Polarimetry of an Intermediate-age Open Cluster: NGC 5617

We present polarimetric observations in the UBVRI bands of 72 stars located in the direction of the medium age open cluster NGC 5617. Our intention is to use polarimetry as a tool membership identification, by building on previous investigations intended mainly to determine the cluster's general characteristics rather than provide membership suitable for studies such as stellar content and metallicity, as well as study the characteristics of the dust lying between the Sun and the cluster. The obsevations were carried out using the five-channel photopolarimeter of the Torino Astronomical Observatory attached to the 2.15m telescope at the Complejo Astron\'omico El Leoncito (CASLEO; Argentina. We are able to add 32 stars to the list of members of NGC 5617, and review the situation for others listed in the literature. In particular, we find that five blue straggler stars in the region of the cluster are located behind the same dust as the member stars are and we confirm the membership of two red giants. The proposed polarimetric memberships are compared with those derived by photometric and kinematical methods, with excellent results. Among the observed stars, we identify 10 with intrinsic polarization in their light. NGC 5617 can be polarimetrically characterized with $P_{max}= 4.40$ and $\theta_{v}= 73^\circ.1$. The spread in polarization values for the stars observed in the direction of the cluster seems to be caused by the uneven distribution of dust in front of the cluster's face. Finally, we find that in the direction of the cluster, the interstellar medium is apparently free of dust, from the Sun's position up to the Carina-Sagittarius arm, where NGC 5617 seems to be located at its farthest border

Faint open clusters with 2MASS: BH 63, Lyng\aa 2, Lyng\aa 12 and King 20

Structural and dynamical parameters of faint open clusters are probed with quality 2MASS-photometry and analytical procedures developed for bright clusters. We derive fundamental parameters of the faint open clusters Lynga2, BH63, Lyng12 and King20, the last three of which have no prior determinations. We also focus on the structure and dynamical state of these clusters. 2MASS photometry with errors smaller than 0.2mag are used to build CMDs, RDPs, CMDs, luminosity and mass functions. Colour-magnitude filters are used to isolate probable member stars. Field-star decontamination is applied to Lynga2, Lynga12 and King20. Reddening values are in the range 0.22-1.9, with BH63 the most reddened object. Ages of Lynga2, King20, Lynga12 and BH63 are ~90, ~200, ~560 and 700Myr, respectively. The RDPs of Lynga12 and King20 are well-represented by King profiles. Total stellar masses (extrapolating the MFs to stars with 0.08Mo) range from ~340Mo (BH63) to ~2300Mo (Lynga12). Observed masses are \~1/4$ of these values. In all clusters the core mass function is flatter than the halo's. Faint open clusters can be probed with 2MASS when associated with colour-magnitude filters and field-star decontamination. BH63 appears to be in an advanced dynamical state, both in the core and halo. To a lesser degree the same applies to King20. Marginal evidence of dynamical evolution is present in the cores of Lynga2 and Lynga12.Comment: 11 pages, 8 figures. Astronomy & Astrophysics, accepted, 04/09/200

Kepler observations of variability in B-type stars

The analysis of the light curves of 48 B-type stars observed by Kepler is presented. Among these are 15 pulsating stars, all of which show low frequencies characteristic of SPB stars. Seven of these stars also show a few weak, isolated high frequencies and they could be considered as SPB/beta Cep hybrids. In all cases the frequency spectra are quite different from what is seen from ground-based observations. We suggest that this is because most of the low frequencies are modes of high degree which are predicted to be unstable in models of mid-B stars. We find that there are non-pulsating stars within the beta Cep and SPB instability strips. Apart from the pulsating stars, we can identify stars with frequency groupings similar to what is seen in Be stars but which are not Be stars. The origin of the groupings is not clear, but may be related to rotation. We find periodic variations in other stars which we attribute to proximity effects in binary systems or possibly rotational modulation. We find no evidence for pulsating stars between the cool edge of the SPB and the hot edge of the delta Sct instability strips. None of the stars show the broad features which can be attributed to stochastically-excited modes as recently proposed. Among our sample of B stars are two chemically peculiar stars, one of which is a HgMn star showing rotational modulation in the light curve.Comment: 19 pages, 11 figures, 4 table

Methods for improving open cluster fundamental parameters applied to M 52 and NGC 3960

We derive accurate parameters related to the CMD, structure and dynamical state of M52 and NGC3960, whose fields are affected by differential reddening. Compared to open clusters in different dynamical states studied with similar methods, the core and overall parameters of M52 are consistent with an open cluster more massive than 1000Mo and ~60Myr old, with some mass segregation in the inner region. The core of NGC3960 is in an advanced dynamical state with strong mass segregation in the core/halo region, while the somewhat flat overall MF (x~1.07) suggests low-mass star evaporation. The excess stellar density in the core may suggest post-core collapse. The dynamical evolution of NGC3960 may have been accelerated by the tidal Galactic field, since it lies \~0.5kpc inside the Solar circle.Comment: 15 pages and 8 figures. Astronomy and astrophysics, in pres

Detailed chemical composition of the open cluster IC 4651: The iron peak, alpha elements, and Li

We present a detailed chemical analysis of 22 stars along the colour-magnitude sequence of the intermediate-age (1.7 Gyr) open cluster IC 4651. We find for the cluster a well-defined Fe abundance of [Fe/H]= 0.10 +/- 0.03 (internal errors), with a reddening E(b-y)=0.091. We also derive abundances for the alpha elements Mg, Si, Ti, and Ca and find a moderate enhancement of the three former elements. Among the Fe group elements, Cr and Ni are slightly overabundant ([X/Fe] ~ 0.05). The Na abundance among the giants is more than 0.2 dex higher than in the dwarfs. We interpret this as due to dredge-up of 23Na in the giants. Li abundances show a well-defined pattern: the Solar-type stars have an almost constant Li abundance, just below that of the Hyades, and the Li-dip is pronounced and well determined. Turnoff stars just above the dip have a `cosmic' Li abundance, but within a very small range of magnitudes (0.25 mag) higher on the turnoff, Li drops by more than a factor 10 implying that some extra mixing is required. Among the giants, two probable clump stars show detectable Li, while all the other (likely) RGB stars do not. We show that rotating stellar models including the most recent developments for meridional circulation and turbulence by shear instabilities explain very well the observed Li pattern. The possibility remains open that the giants exhibiting the highest Li abundances are actual RGB bump stars which have just been through the so-called "lithium flash".Comment: To appear in A&

Atmospheric parameters and pulsational properties for a sample of δ\delta\,Sct, γ\gamma\,Dor, and hybrid {\it Kepler} targets

We report spectroscopic observations for 19 $\delta$\,Sct candidates observed by the {\it Kepler} satellite both in long and short cadence mode. For all these stars, by using spectral synthesis, we derive the effective temperature, the surface gravity and the projected rotational velocity. An equivalent spectral type classification has been also performed for all stars in the sample. These determinations are fundamental for modelling the frequency spectra that will be extracted from the {\it Kepler} data for asteroseismic inference. For all the 19 stars, we present also periodograms obtained from {\it Kepler} data. We find that all stars show peaks in both low- ($\gamma$\,Dor; g mode) and high-frequency ($\delta$\,Sct; p mode) regions. Using the amplitudes and considering 5\,c/d as a boundary frequency, we classified 3 stars as pure $\gamma$\,Dor, 4 as $\gamma$\,Dor\,-\,$\delta$\ hybrid, Sct, 5 as $\delta$\,Sct\,-\,$\gamma$\,Dor hybrid, and 6 as pure $\delta$\,Sct. The only exception is the star KIC\,05296877 which we suggest could be a binary.Comment: 11 pages, 6 figures, MNRAS main journa

The Evolutionary Status of Be Stars: Results from a Photometric Study of Southern Open Clusters

Be stars are a class of rapidly rotating B stars with circumstellar disks that cause Balmer and other line emission. There are three possible reasons for the rapid rotation of Be stars: they may have been born as rapid rotators, spun up by binary mass transfer, or spun up during the main-sequence (MS) evolution of B stars. To test the various formation scenarios, we have conducted a photometric survey of 55 open clusters in the southern sky. Of these, five clusters are probably not physically associated groups and our results for two other clusters are not reliable, but we identify 52 definite Be stars and an additional 129 Be candidates in the remaining clusters. We use our results to examine the age and evolutionary dependence of the Be phenomenon. We find an overall increase in the fraction of Be stars with age until 100 Myr, and Be stars are most common among the brightest, most massive B-type stars above the zero-age MS (ZAMS). We show that a spin-up phase at the terminal-age MS (TAMS) cannot produce the observed distribution of Be stars, but up to 73% of the Be stars detected may have been spun-up by binary mass transfer. Most of the remaining Be stars were likely rapid rotators at birth. Previous studies have suggested that low metallicity and high cluster density may also favor Be star formation. Our results indicate a possible increase in the fraction of Be stars with increasing cluster distance from the Galactic center (in environments of decreasing metallicity). However, the trend is not significant and could be ruled out due to the intrinsic scatter in our data. We also find no relationship between the fraction of Be stars and cluster density.Comment: 44 pages, accepted by ApJS (minor changes to introduction, expanded conclusions per referee comments

Treatment with a GnRH analogue: effects on hemostatic risk factors for thrombo-embolic disease

OBJECTIVE--Steroid hormones, especially estrogens, are known to affect hemostatic risk factors for thromboembolism, cardiovascular disease, and stroke. We examined these risk factors during depression of the serum estradiol concentration by a GnRH analogue. DESIGN--Patients were treated with a GnRH analogue, goserelin (Zoladex), 3.6 mg/inj monthly, for a period of 6 months. Blood samples were collected during and after treatment and in a control group. In ten patients a blood sample was also drawn before treatment. Measurements were made of serum estradiol, and the plasma concentrations of tissue-type plasminogen activator (t-PA) antigen, plasminogen activator inhibitor (PAI-1) antigen, antithrombin III (AT III) and protein C activity, factor VII (FVII) antigen, and fibrinogen. SETTING--Outpatient clinics at the Departments of Obstetrics and Gynecology at two university hospitals in southern Sweden. PARTICIPANTS--Twenty-seven women with endometriosis were consecutively included. A control group comprised 20 women with normal menstrual cycles. MAIN OUTCOME MEASURES--The concentrations of the hemostatic components during depression of the serum estradiol concentrations, as compared to those during normal ovulatory cycles. RESULTS--Serum estradiol concentrations during treatment were comparable to those of postmenopausal women (mean, 23.2 pmol/L), and both AT III and protein C activity were significantly increased (P < .005 and P < .02, respectively). As compared to controls, plasma concentrations of PAI-1 and t-PA of patients were significantly higher both during and after treatment. In the subgroup also studied prior to treatment, there were no differences in hemostatic components, when comparing pretreatment and posttreatment values. CONCLUSIONS--Treatment with this type of GnRH analogue for 6 months is safe with regard to its effect on hemostatic risk factors. The similar responses of t-PA and its inhibitor, PAI-1, to alterations in estrogen levels as well as inflammatory reactivity presumably constitute a balance mechanism preserving fibrinolytic defenses

Increased expression of interleukin 6 in term compared to the first trimester human placental villi

Hormone and Metabolic Research325164-168HMMR

Brain-specific NSE and S-100 proteins in umbilical blood after normal delivery

BACKGROUND: To determine normal blood levels of brain-specific proteins S-100 and neuron specific enolase (NSE) in healthy newborns and their mothers following uncomplicated birth. METHODS: Umbilical artery and vein blood and maternal venous blood was collected at 112 consecutive uncomplicated deliveries. Venous blood samples were taken from 18 of the neonates 3 days after birth. S-100 and NSE were analyzed quantitatively by double antibody immunoluminometric assay (Sangtec Medical AB, Sweden). RESULTS: Compared with adults, healthy neonates had higher levels of both S-100 and NSE. For S-100, median levels (range) were 1.10 microg/l (0.38-5.50 microg/l and 0.98 microg/l (0.43-2.70 microg/l) in umbilical artery and vein, respectively. For NSE, median levels (range) in umbilical artery blood and vein were 27 microg/l (10-140 microg/l) and 10.75 microg/l (8.80->/=200 microg/l) respectively. The maternal venous blood levels of both S-100 and NSE were significantly lower than in their infants. At 3 days of life, neonatal venous levels of the proteins were still high: S-100, 0.48-9.70 microg/l; NSE, 17->/=200 microg/l. In contrast to adults, haemolysis affected the S-100 levels in umbilical blood significantly. CONCLUSION: Concentrations of both S-100 and NSE in blood are greater in newborns after normal birth than in healthy adults. The higher levels in umbilical artery blood than in umbilical vein blood are consistent with a fetal origin of these proteins. High levels in venous blood at 3 days of life suggest that the high levels at birth are not related to the birth process but reflect a high activity of these proteins during fetal development