The Formation and Evolution of Massive Stellar Clusters in IC 4662

We present a multiwavelength study of the formation of massive stellar clusters, their emergence from cocoons of gas and dust, and their feedback on surrounding matter. Using data that span from radio to optical wavelengths, including Spitzer and Hubble ACS observations, we examine the population of young star clusters in the central starburst region of the irregular Wolf-Rayet galaxy IC 4662. We model the radio-to-IR spectral energy distributions of embedded clusters to determine the properties of their HII regions and dust cocoons (sizes, masses, densities, temperatures), and use near-IR and optical data with mid-IR spectroscopy to constrain the properties of the embedded clusters themselves (mass, age, extinction, excitation, abundance). The two massive star-formation regions in IC 4662 are excited by stellar populations with ages of ~ 4 million years and masses of ~ 3 x 10^5 M_sun (assuming a Kroupa IMF). They have high excitation and sub-solar abundances, and they may actually be comprised of several massive clusters rather than the single monolithic massive compact objects known as Super Star Clusters (SSCs). Mid-IR spectra reveal that these clusters have very high extinctions, A_V ~ 20-25 mag, and that the dust in IC 4662 is well-mixed with the emitting gas, not in a foreground screen.Comment: 7 pages, 11 figures, to appear in proceedings of the conference "Young Massive Star Clusters: Initial Conditions and Environments ", held in Granada, Spain, September 200

Stellar dynamics in young clusters: the formation of massive runaways and very massive runaway mergers

In the present paper we combine an N-body code that simulates the dynamics of young dense stellar systems with a massive star evolution handler that accounts in a realistic way for the effects of stellar wind mass loss. We discuss two topics: 1. The formation and the evolution of very massive stars (with a mass >120 Mo) is followed in detail. These very massive stars are formed in the cluster core as a consequence of the successive (physical) collison of 10-20 most massive stars of the cluster (the process is known as runaway merging). The further evolution is governed by stellar wind mass loss during core hydrogen burning and during core helium burning (the WR phase of very massive stars). Our simulations reveal that as a consequence of runaway merging in clusters with solar and supersolar values, massive black holes can be formed but with a maximum mass of 70 Mo. In small metallicity clusters however, it cannot be excluded that the runaway merging process is responsible for pair instability supernovae or for the formation of intermediate mass black holes with a mass of several 100 Mo. 2. Massive runaways can be formed via the supernova explosion of one of the components in a binary (the Blaauw scenario) or via dynamical interaction of a single star and a binary or between two binaries in a star cluster. We explore the possibility that the most massive runaways (e.g., zeta Pup, lambda Cep, BD+433654) are the product of the collision and merger of 2 or 3 massive stars.Comment: Updated and final versio

The Athena X-ray Integral Field Unit: a consolidated design for the system requirement review of the preliminary definition phase

Instrumentatio

A survey of interstellar sulphur abundance and implications for PII oscillator strengths

SIGLEAvailable from British Library Document Supply Centre- DSC:8053.4153(RAL--86-017) / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Optical/X-ray correlations during the V404 Cygni June 2015 outburst

International audienceContext. We present a multiwavelength analysis of the simultaneous optical and X-ray light curves of the microquasar V404 Cyg during the June 2015 outburst.Aims. We have performed a comprehensive analysis of all the INTEGRAL/IBIS, JEM–X, and OMC observations during the brightest epoch of the outburst, along with complementary NuSTAR, AAVSO, and VSNET data, to examine the timing relationship between the simultaneous optical and X-ray light curves, in order to understand the emission mechanisms and physical locations.Methods. We have identified all optical flares that have simultaneous X-ray observations, and performed a cross-correlation analysis to estimate the time delays between the optical and soft and hard X-ray emission. We also compared the evolution of the optical and X-ray emission with the hardness ratios.Results. We have identified several types of behaviour during the outburst. On many occasions, the optical flares occur simultaneously with X-ray flares, but at other times, positive and negative time delays between the optical and X-ray emission are measured.Conclusions. We conclude that the observed optical variability is driven by different physical mechanisms, including reprocessing of X-rays in the accretion disc and/or the companion star, interaction of the jet ejections with surrounding material or with previously ejected blobs, and synchrotron emission from the jet.Key words: X-rays: binaries / stars: black holes / accretion, accretion disk

Notes on Old Stone Constructions of West and Central Sahara

[ES] El presente trabajo trata acerca de la tumba de TIN-HUMAN, HOGGAR, y la describe presentándola en relacón con los «monumentos en capilla» de Négrine, Tafilalet y Oeste del Sahara. Además, incluye comentarios sobre la rareza de las tumbas rectangulares con habitaciones interiores. Se hace una razonable exposición de los «monumentos fusiformes», conectados con la tradición del tránsito por barco a la vida futura. La tumba de TIN-HINAN combina características de los monumentos en capilla o habitación con aquellas otras de «monumentos de deambulatorio complejo».[EN] This work deals with the tomb of Tin-Hinan, Hoggar, and describes it as presenting a relationship with the «monuments à chapelle» of Négrine, Tafilalet and West Sahara which also have very large chambers. It also includes a commentarity on the rarity of rectangular tombs with interior chambers. It proposes a reasonable explanation of the «fusiformes monuments» as being connected with a tradition of a journey by ship to the after-life (this being suggested by their very shape). The tomb of Tin-Hinan combines characteristics of the «monument à chapelle ou à chambre» with those of a «monument à déambulatoire complexe»

Long-term optical and X-ray variability of the Be/X-ray binary H 1145–619: Discovery of an ongoing retrograde density wave

Context. Multiwavelength monitoring of Be/X-ray binaries is crucial to understand the mechanisms producing their outbursts. H 1145-619 is one of these systems, which has recently displayed X-ray activity.Aims. We investigate the correlation between the optical emission and X-ray activity to predict the occurrence of new X-ray outbursts from the inferred state of the circumstellar disc.Methods. We have performed a multiwavelength study of H 1145-619 from 1973 to 2017 and present here a global analysis of its variability over the last 40 yr. We used optical spectra from the SAAO, SMARTS, and SALT telescopes and optical photometry from the Optical Monitoring Camera (OMC) onboard INTEGRAL and from the All Sky Automated Survey (ASAS). We also used X-ray observations from INTEGRAL/JEM-X, and IBIS to generate the light curves and combined them with Swift/XRT to extract the X-ray spectra. In addition, we compiled archival observations and measurements from the literature to complement these data.Results. Comparing the evolution of the optical continuum emission with the Hα line variability, we identified three different patterns of optical variability: first, global increases and decreases of the optical brightness, observed from 1982 to 1994 and from 2009 to 2017, which can be explained by the dissipation and replenishment of the circumstellar disc; second, superorbital variations with a period of Psuperorb ≈ 590 days, observed in 2002–2009, which seems to be related to the circumstellar disc; and third, optical outbursts, observed in 1998–1999 and 2002–2005, which we interpret as mass ejections from the Be star. We discovered the presence of a retrograde one-armed density wave, which appeared in 2016 and is still present in the circumstellar disc.Conclusions. We carried out the most complete long-term optical study of the Be/X-ray binary H 1145-619 in correlation with its X-ray activity. For the first time, we found the presence of a retrograde density perturbation in the circumstellar disc of a Be/X-ray binary