Search

The recent discovery of hidden non-axysimmetric and disk-like structures in bright Virgo dwarf elliptical and lenticular galaxies (dE/dSph/dS0) indicates that they may have late-type progenitors. Using N-body simulations we follow the evolution of disk galaxies within aCDM cluster simulated with 10 7 particles, where the hierarchical growth and galaxy harassment are modeled self-consistently. Most of the galaxies undergo significant morphological transformation, even at the outskirts of the cluster, and move through the Hubble sequence from late type disks to dwarf spheroidals. None of the disks are completely destroyed therefore they can not be the progenitors of ultra compact dwarf galaxies (UCDs). The time evolution of the simulated galaxies is compared with unsharp-masked images obtained from VLT data and the projected kinematics of our models with the latest high resolution spectroscopic studies from the Keck and Palomar telescopes.

We present the first in a series of papers that attempt to investigate the relation between binarity, magnetic activity, and chemical surface abundances of cool stars. In the current paper, we lay out and test two abundance analysis methods and apply them to two well-known, active, single stars, HD 27536 (G8IV-III) and HD 216803 (K5V), presenting photospheric fundamental parameters and abundances of Li, Al, Ca, Si, Sc, Ti, V, Cr, Fe, Co and Ni. The abundances from the two methods agree within the errors for all elements except calcium in \hdeen, which means that either method yields the same fundamental model parameters and the same abundances. Activity is described by the radiative loss in the Ca II H & K lines with respect to the bolometric luminosity, through the activity index R_{HK}. Binarity is established by very precise radial velocity (RV) measurements using HARPS spectra. The spectral line bisectors are examined for correlations between RV and bisector shape to distinguish between the effects of stellar activity and unseen companions. We show that HD 27536 exhibit RV variations mimicking the effect of a low-mass (m ~ 4M_J) companion in a relatively close (a ~ 1AU) orbit. The variation is strongly correlated with the activity, and consistent with the known photometric period P = 306.9 d, demonstrating a remarkable coherence between R_{HK} and the bisector shape, i.e. between the photosphere and the chromosphere. We discuss the complications involved in distinguishing between companion and activity induced RV variations., 11 pages, 12 figures. A&A accepted

In this paper we present a modification of a local approximation of the so-called interface dynamo in an attempt to reproduce the length of the magnetic cycles for a sample of late-type stars. The sample consists of 25 stars, observed during the Mount Wilson and Las Campanas long-term monitoring campaigns, for which well-defined cycles have been detected. We have focused our efforts on reproducing general trends observed, namely, the dependence of the cycle length, Pcyc, on the stellar rotation period, Prot, rather than attempting to infer from the dynamo model individual cycle lengths for each star. In spite of the simplicity of the model, the results are promising. The trend of increasing cycle length with increasing rotation period is reproduced with a minimum of assumptions.

Using modern astronomical databases, particularly 2MASS All - Sky Data Release Point Source Catalog and USNO-B1.0 catalog, we investigate the properties of about 840 FBS red stars in order to clarifiy their nature. We use and analyse their JHK 2MASS photometry, together with the R-band magnitudes and the proper motions provided by USNO - B1.0. Approximately 70% of all objects appear to be Asymptotic Giant Branch stars, 18% are giants, and close to 12% are objects with detectable proper motions, allowing to consider them as dwarf M-type stars. When plotted in a J - K versus R - K colour-colour diagram, one finds that objects with proper motions are well separated into a narrow belt.

High-dispersion coude spectra were observed and measured for 43 field subgiants of the G and K spectral types, with the intent of searching for hitherto undiscovered spectroscopic binaries. Statistical analysis of the measurements revealed no definite but two possible new binaries. We present the data and discuss the statistical analysis used to test for new binaries. Additionally, we discuss the techniques for high precision of radial-velocity measurement, and the systematic errors that interfere with that goal.

Based on a collection of high-dispersion spectra obtained at Okayama Astrophysical Observatory, the atmospheric parameters (Teff ,l ogg, vt ,a nd [Fe/H]) of 160 mid-F through early-K stars were extensively determined by the spectroscopic method using the equivalent widths of Fe I and Fe II lines along with the numerical technique of Takeda et al. (2002, PASJ, 54, 451). The results are comprehensively discussed and compared with the parameter values derived by different approaches (e.g., photometric colors, theoretical evolutionary tracks, Hipparcos parallaxes, etc.) as well as with the published values found in various literature. It has been confirmed that our purely spectroscopic approach yields fairly reliable and consistent results.

Towards clarifying the properties of late-G giants, for which we are currently conducting a planet-search project at Okayama Astrophysical Observatory, an extensive spectroscopic study has been performed for our first target sample of fifty-seven G6–G9 III stars, in order to establish the atmospheric parameters (Teff ,l ogg, vt ,a nd [Fe/H]), the stellar mass along with the evolutionary status, and the photospheric abundances of various elements. It was confirmed that the conventionalspectroscopicmethod of parameter determination usingFe I/ IIlineswith the assumption of LTE works successfully for these evolved stars. We determined the abundances (relative to the Sun) of 19 elements, and examined how their [X/Fe] ratios behave themselves with the run of [Fe/H]. While the trends appear to be similar to those exhibited by disk dwarfs for a number of elements, some elements (C, O, Na) showed appreciable anomalies, which may be interpreted as being due to a dredge-up of nuclear-processed material. Since the [Fe/H] values of these stars tend to be somewhat biased towards a subsolar regime, some mechanism of slightly reducing the metallicity might be suspected.

We present measurements of the UV galaxy luminosity function and the evolution of luminosity density from GALEX observations matched to the Sloan Digital Sky Survey (SDSS). We analyze galaxies in the Medium Imaging Survey overlapping the SDSS DR1 with a total coverage of 44 deg^2. Using the combined GALEX+SDSS photometry, we compute photometric redshifts and study the LF in three redshift shells between z=0.07 and 0.25. The Schechter function fits indicate that the faint-end slope alpha is consistent with -1.1 at all redshifts but the characteristic UV luminosity M* brightens by 0.2 mag from z=0.07 to 0.25. In the lowest redshift bin, early and late type galaxies are studied separately and we confirm that red galaxies tend to be brighter and have a shallower slope alpha than blue ones. The derived luminosity densities are consistent with other GALEX results based on a local spectroscopic sample from 2dF and the evolution follows the trend reported by deeper studies., This paper will be published as part of the Galaxy Evolution Explorer (GALEX) Astrophysical Journal Letters Special Issue. Links to the full set of papers will be available at http://www.galex.caltech.edu/PUBLICATIONS/ after November 22, 2004

The spectral and reddening properties of 211 highly reddened proper motion members with $V $70%) of program stars in NGC 1976, NGC 2244, NGC 6530 and NGC 6611 show anomalous reddening with $R_{V}$ = $5.11\pm0.11$, $3.60\pm0.05$, $3.87\pm0.05$ and $3.56\pm 0.02$, respectively, indicating the presence of grain size dust larger than that typical to the diffuse medium. A small number of stars in NGC 1976, NGC 2244 and NGC 6611 also show normal behavior while the cluster NGC 6823 appears to have a normal reddening. Three highly luminous late type giants, one in NGC 2244 and two in NGC 6530, appears to be member and are in post-hydrogen-core-burning stages suggesting a prolonged duration ($\sim$ 25 Myrs) of star formation.

The extremely sensitive Chandra Deep Field-North (CDF-N) pencil-beam X-ray survey is used to identify and characterize the X-ray emission from old high-latitude main sequence Galactic stars. Our principal goal is to investigate the expected long-term decay of magnetic activity of late-type stars due to the gradual spindown of stellar rotation from a magnetized stellar wind. Eleven X-ray sources constitute a well-defined sample of 2 G, 2 K0-K4, and 7 M2-M5 stars with median distance around 300 pc. X-ray luminosities are typically log Lx ~ 27 erg/s and is dominated by flares rather than quiescent coronal emission. Models of the population indicates that the CDF-N stars are the most magnetically active old disk stars. A substantial decline in X-ray luminosities over the 1, Comment: 22 pages, 5 figures, accepted for publication in the Astrophysical Journal

We report the confirmation of three X-ray and radio stars at high galactic latitudes as a by-product of a search originally aiming to find new microquasars. The objects are the late type, optically bright stars HD 135743, CD-2412231 and HD 220338. Interestingly, the last of them has displayed, on time scales of years, what could be considered as a radio flaring behaviour and deserves follow up. The observational evidence gathered, at radio and optical wavelengths, suggests that these objects are likely new chromospherically active stars relatively close to the Sun.

The ‘flip-flop’ phenomenon has now been found to occur on several late-type stars: active longitudes, associated with dark regions of the surface, are seen to jump by 180 ◦ . A simple non-linear non-axisymmetric mean field dynamo model is described, in which for the first time magnetic behaviour is found that is akin to the observed flip-flop.

We investigated the main-line spectral evolution with shell thickness of oxygen rich AGB stars. The study is based on a sample of 30 sources distributed along the IRAS colour-colour diagram. The sources were chosen to trace the Miras with thick shells and the whole range of OH/IR stars. The Miras exhibit a 1665 MHz emission strength comparable to that at 1667 MHz. Even though the Miras of the study have quite thick shells, their spectral characteristics in both main lines attest to a strong heterogeneity in their OH shell with, in particular, the presence of significant turbulence and acceleration. The expansion velocity has been found to be about the same at 1665 and 1667 MHz, taking into account a possible velocity turbulence of 1-2km/s at the location of the main-line maser emission. An increase in the intensity ratio 1667/1665 with shell thickness has been found. A plausible explanation for such a phenomenon is that competitive gain in favour of the 1667 MHz line increases when the shell is getting thicker. There is an evolution in the spectral profile shape with the appearance of a substantial inter-peak signal when the shell is getting thicker. Also, inter-peak components are found and can be as strong as the external standard peaks when the shell is very thick. This trend for an increase of the signal in between the two main peaks is thought to be the result of an increase of the saturation with shell thickness. All sources but two - a Mira and an OH/IR star from the lower part of the colour-colour diagram - are weakly polarized. The strong polarization observed for those two particular objects is thought to be the result of perturbations in their shells., Comment: 19 pages, 12 figures, accepted for publication in A&A

We present and discuss VBLUW photometry (Walraven system) of five supergiants in the LMC. For one well- known variable, the hypergiant R 59 = HDE 268757 (G7 Ia + ) also Hipparcos photometry and numerous visual observations are available. The second variable is HDE 269612 (F0 Ia), and a third one is HDE 268822 (F6 Ia). Two F6 Ia supergiants turned out to be constant: HDE 269355 and HDE 270025.

We present 12 CO(J= 1-0) line observations of 99 galaxies obtained with the SEST 15 m, the Kitt Peak 12 m and the IRAM 30 m telescopes. The target galaxies were selected from the catalogue of isolated galaxies of Karachentseva (1973). These data are thus representative of the CO properties of isolated late-type galaxies. All objects were observed in their central position, those with large angular sizes were mapped. These new measurements are used to estimate the molecular gas mass of the target galaxies. The molecular gas is on average18% of the atomic gas mass.

We study HST/NICMOS H-band images of bulges of two equal-sized samples of early- (T(RC3) < 4) and late-type spiral (mainly Sbc-Sc) galaxies matched in outer disk axis ratio. We find that bulges of late-type spirals are more elongated than their counterparts in early-type spirals. Using a KS-test we find that the two distributions are different at the 98.4% confidence level. We conclude that the two data sets are different, i.e. late-type galaxies have a broader ellipticity distribution and contain more elongated features in the inner regions. We discuss the possibility that these would correspond to bars at a later evolutionary stage, i.e. secularly evolved bars. Consequent implications are raised, and we discuss relevant questions regarding the formation and structure of bulges. Are bulges of early-type and late-type spirals different? Are their formation scenarios different? Can we talk about bulges in the same way for different types of galaxies?, Submitted to A & A (accepted); Please find high resolution version on http://www.astro.uu.se/~kambiz/DOC/paper-bulges.pdf

We confirm the existence of an "excess" in the mean dereddened ( U B)0 colour of active single-lined spectroscopic giants over quiescent stars of the same spectral type and find evidence for this "excess" in ( B V)0, although at a lower scale, when plotted against (R I)0. This result suggests that the use of ( B V)0 calibrations to determine fundamental parameters or spectral types for late-type active stars should be taken with caution. Since magnetic activity is definitely involved, these and similar calibrations using (U B)0 and/or (B V)0 should not be used for the study of late-type young clusters' members or late-type pre-main sequence stars without some consideration. Instead, near-infrared colours like ( R I)0 should be better temperature indicators for these stars.

Long-term (5 years) outcome of 30 patients whose aneurysm was excluded using the Parodi endograft (PE) was assessed. Thirty patients with a mean follow-up of 59 months were the basis of the analysis. Additionally, 100 consecutive patients treated with the Vanguard Endograft (VE) were followed up for 28 months (range, 7 to 56 months). Results were analyzed and both groups compared. There were no late failures related to the loss of the integrity of the device in the PE group. Aorto aortic systems showed distal neck dilatation in high proportion of patients (80%). Aorto-uni-iliac endograft was successful in 80% of the patients. Only one late type I endoleak developed in a patient in whom the proximal stent was placed far from the renal arteries and in contact with thrombus. Also, persistent type II endoleaks were the cause of failure. No neck dilatation was noted. In the VE group, most of the failures were device related.

The dynamical evolution of super star clusters (SSCs) moving in the background of a dark matter halo has been investigated as a possible event responsible for the formation of bulges in late-type spirals. The underlying physical processes include sinking of SSCs due to the dynamical friction and stripping of SSCs on their way to the center. Our model calculations show that only sinking of circumnuclear SSCs contributes to the formation of galactic bulges at the early stage. Based on the assumption of a universal density profile for the dark matter halo, and an isothermal model for the SSCs, our simulations have yielded bulges that are similar in many aspects to the observational ones. In particular, the derived surface density profiles can be well fitted by anexponential structure with nuclear cusps, which is consistent with HST observations.

We have used the infrared flux method (IRFM) temperatures of a large sample of late type dwarfs given by Alonso et al. (1996a) to calibrate empirically the relations T e f f = f (colour, [Fe/H]) for the Vilnius, Geneva, RI ( C ) (Cousins) and DDO photometric systems. The resulting temperature scale and intrinsic colour-colour diagrams for these systems are also obtained. From this scale, the solar colours are derived and compared with those of the solar twin 18 Sco. Since our work is based on the same T e f f and [Fe/H] values used by Alonso et al. (1996b) to calibrate other colours, we now have an homogeneous calibration for a large set of photometric systems.

We present the first results of analysis of infrared properties of the faint M and C type stars found on the FBS plates. By cross - correlating the subsample of FBS late - type stars with infrared catalogues, we have shown that several families of objects can be separated. It provides ways to better characterize the properties of these families, their nature and their typical distances.

We have analyzed high-resolution (Δλ ≅ 0.06 A) X-ray spectra in the region 6–180 A of the coronae of the cool stars Capella, Procyon, and α Centauri. These stars were observed with the the CHANDRA Low Energy Transmission Grating Spectrometer (LETGS) between Sep. and Dec. 1999. Temperatures are derived from line ratios of helium-like lines and long-wavelength iron lines. Electron densities are obtained for the relatively cooler (few MK) and more tenuous (⪅ 1011 cm−3) plasma components from the forbidden to intercombination line ratios in the helium-like triplets of O, N, and C and for the hotter (⪆ 5 MK) and denser (⪆ 1012 cm−3) components (such as occur in Capella) from the helium-like triplets of Mg and Si and the ratios of Fe XIX-Fe XXII 2l-2l′ lines above 90 A. The implications of these results for the coronal structure are discussed.

We present the results of an extensive survey of superflares on late-type stars (G, K, and M-type main sequence stars) using the Kepler satellite data. Wefound about 6,800 superflares on late-type stars from the data of about 120,000 stars observed over 500 days. The total bolometric energy of superflares in oursample ranges from 1032 erg to 1036 erg. Our data suggest that the occurrencefrequency of superflares depends on the surface temperature and the rotationperiod of stars. Superflares on M-type stars occur about 10-100 times morefrequently than those on G-type stars. Our results suggest that the average frequency ofsuperflares releasing 1034–1035 erg of energy (100-1,000 times larger than the largestsolar flares) on M-type stars and Sun-like stars is once in 10 years and once in a few thousand years respectively.

We have undertaken a comprehensive search for 5-cm excited OH maser emission from evolved stars representative of various stages of late stellar evolution. Observed sources were selected from known 18-cm OH sources. This survey was conducted with the 100-m Effelsberg telescope to achieve high signal to noise ratio observations and a sensitivity limit of about 0.05 to 0.1 Jy. A total of 64 stellar sources were searched for both main line and satellite line emission. We confirm the previous detection of 5 cm OH in Vy 2-2, do not confirm emission from NML-Cyg and do not report any other new detection within the above sensitivity limit. Implications of these results on the pumping mechanism of the OH radical in circumstellar envelopes are briefly discussed., Comment: 8 pages, 5 figures, A&A in press

All the Extreme Ultraviolet Explorer (EUVE) observations of AD Leo, totalling 1.1 Ms of exposure time, have been employed to analyze the corona of this single M dwarf. The light curves show a well defined quiescent stage, and a distribution of amplitude of variability following a power law with a ~-2.4 index. The flaring behavior exhibits much similarity with other M active stars like FK Aqr or YY Gem, and flares behave differently from late type active giants and subgiants. The Emission Measure Distribution (EMD) of the summed spectrum, as well as that of quiescent and flaring stages, were obtained using a line-based method. The average EMD is dominated by material at log T(K)~6.9, with a second peak around log T(K)~6.3, and a large increase in the amount of material with log T(K)>~7.1 during flares, material almost absent during quiescence. The results are interpreted as the combination of three families of loops with maximum temperatures at log T(K)~6.3, ~6.9 and somewhere beyond log T(K)>~7.1. A value of the abundance of [Ne/Fe]=1.05+-0.08 was measured at log T(K)~5.9. No significative increment of Neon abundance was detected between quiescence and flaring states., Full PS version can be found also at http://www.astropa.unipa.it/~jsanz/papers0002.html

In the present study, we analyze the effects of a flux of Alfven waves acting together with radiation pressure on grains as an acceleration mechanism of the wind of late-type stars. In the wind model we simulate the presence of grains through a strong damping of the waves, we used a non-isothermal profile for temperature, coherent with grain formation theories. We examine the changes in the velocity profile of the wind and we show that if the grains are created in the region 1.1 < r/r_0 < 2.0 their presence will affect the mass loss and terminal velocity. The model is applied to a K5 supergiant star and for Betelgeuse (alpha Ori)., 6 pages, 3 figures, accepted in ApJ (Sep, 2002)

We show that the mean percentage of stellar light re-radiated by dust is ~30 percent for the Virgo Cluster late-spirals measured with ISOPHOT by Tuffs et al. (2002). A strong dependence of this ratio with morphological type was found, ranging from typical values of ~15 percent for early spirals to up to ~50 percent for some late spirals. The extreme BCDs can have even higher percentages of their bolometric output re-radiated in the thermal infrared. Luminosity correction factors for the cold dust component are given for general use in converting far-infrared (FIR) luminosities derived from IRAS., 5 pages, 3 eps figures, accepted for publication in MNRAS Letters

Neutral hydrogen observations with the Westerbork Synthesis Radio Telescope are presented for a sample of 73 late-type dwarf galaxies. These observations are part of the WHISP project (Westerbork HI Survey of Spiral and Irregular Galaxies). Here we present HI maps, velocity fields, global profiles and radial surface density profiles of HI, as well as HI masses, HI radii and line widths. For the late-type galaxies in our sample, we find that the ratio of HI extent to optical diameter, defined as 6.4 disk scale lengths, is on average 1.8+-0.8, similar to that seen in spiral galaxies. Most of the dwarf galaxies in this sample are rich in HI, with a typical M_HI/L_B of 1.5. The relative HI content M_HI/L_R increases towards fainter absolute magnitudes and towards fainter surface brightnesses. Dwarf galaxies with lower average HI column densities also have lower average optical surface brightnesses. We find that lopsidedness is as common among dwarf galaxies as it is in spiral galaxies. About half of the dwarf galaxies in our sample have asymmetric global profiles, a third has a lopsided HI distribution, and about half shows signs of kinematic lopsidedness., Comment: Accepted for publication in A&A. 18 pages. 39 MB version with all figures is available http://www.robswork.net/publications/WHISPI.ps.gz

The O-C curve of the very late type close binary (dMle+dMle)YY Geminorum is formed and analyzed based on all available times of minimum light. It is found that the orbital period shows a secular decrease with rate dP/dt = -1.08x10(-8) days yr(-1). There is weak evidence indicating that a small-amplitude period oscillation is superposed on the period decrease. YY Gem is a well-detached eclipsing binary containing two very active components. The secular period decrease may suggest that the system is undergoing secular mass and angular momentum loss via a magnetic stellar wind. If the small-amplitude oscillation is real, it can be explained either by magnetic activity cycles or by the presence of a giant planet or brown dwarf.

Surface-averaged longitudinal magnetic-field components (by analogy with the Sun called the general magnetic field) have been measured for 15 late-type giants with an accuracy of several Gauss. Statistically significant fields were detected for nine of these stars. The magnetic-field values obtained suggest the existence of general magnetic fields in these giants.

This paper presents speckle observations of Mira (o Cet) and late-type stars with the PISCO speckle camera of Pic du Midi during the period 1995-1998. A survey for binarity among a sample of late-type stars was performed, which led to seven positive detections out of 36 objects. Photometric and color variations of the companion of Mira were searched for, but no significant brightness variations could be found over a timescale of ~5-10 minutes. The position and photometry measurements, the restored images with high angular resolution of the binary system Mira A-B (ADS 1778) are in full agreement with Hubble Space Telescope data obtained at the same epoch. A new orbit has been derived for Mira A-B.

We have statistically analyzed the spatially integrated far-infrared (FIR) emissions of the complete volume- and luminosity-limited sample of late-type (later than S0) Virgo cluster galaxies measured using the Infrared Space Observatory (ISO) by Tuffs et al. (2002) in bands centered on 60, 100 and 170 microns. 30 out of 38 galaxies detected at all three wavelengths contain a cold dust emission component, present within all morphological types of late-type systems ranging from early giant spirals to Blue Compact Dwarfs (BCDs), and which could not have been recognized by IRAS. The temperatures of the cold dust were found to be broadly distributed, with a median of 18 K, some 8-10 K lower than would have been predicted from IRAS. The derived total dust masses are correspondingly increased by factors of typically 6 - 13. A particularly significant result concerns the low dust temperatures (ranging down to less than 10 K) and large dust masses associated with the Im and BCD galaxies in our sample. We propose two scenarios to account for the FIR characteristics of these systems., 38 pages (Latex); 9 figures; complete version of Fig. 2 can be found at http://nedwww.ipac.caltech.edu/level5/Sept01/Popescu/Popescu_contents.html; to be published in ApJ, v567, 2002

We present new HST I-band images of a sample of 77 nearby, late-type spiral galaxies with low inclination. The main purpose of this catalog is to study the frequency and properties of nuclear star clusters. In 59 galaxies of our sample, we have identified a distinct, compact (but resolved), and dominant source at or very close to their photocenter. In many cases, these clusters are the only prominent source within a few kpc from the galaxy nucleus. We present surface brightness profiles, derived from elliptical isophote fits, of all galaxies for which the fit was successful. We use the fitted isophotes at radii larger than 2" to check whether the location of the cluster coincides with the photocenter of the galaxy, and confirm that in nearly all cases, we are truly dealing with ``nuclear'' star clusters. From analytical fits to the surface brightness profiles, we derive the cluster luminosities after subtraction of the light contribution from the underlying galaxy disk and/or bulge.

We have assembled a catalogue of relative ages, metallicities and abundance ratios for about 150 local galaxies in field, group and cluster environments. The galaxies span morphological types from cD and ellipticals, to late type spirals. Ages and metallicities were estimated from high quality published spectral line indices using Worthey & Ottaviani (1997) single stellar population evolutionary models. The identification of galaxy age as a fourth parameter in the fundamental plane (Forbes et al. 1998) is confirmed by our larger sample of ages. We investigate trends between age and metallicity, and with other physical parameters of the galaxies, such as ellipticity, luminosity, and kinematic anisotropy. We demonstrate the existence of a galaxy age-metallicity relation similar to that seen for local galactic disk stars, whereby young galaxies have high metallicity, while old galaxies span a large range in metallicities. We also investigate the influence of environment and morphology on the galaxy age and metallicity, especially the predictions made by semi-analytic hierarchical clustering models (HCM). We confirm that non-cluster ellipticals are indeed younger on average than cluster ellipticals as predicted by the HCM models. However we also find a trend for the more luminous galaxies to have a higher [Mg/Fe] ratio than the lower luminosity galaxies, which is opposite to the expectation from HCM models., 17 pages, Latex, 16 figures, 4 tables, submitted to MNRAS

Far-infrared flux densities are newly extracted from the IRAS database for the RSA and CfA complete samples of Seyfert galaxies. These data are used to classify the Seyfert galaxies into those where the far-infrared continuum emission is dominated by the active galactic nucleus (AGN), circumnuclear starburst, or host galaxy. While AGN-dominant objects consist of comparable numbers of Seyfert 1 and 2 galaxies, starburst- and host-dominant objects consist preferentially of Seyfert 2 galaxies. Thus, in addition to the dusty torus, the circumnuclear starburst region and host galaxy are important in hiding the broad-line region. Morphologically, starburst-dominant Seyfert galaxies are of later types and more strongly interacting than AGN-dominant Seyfert galaxies. In a later-type galaxy, the AGN central engine has a lower Eddington luminosity, and the gaseous content is higher. The gas is efficiently supplied to the starburst via a galaxy-galaxy interaction. Morphologies of host-dominant Seyfert galaxies are of various types. Since starbursts in Seyfert galaxies are older than those in classical starburst galaxies, we propose an evolution from starburst to starburst-dominant Seyfert to host-dominant Seyfert for a late-type galaxy. An evolution from AGN-dominant Seyfert to host-dominant Seyfert is proposed for an early-type galaxy. These sequences have durations of a few x 10^8 yr and occur repeatedly within a galaxy during its evolution from a late type to an early type., 27 pages (AASTeX 5.0), 3 ps files for 6 figures, to appear in The Astrophysical Journal

We present the results of X-ray luminosities of some active late-type stars, based on data primarily from the ROSAT position sensitive proportional counter (PSPC). According to the observations, we divide the stars into four groups: single, wide binary, binary and RS CVn. We investigated the correlation between the X-ray emission and the hardness ratio, coronal temperature, magnetic field strength, magnetic flux density. Our results suggest that the magnetic field plays a very important role in stellar X-ray emission.

Interacting binaries in which a white dwarf accretes material from a companion - cataclysmic variables (CVs) in which the mass donor is a Roche-lobe filling star on or near the main sequence, and symbiotic stars in which the mass donor is a late type giant - are relatively commonplace. They display a wide range of behaviors in the optical, X-rays, and other wavelengths, which still often baffle observers and theorists alike. Here I review the existing body of research on X-ray emissions from these objects for the benefits of both experts and newcomers to the field. I provide introductions to the past and current X-ray observatories, the types of known X-ray emissions from these objects, and the data analysis techniques relevant to this field. I then summarize of our knowledge regarding the X-ray emissions from magnetic CVs, non-magnetic CVs and symbiotic stars, and novae in eruption. I also discuss space density and the X-ray luminosity functions of these binaries and their contribution to the integrated X-ray emission from the Galaxy. I then discuss open questions and future prospects., Comment: Invited review for Publications of the Astronomical Society of the Pacific (accepted) - 48 pages including 12 figures

We present a case of ovarian hyperstimulation syndrome (OHSS) occurring 8 days after human chorionic gonadotropin (hCG) administration. OHSS is classified as late type if it occurs 12 to 17 days after hCG administration and early type if it occurs within 7 days. Thus, the condition in this patient did not fit the definition of early or late OHSS. The OHSS was mild, and she recovered in approximately 10 days without requiring admission. The patient was not pregnant, and the OHSS was shown to be induced by exogenous hCG administration not endogenous hCG. In conclusion, OHSS can occur 8 to 11 days after hCG administration and it is important to distinguish whether OHSS is induced by endogenous or exogenous hCG.

We discuss the possibilities of investigating the semiregular and irregular light change found in evolved late type giant stars with photometric and visually obtained (amateur) data. Period analysis has been done on light curve data from both sources for a sample of semiregular variables. The results are compared to test the ability of visual data to show the frequency contents present in these variables. We nd that both sources of data complete each other, as tting the ne structure visible only in the photometric data needs long-term visual monitoring to guarantee the uniqueness of the t.

We explore the rich globular cluster (GC) system of the nearby Sa galaxy M104, the "Sombrero" (NGC 4594), using archive WFPC2 data. The GC colour distribution is found to be bimodal at the > 99% level, with peaks at V-I = 0.96+/-0.03 and 1.21+/-0.03 (corrected for foreground reddening). The inferred metallicities are very similar to those of globular clusters in our Galaxy and M31. However the Sombrero reveals a much enhanced number of red (metal-rich) GCs compared to other well-studied spirals. Because the Sombrero is dominated by a huge bulge and only has a modest disk, we associate the two sub-populations with the halo and bulge components respectively. Thus our analysis supports the view that the metal-rich GCs in spirals are associated with the bulge rather than with the disk. The Sombrero GCs have typical effective (half-light) radii of about 2 pc with the red ones being about 30% smaller than the blue ones. We identify many similarities between the Sombrero's GC system and those of both late type spirals and early-type galaxies. Thus both the GC system and the Hubble type of the Sombrero galaxy appear to be intermediate in their nature.

Theoretical time-dependent and two-component chromospheric models for late-type dwarfs are constructed based on acoustic and magnetic wave heating mechanisms. The models are used to predict the theoretical range of chromospheric activity for these stars. Comparison of this range with the one established observationally shows that the wave heating alone can explain most but not all of the observed range of stellar activity.

WOS: 000171087200026, The RS CVn type eclipsing binary MM Herculis was observed photo-electrically using B, V and R filters in 1998 and 1999 and the light and colour curves were obtained. Spectroscopic observations were carried out in 1999. The new light and colour curves are anti-correlated with the observations of 1997, i.e. the system is bluer when it is faintest. The variations of the brightnesses at each special phase (0.0, 0.25, 0.5, and 0.75) show an almost cyclic change with a period of about 6 years. This value is in good agreement with the migration periods of the spots suggested by us previously. The outside-of-eclipse wave in the light curve shows a minimum at phase approximate to0.50, and the mean colour of the system is the bluest at the same phase. When the spots located on the cooler component are seen around phase 0.50, the amplitude of the light variation outside eclipse is larger than the others. Such variation may be caused by the effect of the hotter component. Spectroscopic observations of the system were carried out in the spectral range 5860-6700 Angstrom. The subtraction of a "synthetic" spectrum, built up with spectra of inactive standard stars, allows us to detect an H alpha emission excess only from the cool component. New radial velocity measurements of the system were obtained and analyzed for the orbital parameters.

We present a study of the broadband UBV color profiles for 257 Sbc barred and non-barred galaxies. In our sample, the color gradients are negative (reddish inward) in approximately 59% of the objects, are almost null in 27%, and are positive in 14%, considering only the face-on galaxies, which represent approximately 51% of the sample. We have also found that barred galaxies are over-represented among the objects having null or positive gradients, indicating that bars act as a mechanism of homogenization of the stellar population. A correlation between the total and bulge colors was found, which is a consequence of an underlying correlation between the colors of bulges and disks found by others. Moreover, the mean total color is the same irrespective of the gradient regime, while bulges are bluer in galaxies with null or positive gradients, which indicates an increase of the star formation rate in the central regions of these objects. We found no correlation between color and O/H abundance gradients. We discuss this result considering a picture in which bars are a relatively fast recurrent phenomenon. These results are not compatible with a pure classical monolithic scenario for bulge and disk formation. On the contrary, they favor a scenario where both these components are evolving in a correlated process, in which stellar bars play a crucial role.(Abridged), Comment: Accepted for publication in The Astronomical Journal; 43 pages, 9 figures, 6 tables

We discuss Australia Telescope Compact Array (ATCA) HI 21cm data for the galaxy cluster A3128. Our observations are intentionally relatively shallow, and a blind search through our data cube yields (tentative) detections of only two galaxies, of which one is probably spurious. A3128 is part of the ESO Nearby Abell Cluster Survey (ENACS); redshifts are available for 193 galaxies in the A3128 region. For 148 of these galaxies the redshifts are such that the HI emission (if any) would lie within our data cube. We use the known redshifts of these galaxies to coadd their spectra and thus improve our sensitivity to HI emission. The technique is fairly successful -- the coadded spectra allow detection of an average mass content of ~ 9x10^8 Msun, almost an order of magnitude lower than for direct detection of individual objects. By dividing the total galaxy sample into subsamples we find that the gas content of late type galaxies that lie outside the X-ray emitting core of the cluster is substantially higher than that of those within the core. Even outside the X-ray emitting region the distribution of gas-rich galaxies in the cluster is not uniform, we find that gas-rich galaxies are concentrated in the east of the cluster. This is consistent with earlier analyses of the kinematics of the galaxies in A3128 which indicate the presence of subclustering. In summary we find that coadding spectra is a powerful tool for the study of HI in cluster galaxies, and suggest that this technique could be applied to substantially increase the redshift range over which such observations could be carried out., Comment: 8pages, 7 figures accepted for publication in A&A

Measurements of the general magnetic fields of active, late-type stars obtained with the 2.6-m Sha % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0Jd9sq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaqcKbay-lqadY% gagaafaaaa!38A5! $$\overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\smile}$}}{l} $$ n telescope of the Crimean Astrophysical Observatory are reported. Statistically significant values of the magnetic fields of ∈ Eri and 61 Cyg A have been detected. The magnetic fields range from −10 to 21 G. The magnetic-field values for ∈ Eri and 61 Cyg A exceed the solar field by an order of magnitude; ∈ Eri is more active than the Sun, while 61 Cyg A has approximately the same activity level as the Sun. There is some evidence for variations in the general magnetic fields of these stars associated with their axial rotation.

We present a statistical analysis of mid/far-IR emission properties for a mixed morphology (E/S0 + S/I) sample of galaxy pairs based on a new co-addition of the IRAS database. The sample is large and diverse enough (~130 pairs) to permit discrimination of pairs by component morphologies and interaction classes. It samples a large enough volume of space to enable a nonparametric estimate of the far-infrared luminosity function (FIRLF). We find average factors of 3 and 5 enhancement in FIR and 25 μm luminosities, respectively, for the late-type components relative to an isolated galaxy control sample. This is interpreted as the MIR/FIR signature of interaction induced star formation. A more detailed study reveals (1) a strong correlation between the IR luminosity and interaction class, (2) a poor anticorrelation between IR luminosity and projected separation in pairs where 25 μm seems to be more sensitive than FIR, (3) an increase in the ratio of present to past star formation (IR luminosities scaled to LB luminosity) from early to late type spiral pair components, and (4) a high-mass (M ≥ 10 M⊙) star formation rate (SFR) higher in paired Sc spirals than that in isolated Sc galaxies by a factor ~2–3.