On the nature of the galactic early-B hypergiants

Aims. Despite their importance to a number of astrophysical fields, the lifecycles of very massive stars are still poorly defined. In order to address this shortcoming, we present a detailed quantitative study of the physical properties of four early-B hypergiants (BHGs) of spectral type B1-4 Ia+; Cyg OB2 #12, ζ1 Sco, HD 190603 and BP Cru. These are combined with an analysis of their long-term spectroscopic and photometric behaviour in order to determine their evolutionary status. Methods. Quantitative analysis of UV–radio photometric and spectroscopic datasets was undertaken with a non-LTE model atmosphere code in order to derive physical parameters for comparison with apparently closely related objects, such as B supergiants (BSGs) and luminous blue variables (LBVs), and theoretical evolutionary predictions. Results. The long-term photospheric and spectroscopic datasets compiled for the early-B HGs revealed that they are remarkably stable over long periods ( ≥ 40 yrs), with the possible exception of ζ1 Sco prior to the 20th century; in contrast to the typical excursions that characterise LBVs. Quantitative analysis of ζ1 Sco, HD 190603 and BP Cru yielded physical properties intermediate between BSGs and LBVs; we therefore suggest that BHGs are the immediate descendants and progenitors (respectively) of such stars, for initial masses in the range ~30−60 M⊙. Comparison of the properties of ζ1 Sco with the stellar population of its host cluster/association NGC 6231/Sco OB1 provides further support for such an evolutionary scenario. In contrast, while the wind properties of Cyg OB2 #12 are consistent with this hypothesis, the combination of extreme luminosity and spectroscopic mass (~110 M⊙) and comparatively low temperature means it cannot be accommodated in such a scheme. Likewise, despite its co-location with several LBVs above the Humphreys-Davidson (HD) limit, the lack of long term variability and its unevolved chemistry apparently excludes such an identification. Since such massive stars are not expected to evolve to such cool temperatures, instead traversing an O4-6Ia → O4-6Ia+ → WN7-9ha pathway, the properties of Cyg OB2 #12 are therefore difficult to understand under current evolutionary paradigms. Finally, we note that as with AG Car in its cool phase, despite exceeding the HD limit, the properties of Cyg OB2 #12 imply that it lies below the Eddington limit – thus we conclude that the HD limit does not define a region of the HR diagram inherently inimical to the presence of massive stars.

On the nature of candidate luminous blue variables in M 33

Context. Luminous blue variables (LBVs) are a class of highly unstable stars that have been proposed to play a critical role in massive stellar evolution as well as being the progenitors of some of the most luminous supernovae known. However the physical processes underlying their characteristic instabilities are currently unknown. Aims. In order to provide observational constraints on this behaviour we have initiated a pilot study of the population of (candidate) LBVs in the Local Group galaxy M 33. Methods. To accomplish this we have obtained new spectra of 18 examples within M 33. These provide a baseline of ≥ 4 yr with respect to previous observations, which is well suited to identifying LBV outbursts. We also employed existing multi-epoch optical and mid-IR surveys of M 33 to further constrain the variability of the sample and search for the presence of dusty ejecta. Results. Combining the datasets reveals that spectroscopic and photometric variability appears common, although in the majority of cases further observations will be needed to distinguish between an origin for this behavour in short lived stochastic wind structure and low level photospheric pulsations or coherent long term LBV excursions. Of the known LBVs we report a hitherto unidentified excursion of M 33 Var C between 2001-5, while the transition of the WNLh star B517 to a cooler B supergiant phase between 1993−2010 implies an LBV classification. Proof-of-concept quantitative model atmosphere analysis is provided for Romano’s star; the resultant stellar parameters being consistent with the finding that the LBV excursions of this star are accompanied by changes in bolometric luminosity. The combination of temperature and luminosity of two stars, the BHG [HS80] 110A and the cool hypergiant B324, appear to be in violation of the empirical Humphreys-Davidson limit. Mid-IR observations demonstrate that a number of candidates appear associated with hot circumstellar dust, although no objects as extreme as η Car are identified. The combined dataset suggests that the criteria employed to identify candidate LBVs results in a heterogeneous sample, also containing stars demonstrating the B[e] phenomenon. Of these, a subset of optically faint, low luminosity stars associated with hot dust are of particular interest since they appear similar to the likely progenitor of SN 2008S and the 2008 NGC 300 transient (albeit suffering less intrinsic extinction). Conclusions. The results of such a multiwavelength observational approach, employing multiplexing spectrographs and supplemented with quantitative model atmosphere analysis, appears to show considerable promise in both identifying and characterising the physical properties of LBVs as well as other short lived phases of massive stellar evolution.

The micrographic dictionary; a guide to the examination and investigation of the structure and nature of microscopic objects, by J. W. Griffith and Arthur Henfrey.

1, Text

On the nature of the holotype of Nipterella paradoxica (Billings) / [by] Matthew H. Nitecki --

v.16:no.11(1968)

[Forensic dispute on the nature of virtue], undated

Two drafts of a handwritten essay on the nature of virtue, beginning with the prompt, "Whether there be any Virtue in doing good to another merely for the sake of benefiting [sic] ourselves." The last verso is inscribed: "4 Forensic. read."

The Paradoxes of Moldovan Sports. An insight into the nature of the Transnistrian conflict. OSW Point of View, November 2011

Mutual relations in the area of sports, which in contemporary international contacts often not only reflect the true nature of political relations but sometimes even affect them, can be a valuable contribution to the analysis of this conflict’s nature. Why did the Transnistrian government, despite the use of anti-Moldovan rhetoric, agree to Transnistrian athletes representing Moldova during the Olympics and in other international competitions? Why does it accept the presence of sports teams from both banks of the Dniester playing in the same leagues? Why does Transnistria, despite being much smaller, predominate in many sports? How is it that Sheriff Tiraspol, the flagship football club of the business and political circles controlling Transnistria, managed to win the Moldovan championship ten times in a row and is the main source of players for Moldova’s national team? Does sport really ‘know no borders’ or perhaps the border on the Dniester is different than seems at first sight?

Reflections on the Nature of Preferentialism in Services Trade

The Graduate Institute organized an academic workshop and roundtable on the occasion of EFTA's 50th Anniversary in Geneva under the chairmanship of H.E. Doris Leuthard, President of the Swiss Confederation. Pierre Sauve, Deputy Managing Director and Director of Studies, WTI and Co-leader, NCCR-Trade work programme on preferentialism and Anirudh Shingal, Senior Research Fellow, WTI and Co-leader, NCCR-Trade work programme on impact assessment of trade, co-authored a paper on the nature of preferentialism in services trade, which Anirudh presented at the workshop. The event was extremely well-attended by high profile dignitaries and academics including President Leuthard; Director General of the WTO, Pascal Lamy; trade ministers of Brazil and Finland; Jan Kubis, Executive Secretary of the UNECE and several current and former ambassadors. The academic workshop, moderated by Theresa Carpenter (Graduate Institute, Geneva), began in the morning with Prof. Victor Norman's (Norwegian School of Economics & Business Administration) presentation on the future of EFTA. Other presentations included those by Prof. Peter Egger (ETH Zurich) on the structural estimation of gravity models with market entry dynamics and by Prof. Richard Baldwin (Graduate Institute, Geneva) on 21st century regionalism. The high-profile Panel in the afternoon, moderated by Prof. Richard Baldwin, was led by President Leuthard who spoke on free trade agreements and the multilateral trading system in 2020. The keynote address at the Panel was delivered by Prof. Jagdish Bhagwati (Coulmbia University), who spoke on strengthening defences against protectionism and liberalizing trade.