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Angular diameter amplitudes of bright Cepheids.
Expected mean angular diameters and amplitudes of angular diametervariations are estimated for all monoperiodic Classical Cepheidsbrighter than < V > = 8.0 mag. The catalog is intended to helpselecting best Cepheid targets for interferometric observations.
| The projection factor for Cepheid distances determination .
The distance of galactic Cepheids can be derived through theinterferometric Baade-Wesselink method. In this method, the projectionfactor which is the ratio of the pulsation velocity (V_{ puls}) to theradial velocity deduced from line profile position (V_{ rad}) is ofcrucial importance. Using a geometric model, we compare differentdefinitions of the radial velocity. The so-called barycentric velocity,which is independent of the Full-Width at Half-Maximum (FWHM) of theline and the rotation, is certainly the most adapted for Cepheidsdistance determination. However, the projection factor remains sensitiveto velocity gradient effects. Then, a self-consistent and time-dependentmodel of the star delta Cep is computed in order to study the dynamicalstructure of its atmosphere together with the induced line profile.Different kinds of pulsation velocities are then derived. In particular,we deduce a suitable average value for the projection factor related todifferent observational techniques, such as spectroscopy, andspectral-line or wide-band interferometry. We show that the impact ofvelocity gradient on the average projection factor, and consequently onthe final distance deduced from this method, is of the order of 6%.Finally, we point out that spectro-interferometry can provide a new wayto constrain directly the projection factor by observations.
| Interferometric Observations of Cepheids. p-factor and center to limb darkening measurements.
Cepheids distances are usually inferred from the Period-Luminosityrelationship, calibrated using the semi-empirical Baade-Wesselink (BW)method. Using this method, the distance is known to a multiplicativefactor, called the projection factor. Presently, this factor is computedusing numerical models - it has hitherto never been measured directly.Based on our new interferometric measurements obtained with the CHARAArray and the already published parallax, we present a geometricalmeasurement of the projection factor of a Cepheid, delta Cep. The valuewe determined, p=1.27±0.06, confirms the generally adopted valueof p=1.36 within 1.5 sigmas. Our value is in line with recenttheoretical predictions of \citet{Nardetto2004}. Moreover,center-to-limb variation (CLV) remains a possible slight source of biasfor the interferometric BW method. In order to address this problem, weare in the process of measuring the CLV of Polaris.
| Cepheid distances from interferometry .
Long baseline interferometry is now able to resolve the pulsationalchange of the angular diameter of a significant number of Cepheids inthe solar neighborhood. This allows the application of a new version ofthe Baade-Wesselink (BW) method to measure their distance, for which wedo not need to estimate the star's temperature. Using angular diametermeasurements from the VLT Interferometer, we derived the distances tofour nearby Cepheids. For three additional stars, we obtained averagevalues of their angular diameters. Based on these new measurements andalready existing data, we derived calibrations of the Period-Luminosityand Period-Radius relations. We also obtained reliable surfacebrightness-color relations, that can be employed for the infraredsurface brightness version of the BW method.
| How good are RR Lyrae and Cepheids really as distance indicators? . The observational approach
A number of recent technical developments, including the Hipparcossatellite, the Hubble Space Telescope fine guidance sensors and longbase line near-IR interferometry has made it possible to employ severallargely geometrical methods to determine direct distances to RR Lyraestars and Cepheids. The distance scale now rests on a much firmer basisand the significant differences between the distances based on RR Lyraestars (short) and Cepheids (long) to the LMC have been largelyeliminated. The effects of metallicity on the RR Lyrae period-luminosity(PL) relation in the K-band as well as on the Cepheid PL relationappears to be the main remaining issues but even here empirical resultsare beginning to show convergence. I review here some of these recentdevelopments seen from the perspective of the near-IR surface brightnessmethod.
| Strichspuraufnahmen zur Veraenderlichenbeobachtung.
Not Available
| Elemental Abundance Ratios in Stars of the Outer Galactic Disk. III. Cepheids
We present metallicities, [Fe/H], and elemental abundance ratios,[X/Fe], for a sample of 24 Cepheids in the outer Galactic disk based onhigh-resolution echelle spectra. The sample members have galactocentricdistances covering 12 kpc<=RGC<=17.2 kpc, making themthe most distant Galactic Cepheids upon which detailed abundanceanalyses have been performed. We find subsolar ratios of [Fe/H] andoverabundances of [α/Fe], [La/Fe], and [Eu/Fe] in the programstars. All abundance ratios exhibit a dispersion that exceeds themeasurement uncertainties. As seen in our previous studies of old openclusters and field giants, enhanced ratios of [α/Fe] and [Eu/Fe]reveal that recent star formation has taken place in the outer disk withType II supernovae preferentially contributing ejecta to theinterstellar medium and with Type Ia supernovae playing only a minorrole. The enhancements for La suggest that asymptotic giant branch starshave contributed to the chemical evolution of the outer Galactic disk.Some of the young Cepheids are more metal-poor than the older openclusters and field stars at comparable galactocentric distances. Thisdemonstrates that the outer disk is not the end result of the isolatedevolution of an ensemble of gas and stars. We showed previously that theolder open clusters and field stars reached a basement metallicity atabout 10-11 kpc. The younger Cepheids reach the same metallicity but atlarger galactocentric distances, roughly 14 kpc. This suggests that theGalactic disk has been growing with time, as predicted from numericalsimulations. The outer disk Cepheids appear to exhibit a bimodaldistribution for [Fe/H] and [α/Fe]. Most of the Cepheids continuethe trends with galactocentric distance exhibited by S. M. Andrievsky'slarger Cepheid sample, and we refer to these stars as the ``GalacticCepheids.'' A minority of the Cepheids show considerably lower [Fe/H]and higher [α/Fe], and we refer to these stars as the ``MergerCepheids.'' One signature of a merger event would be compositiondifferences between the Galactic and Merger Cepheids. The Cepheidssatisfy this requirement, and we speculate that the distinctcompositions suggest that the Merger Cepheids may have formed under theinfluence of significant merger or accretion events. The short lifetimesof the Cepheids reveal that the merger event may be ongoing, with theMonoceros Ring and Canis Major galaxy being possible merger candidates.This paper makes use of observations obtained at the National OpticalAstronomy Observatory, which is operated by the Association ofUniversities for Research in Astronomy (AURA), Inc., under contract fromthe National Science Foundation. We also employ data products from theTwo Micron All Sky Survey, which is a joint project of the University ofMassachusetts and the Infrared Processing and Analysis Center,California Institute of Technology, funded by the National Aeronauticsand Space Administration and the National Science Foundation.
| Probing the dynamical structure of δ Cephei atmosphere
Context: .Limb darkening and the projection factor are currently twolimiting aspects of the interferometric Baade-Wesselink method ofCepheid distance determination. Aims: .We first quantify theimpact of the phase dependence of limb darkening on the deriveddistance. We then study a new way to probe the dynamical structure ofCepheid's atmosphere through spectro-interferometric observations. Methods: .A hydrodynamical model of δ Cep is used to derivestellar disk intensity distribution in the continuum and in differentspectral lines, together with the corresponding wavelength- andphase-dependent visibility curves. Results: .We find thatconsidering a constant limb darkening in the visible leads to asystematic shift of about 0.02 in phase on the angular diameter curve.The derived distance is, however, not affected by this effect.Otherwise, for a spectroscopic resolution of R=12 000 in the visible, wefind in the most favourable case (maximum contraction velocity) asignature on the visibility curve of about 7% that is clearly detectableby current spectro-interferometers. Nevertheless, the projection factorhas only a 1% (or less) effect on the visibility curve.Conclusions: .The spectro-interferometry provides a new geometric viewof Cepheid's atmosphere. However, the combination of differenttechniques (high resolution spectroscopy, spectro- anddifferential-interferometry) are now needed to efficiently constrain thephysical parameters of Cepheids' atmosphere and, in particular theprojection factor.
| Extended envelopes around Galactic Cepheids. II. Polaris and δ Cephei from near-infrared interferometry with CHARA/FLUOR
We present the results of long-baseline interferometric observations ofthe classical Cepheids Polaris and δ Cep in the near infrared K'band (1.9-2.3 μm), using the FLUOR instrument of the CHARA Array.Following our previous detection of a circumstellar envelope (CSE)around ℓ Car (Kervella et al. 2006), we report similar detectionsaround Polaris and δ Cep. Owing to the large data set acquired onPolaris, in both the first and second lobes of visibility function, wehave detected the presence of a circum-stellar envelope (CSE), locatedat 2.4±0.1 stellar radii, accounting for 1.5±0.4% of thestellar flux in the K band. A similar model is applied to the δCep data, which shows improved agreement compared to a model withoutCSE. Finally, we find that the bias in estimating the angular diameterof δ Cep in the framework of the Baade-Wesselink method(Mérand et al 2005b) is of the order of 1% or less in the K band.A complete study of the influence of the CSE is proposed in thiscontext, showing that at the optimum baseline for angular diametervariation detection, the bias is of the order of the formal precision inthe determination of the δ Cep pulsation amplitude (1.6%).
| Extended envelopes around Galactic Cepheids. I. ℓ Carinae from near and mid-infrared interferometry with the VLTI
We present the results of long-baseline interferometric observations ofthe bright southern Cepheid ℓ Carinae in the infrared N (8-13 μm)and K (2.0-2.4 μm) bands, using the MIDI and VINCI instruments of theVLT Interferometer. We resolve in the N band a large circumstellarenvelope (CSE) that we model with a Gaussian of 3 Rstar(≈500 Rȯ ≈ 2-3 AU) half width at half maximum. Thesignature of this envelope is also detected in our K band data as adeviation from a single limb darkened disk visibility function. Thesuperimposition of a Gaussian CSE on the limb darkened disk model of theCepheid star results in a significantly better fit of our VINCI data.The extracted CSE parameters in the K band are a half width at halfmaximum of 2 Rstar, comparable to the N band model, and atotal brightness of 4% of the stellar photosphere. A possibility is thatthis CSE is linked to the relatively large mass loss rate of ℓ Car.Though its physical nature cannot be determined from our data, wediscuss an analogy with the molecular envelopes of RV Tauri, redsupergiants and Miras.
| Fred Lawrence Whipple (1906-2004)
Not Available
| Galactic Cepheids. II. Lithium
We report on the discovery of two lithium Cepheids in the Galaxy, basedon observations made with the echelle spectrograph of the Apache PointObservatory. We have used high-resolution, high signal-to-noise ratiospectra to determine abundances of chemical elements in 16 classicalCepheids. Only two of our program stars show a lithium line, RX Aur andYZ Aur (RX Aur has been also classified by us as a new nonradialpulsator). For the others, including the stars with [N/C]<0.2, Li isdepleted up to logN(Li)<1.0. Hence, it appears that mixing depletesLi before stars enter the instability strip. According to stellarmodels, the main mixing event takes place when Teff dropsbelow 4000 K, which is outside the red edge of the instability strip;i.e., after stars have crossed the instability strip for the first time.
| A spectroscopic study of bright southern Cepheids - a high-resolution view of Cepheid atmospheres
We present high-resolution spectroscopic observations andspecies-by-species radial velocities of a number of southern Cepheids.The stars (BP Cir, V350 Sgr, AX Cir, V636 Sco, W Sgr, S Mus, β Dor,TT Aql, Y Oph, YZ Car, SW Vel, X Pup, T Mon and l Car) were observed aspart of a long-term programme at Mt John University Observatory. Radialvelocities were determined with the line bisector technique, and have aprecision of ~300 ms-1. Velocity differences as large as 30kms-1 were found for Hα and CaII when referenced to themetallic line velocity curves, but more subtle variations (of 1-2kms-1) were also detected in many other species. Pulsationalphase anticorrelations are found between lines of SiII and BaII,confirming the propagation time delay between line-forming layersproducing these two species. We find that the amplitude and phasedifferences between the various species increase with period.
| Predicting accurate stellar angular diameters by the near-infrared surface brightness technique
I report on the capabilities of the near-infrared (near-IR) surfacebrightness technique to predict reliable stellar angular diameters asaccurate as <~2 per cent using standard broad-band Johnson photometryin the colour range -0.1 <= (V-K)O<= 3.7 includingstars of A, F, G, K spectral type. This empirical approach is fast toapply and leads to estimated photometric diameters in very goodagreement with recent high-precision interferometric diametermeasurements available for non-variable dwarfs and giants, as well asfor Cepheid variables. Then I compare semi-empirical diameters predictedby model-dependent photometric and spectrophotometric (SP) methods withnear-IR surface brightness diameters adopted as empirical referencecalibrators. The overall agreement between all these methods is withinapproximately +/-5 per cent, confirming previous works. However, on thesame scale of accuracy, there is also evidence for systematic shiftspresumably as a result of an incorrect representation of the stellareffective temperature in the model-dependent results. I also comparemeasurements of spectroscopic radii with near-IR surface brightnessradii of Cepheids with known distances. Spectroscopic radii are found tobe affected by a scatter as significant as >~9 per cent, which is atleast three times greater than the formal error currently claimed by thespectroscopic technique. In contrast, pulsation radii predicted by theperiod-radius (PR) relation according to the Cepheid period result aresignificantly less dispersed, indicating a quite small scatter as aresult of the finite width of the Cepheid instability strip, as expectedfrom pulsation theory. The resulting low level of noise stronglyconfirms our previous claims that the pulsation parallaxes are the mostaccurate empirical distances presently available for Galactic andextragalactic Cepheids.
| Zur Beobachtung und Auswertung von Cepheiden-Lichtkurven.
Not Available
| Welchen Lichtwechsel kann ein Beobachter bei Cepheiden erwarten?
Not Available
| Bericht uber die Veranderlichen-Beobachtungswoche an der VdS-Sternwarte in Kirchheim.
Not Available
| Radial Velocities of Galactic Cepheids
We report 490 radial velocities for 16 Galactic Cepheid variables. Thetypical uncertainty of a single velocity is +/-0.40 km s-1.Comparison with published velocities shows excellent agreement. Two ofthe Cepheids (Z Lac, S Sge) are known binaries and exhibit orbitalvelocity changes in our observing interval.
| Infrared Surface Brightness Distances to Cepheids: A Comparison of Bayesian and Linear-Bisector Calculations
We have compared the results of Bayesian statistical calculations andlinear-bisector calculations for obtaining Cepheid distances and radiiby the infrared surface brightness method. We analyzed a set of 38Cepheids using a Bayesian Markov Chain Monte Carlo method that had beenrecently studied with a linear-bisector method. The distances obtainedby the two techniques agree to 1.5%+/-0.6%, with the Bayesian distancesbeing larger. The radii agree to 1.1%+/-0.7%, with the Bayesiandeterminations again being larger. We interpret this result asdemonstrating that the two methods yield the same distances and radii.This implies that the short distance to the Large Magellanic Cloud foundin recent linear-bisector studies of Cepheids is not caused bydeficiencies in the mathematical treatment. However, the computeduncertainties in distance and radius for our data set are larger in theBayesian calculation by factors of 1.4-6.7. We give reasons to favor theBayesian computations of the uncertainties. The larger uncertainties canhave a significant impact on interpretation of Cepheid distances andradii obtained from the infrared surface brightness method.
| Pulsation and Evolutionary Masses of Classical Cepheids. I. Milky Way Variables
We investigate a selected sample of Galactic classical Cepheids withavailable distance and reddening estimates in the framework of thetheoretical scenario provided by pulsation models, computed with metalabundance Z=0.02, helium content in the range of Y=0.25-0.31, andvarious choices of the stellar mass and luminosity. After transformingthe bolometric light curve of the fundamental models into BVRIJKmagnitudes, we derived analytical relations connecting the pulsationperiod with the stellar mass, the mean (intensity averaged) absolutemagnitude, and the color of the pulsators. These relations are usedtogether with the Cepheid observed absolute magnitudes in order todetermine the ``pulsation'' mass, Mp, of each individualvariable. The comparison with the ``evolutionary'' masses,Me,can, given by canonical (no convective core overshooting,no mass loss) models of central He-burning stellar structures revealsthat the Mp/Me,can ratio is correlated with theCepheid period, ranging from ~0.8 at logP=0.5 to ~1 at logP=1.5. Wediscuss the effects of different input physics and/or assumptions on theevolutionary computations, as well as of uncertainties in the adoptedCepheid metal content, distance, and reddening. Eventually, we find thatthe pulsational results can be interpreted in terms of mass loss duringor before the Cepheid phase, whose amount increases as the Cepheidoriginal mass decreases. It vanishes around 13 Msolar andincreases up to ~20% at 4 Msolar.
| Direct Distances to Cepheids in the Large Magellanic Cloud: Evidence for a Universal Slope of the Period-Luminosity Relation up to Solar Abundance
We have applied the infrared surface brightness (ISB) technique toderive distances to 13 Cepheid variables in the LMC that span a periodrange from 3 to 42 days. From the absolute magnitudes of the variablescalculated from these distances, we find that the LMC Cepheids definetight period-luminosity (PL) relations in the V, I, W, J, and K bandsthat agree exceedingly well with the corresponding Galactic PL relationsderived from the same technique and are significantly steeper than theLMC PL relations in these bands observed by the OGLE-II Project in V, I,and W and by Persson and coworkers in J and K. We find that the LMCCepheid distance moduli we derive, after correcting them for the tilt ofthe LMC bar, depend significantly on the period of the stars, in thesense that the shortest period Cepheids have distance moduli near 18.3,whereas the longest period Cepheids are found to lie near 18.6. Sincesuch a period dependence of the tilt-corrected LMC distance modulishould not exist, there must be a systematic, period-dependent error inthe ISB technique not discovered in previous work. We identify as themost likely culprit the p-factor, which is used to convert the observedCepheid radial velocities into their pulsational velocities. Bydemanding (1) a zero slope on the distance modulus versus period diagramand (2) a zero mean difference between the ISB and ZAMS fitting distancemoduli of a sample of well-established Galactic cluster Cepheids, wefind that p=1.58(+/-0.02)-0.15(+/-0.05)logP, with the p-factor dependingmore strongly on Cepheid period (and thus luminosity) than indicated bypast theoretical calculations. When we recalculate the distances of theLMC Cepheids with the revised p-factor law suggested by our data, we notonly obtain consistent distance moduli for all stars but also decreasethe slopes in the various LMC PL relations (and particularly in thereddening-independent K and W bands) to values that are consistent withthe values observed by OGLE-II and Persson and coworkers. From our 13Cepheids, we determine the LMC distance modulus to be 18.56+/-0.04 mag,with an additional estimated systematic uncertainty of ~0.1 mag. Usingthe same corrected p-factor law to redetermine the distances of theGalactic Cepheids, the new Galactic PL relations are also foundconsistent with the observed optical and near-infrared PL relations inthe LMC. Our main conclusion from the ISB analysis of the LMC Cepheidsample is that, within current uncertainties, there seems to be nosignificant difference between the slopes of the PL relations in theMilky Way and LMC. With literature data on more metal-poor systems, itseems now possible to conclude that the slope of the Cepheid PL relationis independent of metallicity in the broad range in [Fe/H] from -1.0 dexto solar abundance, within a small uncertainty. The new evidence fromthe first ISB analysis of a sizable sample of LMC Cepheids suggests thatthe previous, steeper Galactic PL relations obtained from this techniquewere caused by an underestimation of the period dependence in themodel-based p-factor law used in the previous work. We emphasize,however, that our current results must be substantiated by newtheoretical models capable of explaining the steeper period dependenceof the p-factor law, and we will also need data on more LMC fieldCepheids to rule out remaining concerns about the validity of ourcurrent interpretation.
| Phase-dependent Variation of the Fundamental Parameters of Cepheids. III. Periods between 3 and 6 Days
We present the results of a detailed multiphase spectroscopic analysisof six classical Cepheids with pulsation periods between 3 and 6 days.For each star we have derived phased values of effective temperature,surface gravity, microturbulent velocity, and elemental abundances. Weshow that the elemental abundance results for these Cepheids areconsistent for all pulsational phases.
| Mean Angular Diameters and Angular Diameter Amplitudes of Bright Cepheids
We predict mean angular diameters and amplitudes of angular diametervariations for all monoperiodic PopulationI Cepheids brighter than=8.0 mag. The catalog is intended to aid selecting mostpromising Cepheid targets for future interferometric observations.
| The projection factor of δ Cephei. A calibration of the Baade-Wesselink method using the CHARA Array
Cepheids play a key role in astronomy as standard candles for measuringintergalactic distances. Their distance is usually inferred from theperiod-luminosity relationship, calibrated using the semi-empiricalBaade-Wesselink method. Using this method, the distance is known to amultiplicative factor, called the projection factor. Presently, thisfactor is computed using numerical models - it has hitherto never beenmeasured directly. Based on our new interferometric measurementsobtained with the CHARA Array and the already published parallax, wepresent a geometrical measurement of the projection factor of a Cepheid,δ Cep. The value we determined, p=1.27 ±0.06, confirms the generally adopted value of p=1.36 within 1.5 sigmas.Our value is in line with recent theoretical predictions of Nardetto etal. (2004, A&A, 428, 131).
| CHARM2: An updated Catalog of High Angular Resolution Measurements
We present an update of the Catalog of High Angular ResolutionMeasurements (CHARM, Richichi & Percheron \cite{CHARM}, A&A,386, 492), which includes results available until July 2004. CHARM2 is acompilation of direct measurements by high angular resolution methods,as well as indirect estimates of stellar diameters. Its main goal is toprovide a reference list of sources which can be used for calibrationand verification observations with long-baseline optical and near-IRinterferometers. Single and binary stars are included, as are complexobjects from circumstellar shells to extragalactic sources. The presentupdate provides an increase of almost a factor of two over the previousedition. Additionally, it includes several corrections and improvements,as well as a cross-check with the valuable public release observationsof the ESO Very Large Telescope Interferometer (VLTI). A total of 8231entries for 3238 unique sources are now present in CHARM2. Thisrepresents an increase of a factor of 3.4 and 2.0, respectively, overthe contents of the previous version of CHARM.The catalog is only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/431/773
| Cepheid pulsations resolved by the VLTI.
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| Improved Baade-Wesselink surface brightness relations
Recent, and older accurate, data on (limb-darkened) angular diameters iscompiled for 221 stars, as well as BVRIJK[12][25] magnitudes for thoseobjects, when available. Nine stars (all M-giants or supergiants)showing excess in the [12-25] colour are excluded from the analysis asthis may indicate the presence of dust influencing the optical andnear-infrared colours as well. Based on this large sample,Baade-Wesselink surface brightness (SB) relations are presented fordwarfs, giants, supergiants and dwarfs in the optical and near-infrared.M-giants are found to follow different SB relations from non-M-giants,in particular in V versus V-R. The preferred relation for non-M-giantsis compared to the earlier relation by Fouqué and Gieren (basedon 10 stars) and Nordgren et al. (based on 57 stars). Increasing thesample size does not lead to a lower rms value. It is shown that theresiduals do not correlate with metallicity at a significant level. Thefinally adopted observed angular diameters are compared to thosepredicted by Cohen et al. for 45 stars in common, and there isreasonable overall, and good agreement when θ < 6 mas.Finally, I comment on the common practice in the literature to average,and then fix, the zero-point of the V versus V-K, V versus V-R and Kversus J-K relations, and then rederive the slopes. Such a commonzero-point at zero colour is not expected from model atmospheres for theV-R colour and depends on gravity. Relations derived in this way may bebiased.
| Period-luminosity relations for Galactic Cepheid variables with independent distance measurements
In this paper, we derive the period-luminosity (PL) relation forGalactic Cepheids with recent independent distance measurements fromopen cluster, Barnes-Evans surface brightness, interferometry and HubbleSpace Telescope astrometry techniques. Our PL relation confirms theresults from recent works, which showed that the Galactic Cepheidsfollow a different PL relation to their Large Magellanic Cloud (LMC)counterparts. Our results also show that the slope of the Galactic PLrelation is inconsistent with the LMC slope with more than 95 per centconfidence level. We apply this Galactic PL relation to find thedistance to NGC 4258. Our result of μo= 29.49 +/- 0.06 mag(random error) agrees at the ~1.4σ level with the geometricaldistance of μgeo= 29.28 +/- 0.15 mag from water masermeasurements.
| Cepheidenbeobachtung in der BAV: Ruckblick und Ausblick.
Not Available
| Beobachtungsergebnisse Bundesdeutsche Arbeitsgemeinschaft fur Veranderlichen Serne e.V.
Not Available
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Observation and Astrometry data
| Constellation: | Cepheus |
| Right ascension: | 22h29m10.30s |
| Declination: | +58°24'55.0" |
| Apparent magnitude: | 3.75 |
| Distance: | 301.205 parsecs |
| Proper motion RA: | 15.2 |
| Proper motion Dec: | 4.7 |
| B-T magnitude: | 5.097 |
| V-T magnitude: | 4.207 |
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