Coma Berenices Research Articles

An astrometric catalogue for the area of Coma Berenices

A catalogue of stellar positions and proper motions down to the 14th photographic magnitude in the area of the open cluster in Coma Berenices is compiled from data of 12 different sources. The accuracy of the proper motion data is comparable to that of the Hipparcos Catalogue.

The Coma Berenices star cluster and its moving group

We report on the analysis of astrometric and photometric data from Hipparcos, Tycho and the ACT catalogue in a 1200 sq. degree field around the nearby open star cluster in Coma Berenices and infer the characteristic features of this cluster. From a sample of 51 kinematic members we derive the cluster's distance, size and spatial structure as well as its stellar content, mass and age. We find that the cluster consists of an elliptical core-halo system with major axis parallel to the direction of galactic motion, and of a moving group of extratidal stars. The latter have tangential distances ≥10pc from the cluster center, but have the same distance from the Sun, the same motion and the same age as the stars in the core and halo. The luminosity function of the core-halo system steeply declines beyond absolute magnitude MV=4.5, but that of the moving group rises towards fainter magnitudes and suggests the existence of further low-mass members below the current magnitude limit. The cloud of extratidal stars witnesses the process of dissolution of the cluster.

The Problem ofHipparcosDistances to Open Clusters. I. Constraints from Multicolor Main‐Sequence Fitting

Parallax data from the Hipparcos mission allow the direct distance to open clusters to be compared with the distance inferred from main-sequence (MS) fitting. There are surprising differences between the two distance measurements, indicating either the need for changes in the cluster compositions or reddening, underlying problems with the technique of MS fitting, or systematic errors in the Hipparcos parallaxes at the 1 mas level. We examine the different possibilities, focusing on MS fitting in both metallicity-sensitive B-V and metallicity-insensitive V-I for five well-studied systems (the Hyades, Pleiades, α Per, Praesepe, and Coma Ber). The Hipparcos distances to the Hyades and α Per are within 1 σ of the MS-fitting distance in B-V and V-I, while the Hipparcos distances to Coma Ber and the Pleiades are in disagreement with the MS-fitting distance at more than the 3 σ level. There are two Hipparcos measurements of the distance to Praesepe; one is in good agreement with the MS-fitting distance and the other disagrees at the 2 σ level. The distance estimates from the different colors are in conflict with one another for Coma but in agreement for the Pleiades. Changes in the relative cluster metal abundances, age related effects, helium, and reddening are shown to be unlikely to explain the puzzling behavior of the Pleiades. We present evidence for spatially dependent systematic errors at the 1 mas level in the parallaxes of Pleiades stars. The implications of this result are discussed.

FAUST observations of ultraviolet sources in the direction of Coma

We analyse an ultraviolet observation toward the Coma cluster by means of the FAUST shuttle-borne telescope. We detect 56 candidate sources to a signal-to-noise ratio of 6.5. Most sources have optical counterparts in existing catalogues and are stars. 10 sources with no listed counterparts were observed at the Wise Observatory. We present identifications based on low-resolution spectrophotometry, and discuss the foreground stars and the galaxies, all in the foreground of the Coma cluster. The FAUST image yields a higher fraction of hot evolved stars than either of the North Galactic Pole or the Virgo regions, analysed previously. We identify these tentatively as cooling white dwarfs in the Coma Berenices (Mel 111) open cluster.

Helium, [Fe/H] Abundances and the HR (Log TEFF, MBol) Diagram With Hipparcos Data of The Four Nearest Open Clusters: Hyades, Coma Berenices, The Pleiades and Praesepe

After having studied in great detail the observational HR diagram (log Teff, Mbol) composed by 40 main sequence stars of the Hyades (Perryman et al.,1997, A&A., in press), we have tried to apply the same method to the observational main sequences of the three next nearest open clusters: Coma Berenices, the Pleiades, and Praesepe. This method consists in comparing the observational main sequence of the clusters with a grid of theoretical ZAMSs. The stars composing the observational main sequences had to have reliable absolute bolometric magnitudes, coming all from individual Hipparcos parallaxes, precise bolometric corrections, effective temperatures and metal abundances from high resolution detailed spectroscopic analyses. If we assume, following the work by Fernandez et al. (1996, A&A,311,127), that the mixing-lenth parameter is solar, the position of a theoretical ZAMS, in the (log Teff, Mbol) plane, computed with given input physics, only depends on two free parameters: the He content Y by mass, and the metallicity Z by mass. If effective temperature and metallicity of the constituting stars of the 4 clusters are previously known by means of detailed analyses, one can deduce their helium abundances by means of an appropriate grid of theoretical ZAMS’s. The comparison between the empirical (log Teff, Mbol) main sequence of the Hyades and the computed ZAMS corresponding to the observed metallicity Z of the Hyades (Z= 0.0240 ± 0.0085) gives a He abundance for the Hyades, Y= 0.26 ± 0.02. Our interpretation, concerning the observational position of the main sequence of the three nearest clusters after the Hyades, is still under way and appears to be greatly more difficult than for the Hyades. For the moment we can say that:‒ The 15 dwarfs analysed in detailed in Coma have a solar metallicity: [Fe/H] = -0.05 ± 0.06. However, their observational main sequence fit better with the Hyades ZAMS.‒ The mean metallicity of 13 Pleiades dwarfs analysed in detail is solar. A metal deficient and He normal ZAMS would fit better. But, a warning for absorption in the Pleiades has to be recalled.‒ The upper main sequence of Praesepe, (the more distant cluster: 180 pc) composed by 11 stars, analysed in detail, is the one which has the best fit with the Hyades ZAMS. The deduced ‘turnoff age’ of the cluster is slightly higher than that of the Hyades: 0.8 Gyr instead of 0.63 Gyr.

Spectroscopic Radial Velocities: Photospheric Lineshifts Calibrated By Hipparcos

Wavelengths of stellar spectral lines depend not only on the star’s motion. Until recently, accurate studies of shifts not caused by radial motion were feasible only for the Sun. Solar lineshifts are interpreted as gravitational redshift (636 m/s) and convective blueshifts (~ 400 m/s; caused by velocity-brightness correlations). In other stars, such effects may be greater (Dravins & Nordlund 1990). Accurate astrometric radial velocities are now available from Hipparcos (Dravins et al. 1997a; 1997b), permitting studies of such shifts also in some other stars.For such stars in the open clusters of Hyades, Ursa Major and Coma Berenices, a spectroscopic program is in progress, analyzing wavelength shifts in groups of lines with different strengths, excitation potentials, etc., using the ELODIE high-precision radial-velocity instrument (Baranne et al. 1996) at Haute-Provence Observatory.

Astrometric Radial Velocities From Hipparcos

AbstractSpace astrometry now permits accurate determinations of stellar radial motion, without using spectroscopy. Although the feasibility of deducing astrometric radial velocities from geometric projection effects was realized already by Schlesinger (1917), only with Hipparcos has it become practical. Such a program has now been carried out for the moving clusters of Ursa Major, Hyades, and Coma Berenices. Realized inaccuracies reach about 300 m/s (Dravins et al. 1997).Discrepancies between astrometric and spectroscopic radial velocities reveal effects (other than stellar motion) that affect wavelength positions of spectral lines. Such are caused by stellar surface convection, and by gravitational redshifts. A parallel program (Gullberg & Dravins 1997) is analyzing high-precision spectroscopic radial velocities for different spectral lines in these stars, using the ELODIE radial-velocity instrument atHaute-Provence.

Divided Allusion: Virgil and the Coma Berenices

HE study of allusion or reference usually entails the process of evaluating and analysing the consequences of a reference, that is to say, how we interpret the dialogue established between two texts. There is, however, a prior question about a prior process: How do we as readers even recognize something called allusion?' In general, there seem to be two approaches to these questions: formal and thematic. The formal approach tries to establish the multitude of overlapping features in the two texts and the infrequent combination of these features outside of the two texts. On the linguistic level the search is for shared diction, word order, line position, etc.; on the narrative level the search is for similar characters and contexts. Like objects in a matching game, texts which distinctively share an intricate pattern can be paired correctly once the pieces are isolated. A successful join thus makes an allusion. For less distinctive passages which share just a word or two, this problem of allusion is expressed in terms of chance: whether a parallel text is a reference to another text or simply the inevitable reuse of common language. The second or thematic approach asks how our interpretation benefits from pairing two texts. What new view of a character is offered by an echo of another character? In the end, these two approaches must go together, for a full poetic or philological reading requires the integrity and value of both form and function.

Nearby Open Clusters and HR Diagram Calibration

13 clusters have been analysed (Coma Ber, the Pleiades, IC 2602, IC 2391, Praesepe, Alpha Per, NGC 6475, Blanco 1, Stock 2, NGC 6633, IC 4756, NGC 2516 and NGC 3532). Cluster members have been selected using Hipparcos proper motions and parallaxes. The mean cluster parallaxes have been determined using Hipparcos intermediate data (abscissae on the Reference Great Circles) taking into account star to star correlations. Both selection of members and computation of cluster mean parallaxes are described in Mermilliod et al., 1997 and Robichon et al., 1997.For each cluster, a selection of fainter stars in the ‘Base des Amas’ (Mermilliod, 1988), based on photometric data as well as radialvelocities and proper motions when available, has been done. From this selection and the computed mean parallaxes, the location of the 13 cluster sequences in the observational HR diagram is derived very accurately, at least for the closest clusters for which good photometry and small errors on the mean parallaxes are available. Relative positions of cluster sequences cannot only be explained by differences between cluster metallicities. For example, the Pleiades sequence is 0.5 magnitude bellow the Praesepe sequence whereas the adopted metallicities (obtained spectroscopically i.e. whithout any assumption on the helium content) are respectively -0.034 and +0.10.

Spectrophotometry of 237 Stars in 7 Open Clusters

Photoelectric spectrophotometry is presented for 237 stars in the Hyades, Pleiades, Alpha Persei, Praesepe, Coma Berenices, IC~4665, and M39 open clusters. 16 bandpasses were observed from 350 nm to 778 nm, with 3.2 to 6.4 nm bandwidth. Data are standardized to the Hayes-Latham system to mutual accuracy of 0.016 mag per passband. By comparison to SIMBAD-available BV and ubvy colors on the one hand, and to 1993 Kurucz synthetic spectra on the other, we show our data to be accurate to 0.01 mag for the 13 passbands at or above 400 nm, and 0.02 mag for the 3 passbands below 400 nm. We also show that the scatter in the fits of the spectrophotometric colors and the uvby filter colors is a reasonable way to identify the observations of which specific stars are accurate to 1-sigma, 2-sigma, ... The very good agreement between the models and these data verifies the accuracy of these data, and also verifies the usefulness of the Kurucz models to define spectrophotometry for stars in this temperature range (>5000 K). These data define accurate spectrophotometry of bright, open cluster stars that can be used as a secondary flux calibration for CCD-based spectrophotometric surveys.

Lithium Abundances in delta Scuti Stars and Their Relationship with the Lithium Dip

view Abstract Citations (24) References (41) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Lithium Abundances in delta Scuti Stars and Their Relationship with the Lithium Dip Russell, Stephen C. Abstract Several years ago it was suggested that mass loss from δ Scuti stars may transform them into the lithium "dip,, stars seen in open clusters like Coma Berenices and the Hyades. Although there is evidence to indicate that this is unlikely, there has never been a study made of the lithium abundances in δ Scuti stars themselves. This paper reports the results of a survey of lithium in these stars. Lithium was detected in about half of the stars studied, with only upper limits being determined for the others. For those stars with measurable lithium there is evidence for a moderate depletion at the cooler temperatures. For those stars with no measurable lithium, the upper limits are consistent with only moderate depletion in all except one or two cases. There is no correlation between lithium depletion and a star's rotational velocity, mass, gravity, period of pulsation, or metallicity. There is, therefore, no support for the suggestion that mass loss on the main sequence due to δ Scuti pulsation may be responsible for the lithium dip stars. However, the data cannot exclude the possibility that mass loss may be responsible for a degree of lithium depletion in δ Scuti stars. Interestingly, though most elements are in solar ratio to iron, there is evidence for a pronounced carbon abundance deficiency in all of the stars with measurable carbon. Publication: The Astrophysical Journal Pub Date: October 1995 DOI: 10.1086/176261 Bibcode: 1995ApJ...451..747R Keywords: STARS: DELTA SCUTI; STARS: ABUNDANCES; STARS: EVOLUTION; STARS: MASS LOSS full text sources ADS | data products SIMBAD (24)

Catullus' Coma Berenices and Aeneas' Farewell to Dido

Recent studies of the Aeneid have focused on that poem's relation to other, prior texts via Vergil's arte allusiva, whether conceived under the psychological guise of a Bloomian anxiety of influence, or aemulatio, or under the more austere rubric of Riffaterrian intertextuality, or imitatio. A test case in this debate by virtue of its subtlety and complexity is the riddling line 6.460, which, in a context of great emotional pathos, quotes a lighthearted Greek poem by Callimachus as rendered into Latin by Catullus, who-a major poet in his own right-is a singularly untrustworthy translator. I suggest in the remarks that follow both that Catullus has used Callimachus' poem ironically as a cover for his underlying model, the funeral of Patroclus episode of the Iliad, and that the Aeneid, across the space of the Callimachean and Catullan texts, reappropriates that Iliadic model to itself. My remarks fall into three parts: a review of the scholarly debate so far, a reevaluation of Catullus' poem, and an assessment of the relevance of Catullus' poem as so reevaluated to Aeneid 6.460.

Star-hopping: your visa to viewing the universe

Introduction Preface Acknowledgements 1. How to use this book and what you are going to see 2. How the sky works, determining your field of view, observing tips and how to navigate in the night sky 3. January - Taurus and Orion: the bull and hunter 4. February - Canis Minor, Canis Major, and Puppis: dog days in February and Jason's Argo 5. March - Cancer, Leo, and Corvus: a crab, the king of the beasts, and a crow 6. April - Ursa Major: a dipper round tripper 7. May - Coma Berenices and Virgo: the sparkling hair of Berenice and the wheat maiden and her bushel of galaxies 8. June - Libra and Lupus: the balance scales and the wolf 9. July - Scorpius, Sagittarius, and Scutum: the scorpion, archer, and shield of John Sobieski 10. August - Draco: following the trail of the dragon 11. September - Cygnus, Lyra, Vulpecula, and Sagitta: the swan, lyre, fox, and arrow 12. October - Andromeda and Perseus: the chained lady and her rescuer 13. November - Cepheus and Cassiopeia: the king and queen of Joppa 14. December - Pisces, Triangulum, and Aries: of fishes, a triangle, and a ram 15. Messier Marathon, a sundown to sunup hop across the skies Appendix A: Classification tables Appendix B: The constellations Appendix C: The Greek alphabet Appendix D: Decimalization of the day Glossary Bibliography Index.

Myrrh and Unguents in the Coma Berenices

Myrrh and Unguents in the Coma Berenices

The evolution of the lithium abundances of solar-type stars. I - The Hyades and Coma Berenices clusters

High-resolution, high signal-to-noise spectra of the lithium region at 6708 A in 28 solar-type stars of the Hyades and Coma Berenices clusters are reported. Given an observational uncertainty of less than about 5 mA in W-lambda (Li), no significant scatter about the mean relation was seen for most stars. However, there are several stars that have anomalous abundances. Two of them fall well below the mean relation, and appear to have no distinctive qualities that might account for their low Li. Two others are close binaries and have significantly greater than average Li. A means by which close binaries might preserve Li is suggested, and Li depletion timescales for stars near the zero-age main sequence (ZAMS) are estimated by comparing the Hyades to the Pleiades. This comparison indicates that Li depletion for stars near 1 solar mass starts on the ZAMS, not before, and that depletion occurs at a much slower rate after the age of the Hyades than before. 87 refs.

The Iron Abundances, [Fe/H] in the Four Nearest Open Clusters: Pleiades, Ursa Major Stream, Coma Berenices and Hyades

Iron abundances, [Fe/H] have been studied in G and K dwarfs of the four nearest clusters. With the exception of the Pleiades stars which are all fainter than the 10th magnitude, the observational material consists of high resolution, high S/N spectra taken at the coudé Reticon spectrograph of the Canada, France Hawaii Telescope. The Hyades is the only cluster with a significative overmetallicity with respect to the Sun.

The composition of Callimachus' Aetia in the Light of P. Oxy. 2258

Rudolf Pfeiffer (Callimachus, ii.xxxvi–xxxvii) believed that, as a young man, Callimachus wrote four books of Aetia. To these the poet added in his old age a Reply to his Critics (fr. 1), and a slightly revised version of his recent occasional elegy, the Lock of Berenice (fr. 110, now including a nuptial rite which has survived only in the translation by Catullus, 66.79–88); this revised Coma became the last poem in Aetia book 4, to be followed by an Epilogue (fr. 112) which may mark a transition to the Iambi. Pfeiffer's theory generally held the field until the brilliant article of P. J. Parsons, in ZPE 25 (1977), 1–50. With the help of newly recovered papyrus fragments Parsons showed that a previously unplaced elegy celebrating a Nemean victory (fr. 383 Pf.) was connected to the story of Molorchus (frs. 54–9), who entertained Heracles before that hero killed the Nemean lion and instituted the Nemean Games; thus the poem belonged to Aetia book 3. Furthermore, various pieces of evidence converge (Parsons, pp. 46–8) to make it probable, if not wholly certain, that this substantial poem (some 200 lines long) stood first in its book. So it appears that, at least in the final form of the Aetia, books 3–4 were framed by two poems honouring the wife of Ptolemy III Euergetes, namely Victoria Berenices (Parsons' title) and Coma Berenices.Soon afterwards a further important advance was made by E. Livrea (ZPE 34 [1979], 37ff.), who perceived, on grounds of subject-matter as well as papyrology, that the poor man who sets a mousetrap in fr. 177 Pf. must be none other than Molorchus; note particularly the probable mention of Cleonae in fr. 177.37 Pf. = Supplementum Hellenisticum 259.37. Thus a new fragment of 38 lines accrued to the poem.These discoveries have some implications for the composition of the Aetia. Addition of a Coma Berenices (94 lines in Catullus' version) to a pre-existent Aetia book 4 could be countenanced easily enough, but, as Parsons says (p. 50), it would have required a much more radical, and therefore less plausible, revision for Callimachus to have added Victoria Berenices to a pre-existent Aetia book 3. Accordingly Parsons suggested that the original Aetia contained only books 1–2, united by the conversation with the Muses; then in his old age Callimachus compiled two more books, partly at least from poems already composed, and gave them a frame of two poems honouring Queen Berenice. Parsons' view has, I think, been widely accepted; Professor Lloyd-Jones wrote in SIFC 77 (1984), 56 ‘No-one has yet argued against the simple modification of Pfeiffer's theory of the two editions of the Aetia which Mr. Parsons based on this discovery. The first edition comprised two books only.’

Radial velocities with CORAVEL: results on stellar variability and duplicity

The complete radial velocity curve has been determined with CORAVEL for many pulsating stars of various classes: cepheid stars in the Galaxy and in the Magellanic Clouds, RR Lyrae, δ Scuti and SX Phoenicis stars. These measurements allow the determination of the radius variation and of the surface acceleration of these stars. In addition, the mean stellar radius of many of these stars has been determined by applying the Baade-Wesselink method.Systematic surveys of definite groups of binary or multiple stars are in progress with CORAVEL in order to determine the distribution functions of the orbital parameters. The eccentricity distributions for the binaries in the open clusters Pleiades, Praesepe, Coma Ber and Hyades are presented and their dependence on the physical processes (star formation mechanisms, mass exchange, tidal circularization, dynamical evolution) is briefly discussed.

Venus observed? A note on Callimachus, Fr. 110

Since we cannot hope to witness a catasterism for ourselves, we are fortunate to have a detailed first-hand account of the inauguration of Coma Berenices, the last constellation to be added to the ancient list until the seventeenth century. However, the description of the critical stages in the process presents various difficulties resulting not so much from obfuscation on Callimachus' part (natural though this might be in an account of a miracle) as from the circumstances of the poem's transmission and the problems to be expected in interpreting occasional verses more than two millennia after the event to which they refer. In this note I shall attempt to clarify some of the obscurities surrounding the Lock's translation.

ΒΟΥΠΟΡΟΣ ΑΡΣΙΝΟΗΣ

In the Coma Berenices (fr. 110.44-6 Pfeiffer) Callimachus mentioned Mount Athos and the canal dug for Xerxes at the northern end of the Akte peninsula:ἀμνά]μῳ[ν Θείης ἀργὸς ὑ]περφέ[ρ]ετ[αι,βουπόρος ᾿Αρσινόης μητρὸς σέο, καὶ διὰ μέ[σσουΜηδείων ὀλοαὶ νῆες ἔβησαν ᾿´ ΑθωTwo problems require solutions in these lines: (1) Why is Athos called the ‘ox-piercer of Arsinoe’? (2) Who is the descendant of Theia? The second of these problems, I shall argue, is solved by the solution to the first.Arsinoe, wife of Ptolemy II Philadelphus, is here given the courtesy-title ‘mother’ of Berenike. There is no difficulty in the poet’s association of her with Mount Athos: she had formerly been married to King Lysimachos of Thrace, who won Macedonia and Thessaly from Demetrius, and her ties with the northern Aegean world were close. As queen in Thrace she had made a dedication to the Great Gods of Samothrace;’ it was to Samothrace also that she came after Ptolemy Keraunos had murdered her sons by Lysimachos. Callimachus has these northern Aegean connexions of Arsinoe in mind in another poem, the Ektheosis Arsinoes, in which Chans sees from Athos the funeral smoke of the queen’s pyre at Alexandria (fr. 228.57), having been sent from Lemnos to the mountain by the spirit of Arsinoe’s dead sister Philotera (fr. 228.44-7).