Neon and CNO Abundances for Extreme Helium Stars -- A Non-LTE Analysis

A non-LTE (NLTE) abundance analysis was carried out for three extreme helium stars (EHes): BD+10 2179, BD-9 4395, and LS IV+6 002, from their optical spectra with NLTE model atmospheres. NLTE TLUSTY model atmospheres were computed with H, He, C, N, O, and Ne treated in NLTE. Model atmosphere parameters were chosen from consideration of fits to observed He I line profiles and ionization equilibria of C and N ions. The program SYNSPEC was then used to determine the NLTE abundances for Ne as well as H, He, C, N, and O. LTE neon abundances from Ne I lines in the EHes: LSE 78, V1920 Cyg, HD 124448, and PV Tel, are derived from published models and an estimate of the NLTE correction applied to obtain the NLTE Ne abundance. We show that the derived abundances of these key elements, including Ne, are well matched with semi-quantitative predictions for the EHe resulting from a cold merger (i.e., no nucleosynthesis during the merger) of a He white dwarf with a C-O white dwarf.Comment: Astrophysical Journal, accepte

Issues Regarding the Early Development of Caddo Culture Discussion Topics for the East Texas Caddo Research Group, December 2008

Is there a consensus regarding which archaeological traits are diagnostic of Caddo culture? What are the necessary and sufficient traits for designating a context as “Caddo” as opposed to, for example, “pre-Caddo” or “Coles Creek?

Recent Investigations at the Mounds Plantation Site (16CD12), Caddo Parish, Louisiana

Dr. Montroville Wilson Dickeson, born in Philadelphia in 1810, was a medical doctor, taxidermist and avid collector of fossils. Between 1837 and 1844 he pursued another interest—excavating Indian burial mounds in the Ohio and Mississippi River valleys. He claimed to have “opened up” more than a thousand mounds and collected more than 40,000 objects. He also made drawings of the mounds and later provided these to an artist by the name of John J. Egan, who, about 1850, converted the drawings into a series of large paintings on huge canvases. Dickeson toured the country in 1852 allowing the public to view the canvasses and his artifact collections for a fee of 25 cents. The panorama, titled “Monumental Grandeur of the Mississippi Valley”, was nine feet high, 400 feet long, and consisted of 27 scenes. The canvasses later were curated at the University Museum, University of Pennsylvania until 1953 when purchased by the St. Louis Art Museum where they remain today. Dickeson’s lecture notes refer to Scene 21 as follows: “The following picture shows a group of connected mounds in Caddo Parish, in Northwestern Louisiana, with some of the aboriginal inhabitants of the region . . .” The scene depicts a cluster of nine mounds, some of which are connected by low earthen walls. In the background are mountains, and a group of Indians with elaborate headdresses are shown in front of tents. Similar mountains and the same Indian scene appear in other segments of the Mississippi Panorama and are understandable in light of the Romantic artistic style of the times, as well as the fact that the panorama was part of a show intended to evoke wonder and awe in its audience. Today we know of only one place in Caddo Parish where there is a cluster of at least nine mounds. Located on the western side of the Red River, north of the present city of Shreveport, is the Mounds Plantation Site (16CD12), the single largest Caddo ceremonial center in northwestern Louisiana. It seems fitting that the earliest reference that we have to a prehistoric site in northwest Louisiana likely pertains to Mounds Plantation, a place of primary importance to its ancient Caddo inhabitants, as well as to modern archaeological research

Comments on Caddo Origins in Northwest Louisiana

This paper presents some of my thoughts on the issue of Caddo origins from the perspective of the Red River drainage in northwest Louisiana. These ideas were assembled prior to the Caddo discussion group meeting held in December 2008 and have been only slightly modified here. The paper was not given as a formal presentation, but I attempted to introduce the main points during the group discussion. Development of better chronological controls is crucial for addressing problems of Caddo origins, and I discuss this issue first. Although much has been settled since the early Krieger-Ford discussions, a finer-grained chronology is necessary to answer questions that are now of interest. We remain largely dependent on our understanding of changes in ceramic assemblages and how we can tie these to chronometric scales based primarily on radiocarbon dating. I next review the cultural taxonomic units that have been used to classify the pre-Caddo archaeological record in the Trans-Mississippi South. Rather than taking the view that one or more of these cultural entities transformed into Caddo culture, I suggest that Caddo origins might be better viewed as the development of social and economic behaviors that linked relatively small-scale social units previously only loosely and sporadically associated. I then discuss the possible importance of the development of ceremonial centers, the appearance of elite mortuary traits, and the circulation of finely engraved ceramic vessels for understanding changes in social and economic integration that took place in the Trans- Mississippi South between approximately A.D. 900 and A.D. 1050. Finally, I offer a list of some basic questions that I feel are important for furthering our understanding of Caddo origins