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A Newly Identified Younger Dryas Component in Eagle Cave, Texas
- Charles W. Koenig, J. David Kilby, Christopher J. Jurgens, Lorena Becerra-Valdivia, Christopher W. Ringstaff, J. Kevin Hanselka, Leslie L. Bush, Charles D. Frederick, Stephen L. Black, Amanda M. Castañeda, Ken L. Lawrence, Madeline E. Mackie, Jim I. Mead
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- Journal:
- American Antiquity / Volume 87 / Issue 2 / April 2022
- Published online by Cambridge University Press:
- 07 December 2021, pp. 377-388
- Print publication:
- April 2022
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Recent excavations by the Ancient Southwest Texas Project of Texas State University sampled a previously undocumented Younger Dryas component from Eagle Cave in the Lower Pecos Canyonlands of Texas. This stratified assemblage consists of bison (Bison antiquus) bones in association with lithic artifacts and a hearth. Bayesian modeling yields an age of 12,660–12,480 cal BP, and analyses indicate behaviors associated with the processing of a juvenile bison and the manufacture and maintenance of lithic tools. This article presents spatial, faunal, macrobotanical, chronometric, geoarchaeological, and lithic analyses relating to the Younger Dryas component within Eagle Cave. The identification of the Younger Dryas occupation in Eagle Cave should encourage archaeologists to revisit previously excavated rockshelter sites in the Lower Pecos and beyond to evaluate deposits for unrecognized, older occupations.
Contributors
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- By Mitchell Aboulafia, Frederick Adams, Marilyn McCord Adams, Robert M. Adams, Laird Addis, James W. Allard, David Allison, William P. Alston, Karl Ameriks, C. Anthony Anderson, David Leech Anderson, Lanier Anderson, Roger Ariew, David Armstrong, Denis G. Arnold, E. J. Ashworth, Margaret Atherton, Robin Attfield, Bruce Aune, Edward Wilson Averill, Jody Azzouni, Kent Bach, Andrew Bailey, Lynne Rudder Baker, Thomas R. Baldwin, Jon Barwise, George Bealer, William Bechtel, Lawrence C. Becker, Mark A. Bedau, Ernst Behler, José A. Benardete, Ermanno Bencivenga, Jan Berg, Michael Bergmann, Robert L. Bernasconi, Sven Bernecker, Bernard Berofsky, Rod Bertolet, Charles J. Beyer, Christian Beyer, Joseph Bien, Joseph Bien, Peg Birmingham, Ivan Boh, James Bohman, Daniel Bonevac, Laurence BonJour, William J. Bouwsma, Raymond D. Bradley, Myles Brand, Richard B. Brandt, Michael E. Bratman, Stephen E. Braude, Daniel Breazeale, Angela Breitenbach, Jason Bridges, David O. Brink, Gordon G. Brittan, Justin Broackes, Dan W. Brock, Aaron Bronfman, Jeffrey E. Brower, Bartosz Brozek, Anthony Brueckner, Jeffrey Bub, Lara Buchak, Otavio Bueno, Ann E. Bumpus, Robert W. Burch, John Burgess, Arthur W. Burks, Panayot Butchvarov, Robert E. Butts, Marina Bykova, Patrick Byrne, David Carr, Noël Carroll, Edward S. Casey, Victor Caston, Victor Caston, Albert Casullo, Robert L. Causey, Alan K. L. Chan, Ruth Chang, Deen K. Chatterjee, Andrew Chignell, Roderick M. Chisholm, Kelly J. Clark, E. J. Coffman, Robin Collins, Brian P. Copenhaver, John Corcoran, John Cottingham, Roger Crisp, Frederick J. Crosson, Antonio S. Cua, Phillip D. Cummins, Martin Curd, Adam Cureton, Andrew Cutrofello, Stephen Darwall, Paul Sheldon Davies, Wayne A. Davis, Timothy Joseph Day, Claudio de Almeida, Mario De Caro, Mario De Caro, John Deigh, C. F. Delaney, Daniel C. Dennett, Michael R. DePaul, Michael Detlefsen, Daniel Trent Devereux, Philip E. Devine, John M. Dillon, Martin C. Dillon, Robert DiSalle, Mary Domski, Alan Donagan, Paul Draper, Fred Dretske, Mircea Dumitru, Wilhelm Dupré, Gerald Dworkin, John Earman, Ellery Eells, Catherine Z. Elgin, Berent Enç, Ronald P. Endicott, Edward Erwin, John Etchemendy, C. Stephen Evans, Susan L. Feagin, Solomon Feferman, Richard Feldman, Arthur Fine, Maurice A. Finocchiaro, William FitzPatrick, Richard E. Flathman, Gvozden Flego, Richard Foley, Graeme Forbes, Rainer Forst, Malcolm R. Forster, Daniel Fouke, Patrick Francken, Samuel Freeman, Elizabeth Fricker, Miranda Fricker, Michael Friedman, Michael Fuerstein, Richard A. Fumerton, Alan Gabbey, Pieranna Garavaso, Daniel Garber, Jorge L. A. Garcia, Robert K. Garcia, Don Garrett, Philip Gasper, Gerald Gaus, Berys Gaut, Bernard Gert, Roger F. Gibson, Cody Gilmore, Carl Ginet, Alan H. Goldman, Alvin I. Goldman, Alfonso Gömez-Lobo, Lenn E. Goodman, Robert M. Gordon, Stefan Gosepath, Jorge J. E. Gracia, Daniel W. Graham, George A. Graham, Peter J. Graham, Richard E. Grandy, I. Grattan-Guinness, John Greco, Philip T. Grier, Nicholas Griffin, Nicholas Griffin, David A. Griffiths, Paul J. Griffiths, Stephen R. Grimm, Charles L. Griswold, Charles B. Guignon, Pete A. Y. Gunter, Dimitri Gutas, Gary Gutting, Paul Guyer, Kwame Gyekye, Oscar A. Haac, Raul Hakli, Raul Hakli, Michael Hallett, Edward C. Halper, Jean Hampton, R. James Hankinson, K. R. Hanley, Russell Hardin, Robert M. Harnish, William Harper, David Harrah, Kevin Hart, Ali Hasan, William Hasker, John Haugeland, Roger Hausheer, William Heald, Peter Heath, Richard Heck, John F. Heil, Vincent F. Hendricks, Stephen Hetherington, Francis Heylighen, Kathleen Marie Higgins, Risto Hilpinen, Harold T. Hodes, Joshua Hoffman, Alan Holland, Robert L. Holmes, Richard Holton, Brad W. Hooker, Terence E. Horgan, Tamara Horowitz, Paul Horwich, Vittorio Hösle, Paul Hoβfeld, Daniel Howard-Snyder, Frances Howard-Snyder, Anne Hudson, Deal W. Hudson, Carl A. Huffman, David L. Hull, Patricia Huntington, Thomas Hurka, Paul Hurley, Rosalind Hursthouse, Guillermo Hurtado, Ronald E. Hustwit, Sarah Hutton, Jonathan Jenkins Ichikawa, Harry A. Ide, David Ingram, Philip J. Ivanhoe, Alfred L. Ivry, Frank Jackson, Dale Jacquette, Joseph Jedwab, Richard Jeffrey, David Alan Johnson, Edward Johnson, Mark D. Jordan, Richard Joyce, Hwa Yol Jung, Robert Hillary Kane, Tomis Kapitan, Jacquelyn Ann K. Kegley, James A. Keller, Ralph Kennedy, Sergei Khoruzhii, Jaegwon Kim, Yersu Kim, Nathan L. King, Patricia Kitcher, Peter D. Klein, E. D. Klemke, Virginia Klenk, George L. Kline, Christian Klotz, Simo Knuuttila, Joseph J. Kockelmans, Konstantin Kolenda, Sebastian Tomasz Kołodziejczyk, Isaac Kramnick, Richard Kraut, Fred Kroon, Manfred Kuehn, Steven T. Kuhn, Henry E. Kyburg, John Lachs, Jennifer Lackey, Stephen E. Lahey, Andrea Lavazza, Thomas H. Leahey, Joo Heung Lee, Keith Lehrer, Dorothy Leland, Noah M. Lemos, Ernest LePore, Sarah-Jane Leslie, Isaac Levi, Andrew Levine, Alan E. Lewis, Daniel E. Little, Shu-hsien Liu, Shu-hsien Liu, Alan K. L. Chan, Brian Loar, Lawrence B. Lombard, John Longeway, Dominic McIver Lopes, Michael J. Loux, E. J. Lowe, Steven Luper, Eugene C. Luschei, William G. Lycan, David Lyons, David Macarthur, Danielle Macbeth, Scott MacDonald, Jacob L. Mackey, Louis H. Mackey, Penelope Mackie, Edward H. Madden, Penelope Maddy, G. B. Madison, Bernd Magnus, Pekka Mäkelä, Rudolf A. Makkreel, David Manley, William E. Mann (W.E.M.), Vladimir Marchenkov, Peter Markie, Jean-Pierre Marquis, Ausonio Marras, Mike W. Martin, A. P. Martinich, William L. McBride, David McCabe, Storrs McCall, Hugh J. McCann, Robert N. McCauley, John J. McDermott, Sarah McGrath, Ralph McInerny, Daniel J. McKaughan, Thomas McKay, Michael McKinsey, Brian P. McLaughlin, Ernan McMullin, Anthonie Meijers, Jack W. Meiland, William Jason Melanson, Alfred R. Mele, Joseph R. Mendola, Christopher Menzel, Michael J. Meyer, Christian B. Miller, David W. Miller, Peter Millican, Robert N. Minor, Phillip Mitsis, James A. Montmarquet, Michael S. Moore, Tim Moore, Benjamin Morison, Donald R. Morrison, Stephen J. Morse, Paul K. Moser, Alexander P. D. Mourelatos, Ian Mueller, James Bernard Murphy, Mark C. Murphy, Steven Nadler, Jan Narveson, Alan Nelson, Jerome Neu, Samuel Newlands, Kai Nielsen, Ilkka Niiniluoto, Carlos G. Noreña, Calvin G. Normore, David Fate Norton, Nikolaj Nottelmann, Donald Nute, David S. Oderberg, Steve Odin, Michael O’Rourke, Willard G. Oxtoby, Heinz Paetzold, George S. Pappas, Anthony J. Parel, Lydia Patton, R. P. Peerenboom, Francis Jeffry Pelletier, Adriaan T. Peperzak, Derk Pereboom, Jaroslav Peregrin, Glen Pettigrove, Philip Pettit, Edmund L. Pincoffs, Andrew Pinsent, Robert B. Pippin, Alvin Plantinga, Louis P. Pojman, Richard H. Popkin, John F. Post, Carl J. Posy, William J. Prior, Richard Purtill, Michael Quante, Philip L. Quinn, Philip L. Quinn, Elizabeth S. Radcliffe, Diana Raffman, Gerard Raulet, Stephen L. Read, Andrews Reath, Andrew Reisner, Nicholas Rescher, Henry S. Richardson, Robert C. Richardson, Thomas Ricketts, Wayne D. Riggs, Mark Roberts, Robert C. Roberts, Luke Robinson, Alexander Rosenberg, Gary Rosenkranz, Bernice Glatzer Rosenthal, Adina L. Roskies, William L. Rowe, T. M. Rudavsky, Michael Ruse, Bruce Russell, Lilly-Marlene Russow, Dan Ryder, R. M. Sainsbury, Joseph Salerno, Nathan Salmon, Wesley C. Salmon, Constantine Sandis, David H. Sanford, Marco Santambrogio, David Sapire, Ruth A. Saunders, Geoffrey Sayre-McCord, Charles Sayward, James P. Scanlan, Richard Schacht, Tamar Schapiro, Frederick F. Schmitt, Jerome B. Schneewind, Calvin O. Schrag, Alan D. Schrift, George F. Schumm, Jean-Loup Seban, David N. Sedley, Kenneth Seeskin, Krister Segerberg, Charlene Haddock Seigfried, Dennis M. Senchuk, James F. Sennett, William Lad Sessions, Stewart Shapiro, Tommie Shelby, Donald W. Sherburne, Christopher Shields, Roger A. Shiner, Sydney Shoemaker, Robert K. Shope, Kwong-loi Shun, Wilfried Sieg, A. John Simmons, Robert L. Simon, Marcus G. Singer, Georgette Sinkler, Walter Sinnott-Armstrong, Matti T. Sintonen, Lawrence Sklar, Brian Skyrms, Robert C. Sleigh, Michael Anthony Slote, Hans Sluga, Barry Smith, Michael Smith, Robin Smith, Robert Sokolowski, Robert C. Solomon, Marta Soniewicka, Philip Soper, Ernest Sosa, Nicholas Southwood, Paul Vincent Spade, T. L. S. Sprigge, Eric O. Springsted, George J. Stack, Rebecca Stangl, Jason Stanley, Florian Steinberger, Sören Stenlund, Christopher Stephens, James P. Sterba, Josef Stern, Matthias Steup, M. A. Stewart, Leopold Stubenberg, Edith Dudley Sulla, Frederick Suppe, Jere Paul Surber, David George Sussman, Sigrún Svavarsdóttir, Zeno G. Swijtink, Richard Swinburne, Charles C. Taliaferro, Robert B. Talisse, John Tasioulas, Paul Teller, Larry S. Temkin, Mark Textor, H. S. Thayer, Peter Thielke, Alan Thomas, Amie L. Thomasson, Katherine Thomson-Jones, Joshua C. Thurow, Vzalerie Tiberius, Terrence N. Tice, Paul Tidman, Mark C. Timmons, William Tolhurst, James E. Tomberlin, Rosemarie Tong, Lawrence Torcello, Kelly Trogdon, J. D. Trout, Robert E. Tully, Raimo Tuomela, John Turri, Martin M. Tweedale, Thomas Uebel, Jennifer Uleman, James Van Cleve, Harry van der Linden, Peter van Inwagen, Bryan W. Van Norden, René van Woudenberg, Donald Phillip Verene, Samantha Vice, Thomas Vinci, Donald Wayne Viney, Barbara Von Eckardt, Peter B. M. Vranas, Steven J. Wagner, William J. Wainwright, Paul E. Walker, Robert E. Wall, Craig Walton, Douglas Walton, Eric Watkins, Richard A. Watson, Michael V. Wedin, Rudolph H. Weingartner, Paul Weirich, Paul J. Weithman, Carl Wellman, Howard Wettstein, Samuel C. Wheeler, Stephen A. White, Jennifer Whiting, Edward R. Wierenga, Michael Williams, Fred Wilson, W. Kent Wilson, Kenneth P. Winkler, John F. Wippel, Jan Woleński, Allan B. Wolter, Nicholas P. Wolterstorff, Rega Wood, W. Jay Wood, Paul Woodruff, Alison Wylie, Gideon Yaffe, Takashi Yagisawa, Yutaka Yamamoto, Keith E. Yandell, Xiaomei Yang, Dean Zimmerman, Günter Zoller, Catherine Zuckert, Michael Zuckert, Jack A. Zupko (J.A.Z.)
- Edited by Robert Audi, University of Notre Dame, Indiana
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- The Cambridge Dictionary of Philosophy
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- 05 August 2015
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- 27 April 2015, pp ix-xxx
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Alluvial Stratigraphy and the Search for Preceramic Open-air Sites in Highland Mesoamerica
- Aleksander Borejsza, Charles D. Frederick, Luis Morett Alatorre, Arthur A. Joyce
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- Latin American Antiquity / Volume 25 / Issue 3 / September 2014
- Published online by Cambridge University Press:
- 20 January 2017, pp. 278-299
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- September 2014
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The Preceramic archaeological record of highland Mesoamerica is biased toward rockshelter sites. We advocate more fieldwork in streamside settings, where open-air sites are likely to be found for reasons related both to the systemic context of hunter-gatherer lifeways and to the geoarchaeological context of site burial and preservation. Predicting site location requires attention to the peculiar nature and behavior of incised ephemeral streams (barrancas) and to the complex alluvial stratigraphic sequences that they leave behind. Four case studies—from the Mexican states ofTlaxcala, México, Morelos, and Oaxaca—reconstruct the geometry and age structure of late Quaternary alluvium from exposures in cutbanks, brickyards, and purposefully dug trenches. We identify deeply buried locales with the remains of extinct megafauna, intentionally set fires, and lithic debitage. We distinguish between geographical areas, stream reaches, and time intervals that do or do not hold much promise for further research. The fragmentary nature of the alluvial record and the paucity of sites can be explained by changes in stream behavior wrought by agricultural land use and are conditioned by the intensity and antiquity of agriculture in any given area. Deposits and sites of Paleoindian age may be more commonly preserved than those of Archaic age.
Preface to the Berkeley Physics Course
- Edward Purcell
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- Electricity and Magnetism
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- 05 June 2012
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- 22 September 2011, pp xvii-xx
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Summary
This is a two-year elementary college physics course for students majoring in science and engineering. The intention of the writers has been to present elementary physics as far as possible in the way in which it is used by physicists working on the forefront of their field. We have sought to make a course which would vigorously emphasize the foundations of physics. Our specific objectives were to introduce coherently into an elementary curriculum the ideas of special relativity, of quantum physics, and of statistical physics.
This course is intended for any student who has had a physics course in high school. A mathematics course including the calculus should be taken at the same time as this course.
There are several new college physics courses under development in the United States at this time. The idea of making a new course has come to many physicists, affected by the needs both of the advancement of science and engineering and of the increasing emphasis on science in elementary schools and in high schools. Our own course was conceived in a conversation between Philip Morrison of Cornell University and C. Kittel late in 1961. We were encouraged by John Mays and his colleagues of the National Science Foundation and by Walter C. Michels, then the Chairman of the Commission on College Physics. An informal committee was formed to guide the course through the initial stages.
Contributors
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- By Jane E. Adcock, Yahya Aghakhani, A. Anand, Eva Andermann, Frederick Andermann, Alexis Arzimanoglou, Sandrine Aubert, Nadia Bahi-Buisson, Carman Barba, Agatino Battaglia, Geneviève Bernard, Nadir E. Bharucha, Laurence A. Bindoff, William Bingaman, Francesca Bisulli, Thomas P. Bleck, Stewart G. Boyd, Andreas Brunklaus, Harry Bulstrode, Jorge G. Burneo, Laura Canafoglia, Laura Cantonetti, Roberto H. Caraballo, Fernando Cendes, Kevin E. Chapman, Patrick Chauvel, Richard F. M. Chin, H. T. Chong, Fahmida A. Chowdhury, Catherine J. Chu-Shore, Rolando Cimaz, Andrew J. Cole, Bernard Dan, Geoffrey Dean, Alessio De Ciantis, Fernando De Paolis, Rolando F. Del Maestro, Irissa M. Devine, Carlo Di Bonaventura, Concezio Di Rocco, Henry B. Dinsdale, Maria Alice Donati, François Dubeau, Michael Duchowny, Olivier Dulac, Monika Eisermann, Brent Elliott, Bernt A. Engelsen, Kevin Farrell, Natalio Fejerman, Rosalie E. Ferner, Silvana Franceschetti, Robert Friedlander, Antonio Gambardella, Hector H. Garcia, Serena Gasperini, Lorenzo Genitori, Gioia Gioi, Flavio Giordano, Leif Gjerstad, Daniel G. Glaze, Howard P. Goodkin, Sidney M. Gospe, Andrea Grassi, William P. Gray, Renzo Guerrini, Marie-Christine Guiot, William Harkness, Andrew G. Herzog, Linda Huh, Margaret J. Jackson, Thomas S. Jacques, Anna C. Jansen, Sigmund Jenssen, Michael R. Johnson, Dorothy Jones-Davis, Reetta Kälviäinen, Peter W. Kaplan, John F. Kerrigan, Autumn Marie Klein, Matthias Koepp, Edwin H. Kolodny, Kandan Kulandaivel, Ruben I. Kuzniecky, Ahmed Lary, Yolanda Lau, Anna-Elina Lehesjoki, Maria K. Lehtinen, Holger Lerche, Michael P. T. Lunn, Snezana Maljevic, Mark R. Manford, Carla Marini, Bindu Menon, Giulia Milioli, Eli M. Mizrahi, Manish Modi, Márcia Elisabete Morita, Manuel Murie-Fernandez, Vivek Nambiar, Lina Nashef, Vincent Navarro, Aidan Neligan, Ruth E. Nemire, Charles R. J. C. Newton, John O'Donavan, Hirokazu Oguni, Teiichi Onuma, Andre Palmini, Eleni Panagiotakaki, Pasquale Parisi, Elena Parrini, Liborio Parrino, Ignacio Pascual-Castroviejo, M. Scott Perry, Perrine Plouin, Charles E. Polkey, Suresh S. Pujar, Karthik Rajasekaran, R. Eugene Ramsey, Rahul Rathakrishnan, Roberta H. Raven, Guy M. Rémillard, David Rosenblatt, M. Elizabeth Ross, Abdulrahman Sabbagh, P. Satishchandra, Swati Sathe, Ingrid E. Scheffer, Philip A. Schwartzkroin, Rod C. Scott, Frédéric Sedel, Michelle J. Shapiro, Elliott H. Sherr, Michael Shevell, Simon D. Shorvon, Adrian M. Siegel, Gagandeep Singh, S. Sinha, Barbara Spacca, Waney Squier, Carl E. Stafstrom, Bernhard J. Steinhoff, Andrea Taddio, Gianpiero Tamburrini, C. T. Tan, Raymond Y. L. Tan, Erik Taubøll, Robert W. Teasell, Mario Giovanni Terzano, Federica Teutonico, Suzanne A. Tharin, Elizabeth A. Thiele, Pierre Thomas, Paolo Tinuper, Dorothée Kasteleijn-Nolst Trenité, Sumeet Vadera, Pierangelo Veggiotti, Jean-Pierre Vignal, J. M. Walshe, Elizabeth J. Waterhouse, David Watkins, Ruth E. Williams, Yue-Hua Zhang, Benjamin Zifkin, Sameer M. Zuberi
- Edited by Simon D. Shorvon, Frederick Andermann, Renzo Guerrini
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- The Causes of Epilepsy
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- 05 March 2012
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- 14 April 2011, pp ix-xvi
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SWIDDEN AGRICULTURE IN THE TIERRA FRÍA? EVIDENCE FROM SEDIMENTARY RECORDS IN TLAXCALA
- Aleksander Borejsza, Charles D. Frederick, Richard G. Lesure
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- Ancient Mesoamerica / Volume 22 / Issue 1 / Spring 2011
- Published online by Cambridge University Press:
- 05 October 2011, pp. 91-106
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- Spring 2011
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Swidden agriculture in Mesoamerica is commonly associated with the hot and humid lowlands and with small isolated communities. Charcoal-rich sediments discovered in Tlaxcala, however, suggest that it was practiced in the cold highlands in the Formative and Classic periods. The headwaters of the Xilomantla drainage incised a nine-meter deep channel shortly before 200 b.c., in response to increased runoff from slopes degraded by agriculture. It was filled back within a few hundred years with sands and muds containing recurrent laminae of charred plant matter that reflect the annual burning of secondary scrub in fallowed fields. A gully in the La Ladera drainage received high inputs of charcoal from the surroundings of a nearby settlement between ca. a.d. 400 and 900. The farming practices inferred from these deposits have no exact ethnographic analog. They inflicted lasting environmental damage, but were upheld for several centuries despite changes in settlement patterns.
Chapter 9 - Neutron stars, pulsars, pulsar wind nebulae, and more supernova remnants
- Frederick D. Seward, Harvard-Smithsonian Center for Astrophysics, Philip A. Charles, South African Astronomical Observatory, Sutherland
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- Exploring the X-ray Universe
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- 05 June 2012
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- 26 August 2010, pp 123-142
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Summary
Discovery and nature of neutron stars
Until the discovery of radio pulsars by Jocelyn Bell and Antony Hewish in 1967 (Hewish et al., 1968), neutron stars had existed only in the minds of theoretical physicists. First proposed as an end state of stellar evolution by Robert Oppenheimer and George Volkoff (1939), they are now accepted as the only explanation for radio pulsars. The discovery was serendipitous. No one had conjectured or even dreamed that this sort of signal might be generated.
Bell, then a student, had just spent months wiring antennas for a new radio telescope. In the course of testing, she noticed ‘a bit of scruff’ in the recorded signal. This ‘scruff’ was found to repeat, not every 24 hours (the solar day), but every 23 hours and 56 minutes (the sidereal day), showing that the source was anchored in the sky, not to the rotating Earth. Furthermore, when present, the signal was periodic with a remarkably stable period of 1.337 s. Thus CP 1919, the first of the radio pulsars, was discovered. The stable period could only be explained by rotation, and only a small object with strong gravity could rotate this fast without breaking up. A neutron star was the only reasonable explanation (Gold, 1968).
Chapter 1 - Birth and childhood of X-ray astronomy
- Frederick D. Seward, Harvard-Smithsonian Center for Astrophysics, Philip A. Charles, South African Astronomical Observatory, Sutherland
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- Exploring the X-ray Universe
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- 05 June 2012
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- 26 August 2010, pp 1-11
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The discovery of X-rays
On the second story of the building at Röntenring 8 in Würzburg, Germany, there is a plaque: ‘In diesem Hause entdekte W. C. Röntgen im Jahre 1895 die nach ihm benannten Strahlen’ – In this building, in the year 1895, W. C. Röntgen discovered the radiation named for him. Here was the laboratory of Wilhelm C. Röntgen, a 50-year-old professor of physics, who was studying phenomena associated with electrical discharge in gasses. On the afternoon of 8 November, working alone in his laboratory, he noticed a curious phenomenon. When high voltage was applied to the electrodes in the partially evacuated glass discharge tube, he noticed a faint glow from a fluorescent screen placed at the other end of the laboratory table. The room was dark and he had previously covered the tube with black cardboard so no light would escape. Why was the screen glowing?
That evening he verified that the discharge tube was indeed the source of the energy that caused the screen to glow, and that no visible radiation was escaping from the shrouded tube. He quickly found that the unknown radiation would pass through paper, wood, and aluminum but was stopped by heavy metals. Then, when holding a lead disc in front of the screen to observe its shadow, Röntgen also saw the shadow of bones in his hand! In a week he had measured the basic characteristics of this new form of radiation.
Contents
- Frederick D. Seward, Harvard-Smithsonian Center for Astrophysics, Philip A. Charles, South African Astronomical Observatory, Sutherland
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- Exploring the X-ray Universe
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- 05 June 2012
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- 26 August 2010, pp v-ix
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List of acronyms
- Frederick D. Seward, Harvard-Smithsonian Center for Astrophysics, Philip A. Charles, South African Astronomical Observatory, Sutherland
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- Exploring the X-ray Universe
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- 05 June 2012
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- 26 August 2010, pp x-xii
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Chapter 10 - Cataclysmic variable stars
- Frederick D. Seward, Harvard-Smithsonian Center for Astrophysics, Philip A. Charles, South African Astronomical Observatory, Sutherland
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- Exploring the X-ray Universe
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- 05 June 2012
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- 26 August 2010, pp 143-170
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Summary
Introduction
Cataclysmic variables are remarkably similar to the low-mass X-ray binaries (LMXBs) described in Chapter 11 but are significantly less luminous in X-rays, particularly at the higher X-ray energies of the first X-ray satellites. Indeed, only one previously known CV, EX Hya, was found in the Uhuru survey of the X-ray sky. But these objects have a long history that goes back well before the era of X-ray astronomy, as they include among their number both dwarf novae and novae. As we shall see in this chapter, dwarf novae and novae are powered by fundamentally different processes than occur in supernova events. Supernovae represent the final, and irreversible, moments in the lives of massive stars, when they collapse rapidly under gravity and then explode catastrophically. For any given object it happens once, whereas nova and dwarf nova eruptions can and do recur. Indeed, it is hypothesised that all novae recur, but the typical recurrence time is long: at least hundreds, perhaps thousands, of years.
Cataclysmic variables are interacting binaries similar to LMXBs, except that the compact object is a white dwarf, accreting material from its (usually) cool, late-type companion star in a short period (approximately hours) binary system. They are one of the few classes of object in this book that were known and observed prior to the twentieth century. Novae have been known to mankind throughout history, and dwarf novae were first recorded in the mid-nineteenth century.
Chapter 16 - The diffuse X-ray background
- Frederick D. Seward, Harvard-Smithsonian Center for Astrophysics, Philip A. Charles, South African Astronomical Observatory, Sutherland
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- Exploring the X-ray Universe
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- 05 June 2012
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- 26 August 2010, pp 325-339
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Summary
Early observations, 1965
The X-ray background was not anticipated. It was discovered in 1962 during the rocket flight which first detected Sco X-1, the first successful attempt to detect X-rays from sources other than the Sun or Earth. An uncollimated detector viewing about 10 000 square degrees of the sky was used. Giacconi et al. (1962) concluded that the background was of ‘diffuse character’ and due to X-rays of about the same energy as those from Sco X-1. The observed diffuse signal in this detector could have been generated by a few moderately strong point sources spread over the sky. The next observations, however, with detectors collimated to observe only 100 square degrees, showed the background to be indeed diffuse and of uniform brightness to at least 10 per cent.
There was no doubt that this background existed. The signals observed were strong and unmistakable. When detectors in rocket payloads were uncovered, pointed at any part of the night sky, the count rate always increased. All early observations, without exception, showed a few bright sources embedded in a uniform X-ray glow. The night sky at X-ray wavelengths was uniformly bright! Sources appeared superposed on this background, rather like stars viewed with the naked eye on a night with a full moon; when the faint stars disappear into the background of moonlight scattered from the atmosphere. Because no structure was observed and the emission was apparently uniform, this phenomenon has been called the ‘diffuse X-ray background’.
Chapter 6 - Active stellar coronae
- Frederick D. Seward, Harvard-Smithsonian Center for Astrophysics, Philip A. Charles, South African Astronomical Observatory, Sutherland
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- Exploring the X-ray Universe
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- 05 June 2012
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- 26 August 2010, pp 60-83
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Summary
The Sun
The Sun is close and has been studied intensively. It radiates strongly from radio- to X-ray frequencies and, because of solar-terrestrial effects, has been monitored by an armada of spacecraft for 50 years. There were the OSO spacecraft (which also observed other cosmic sources) (1962–1978), Skylab (1973), Solar Max (1980–1989), Yohkoh (1991–2001), SOHO (1995–), TRACE (1998), and Hinode (2006). Solar X-ray emission is now continuously measured by a series of GOES spacecraft, and current data are available online almost instantaneously (NOAA/SWPC, 2009a). In this section we show only a few observations which illustrate things to keep in mind when considering the emission of other stars. The data are spectacular, and we regret not having room to include more. For a more thorough overview of solar observations and theory, there is an excellent book by Golub and Pasachoff (1997). Movies of EUV and X-ray images of the Sun can be viewed on several websites (e.g. TRACE, 2009; XRT, 2009).
An historical puzzle
Why should there be detectable X-rays from the Sun at all? Certainly not on the basis of its everyday visible appearance. The optical spectrum of the Sun can be represented quite well by a simple blackbody at a temperature of about 6000 K. Such an object should produce no detectable X-ray flux, whereas the amount actually seen implies the presence of material at a temperature of at least 1 million degrees!
Chapter 2 - X-ray emission and interaction with matter
- Frederick D. Seward, Harvard-Smithsonian Center for Astrophysics, Philip A. Charles, South African Astronomical Observatory, Sutherland
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Summary
Astrophysical mechanisms for generating X-rays
There are three radiation processes – thermal, synchrotron and blackbody – that are the dominant mechanisms for producing X-rays in an astronomical setting, and whenever high-energy electrons are present, we must add inverse Compton scattering of microwave background photons into the X-ray regime. The spectral signature of each process is unique and is therefore one of the first clues to the nature of an unknown X-ray source. If the spectrum can be measured with high resolution over a broad energy band, then usually both the emission process and the physical conditions within the source can be deduced.
Thermal emission from a hot gas
Consider a hot gas of low enough density that it can be described as thin and transparent to its own radiation. This is not difficult to achieve for X-rays. At temperatures above 105 K, atoms are ionised, and a gas consists of positive ions and negative electrons. Thermal energy is shared among these particles and is transferred rapidly from one particle to another through collisions. Indeed thermal equilibrium means that the average energy of all particles is the same and is determined only by the temperature. When an electron passes close to a positive ion, the strong electric force causes its trajectory to change. The acceleration of the electron in such a collision causes it to radiate electromagnetic energy, and this radiation is called bremsstrahlung (literally, ‘braking radiation’).
Exploring the X-ray Universe
- 2nd edition
- Frederick D. Seward, Philip A. Charles
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Capturing the excitement and accomplishments of X-ray astronomy, this second edition now includes a broader range of astronomical phenomena and dramatic new results from the most powerful X-ray telescopes. Covering all areas of astronomical research, ranging from the smallest to the largest objects, from neutron stars to clusters of galaxies, this textbook is ideal for undergraduate students. Each chapter starts with the basic aspects of the topic, explores the history of discoveries, and examines in detail modern observations and their significance. This new edition has been updated with results from the most recent space-based instruments, including ROSAT, BeppoSAX, ASCA, Chandra, and XMM. New chapters cover X-ray emission processes, the interstellar medium, the Solar System, and gamma-ray bursts. The text is supported by over 300 figures, with tables listing the properties of the sources, and more specialized technical points separated in boxes.
Index
- Frederick D. Seward, Harvard-Smithsonian Center for Astrophysics, Philip A. Charles, South African Astronomical Observatory, Sutherland
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Chapter 3 - Tools and techniques
- Frederick D. Seward, Harvard-Smithsonian Center for Astrophysics, Philip A. Charles, South African Astronomical Observatory, Sutherland
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Summary
X-ray detectors
The first instruments used for X-ray astronomy were developed originally for the detection of charged particles and γ rays emitted by radioactive material. These detectors respond to energy deposited by photoelectrons and, for higher energies, Compton electrons (discussed in Chapter 2). A fast electron creates a track of ionised material in the active volume of the detector. The detector collects either this charge or light from recombination of the ions. Electronic circuits then amplify this signal and record the time and amplitude of the event.
The proportional counter
The proportional counter is not only an efficient X-ray detector but also measures the energy of every photon detected. It was the workhorse of early cosmic X-ray observations and is still being used in modern instruments. However, the modifications necessary to adapt the simple laboratory counter to an X-ray detector capable of operating in the harsh environment of space were challenging.
The detector must have a large area to collect photons from weak cosmic sources and obviously a window thin enough to transmit X-rays. Yet the window has to be strong enough to keep the gas inside the detector from leaking into the nearvacuum of space and well supported to withstand the force of the gas pressure inside the detector. Many an early observation was lost by the failure of detector windows during rocket ascent out of the atmosphere and upon first exposure to space.
Chapter 11 - X-ray binaries
- Frederick D. Seward, Harvard-Smithsonian Center for Astrophysics, Philip A. Charles, South African Astronomical Observatory, Sutherland
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Introduction
The discovery of binary behaviour
The very existence of the bright cosmic X-ray sources discovered in the 1960s represented an exciting and challenging astrophysical problem. No physical process known then was capable of generating the enormous X-ray luminosities observed. The subsequent optical identifications of Sco X-1 and Cyg X-2 stimulated theorists and observers alike to learn more about these new ‘X-ray stars’. Why were these extremely powerful X-ray sources associated with such apparently unremarkable optical objects (see Chapter 1)? They were rather faint (13th to 15th magnitude) and did not stand out on optical photographs. However, the optical spectrum of Sco X-1 had similarities with the cataclysmic variables that were being intensively monitored by amateur groups and had been shown, a few years earlier, to be interacting binary systems (see Chapter 10).
As shown in Fig. 11.1, Sco X-1 displayed a smooth blue continuum with superposed emission lines of hydrogen and ionised helium. The absence of absorption features, as in normal stellar spectra, indicated that little or none of the light was coming from a main sequence star. The presence of ionised helium indicated that the source of excitation of the lines was very hot and very likely to be connected with the X-rays. However, despite many observing campaigns dedicated to Sco X-1, which revealed substantial variability on all timescales, no indication of binary behaviour was found. The same was true for Cyg X-2.
Chapter 4 - Solar system X-rays
- Frederick D. Seward, Harvard-Smithsonian Center for Astrophysics, Philip A. Charles, South African Astronomical Observatory, Sutherland
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Summary
The production of planetary X-rays
Planets are small and, compared to the cosmic subjects of other chapters, extremely weak sources of X-rays. Nevertheless, X-rays have now been detected from five planets, moons of Earth and Jupiter, several comets, and diffuse material in the solar neighborhood. These results have been scientifically useful and often surprising. The strongest X-ray source in the Solar System is, of course, the Sun. As in the visible band, orbiting solid objects shine with reflected solar energy. The soft X-ray luminosity of the solar corona is ∼4 × 1027 erg s−1, and that of the planets is a factor of ∼1014 weaker. Cometary X-rays are produced by collisions of energetic solar-wind particles with material in the comet. Some planets have magnetospheres which provide a mechanism for generating auroral X-rays. The energy that drives almost all these X-ray production processes originates in the Sun.
The observations are difficult, as targets move appreciably during the observation and are very bright optically; so bright that star sensors for aspect determination sometimes cannot be used. Soft X-ray detectors are also sensitive to visible light, which makes data reduction difficult. This chapter will cover Solar System objects in approximate order of X-ray detection.
Earth
In some of the very first X-ray astronomy observations, solar X-rays scattered from the upper layers of the Earth's atmosphere were detected with rocket-borne proportional counters (Harries & Francey, 1968; Grader et al., 1968).
Frontmatter
- Frederick D. Seward, Harvard-Smithsonian Center for Astrophysics, Philip A. Charles, South African Astronomical Observatory, Sutherland
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