Metallicity in the Galactic Center: The Arches cluster

We present a quantitative spectral analysis of five very massive stars in the Arches cluster, located near the Galactic center, to determine stellar parameters, stellar wind properties and, most importantly, metallicity content. The analysis uses a new technique, presented here for the first time, and uses line-blanketed NLTE wind/atmosphere models fit to high-resolution near-infrared spectra of late-type nitrogen-rich Wolf-Rayet stars and OfI+ stars in the cluster. It relies on the fact that massive stars reach a maximum nitrogen abundance that is related to initial metallicity when they are in the WNL phase. We determine the present-day nitrogen abundance of the WNL stars in the Arches cluster to be 1.6% (mass fraction) and constrain the stellar metallicity in the cluster to be solar. This result is invariant to assumptions about the mass-luminosity relationship, the mass-loss rates, and rotation speeds. In addition, from this analysis, we find the age of the Arches cluster to be 2-2.5Myr, assuming coeval formation

Suction v. conventional curettage in incomplete abortion A randomised controlled trial

This randomised controlled trial of 357 patients who had had an incomplete abortion compared suction curettage with conventional curettage for evacuation ofthe uterus. The 179 patients undergoing suction curettage had a significantly lower intra-operative blood loss (P < 0,0001) and a significantly higher mean haemoglobin level at follow-up compared with the 178 patients who had conventional curettage. Suction curettage was a faster procedure and less painful. No difference was found between the two groups with regard to the incidence ofpost-abortal sepsis, or the re-evacuation rate. No problems were encountered with the use of suction curettage in the presence of uterine sepsis. In an era where blood transfusions should be kept to an absolute minimum, suction curettage will help to save blood in several ways

A FEROS spectroscopic study of the extreme O supergiant He 3-759

We present a study of the extreme O-type supergiant He 3-759 using new high-resolution FEROS data, revealing that it is a near spectroscopic twin of HD 151804 (O8 Iaf). We investigate the extinction towards He 3-759 using a variety of methods, revealing A_V ~ 4.7 mag. If we assume He 3-759 has an identical absolute K-band magnitude to HD 151804 we find that it lies in the Sagittarius-Carina spiral arm at a distance of ~6.5 kpc. We derive the physical and wind properties for He 3-759, revealing T* = 30.5 kK, log L/L(sun) = 5.9 and dM/dt = 10^-5.17 M(sun)/yr for a clumped wind whose terminal velocity is estimated at 1000 km/s. The atmosphere of He 3-759 is enriched in helium (X_He = 49%) and nitrogen (X_N = 0.3%). A reanalysis of HD 151804 and HD 152408 (WN9ha) reveals similar parameters except that the WN9ha star possesses a stronger wind and reduced surface hydrogen content. HD 151804 and HD 152408 lie within the Sco OB1 association, with initial masses of ~60 M(sun) and ages ~2.7 Myr, consistent with NGC 6231 cluster members using standard Geneva isochrones. Improved agreement with observed surface abundances are obtained for similar initial masses with more recent Geneva group predictions from which higher ages of ~3.75 Myr are obtained. No young, massive star cluster is known to be associated with He 3-759.Comment: 6 pages, 4 figures, accepted for A&

SwSt 1: an O-rich planetary nebula around a C-rich central star

The hydrogen-deficient carbon-rich [WCL] type central star HD167362 and its oxygen-rich planetary nebula (PN) SwSt~1 are investigated. The nebular chemistry might indicate a recent origin for the carbon-rich stellar spectrum. Its stellar and nebular properties might therefore provide further understanding of the origin of the [WCL] central star class. The UV-IR stellar spectra are modelled with state of the codes and show ~40kK central star with a wind and a C/O~3, indicative of efficient third dredge-up. The synthetic stellar flux distribution is used to model the high density, compact PN, which has a solar C/O ratio, is still enshrouded by 1200K and 230K dust shells and, reported here for the first time, in molecular hydrogen. Although it appears that the change in C/O ratio has been recent, the published spectroscopy since 1895 has been re-examined and no clear spectral change is seen. If an event occurred that has turned it into a hydrogen-deficient central star, it did not happen in the last 100 years.Comment: 31 pages, 19 figures (some are gif files), MNRAS in pres

The question of Early Lapita settlements in Remote Oceania and reliance on horticulture revisited: new evidence from plant microfossil studies at Reef/Santa Cruz, south-east Solomon Islands

Since the earliest discoveries of Lapita sites in Remote Oceania there has been ongoing debate about the nature of Pacific island colonisation. In the 1970s, based on the archaeological material from the SE-RF-2 and SE-RF-6 sites on the Reef Islands in the SE Solomons, Roger Green proposed that early Lapita communities there must have relied on horticulture as the mainstay of subsistence. Our analyses of phytoliths and starch in sediments and on pottery has found evidence for burning, food preparation and cooking in conjunction with a suite of wild and domesticated plants indicative of horticulture. Starch and phytoliths from seeded Australimusa (syn: Callimusa) bananas as well as domesticated Eumusa (syn: Musa) bananas were recovered, as well as Colocasia esculenta (taro) starch, and Metroxylon sp. (sago palm) phytoliths. Hence, Green’s early hypothesis finds support, but more analyses, together with more precise dating are needed to clarify the time taken to establish sustainable horticulture. The importation of selected plants is confirmed, with potential sources being the Bismarck region or stop-over islands along the way. This was followed by ongoing on-site breeding and/or new introductions from further human migrations into the region and establishment of trade and exchange networks.Introduction - Site locations and background Methods - Pottery - Sediments - Microfossil recording and identification Results - Starch Analysis - Phytolith Analysis SE-RF-2 SE-RF-6 Musaceae starch Musaceae phytoliths Discussion Conclusio

HII Shells Surrounding Wolf-Rayet stars in M31

We present the results of an ongoing investigation to provide a detailed view of the processes by which massive stars shape the surrounding interstellar medium (ISM), from pc to kpc scales. In this paper we have focused on studying the environments of Wolf-Rayet (WR) stars in M31 to find evidence for WR wind-ISM interactions, through imaging ionized hydrogen nebulae surrounding these stars. We have conducted a systematic survey for HII shells surrounding 48 of the 49 known WR stars in M31. There are 17 WR stars surrounded by single shells, or shell fragments, 7 stars surrounded by concentric limb brightened shells, 20 stars where there is no clear physical association of the star with nearby H-alpha emission, and 4 stars which lack nearby H-alpha emission. For the 17+7 shells above, there are 12 which contain one or two massive stars (including a WR star) and that are <=40 pc in radius. These 12 shells may be classical WR ejecta or wind-blown shells. Further, there may be excess H-alpha point source emission associated with one of the 12 WR stars surrounded by putative ejecta or wind-blown shells. There is also evidence for excess point source emission associated with 11 other WR stars. The excess emission may arise from unresolved circumstellar shells, or within the extended outer envelopes of the stars themselves. In a few cases we find clear morphological evidence for WR shells interacting with each other. In several H-alpha images we see WR winds disrupting, or punching through, the walls of limb-brightened HII shells.Comment: 20 pages, 4 figures (in several parts: some .jpg and others .ps), accepted to AJ (appearing Oct, 1999

Microbotanical signatures of kreb: differentiating inflorescence phytoliths from northern African wild grasses

Throughout northern Africa, evidence for an intensification of wild grass gathering is reflected in Holocene archaeological contexts. However, both the recovery of macrobotanical assemblages and the specificity of their taxonomic classification are heavily influenced by food processing and post-depositional conditions. In contrast, inflorescence phytoliths provide high levels of taxonomic specificity and preserve well in most archaeological contexts. This study analyses the in situ morphology of inflorescence phytoliths from modern specimens of nine wild C4 grass species commonly observed in ethnographic studies and recovered in seed assemblages from archaeological contexts across northern Africa. Morphological differences in Interdigitate phytoliths within the fertile florets of six Paniceae species enabled differentiation between them. The morphological parameters established in this study provide an additional resource for archaeological and palaeoecological analyses using phytoliths, which demonstrates the effectiveness of applying this method to African wild grass species.Introduction Materials and methods - Selected species - Sample preparation and analysis - Phytolith nomenclature Results Variations in phytolith occurrence between inflorescence bracts - Glumes - Lemmas - Paleas Classification of Interdigitate morphotypes Discussion Conclusion

The Arches cluster revisited: II. A massive eclipsing spectroscopic binary in the Arches cluster

We have carried out a spectroscopic variability survey of some of the most massive stars in the Arches cluster, using K-band observations obtained with SINFONI on the VLT. One target, F2, exhibits substantial changes in radial velocity; in combination with new KMOS and archival SINFONI spectra, its primary component is found to undergo radial velocity variation with a period of 10.483+/-0.002 d and an amplitude of ~350 km/s-1. A secondary radial velocity curve is also marginally detectable. We reanalyse archival NAOS-CONICA photometric survey data in combination with our radial velocity results to confirm this object as an eclipsing SB2 system, and the first binary identified in the Arches. We model it as consisting of an 82+/-12 M⊙ WN8-9h primary and a 60+/-8 M⊙ O5-6 Ia+ secondary, and as having a slightly eccentric orbit, implying an evolutionary stage prior to strong binary interaction. As one of four X-ray bright Arches sources previously proposed as colliding-wind massive binaries, it may be only the first of several binaries to be discovered in this cluster, presenting potential challenges to recent models for the Arches' age and composition. It also appears to be one of the most massive binaries detected to date; the primary's calculated initial mass of >~120 M⊙ would arguably make this the most massive binary known in the Galaxy