Supernovae astrophysics from Middle Age documents

The supernova explosion of 1054 AD, which originated the Crab Nebula and Pulsar, is probably the astronomical event which has been most deeply studied by means of historical sources. However, many mysteries and inconsistencies, both among the different sources and between what is deduced by the historical records and the present day astronomical data, are demanding extraordinary efforts by theoretical astrophysicists in order to put all the data in a meaningful framework. An accurate analysis of the historical sources, like the one we are presenting here, may contribute to solve some of these problems.Comment: in: Proc. of the IAU Symposium no.230, "Populations of High Energy Sources in Galaxies", held in Dublin (Ireland), August 15-19, 2005. Evert J.A. Meurs & G. Fabbiano, eds. (in press

The sky from the high terrace. study on the orientation of the Ziqqurat in Ancient Mesopotamia

The ziqqurat is the symbol of the Mesopotamian sacred architecture in the western thought. This monument, standardized at the end of the III millennium BC by the kings of the Third Dynasty of Ur, has changed during the history of Mesopotamia its shape and architecture, but remained till the end of the Neo-Babylonian Period in the I millennium BC the highest structure of the city. The ziqqurat is the only monument visible over the settlements wall with a strong visual impact around the urban and the countryside landscape. Despite its simple structural function, a high mud brick platform to sustain an upper temple, the ziqqurat appears in the Mesopotamian art and literature as a structure of primary importance, a connection between the earth, domain of the god Enlil, with the sky, domain of the god Anu. The ideological function to connect the earth and the sky was related also with the rituals performed in the high temples built above these monuments, usually linked with important seasonal royal rituals. The paper will analyze this particular aspect of ziqqurat, looking also to their orientations and to the changing in the relationship between these monuments and the urban landscape through the centuries

The 2006 hot phase of Romano's star (GR 290) in M33

Understanding the nature of the instabilities of LBVs is important to understand the late evolutionary stages of very massive stars. We investigate the long term, S Dor-type variability of the luminous blue variable GR290 (Romano's star) in M33, and its 2006 minimum phase. New spectroscopic and photometric data taken in November and December 2006 were employed in conjunction with already published data on GR290 to derive the physical structure of GR290 in different phases and the time scale of the variability. We find that by the end of 2006, GR 290 had reached the deepest visual minimum so far recorded. Its present spectrum resembles closely that of the Of/WN9 stars, and is the hottest so far recorded in this star (and in any LBV as well), while its visual brightness decreased by about 1.4 mag. This first spectroscopic record of GR290 during a minimum phase confirms that, similarly to AG Car and other LBVs, the star is subject to ample S Dor-type variations, being hotter at minimum, suggesting that the variations take place at constant bolometric luminosity.Comment: 4 figures, 1 table, accepted for publication in A&A Letter

Raman identification of cuneiform tablet pigments. Emphasis and colour technology in ancient Mesopotamian mid-third millennium

In the modern age, there is a large number of ways to manage a written text, from bolding or underlining some words with the preferred PC editing software down to animated gifs or emoticons for short edited text of mobile messaging and social posting. The task is to catch the eye and rapidly convey the important message. Besides the almost endless opportunities of high-tech displays, to put emphasis on a text written on a hard support mainly relies on changing the editing style, by applying bold, italic or underline style to selected words or phrases and exploiting the characteristic of human eye to be sensible to the change of brightness into a written text

The orientation of the Mithraea in Ostia Antica

We conducted an investigation on the orientations and geometrical content of the Mithraea of Ostia Antica. A geometrical CAD study based on the most reliable plans from the Archives of the Sovrintendenza Speciale per il Colosseo, il MNR e l’Area Archeologica di Roma – Ostia Antica, aside with the identification of geometrical and numerical schemes and associated length units, allowed us to identify the axes of the Mithraea. Then the orientations of the axes were measured on field by means of a professional compass with ± 0.5° uncertainty. The distribution of these measured azimuths follows the topography of the city. On the contrary, the Decumanus, the main street of the town, presents an indubitable orientation toward the Winter Solstice Sunset. This was ascertained by measuring the coordinates of four significant points along the street with the help of a palmar Trimble GPS which averages 100 measures per point. The exceptional density of Mithraea in Ostia led us to suppose that a symbolic cosmic-solar value is to be searched in the orientation as a whole of the town itself, founded half a millennium before the first presence of Mithraism in Rome. The Decumanus could be considered the very holder of this symbolic value with its orientation toward the Winter Solstice Sunset, possibly making of Ostia a very special place for Mithraicism

Chandra Detects the Rare Oxygen-type Wolf-Rayet Star WR 142 and OB Stars in Berkeley 87

We present first results of a Chandra X-ray observation of the rare oxygen-type Wolf-Rayet star WR 142 (= Sand 5 = St 3) harbored in the young, heavily-obscured cluster Berkeley 87. Oxygen type WO stars are thought to be the most evolved of the WRs and progenitors of supernovae or gamma ray bursts. As part of an X-ray survey of supposedly single Wolf-Rayet stars, we observed WR 142 and the surrounding Berkeley 87 region with Chandra ACIS-I. We detect WR 142 as a faint, yet extremely hard X-ray source. Due to weak emission, its nature as a thermal or nonthermal emitter is unclear and thus we discuss several emission mechanisms. Additionally, we report seven detections and eight non-detections by Chandra of massive OB stars in Berkeley 87, two of which are bright yet soft X-ray sources whose spectra provide a dramatic contrast to the hard emission from WR 142.Comment: To appear in the Astrophysical Journa

Wind and nebula of the M33 variable GR290 (WR/LBV)

Context: GR290 (M33/V532=Romano's Star) is a suspected post-LBV star located in M33 galaxy that shows a rare Wolf-Rayet spectrum during its minimum light phase. In spite of many studies, its atmospheric structure, its circumstellar environment and its place in the general context of massive stars evolution is poorly known. Aims: Detailed study of its wind and mass loss, and study of the circumstellar environment associated to the star. Methods: Long-slit spectra of GR290 were obtained during its present minimum luminosity phase with the GTC together with contemporaneous BVRI photometry. The data were compared with non-LTE model atmosphere synthetic spectra computed with CMFGEN and with CLOUDY models for ionized interstellar medium regions. Results: The current $m_V=18.8$ mag, is the faintest at which this source has ever been observed. The non-LTE models indicate effective temperature $T_{eff}$=27-30 kK at radius $R_{2/3}$=27-21 Rsun and mass loss rate $\dot{M}=1.5\times10^{-5}$ Msun yr$^{-1}$. The terminal wind speed $V_\infty$=620 ${\rm km~s^{-1}}$ is faster than ever before recorded while the current luminosity $L_*=(3.1-3.7)\times 10^5$ Lsun is the lowest ever deduced. It is overabundant in He and N and underabundant in C and O. It is surrounded by an unresolved compact HII region with dimensions $\leq$4 pc, from where H-Balmer, HeI lines and [OIII] and [NII] are detected. In addition, we find emission from a more extended interstellar medium (ISM) region which appears to be asymmetric, with a larger extent to the East (16-40 pc) than to the West. Conclusions: In the present long lasting visual minimum, GR290 is in a lower bolometric luminosity state with higher mass loss rate. The nearby nebular emission seems to suggest that the star has undergone significant mass loss over the past $10^4-10^5$ years and is nearing the end stages of its evolution.Comment: submitted to A&A, 12 pages, 9 figures, 7 table