmed it spectroscopically. We find V840 Oph tobe one of very few cataclysmic variables showing C IV emission at 580/1nm. The study of the carbon lines suggests strongly that V 840 Ophcontains a carbon-rich secondary star. So far, only the nova-like QU Carhas been known to have such a companion. We also find spectroscopicevidence that V 840 Oph has a hot, dense accretion disc or stream and isprobably a magnetic system.
| Recovery of the old nova V840 Ophiuchi: A carbon rich system
We present optical spectroscopy and multi colour photometry of the oldnova V840 Oph. We rediscovered the nova based on its position in thecolour-colour diagrams. It stands out as a very blue object with anadditional red component. We present the first optical spectroscopy ofthis candidate and confirm its nova character. Furthermore, V840 Oph hasbeen found as one of very few cataclysmic variables showing C IVemission at lambda = 580/1 nm. From the analysis of the carbon lines itseems probable that V840 Oph contains actually a carbon-rich secondarystar. So far, only the nova-like QU Car has been known to have such acompanion. We furthermore find spectroscopic evidence that V840 Oph hasa hot, dense accretion disc or stream and is probably a magnetic system.Based on observations collected at the European Southern Observatory, LaSilla, Chile.
| QU Car: a very high luminosity nova-like binary with a carbon-enriched companion
QU Car is listed in cataclysmic variable star catalogues as a nova-likevariable. This little-studied, yet bright interacting binary isre-appraised here in the light of new high-quality ultravioletinterstellar line data obtained with STIS on-board the Hubble SpaceTelescope. The detection of a component of interstellar absorption at amean local standard of rest velocity of -14 km s-1 indicatesthat the distance to QU Car may be ~2 kpc or more - a considerableincrease on the previous lower-limiting distance of 500 pc. If so, thebolometric luminosity of QU Car could exceed 1037 ergs-1. This would place this binary in the luminosity domainoccupied by known compact-binary supersoft X-ray sources. Even at 500pc, QU Car appears to be the most luminous nova-like variable known. Newintermediate dispersion optical spectroscopy of QU Car spanning3800-7000 Å is presented. These data yield the discovery thatCIVλλ5801,12 is present as an unusually prominent emissionline in an otherwise low-contrast line spectrum. Using measurements ofthis and other lines in a recombination line analysis, it is shown thatthe C/He abundance as proxied by then(C4+)/n(He2+) ratio may be as high as 0.06 (anorder of magnitude higher than the solar ratio). Furthermore, the C/Oabundance ratio is estimated to be greater than 1. These findingssuggest that the companion in QU Car is a carbon star. If so, it wouldbe the first example of a carbon star in such a binary. An early-type Rstar best matches the required abundance pattern and could escapedetection at optical wavelengths provided the distance to QU Car is ~2kpc or more.
| Hubble Space Telescope Observations of the Old Nova DI Lacertae
We have carried out a synthetic spectral analysis of a Hubble SpaceTelescope Space Telescope Imaging Spectrograph observation of the oldnova DI Lacertae (Nova Lacerta 1910). The spectrum, obtained with theE140M disperser, reveals a rising continuum shortward of 1560 Å, aC IV P Cygni profile indicative of wind outflow associated with diskaccretion, a deep Lyα profile, and strong N V (1238 and 1242Å) and O V (1371 Å) wind/coronal absorption lines. Numeroussharp interstellar resonance lines are also present. A grid of accretiondisk models, spanning a wide range of inclinations, accretion rates, andwhite dwarf masses, was compared with three sets of dereddened data.From the three best fits, we conclude that the most likely parameterscharacterizing the far-UV spectrum of DI Lac are an inclination below18°, a white dwarf mass between 0.6 and 0.8 Msolar, andan accretion rate between 10-9.0 and 10-9.5Msolar yr-1. The scale factors for the threebest-fit disk models indicate distances between 2 and 2.5 kpc. Theextreme weakness or absence of silicon features in the observed spectrumcorresponds to a silicon underabundance of <~10-4 timessolar. The best-fitting high-gravity photosphere model has logg=8,Teff=27,000 K, Vsini=200 km s-1, and a scalefactor distance (for a 0.7 Msolar white dwarf) of only 76 pc.Thus, a white dwarf photosphere cannot be contributing appreciably tothe far-UV spectrum. Based on observations with the NASA/ESA HubbleSpace Telescope, obtained at the Space Telescope Science Institute,which is operated by the Association of Universities for Research inAstronomy, Inc., under NASA contract NAS 5-26555 and with the ApachePoint Observatory 3.5 m telescope, which is owned and operated by theAstrophysical Research Consortium.
| Time-resolved ultraviolet spectroscopy of the compact interacting binary QU Car
We present Hubble Space Telescope STIS (1160-1700 Å) echellespectra of the cataclysmic variable (CV) star QU Car, at three epochs.In catalogues this binary is classified as a nova-like variable. QU Carwas observed three times in time-tag mode for 2300, 2600 and 2600 s,allowing us to study the spectral time evolution on time-scales down to~10 s. We find evidence of a high-state non-magnetic CV at lowinclination, with unusually high ionization. We observed narrowabsorption lines (approximately a few hundred km s-1 wide) inNVλ1240, OVλ1371 and SiIVλ1398, and broader (HWZI ~1000 km s-1) emission in CIIIλ1176, CIVλ1549and HeIIλ1640, all with a superposed absorption component. Highionization is indicated by the HeII emission, which is unusually strongin comparison with CIV, and the relative strength of the OV absorptionline. The dereddened ultraviolet continuum spectral index of, onaverage, -2.3 suggests that disc accretion dominates the spectral energydistribution. In two observations velocity shifting is noted in theabsorption lines on a time-scale long enough not to repeat within the ~2600-s exposures. The absorption superposed on the CIV emission linemoves coherently with the NV and SiIV absorption, suggesting the sameorigin for all absorption lines - most likely to be in the accretiondisc atmosphere. Weak blueshifted absorption in NV and CIV providesevidence of an outflow component and we estimate a maximum outflowvelocity of ~ 2000 km s-1. This may be linked to a windlaunched from further out in the disc than is typically seen in thosehigh-state non-magnetic CVs, the wind speeds of which are observed toreach to >~ 4000 km s-1. Unusually, three ionizationstages of carbon (CII, CIII and CIV) are present in emission, with thelinewidth increasing with higher ionization. The presence of CII inemission and the positive linewidth/ionization correlation are mosteasily reconciled with an origin in a disc chromosphere, beyond theinfluence of the extreme ultraviolet-emitting inner disc.
| New periodic variables from the Hipparcos epoch photometry
Two selection statistics are used to extract new candidate periodicvariables from the epoch photometry of the Hipparcos catalogue. Theprimary selection criterion is a signal-to-noise ratio. The dependenceof this statistic on the number of observations is calibrated usingabout 30000 randomly permuted Hipparcos data sets. A significance levelof 0.1 per cent is used to extract a first batch of candidate variables.The second criterion requires that the optimal frequency be unaffectedif the data are de-trended by low-order polynomials. We find 2675 newcandidate periodic variables, of which the majority (2082) are from theHipparcos`unsolved' variables. Potential problems with theinterpretation of the data (e.g. aliasing) are discussed.
| A Catalog and Atlas of Cataclysmic Variables: The Living Edition
The Catalog and Atlas of Cataclysmic Variables (Edition 1: Downes &Shara; Edition 2: Downes, Webbink, & Shara) has been a valuablesource of information for the cataclysmic variable community. However,the goal of having a central location for all objects is slowly beinglost as each new edition is generated. There can also be a long timedelay between new information becoming available on an object and itspublication in the catalog. To eliminate these concerns, as well as tomake the catalog more accessible, we have created a Web site which willcontain a ``living'' edition of the catalog. We have also added orbitalperiod information, as well as finding charts for novae, to thecatalog.
| Stars with the Largest Hipparcos Photometric Amplitudes
A list of the 2027 stars that have the largest photometric amplitudes inHipparcos Photometry shows that most variable stars are all Miras. Thepercentage of variable types change as a function of amplitude. Thiscompilation should also be of value to photometrists looking forrelatively unstudied, but large amplitude stars.
| Cataclysmic variables as sources of gravitational waves
General relativity predicts that binary systems of stars producegravitational waves of significant intensity. Here we are particularlyinterested in the cataclysmic variable binaries (CVs). These systemsemit low frequency gravitational waves, f < 10-3 Hz. Wepresent here a catalog of CVs and argue that part of them are capable ofbeing detected by the Laser Interferometer Space Antenna (LISA).
| Hipparcos parallaxes of cataclysmic binaries and the quest for their absolute magnitudes
Not Available
| UBV beta Database for Case-Hamburg Northern and Southern Luminous Stars
A database of photoelectric UBV beta photometry for stars listed in theCase-Hamburg northern and southern Milky Way luminous stars surveys hasbeen compiled from the original research literature. Consisting of over16,000 observations of some 7300 stars from over 500 sources, thisdatabase constitutes the most complete compilation of such photometryavailable for intrinsically luminous stars around the Galactic plane.Over 5000 stars listed in the Case-Hamburg surveys still lackfundamental photometric data.
| Catalogue of cataclysmic binaries, low-mass X-ray binaries and related objects (Sixth edition)
The catalogue lists coordinates, apparent magnitudes, orbitalparameters, stellar parameters of the components and other characteristcproperties of 318 cataclysmic binaries, 47 low-mass X-ray binaries and49 related objects with known or suspected orbital periods together witha comprehensive selection of the relevant recent literature. In additionthe catalogue contains a list of references to published finding chartsfor 394 of the 414 objects. A cross-reference list of alias objectdesignations concludes the catalogue. Literature published before 30June 1997 has, as far as possible, been taken into account. Thecatalogue is available in electronic form only via the CDS at ftp130.79.128.5 or http://cdsweb.u-strasbg.fr/Abstract.html
| Cataclysmic variables in the ROSAT PSPC All Sky Survey.
91 cataclysmic variables from a sample of 162 systems with known orsuspected binary periods were detected during the ROSAT XRT-PSPC All SkySurvey. Among the non-magnetic systems, the X-ray to optical/ultravioletflux ratio decreases along the sequence SU UMa type - U Gem type - Z Camtype - UX UMa type, due mainly to variations in the optical/ultravioletflux. 8 of the 10 brightest systems in terms of total PSPC countrate aremagnetic systems. The 0.5-2.5keV X-ray luminosities range up to~10^32^erg/s, the highest luminosities being those of four faraway DQHer type systems. The other types of cataclysmic variables all havesimilar 0.5-2.5keV luminosity distributions. In an Appendix we comparethe X-ray properties of cataclysmic variables with those of the dimX-ray sources in globular clusters.
| A Catalog and Atlas of Cataclysmic Variables-Second Edition
We present a catalog of all 1020 known cataclysmic variables (CVs). Thispaper is a major update of the first edition of the catalog (Downes andShara 1993, PASP, 105, 127), which contained coordinates (measured inthe reference frame of the Hubble Space Telescope Guide Star Survey forthe non-novae, and obtained from the literature for the novae), thevariability type, the magnitude range, and references to both findingcharts and spectroscopy. Also included in the catalog were findingcharts for all dwarf novae, novalike variables, and objects classifiedonly as cataclysmic variables known as of 1993; a similar catalog andatlas for novae has been published by Duerbeck (1978a). This updatededition includes 195 new objects (172 CVs and 23 non-CVs), revisedidentifications for 57 objects, and revised information (classificationand spectral references) when available. We also now include plateidentification information for the coordinate measurements, a referenceto the classification, proper motion information where appropriate, anda table showing the CVs observed by space-based observatories. Thissecond edition is inclusive of the first edition, although only new orupdated charts are presented. (SECTION: Special Issue on CataclysmicVariable Stars)
| A Radial Velocity Database for Stephenson-Sanduleak Southern Luminous Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1997AJ....113..823R&db_key=AST
| The systemic-velocity distribution of cataclysmic variables.
We have collected γ velocities of cataclysmic variables from asurvey of published orbital radial-velocity studies. We argue that forthe non-magnetic cataclysmic variables the γ distribution gives afair description of the systemic radial velocities; for magneticcataclysmic variables the effect of motions within the system appears tobe substantial. Assuming that the distribution of the spatial velocitiesof cataclysmic variables in the solar neighbourhood follows the velocityellipsoid, with dispersions as given by Wielen (1977), we estimate thatthe dispersion of z-velocities of CVs is in the range 16 to 21km/s. Withthe galactic potential of Kuijken and Gilmore (1989) we then derive thedistribution of distances, z, above the galactic plane. Thisdistribution has an exponential scale height in the range 160-230pc,which is nearly a factor of two larger than that obtained for the zdistribution of systems with known distances. This probably reflects theincompleteness of the census of cataclysmic variables at distances evenas small as ~100pc. The velocity distribution of cataclysmic variablesindicates that they are an old disk population, with a mix of ages up to10Gyr.
| Vitesses radiales. Catalogue WEB: Wilson Evans Batten. Subtittle: Radial velocities: The Wilson-Evans-Batten catalogue.
We give a common version of the two catalogues of Mean Radial Velocitiesby Wilson (1963) and Evans (1978) to which we have added the catalogueof spectroscopic binary systems (Batten et al. 1989). For each star,when possible, we give: 1) an acronym to enter SIMBAD (Set ofIdentifications Measurements and Bibliography for Astronomical Data) ofthe CDS (Centre de Donnees Astronomiques de Strasbourg). 2) the numberHIC of the HIPPARCOS catalogue (Turon 1992). 3) the CCDM number(Catalogue des Composantes des etoiles Doubles et Multiples) byDommanget & Nys (1994). For the cluster stars, a precise study hasbeen done, on the identificator numbers. Numerous remarks point out theproblems we have had to deal with.
| The Henry Draper Extension Charts: A catalogue of accurate positions, proper motions, magnitudes and spectral types of 86933 stars
The Henry Draper Extension Charts (HDEC), published in the form offinding charts, provide spectral classification for some 87000 starsmostly between 10th and 11th magnitude. This data, being highlyvaluable, as yet was practically unusable for modern computer-basedastronomy. An earlier pilot project (Roeser et al. 1991) demonstrated apossibility to convert this into a star catalogue, using measurements ofcartesian coordinates of stars on the charts and positions of theAstrographic Catalogue (AC) for subsequent identification. We presenthere a final HDEC catalogue comprising accurate positions, propermotions, magnitudes and spectral classes for 86933 stars of the HenryDraper Extension Charts.
| Time Variability in the Ultraviolet Resonance Lines of the Cataclysmic Variables Mu-Centauri Ah-Herculis and Qu-Carinae
Abstract image available at:http://adsabs.harvard.edu/abs/1994MNRAS.269..891K
| A catalogue of UBV colours of cataclysmic variables.
A catalogue of UBV magnitudes and colours for 179 cataclysmic variablesis presented, updating a similar catalogue published almost a decadeago. The data were compiled from observations published over about 40years. The purpose of the catalogue is to provide a complete and uniformdata base for statistical and other investigations.
| A catalog and atlas of cataclysmic variables
The General Catalogue of Variable Stars contains information necessaryfor obtaining observations of variable stars, and in particular,cataclysmic variables. However, the coordinates presented are notaccurate enough for observatories such as the Hubble Space Telescope,and the references to finding charts are often to journals not easilyaccessible to some astronomers. We have therefore created a catalog ofall cataclysmic variables (known to us as of February 1992) whichcontains coordinates (measured in the reference frame of the HubbleSpace Telescope Guide Star Survey for the nonnovae, and obtained fromthe literature for the novae), the variability type, the magnituderange, and references to both finding charts and spectroscopy. The atlascontains finding charts for the dwarf novae, novalike variables, andobjects classified only as cataclysmic variables, for which we couldobtain valid identifications; a similar catalog and atlas for novae hasbeen published by Duerbeck (1987).
|
Submit a new article
Related links
Submit a new link
Member of following groups:
|
Observation and Astrometry data
| Constellation: | Τρόπις |
| Right ascension: | 11h05m42.49s |
| Declination: | -68°37'58.2" |
| Apparent magnitude: | 11.534 |
| Proper motion RA: | -10.4 |
| Proper motion Dec: | 4.7 |
| B-T magnitude: | 11.425 |
| V-T magnitude: | 11.525 |
Catalogs and designations:
|
