Fixed Stars

Fifteen stars considered especially useful for astrological applications (in the mediæval astrology of Europe and the Arab world) are known as the Behenian Fixed Stars (each marked with † Behenian Star).

The name derives from Arabic bahman, "root," as each was considered a source of astrological power for one or more planets. Each is also connected with a gemstone and plant used in rituals intended to draw the star's influence (e.g., into a talisman).

When a planet was within six degrees of an associated star, this influence was thought to be particularly strong. For Agrippa's table, see the Behenian Fixed Stars; for a different viewpoint, see the Table of Hermes.

This article examines the influence of the Fixed Stars, with a comprehensive table of their year 2000 (& 2010) position and the character of their effects.

"The strength and efficacy of the Fixed Stars is to be considered from their magnitude, their splendours, their natures or properties, their nearness to the Ecliptic, their place in the World, their multitude, their first oriental appearance, the purity of their place, the similitude or agreement of the body or rays of a Planet with them and their circle of position."
— The Seven Segments of Cardan [ed. William Lilly, 1675]

Joseph A Seiss, compiled his own version of the Constellation based on Biblical data and the results are amazing.  Seeing the meaning behind the stars in terms of the Messiah and our Redemption adds new understanding to how everything really is connected.

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A dévák és aszurák harcának egyik fő fejezetét alkotja az a rész, amikor a dévák megkérik Visnut, hogy mivel elfogyott az erejük, a kozmikus óceán kiköpüléséhez az ellenségtől kérjen segítséget. Az istenség eléri, hogy átmeneti fegyverszünet legyen a két fél között és megkéri Vaszukit, az alvilág kígyódémonát, hogy segítsen ezen művelet végrehajtásában. Köpülőkötélként a világhegyet botként használva tizennégy mágikus entitást nyernek ki az óceánból, utolsóként az ambróziát/nektárt/szómát. Bár az aszurák átmenetileg megszerzik az isteni nedüt, Visnu elcsalja tőlük a nemes italt, és a dévák isszák meg az egészet, miáltal visszatér erejük. Ekkor a kígyó ittas dévának álcázva magát a maradék nektárhoz férkőzik és iszik belőle. A Nap és a Hold átlát a szitán, de mivel már ivott az ambróziából, halhatatlanná vált, így Visnu hiába vágja le a fejét, kettévált teste Brahma parancsára Rahuként /fej/ és Ketuként /farok/, árulójukat, a Napot és Holdat örökkön-örökké üldözve az ekliptikán veszélyezteti a fővilágosítókat.

Most of us know that the stars serve as a reliable compass, but it is less known that they can also be an accurate clock. The fact that during the middle of the month of March in Romania the hour hand of the sky clock - formed by the last two stars in the Big Dipper (Dubhe and Merak) - reads exactly zero hours at midnight is the key to the calculations we must make anytime we want to determine the correct hour by the stars. First, read the time by the hour hand of the sky clock to the nearest quarter hour. Second, determine the number of months that have passed since the middle of March and add this to the number indicated by the hour hand of the sky clock. Third step is to multiply by two the figure you have just arrived at in the preceding step. Finally, subtract this number from 24 or 48 and add one hour for Daylight Saving Time (if applicable). This will give you the correct time in hours, from 1 to 24.

Astronomy was very important science in the medieval Islamic world, and we can witness its achievements in modern day science. The copies of the 10th century astronomical illustrated manuscript, “The Book  of Fixed Stars”, by  'Abd ar Raḥman aṣ-Ṣufi, survived to these days and they represent the basis of this paper. Aṣ-Ṣufi left us the list of 48 constellations from Ptolemy’s Almagest, as well as the information about traditional constellations and star names of pre-Islamic Arabia.
By studying the cultural translation and transliteration through the nomenclature and the iconography of the constellations, we can easily understand what were concerns and interests of star-gazing Bedouin Arabs, spot the cultural differences between ancient Greek and the growing Islamic civilization in its golden period, and by observing the transformation of  the  illustrations,  especially  when  representing  human  figures,  we  can  easily  follow  the  history  of  Islamic civilization and the mixture of cultural influences which followed the territorial expansion and the conquests.

We present the results of 22 GHz H 2 O maser observations of a sample of 85 post-Asymptotic Giant Branch (post-AGB) candidate stars, selected on the basis of their OH 1612 MHz maser and far-infrared properties. All sources were observed with the Tidbinbilla 70-m radio telescope and 21 detections were made. 86 GHz SiO Mopra observations of a subset of the sample are also presented. Of the 21 H 2 O detections, 15 are from sources that are likely to be massive AGB stars and most of these show typical, regular H 2 O maser profiles. In contrast, nearly all the detections of more evolved stars exhibited high-velocity H 2 O maser emission. Of the five sources seen, v223 (W43A, IRAS 18450−0148) is a well known 'water-fountain' source which belongs to a small group of post-AGB stars with highly collimated, high-velocity H 2 O maser emission. A second source in our This preprint was prepared with the AAS L A T E X macros v5.2.

Bibliotheca Sacra and Biblical Repository, Vol XX. Edward A. Park and Samuel H. Taylor Editors.  Warren, W.F.  - Biblical Cosmology and the Doctrine of the Fall of the World. London:1863

An excellent analysis of the changes made to ancient cosmological concepts and the damaging results to a clear understanding of the Universe based on modern scientific theories.  Very obscure historical accounts of the Fall and how science has disconnected us from a clear understanding of things that were written by Moses, the Prophets and Paul.  This will open your eyes to many missing details.....

Physical conditions in the atmospheres of tidally locked, slowly rotating hot Jupiters correspond to dynamical circulation regimes with Rhines scales and Rossby deformation radii comparable to the planetary radii. Consequently, the large spatial scales of moving atmospheric structures could generate significant photospheric variability. Here, we estimate the level of thermal infrared variability expected in successive secondary eclipse depths, according to hot Jupiter turbulent "shallow-layer" models. The variability, at the few percent level or more in models with strong enough winds, is within the reach of Spitzer measurements. Eclipse depth variability is thus a valuable tool to constrain the circulation regime and global wind speeds in hot Jupiter atmospheres.

We have carried out a sensitive search for gas emission lines at infrared and millimeter wavelengths for a sample of 15 young sun-like stars selected from our dust disk survey with the Spitzer Space Telescope. We have used mid-infrared lines to trace the warm (300-100 K) gas in the inner disk and millimeter transitions of 12 CO to probe the cold (∼20 K) outer disk. We report no gas line detections from our sample. Line flux upper limits are first converted to warm and cold gas mass limits using simple approximations allowing a direct comparison with values from the literature. We also present results from more sophisticated models following Gorti and Hollenbach (2004) which confirm and extend our simple analysis. These models show that the [S i] line at 25.23 µm can set constraining limits on the gas surface density at the disk inner radius and traces disk regions up to a few AU. We find that none of the 15 systems have more than 0.04 M J of gas within a few AU from the disk inner radius for disk radii from 1 AU up to ∼40 AU. These gas mass upper limits even in the 8 systems younger than ∼30 Myr suggest that most of the gas is dispersed early. The gas mass upper limits in the 10-40 AU region, that is mainly traced by our CO data, are < 2 M ⊕. If these systems are analogs of the Solar System, either they have already formed Uranus-and Neptune-like planets or they will not form them beyond 100 Myr. Finally, the gas surface density upper limits at 1 AU are smaller than 0.01% of the minimum mass solar nebula for most of the sources. If terrestrial planets form frequently and their orbits are circularized by gas, then circularization occurs early.

We report the discovery made using the Australia Telescope Compact Array of a remarkable string of radio emission towards IRAS 16562-3959, a luminous infrared source with a bolometric luminosity of 7.0 × 10 4 L ⊙. The radio emission arises from a compact, bright central component, two inner lobes, which are separated by about 7 ′′ and symmetrically offset from the central source, and two outer lobes which are separated by about 45 ′′. The emission from the central object has a spectral index between 1.4 and 8.6 GHz of 0.85 ± 0.15, consistent with free-free emission from a thermal jet. The radio emission from the lobes have spectral indices in the range characteristic of thermal emission. We suggest

From Sloane 3847, tr. Sergei Belokon, https://new-ot.com (rus), Russia, Samara What stones and hearbes are appropiated unto the 15 starres accordinge to John Gower in his booke intituled de Confessione Amantis, the wich he dedicated unto king Henry the eight. Prima stella. Vocatur, Aldeboran, cuius lapis carbunculus et herba anabulla est. Secunda stella, vocatur, Clota, seu Pliades cuius lapis christallum, et herba feniculus est. Algol. cuius lapis Diamans. Herba heleborum nigrum Alhaiot. Lapis saphirus herba marubium Canis Maior. Lapis berillus, herba sauma est Cаnis minor. Lapis Achatas, herba primula Arial, quid lapis Gonza, herba celidonia est Alacorvi, lapis honochinus, herba lappacia Alaezel. Cuius lapis smaragdus, herba salgea Almareth, lapis jaspis, herba plantago Venenas, cuius lapis adamas et herba cicorea est Alpheta, lapis topasion, herba rasmarineus Cor Scorpionis, lapis sardis, herba astrologia (aristolochia) Boter cadent. Lapis Chrisolitus, herba saturea Quinta decima stella vocatur, Cauda Scorpionis, cuius lapis calcidonis et herba maiorana est

We present millimeter interferometric observations of the molecular envelope around the red supergiant VY CMa with the SubMillimeter Array (SMA) 1. The high angular resolution (< 2 ′′) allows us to derive the structure of the envelope as observed in the 1.3 mm continuum, 12 CO(2-1), 13 CO(2-1) and SO(6 5-5 4) lines emission. The circumstellar envelope is resolved into three components: a dense, compact and dusty central component, embedded in a more diffuse and extended envelope plus a high velocity component. We construct a simple model, consisting of a spherically symmetric slowly expanding envelope and bipolar outflows with a wide opening angle (∼ 120 •) viewed close to the line of sight (i = 15 •). Our model can explain the main features of the SMA data and previous single-dish CO multi-line observations. An episode of enhanced mass loss along the bipolar direction is inferred from our modelling. The SMA data provide a better understanding of the complicated morphology seen in the optical/IR high resolution observations.

We present infrared spectroscopy and imaging of AFGL 4106. The 2.4-5 µm ISO-SWS spectrum reveals the presence of a cool, luminous star (T eff ≈ 3750 K) in addition to an almost equally luminous F star (T eff ≈ 7250 K). The 5-195 µm SWS and LWS spectra are dominated by strong emission from circumstellar dust. We find that the dust consists of amorphous silicates, with a minor but significant contribution from crystalline silicates. The amorphous silicates consist of Fe-rich olivines. The presence of amorphous pyroxenes cannot be excluded but if present they contain much less Fe than the amorphous olivines. Comparison with laboratory data shows that the pure Mg-end members of the crystalline olivine and pyroxene solid solution series are present. In addition, we find strong evidence for simple oxides (FeO and Al 2 O 3) as well as crystalline H 2 O ice. Several narrow emission features remain unidentified. Modelling of the dust emission using a dust radiation transfer code shows that large grains (≈ 1 µm) must be present and that the abundance of the crystalline silicates is between 7 and 15% of the total dust mass, depending on the assumed enstatite to forsterite ratio, which is estimated to be between 1 and 3. The amorphous and crystalline dust components in the shell do not have the same temperature, implying that the different dust species are not thermally coupled. We find a dust mass of ≈ 3.9 • 10 −2 M expelled over a period of ≈ 4 • 10 3 years for a distance of 3.3 kpc. The F-star in the AFGL 4106 binary is likely a post-red-supergiant in transition to a blue supergiant or WR phase.

Context. This is the first paper of a series devoted to the Lambda Orionis star-forming region, Orion's Head, from the X-ray perspective. Our final aim is to provide a comprehensive view of this complex region, which includes several distinct associations and dark clouds. Aims. We aim to uncover the population of the central, young star cluster Collinder 69, and in particular those diskless Class III objects not identified by previous surveys based on near-and mid-infrared searches, and to establish the X-ray luminosity function for the association. Methods. We have combined two exposures taken with the XMM-Newton satellite with an exhaustive data set of optical, near-and mid-infrared photometry to assess the membership of the X-ray sources based on different color-color and color-magnitude diagrams, as well as other properties, such as effective temperatures, masses and bolometric luminosities derived from spectral energy distribution fitting and comparison with theoretical isochrones. The presence of circumstellar disks is discussed using mid-infrared photometry from the Spitzer Space Telescope. Results. With an X-ray flux limit of ∼5 × 10 −15 erg/cm 2 /s we detected a total of 164 X-ray sources, of which 66 are probable and possible cluster members. A total of 16 are newly identified probable members plus another three possible new members. The two XMM-Newton pointings east and west of the cluster center have allowed us to verify the heterogeneous spatial distribution of young stars, which is probably related to the large scale structure of the region. The disk fraction of the X-ray detected cluster sample (complete down to ∼0.3 M) is very low, close to 10%, in remarkable contrast to the low-mass stellar and substellar population (mostly undetected in X-rays) where the disk fraction reaches about 50%. The X-ray luminosity function of Collinder 69 in different mass bins provides support for an age of several Myr when compared with other well known young associations. Conclusions. The X-ray properties of the young stars in Collinder 69 resemble those found in other young stellar associations, with saturation at log (L x /L bol) ∼ −3 and low fractional X-ray luminosities for stars with M ≥ 2 M. With our improved cluster census we confirm previous reports on the untypically low disk fraction compared to other clusters of several Myr age. The different disk fractions of X-ray detected (essentially solar-like) and undetected (mostly low-mass stars and brown dwarfs) members can be understood as a consequence of a mass-dependence of the timescale for disk evolution.

The star ζ Ophiuchi is one of the brightest massive stars in the northern hemisphere and was intensively studied in various wavelength domains. The currently available observational material suggests that certain observed phenomena are related to the presence of a magnetic field. We acquired spectropolarimetric observations of ζ Oph with FORS 1 mounted on the 8-m Kueyen telescope of the VLT to investigate if a magnetic field is indeed present in this star. Using all available absorption lines, we detect a mean longitudinal magnetic field Bz all = 141 ± 45 G, confirming the magnetic nature of this star. We review the X-ray properties of ζ Oph with the aim to understand whether the X-ray emission of ζ Oph is dominated by magnetic or by wind instability processes.

We report the discovery of the likely IR counterpart to the Anomalous X-ray Pulsar (AXP) 1RXS J170849−400910, based on the combination of Chandra HRC-I X-ray position, and deep optical/IR observations carried out from ESO telescopes and the Canada France Hawaii Telescope (CFHT) during 1999-2002. Within the narrow uncertainty region we found two relatively faint (K ′ =20.0 and K ′ =17.53) IR objects. Based on their color and position in the J-K ′ versus J-H diagram only the brighter object is consistent with the known IR properties of the counterparts to other AXPs. No variability was detected for this source, similarly to what is observed in the case of 4U 0142+614. Like in other AXPs, we found that the IR flux of 1RXS J170849−400910 is higher then expected for a simple blackbody component extrapolated from the X-ray data. If confirmed, this object would be the fourth IR counterpart to a source of the AXP class, and would make the IR excess a likely new characteristic of AXPs.

We have investigated the variation of coronal X-ray emission during early post-main-sequence phases for a sample of 120 late-type stars within 100 pc, and with estimated masses in the range 1-3 M , based on Hipparcos parallaxes and recent evolutionary models. These stars were observed with the ROSAT/PSPC, and the data processed with the Palermo-CfA pipeline, including detection and evaluation of X-ray fluxes (or upper limits) by means of a wavelet transform algorithm. We have studied the evolutionary history of X-ray luminosity and surface flux for stars in selected mass ranges, including stars with inactive A-type progenitors on the main sequence and lower mass solar-type stars. Our stellar sample suggests a trend of increasing X-ray emission level with age for stars with masses M > 1.5M , and a decline for lower-mass stars. A similar behavior holds for the average coronal temperature, which follows a power-law correlation with the X-ray luminosity, independently of their mass and evolutionary state. We have also studied the relationship between X-ray luminosity and surface rotation rate for stars in the same mass ranges, and how this relationships departs from the L x ∝ v 2 rot law followed by main-sequence stars. Our results are interpreted in terms of a magnetic dynamo whose efficiency depends on the stellar evolutionary state through the mass-dependent changes of the stellar internal structure, including the properties of envelope convection and the internal rotation profile.

We report the discovery of the likely IR counterpart to the Anomalous X-ray Pulsar (AXP) 1RXS J170849−400910, based on the combination of Chandra HRC-I X-ray position, and deep optical/IR observations carried out from ESO telescopes and the Canada France Hawaii Telescope (CFHT) during 1999-2002. Within the narrow uncertainty region we found two relatively faint (K ′ =20.0 and K ′ =17.53) IR objects. Based on their color and position in the J-K ′ versus J-H diagram only the brighter object is consistent with the known IR properties of the counterparts to other AXPs. No variability was detected for this source, similarly to what is observed in the case of 4U 0142+614. Like in other AXPs, we found that the IR flux of 1RXS J170849−400910 is higher then expected for a simple blackbody component extrapolated from the X-ray data. If confirmed, this object would be the fourth IR counterpart to a source of the AXP class, and would make the IR excess a likely new characteristic of AXPs.

High-resolution K band imaging polarimetry of the β Pic dust disk has been conducted with adaptive optics and a coronagraph using the Subaru 8.2-m telescope. Polarization of ∼10 % is detected out to r ∼ 120 AU with a centrosymmetric vector pattern around the central star, confirming that the disk is seen as an infrared reflection nebula. We have modeled our near-infrared and previous optical polarization results in terms of dust scattering in the disk and have found that both the degrees of polarization and the radial intensity profiles are well reproduced. We argue that the observed characteristics of the disk dust are consistent with the presence of ice-filled fluffy aggregates consisting of submicron grains in the β Pic system. There is a gap around 100 AU in both the intensity and polarization profiles, which suggests a paucity of planetesimals in this region. The radial intensity profile also shows ripple-like structures, which are indicative of the presence of multiple planetesimal belts, as in the case of the M-type Vega-like star AU Mic.

Context. The yellow hypergiant stars (YHGs) are extremely luminous and massive objects whose general properties are poorly known. Only two of this kind of star show massive circumstellar envelopes, IRC +10420 and AFGL 2343. Aims. We aim to study the chemistry of the circumstellar envelopes around these two sources, by comparison with well known AGB stars and protoplanetary nebulae. We also estimate the abundances of the observed molecular species. Methods. We have performed single-dish observations of different transitions for twelve molecular species. We have compared the ratio of the intensities of the molecular transitions and of the estimated abundances in AFGL 2343 and IRC +10420 with those in O-rich and C-rich AGB stars and protoplanetary nebulae. Results. Both YHGs, AFGL 2343, and IRC +10420, have been found to have an O-rich chemistry similar to that in O-rich AGB stars, though for AFGL 2343 the emission of most molecules compared with 13 CO lines is relatively weak. Clear differences with the other evolved sources appear when we compare the line intensity corrected for distance and the profile widths which are, respectively, very intense and very wide in YHGs. The abundances obtained for IRC +10420 agree with those found in AGB stars, but in general those found in AFGL 2343, except for 13 CO, are too low. This apparently low molecular abundance in AFGL 2343 could be due to the fact that these molecules are present only in an inner region of the shell where the mass is relatively low.

We present millimeter interferometric observations of the molecular envelope around the red supergiant VY CMa with the SubMillimeter Array (SMA) 1. The high angular resolution (< 2 ′′) allows us to derive the structure of the envelope as observed in the 1.3 mm continuum, 12 CO(2-1), 13 CO(2-1) and SO(6 5-5 4) lines emission. The circumstellar envelope is resolved into three components: a dense, compact and dusty central component, embedded in a more diffuse and extended envelope plus a high velocity component. We construct a simple model, consisting of a spherically symmetric slowly expanding envelope and bipolar outflows with a wide opening angle (∼ 120 •) viewed close to the line of sight (i = 15 •). Our model can explain the main features of the SMA data and previous single-dish CO multi-line observations. An episode of enhanced mass loss along the bipolar direction is inferred from our modelling. The SMA data provide a better understanding of the complicated morphology seen in the optical/IR high resolution observations.

We report the discovery of a young massive stellar cluster embedded in an extended HII region, invisible at optical wavelengths where the extinction is A V ≈ 28 magnitudes, associated with the IRAS source 16177-5018. J, H and nbK imaging photometry combined with the K S 2MASS data show the presence of sources with infrared excess emission at 2.2 µm, concentrated in an area of about one square parsec around a massive young stellar object identified as the IRAS source. This object has a near-mid infrared spectral index betweem 2.2 and 25 µm α(IR) = d log(λF λ)/d logλ =4.78, characteristic of compact H II regions, with bolometric luminosity, inferred from the integrated near to far-infrared flux density of 2.8 × 10 5 L ⊙ , which corresponds to a ZAMS star of about 42M ⊙. From the color-magnitude diagram we were able to classify the majority of the cluster members as reddened massive stars earlier than spectral type B5.

We report in this paper the direct interferometric measurement of the angular diameter of five nearby Vega-like stars: α PsA, β Leo, β Pic, Eri and τ Cet. The near-infrared (K and H bands) observations were conducted at the VLTI during the commissioning period with the VINCI instrument and three different baselines ranging from 66 m to 140 m. The five stellar photospheres are resolved and we derive their angular diameters with a 1 to 2% accuracy, except for β Pic (14%). We discuss the detectability and the influence of a possible small amount of warm circumstellar dust on our measurements. In addition, we have used the stellar evolution code CESAM (Morel 1997) to compare the computed fundamental parameters to the observed values (linear diameter, luminosity, temperature and chemical abundance). As a result of the simulation, the age of the stars is inferred and found to be in good agreement with previous estimates from various other methods.

We report the discovery of 870 Hz quasi-periodic intensity oscillations with the Rossi X-Ray Timing Explorer from the X-ray burster 4U 1636Ϫ536. This is the fourth Galactic low-mass X-ray binary (LMXB) that has shown this type of oscillations. We present the fractional rms amplitude as a function of energy and compare the characteristics of these oscillations with those discovered in other sources.

We present results of an investigation on a high-galactic latitude sample of late-type field stars selected from the ROSAT All-Sky Survey (RASS). The sample comprises about 200 G, K, and M stars. Lithium abundances were determined for about 180 G-M stars. Radial velocities were measured for most of the circ. 140 G and K type stars. Combined with proper motions these data were used to study the age distribution and the kinematical properties of the sample. Based on the lithium abundances half of the G-K stars were found to be younger than the Hyades (660 Myr). About 30% are comparable in age to the Pleiades (100 Myr). A small subsample of 10 stars is younger than the Pleiades (100 Myr). They are therefore most likely pre-main sequence stars. Kinematically the PMS and Pleiades-type stars appear to form a group with space velocities close to the Castor moving group but clearly distinct from the Local Association.

We report the discovery of a young massive stellar cluster embedded in an extended HII region, invisible at optical wavelengths where the extinction is A V ≈ 28 magnitudes, associated with the IRAS source 16177-5018. J, H and nbK imaging photometry combined with the K S 2MASS data show the presence of sources with infrared excess emission at 2.2 µm, concentrated in an area of about one square parsec around a massive young stellar object identified as the IRAS source. This object has a near-mid infrared spectral index betweem 2.2 and 25 µm α(IR) = d log(λF λ)/d logλ =4.78, characteristic of compact H II regions, with bolometric luminosity, inferred from the integrated near to far-infrared flux density of 2.8 × 10 5 L ⊙ , which corresponds to a ZAMS star of about 42M ⊙. From the color-magnitude diagram we were able to classify the majority of the cluster members as reddened massive stars earlier than spectral type B5.

Owen Bruce Slee is one of the pioneers of Australian radio astronomy. During World War II he independently discovered solar radio emission, and, after joining the CSIRO Division of Radiophysics, used a succession of increasingly more sophisticated radio telescopes to examine an amazing variety of celestial objects and phenomena. These ranged from the solar corona and other targets in our solar system, to different types of stars and the ISM in our Galaxy, and beyond to distant galaxies and clusters of galaxies. Although long retired, Slee continues to carry out research, with emphasis on active stars and clusters of galaxies. A quiet and unassuming man, Slee has spent more than half a century making an important, wide-ranging contribution to astronomy, and his work deserves to be more widely known.

Owen Bruce Slee is one of the pioneers of Australian radio astronomy. During World War II he independently discovered solar radio emission, and, after joining the CSIRO Division of Radiophysics, used a succession of increasingly more sophisticated radio telescopes to examine an amazing variety of celestial objects and phenomena. These ranged from the solar corona and other targets in our solar system, to different types of stars and the ISM in our Galaxy, and beyond to distant galaxies and clusters of galaxies. Although long retired, Slee continues to carry out research, with emphasis on active stars and clusters of galaxies. A quiet and unassuming man, Slee has spent more than half a century making an important, wide-ranging contribution to astronomy, and his work deserves to be more widely known.

We present results of an analysis of new observations of the active M dwarfs AD Leo (GJ 388) and EV Lac (GJ 873), performed with the X-ray satellite SAX, and compare them with both published and new analyses of ROSAT PSPC observations of these stars. The PSPC spectra can be fitted with one-(EV Lac) or two-component (AD Leo) isothermal mekal models, and very low metallicity (∼ 0.1 solar); we have found clear evidence of spectral variations in correspondence of a large flare observed during one of the PSPC observations of EV Lac, requiring the addition of a second component with log T ∼ 7.5 to fit the flare spectrum. The SAX light-curves of AD Leo and EV Lac also show the occurrence of several flares. A two-component model does not provide an adeguate fit of the SAX spectra, regardless of the value of coronal metallicity. These spectra require at least three thermal mekal components and best-fit coronal plasma metallicity below solar for AD Leo and only marginally below solar for EV Lac, with 90% confidence ranges on Z/Z = 0.22-0.35 and 0.36-1.11, respectively. We have also fitted the SAX spectra of AD Leo and EV Lac with model spectra from constant cross-section static coronal loops. One-loop models fail to fit the observed spectra. A second loop component, that accounts for most of the plasma emission at high energy, is required to obtain a fit of statistical quality just slightly worse than the 3-T fits. In the case of EV Lac both the 2-loop and the 3-T fits are unable to reproduce the observed emission below 0.5 keV. The available evidence points toward the existence of various (at least two) main classes of coronal emitting structures: the dominant one is composed of hundreds of compact loops, with relatively low maximum temperature and length smaller than 0.1 the stellar radius, covering no more than 1% of stellar surface; the second class, responsible for the high energy emission, is composed at least of tens of quite elongated loops, covering a very small fraction of stellar surface. We find no-evidence of loops with length comparable to the stellar radius.

We present multifrequency VLA and VLBA observations at 8.4 GHz of the RS CVn system AR Lac, that were performed in autumn 1997 simultaneously with X-ray observations obtained from Rodonò et al. (1999). Our VLBA data indicate a resolved source with dimension close to the system separation, while the study of the flux density curve evidences a small amplitude outside of the eclipse variability. The derived five-frequencies spectra, combined with the size information from VLBA data, are compared with gyrosynchrotron emission from a two component structured source. A comparison with the results of the X-ray observations allow us to exclude the possibility that thermal gyrosynchrotron is responsible for the radio emission, but it is compatible with the hypothesis of co-spatial X-ray and radio emitting sources.

Context. The new VISual and Infrared Telescope for Astronomy (VISTA) has started operations. Over its first five years it will be collecting data for six public surveys, one of which is the near-infrared Y JK s VISTA survey of the Magellanic Clouds system (VMC). This survey comprises the Large Magellanic Cloud (LMC), the Small Magellanic Cloud, the Magellanic Bridge connecting the two galaxies and two fields in the Magellanic Stream. Aims. This paper provides an overview of the VMC survey strategy and presents first science results. The main goals of the VMC survey are the determination of the spatially-resolved star-formation history and the three-dimensional structure of the Magellanic system. The VMC survey is therefore designed to reach stars as faint as the oldest main sequence turn-off point and to constrain the mean magnitude of pulsating variables such as RR Lyrae stars and Cepheids. This paper focuses on observations of VMC fields in the LMC obtained between November 2009 and March 2010. These observations correspond to a completeness of 7% of the planned LMC fields. Methods. The VMC data are comprised of multi-epoch observations which are executed following specific time constraints. The data were reduced using the VISTA Data Flow System pipeline with source catalogues, including astrometric and photometric corrections, produced and made available via the VISTA Science Archive. The VMC data will be released to the astronomical community following the European Southern Observatory's Public Survey policy. The analysis of the data shows that the sensitivity in each wave band agrees with expectations. Uncertainties and completeness of the data are also derived. Results. The first science results, aimed at assessing the scientific quality of the VMC data, include an overview of the distribution of stars in colour-magnitude and colour-colour diagrams, the detection of planetary nebulae and stellar clusters, and the K s band light-curves of variable stars. Conclusions. The VMC survey represents a tremendous improvement, in spatial resolution and sensitivity, on previous panoramic observations of the Magellanic system in the near-infrared, providing a powerful complement to deep observations at other wavelengths.

We present pulse phase resolved spectra of the hypergiant high mass X-ray binary GX 301−2. We observed the source in 2001 October with RXTE continuously for a total on-source time of almost 200 ks. We model the continuum with both, a heavily absorbed partial covering model and a reflection model. In either case we find that the well known cyclotron resonant scattering feature (CRSF) at ∼35 keV is-although present at all pulse phases-strongly variable over the pulse: the line position varies by 25% from 30 keV in the fall of the secondary pulse to 38 keV in the fall of the main pulse where it is deepest. The line variability implies that we are seeing regions of magnetic field strength varying between 3.4 × 10 12 G and 4.2 × 10 12 G.

We present ultraviolet (IUE) and infrared (ISO) observations of the bipolar proto-planetary nebula Hen 401 which, combined with previously available optical and near infrared data, are used to reconstruct the overall spectral energy distribution from 1150Å to 100 µm. The ISO spectrum is dominated by strong PAH emission superimposed on a very cold continuum which is interpreted as thermal emission originating in the C-rich cool dust (∼106 K) present in the circumstellar envelope, the remnant of the previous AGB phase. In addition, a second, hotter component detected in the near infrared is attributed to thermal emission from hot dust (∼640 K), suggesting that mass loss and dust grain formation is still ongoing during the current post-AGB phase. The ultraviolet (IUE) spectrum shows a stellar continuum in the wavelength interval 2400Å to 3200Å which corresponds to a moderately reddened B8-type central star. Unexpectedly, the UV flux in the wavelength interval 1150Å to 1900Å is very weak or absent with no evidence of a hotter binary companion which could explain the detection of the nebular emission lines observed in the available ground-based optical spectra of Hen 401. HST WFPC2 high resolution images also show no indication of a hot companion to the B8-type central star observed both in the optical and in the UV. The evolutionary implications of a possible single nature for the central star of Hen 401 are discussed.

We report new Spitzer Space Telescope observations from the IRAC and MIPS instruments of the young (∼ 3 Myr) σ Orionis cluster. The populous nature of this cluster makes it a good target for statistically-significant studies of disk emission as a function of mass. We identify 336 stars as members of the cluster using optical and near-infrared color magnitude diagrams. Using the spectral energy distribution (SED) slopes in the IRAC spectral range, we place objects in several classes: non-excess stars, stars with optically thick disks (like classical T Tauri stars), class I (protostellar) candidates, and stars with "evolved disks"; the last exhibit smaller IRAC excesses than optically thick disk systems. In general, this classification agrees with the location expected in IRAC-MIPS color-color diagrams for these objects. We find that the evolved disk systems are mostly a combination of objects with optically thick but non-flared disks, suggesting grain growth and/or settling, and transition disks, systems in which the inner disk is partially or fully cleared of small dust. In all, we identify 7 transition disk candidates and 3 possible debris disk systems. There appears to be a spatial extension of infrared excess sources to the northeast , which may be associated with the young (< 1 Myr) embedded cluster NGC 2024. As in other young stellar populations, the fraction of disks depends on the stellar mass, ranging from ∼10%

We are interested in the similarities and differences between the quantum-classical (Q-C) and the noncommutative-commutative (NC-Com) correspondences. As one useful platform to address this issue we derive the superstar Wigner-Moyal equation for noncommutative quantum mechanics (NCQM). A superstar $\bigstar$-product combines the usual phase space $\ast$ star and the noncommutative $\star$ star-product. Having dealt with subtleties of ordering present in this problem we show that the classical correspondent to the NC Hamiltonian has the same form as the original Hamiltonian, but with a non-commutativity parameter $\theta$-dependent, momentum-dependent shift in the coordinates. Using it to examine the classical and the commutative limits, we find that there exist qualitative differences between these two limits. Specifically, if $\theta \neq 0$ there is no classical limit. Classical limit exists only if $\theta \to 0$ at least as fast as $\hbar \to 0$, but this limit does not yield Ne...

Globular cluster stars evolving off the main sequence are known to lose mass, and it is expected that some of the lost material should remain within the cluster as an intracluster medium (ICM). Most attempts to detect such an ICM have been unsuccessful. The Multiband Imaging Photometer for Spitzer on the Spitzer Space Telescope was used to observe eight Galactic globular clusters in an attempt to detect the thermal emission from ICM dust. Most clusters do not have significant detections at 70 µm; one cluster, NGC 6341, has tentative evidence for the presence of dust, but 90 µm observations do not confirm the detection. Individual 70 µm point sources which appear in several of the cluster images are likely to be background galaxies. The inferred dust mass and upper limits are < 4 × 10 −4 M ⊙ , well below expectations for cluster dust production from mass loss in red and asymptotic giant branch stars. This implies that either globular cluster dust production is less efficient, or that ICM removal or dust destruction is more efficient, than previously believed. We explore several possibilities for ICM removal and conclude that present data do not yet permit us to distinguish between them.

VPN as a managed service enables the service provider to offer more demanding and revenue generating services. Some of the common managed VPN services known today include auto discovery, security, and also a potential ability to perform on demand signaling. In this paper we try to tackle an important problem of service providers namely topology dissemination to VPN customers seeking dynamic bandwidth service. Topology dissemination can easily be translated into a VPN service. In this regard we define this service and its associated SLA. Further we elaborate on four basic QoS enabled topology abstraction services: fully meshed, source rooted star, star, and simple node. The paper also describes a generic framework to generate these abstractions and presents simulation results comparing performance of each of these schemes.

Emily Rauscher and Kristen Menou Department of Astronomy, Columbia University, 550 West 120th Street, New York, NY 10027 ... James YK. Cho Astronomy Unit, School of Mathematical Sciences, Queen Mary, University of London, Mile End Road, London E1 4NS, UK

We present the science database produced by the Formation and Evolution of Planetary Systems (FEPS) Spitzer Legacy program. Data reduction and validation procedures for the IRAC, MIPS, and IRS instruments are described in detail. We also derive stellar properties for the FEPS sample from available broad-band

Context. The X-ray emission from B-type main-sequence stars is a longstanding mystery in stellar coronal research. Since there is no theory at hand that explains intrinsic X-ray emission from intermediate-mass main-sequence stars, the observations have often been interpreted in terms of (unknown) late-type magnetically active companion stars. Aims. Resolving the hypothesized companions requires high spatial resolution observations in the infrared and in X-rays. We use Chandra imaging observations to spatially resolve a sample of main-sequence B-type stars with recently discovered companions at arcsecond separation. Methods. Our strategy is to search for X-ray emission at the position of both the B-type primary and the faint companion. Results. We find that all spatially resolved companions are X-ray emitters, but seven out of eleven intermediate-mass stars are also X-ray sources. If this emission is interpreted in terms of additional sub-arcsecond or spectroscopic companions, this implies a high multiplicity of B-type stars. Firm results on B star multiplicity pending, the alternative, that B stars produce intrinsic X-rays, cannot be discarded. An appropriate scenario would be a magnetically confined wind, as suggested for the X-ray emission of the magnetic Ap star IQ Aur. However, the only Ap star in the Chandra sample is not detected in X-rays, and therefore does not support this picture.

Context. Most observational studies conducted so far point toward brown dwarfs sharing a similar formation mechanism as the one that is accepted for low-mass stars. However, larger databases and more systematic studies are needed before strong conclusions can be reached. Aims. In this second paper of a series devoted to studying the spectroscopic properties of the Lambda Orionis star-forming region members, we study accretion, activity and rotation for a wide set of spectroscopically confirmed members of the central star cluster Collinder 69 to assess analogies and/or differences between the brown-dwarf and stellar populations of this cluster. Moreover, we present comparisons with other star-forming regions of similar and different ages to address environmental effects on our conclusions. Methods. We studied prominent photospheric lines to derive rotational velocities and emission lines to distinguish between accretion processes and chromospheric activity. In addition, we include information about disk presence and X-ray emission. Results. We report very strong differences in the disk fractions of low-mass stars and brown dwarfs (∼58%) when compared to higher mass stars (26 +4 −3 %), with 0.6 M being the critical mass we find for this dichotomy. As a byproduct, we address the implications of the spatial distribution of disk and diskless members in the formation scenario of the cluster itself. We used the Hα emission to distinguish among accreting and non-accreting sources, finding that 38 +8 −7 % of sources harboring disks undergo active accretion and that his percentage stays similar in the substellar regime. For these sources we have estimated accretion rates. Finally, regarding rotational velocities, we find a high dispersion in v sin(i) that is even higher among the diskless population.

We present the first results from a series of Chandra observations carried out with the aim to examine the origin of X-ray emission in main-sequence late B-type stars. X-ray detections of late-B and early A-type stars have remained a mystery as none of the two major theories for stellar X-ray emission applies in this spectral range: while O-and early B-type stars drive strong winds that are subject to instabilities, late-type stars produce X-rays as a result of magnetic dynamo action. Since any dynamo works only in the presence of a convective zone, early-type stars are not magnetically active. We use high spatial resolution X-ray observations to enlighten the prevalent speculation that previously unknown late-type or low-mass companion stars are the sites of the X-ray emission, instead of the B-type primaries. Here we present the results for HD 1685, HD 113703, HD 123445, HD 133880, and HD 169978. Adaptive optics observations have recently revealed at least one faint object near each of these B-type stars (at separation of 1 − 6). Four of the new infrared objects show infrared colors and magnitudes typical for low-mass pre-main sequence stars, and are likely true companions to the ∼ 10 − 50 Myr old B-type stars. These multiple systems are now resolved for the first time in X-ray light. We uncover that four of the new companions are X-ray emitters, and the fifth one is likely to be a weak X-ray source below the detection limit. Three of the Btype primaries are X-ray dark down to the detection limit of L x ∼ 10 28 erg/s. But we do detect X-ray emission from the position of HD 1685 A and HD 169978 A. The latter one indeed is a spectroscopic binary. The characteristics of all X-ray sources are compatible with those of typical young late-type stars: hard X-ray spectrum (kT > 0.5 keV) and high X-ray luminosity (lg L x ∼ 29...30 erg/s). Spectroscopic observations in the infrared will solve the question whether the one remaining X-ray detected B-star in our sample, HD 1685 A, also has an even closer companion or whether this is an intrinsic X-ray emitter.

We present the first results from a series of Chandra observations carried out with the aim to examine the origin of X-ray emission in main-sequence late B-type stars. X-ray detections of late-B and early A-type stars have remained a mystery as none of the two major theories for stellar X-ray emission applies in this spectral range: while O-and early B-type stars drive strong winds that are subject to instabilities, late-type stars produce X-rays as a result of magnetic dynamo action. Since any dynamo works only in the presence of a convective zone, early-type stars are not magnetically active. We use high spatial resolution X-ray observations to enlighten the prevalent speculation that previously unknown late-type or low-mass companion stars are the sites of the X-ray emission, instead of the B-type primaries. Here we present the results for HD 1685, HD 113703, HD 123445, HD 133880, and HD 169978. Adaptive optics observations have recently revealed at least one faint object near each of these B-type stars (at separation of 1 − 6). Four of the new infrared objects show infrared colors and magnitudes typical for low-mass pre-main sequence stars, and are likely true companions to the ∼ 10 − 50 Myr old B-type stars. These multiple systems are now resolved for the first time in X-ray light. We uncover that four of the new companions are X-ray emitters, and the fifth one is likely to be a weak X-ray source below the detection limit. Three of the Btype primaries are X-ray dark down to the detection limit of L x ∼ 10 28 erg/s. But we do detect X-ray emission from the position of HD 1685 A and HD 169978 A. The latter one indeed is a spectroscopic binary. The characteristics of all X-ray sources are compatible with those of typical young late-type stars: hard X-ray spectrum (kT > 0.5 keV) and high X-ray luminosity (lg L x ∼ 29...30 erg/s). Spectroscopic observations in the infrared will solve the question whether the one remaining X-ray detected B-star in our sample, HD 1685 A, also has an even closer companion or whether this is an intrinsic X-ray emitter.

We report results of a BeppoSAX observation of the low-mass X-ray binary (LMXB) dipping source XB 1916−053. The source joins the small group of LMXB detected at energies ∼ > 100 keV. The non-dip spectrum is well fitted by an absorbed blackbody with a temperature of 1.62±0.05 keV and an absorbed cutoff power law with a photon index of 1.61±0.01 and a cutoff energy of 80±10 keV. Below 10 keV, where photoelectric absorption is dominant, the dramatic spectral changes observed during dips can be simply modelled by progressive covering of the blackbody and cutoff power law components. The blackbody component is very rapidly absorbed during dips, consistent with it being point-like, while the cutoff power law is more gradually absorbed, consistent with it being extended. The most likely locations for the blackbody component are the surface of the neutron star or the boundary layer between the neutron star and the accretion disk. The extended emission most probably originates in an accretion disk corona. Above 10 keV, dipping is detected up to ∼40 keV, and there is some evidence for an energy-independent reduction in intensity of up to 15%. This reduction could be caused by electron scattering or obscuration. In the first case, the change is consistent with an electron column density of ∼2.9 × 10 23 cm −2 , several times smaller than the average hydrogen column measured simultaneously.

We present results from two deep ROSAT HRI exposures on the Blanco 1 open cluster. Blanco 1 is one of the few open clusters at large distance from the Galactic Plane. This circumstance has suggested that it may have formed through a mechanism different from that responsible for the other nearby clusters. The age of Blanco 1 is rather uncertain since, depending on the adopted age indicator, it ranges between 30 and 90 Myr. Many cluster members show chromospheric emission typical of young stars. The X-ray observations presented here reveal a high number of X-ray sources, consistent with the young age of the cluster. The typical X-ray luminosity of the cluster members is consistent with that of the Pleiades and significantly lower than the α Per members. These results suggest than the age of Blanco 1 is more similar to the age of the Pleiades than to that of α Per. The time sampling of the X-ray observations allows us to study the variability of the sources on time scales from hours to 6 months-1 year.

A survey of the 12 C/ 13 C ratio toward circumstellar envelopes has been conducted at millimeter wavelengths using the facilities of the Arizona Radio Observatory (ARO). The ratios were obtained for a sample of local C-and O-rich asymptotic giant branch and supergiant stars from observations of the 12 C and 13 C isotopologues of CO and CN, respectively. The J = 1 → 0 transitions of both molecules were observed at λ = 3 mm using the ARO 12 m telescope, while the J = 2 → 1 lines of the two species were measured using the ARO Sub-Millimeter Telescope (SMT) at λ = 1 mm. The 12 C/ 13 C ratios were determined from the CO data by modeling both transitions simultaneously with a circumstellar radiative transfer code, which can account for the high opacities present in the emission from this species. In the case of CN, the hyperfine structure was used to evaluate opacity effects. Ratios obtained independently from CO and CN are in good agreement. For the C-rich envelopes, the ratios fall in the range 12 C/ 13 C ∼ 25-90, while the O-rich shells have values of 10-35. Ratios of 12 C/ 13 C ∼ 3-14 are found for the supergiant stars, with the exception of VY CMa, where the values lie in the range 25-46. All ratios obtained in this study are 89, the solar value, suggesting that substantial carbon-13 enrichment may be currently occurring in the local interstellar medium. A qualitative model was constructed based on first and third dredge-up convective mixing that can reproduce the observed ratios. Substantial mixing of H-burning products must occur to explain the ratios in the O-rich objects, while a wide range of 12 C/ 13 C values can be generated by only a few percent mixing of He-burning ashes in the C-rich case. The 12 C/ 13 C ratios obtained in this study should help improve stellar yield models and contribute to the understanding of Galactic chemical evolution.