2019 Spring Symposium Contributing Speakers
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Exploring Pulsars
High-energy astrophysics Explore the PUL SAR menagerie Astronomers are discovering many strange properties of compact stellar objects called pulsars. Here’s how they fit together. by Victoria M. Kaspi f you browse through an astronomy book published 25 years ago, you’d likely assume that astronomers understood extremely dense objects called neutron stars fairly well. The spectacular Crab Nebula’s central body has been a “poster child” for these objects for years. This specific neutron star is a pulsar that I rotates roughly 30 times per second, emitting regular appar- ent pulsations in Earth’s direction through a sort of “light- house” effect as the star rotates. While these textbook descriptions aren’t incorrect, research over roughly the past decade has shown that the picture they portray is fundamentally incomplete. Astrono- mers know that the simple scenario where neutron stars are all born “Crab-like” is not true. Experts in the field could not have imagined the variety of neutron stars they’ve recently observed. We’ve found that bizarre objects repre- sent a significant fraction of the neutron star population. With names like magnetars, anomalous X-ray pulsars, soft gamma repeaters, rotating radio transients, and compact Long the pulsar poster child, central objects, these bodies bear properties radically differ- the Crab Nebula’s central object is a fast-spinning neutron star ent from those of the Crab pulsar. Just how large a fraction that emits jets of radiation at its they represent is still hotly debated, but it’s at least 10 per- magnetic axis. Astronomers cent and maybe even the majority. -
R-Process Elements from Magnetorotational Hypernovae
r-Process elements from magnetorotational hypernovae D. Yong1,2*, C. Kobayashi3,2, G. S. Da Costa1,2, M. S. Bessell1, A. Chiti4, A. Frebel4, K. Lind5, A. D. Mackey1,2, T. Nordlander1,2, M. Asplund6, A. R. Casey7,2, A. F. Marino8, S. J. Murphy9,1 & B. P. Schmidt1 1Research School of Astronomy & Astrophysics, Australian National University, Canberra, ACT 2611, Australia 2ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), Australia 3Centre for Astrophysics Research, Department of Physics, Astronomy and Mathematics, University of Hertfordshire, Hatfield, AL10 9AB, UK 4Department of Physics and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA 5Department of Astronomy, Stockholm University, AlbaNova University Center, 106 91 Stockholm, Sweden 6Max Planck Institute for Astrophysics, Karl-Schwarzschild-Str. 1, D-85741 Garching, Germany 7School of Physics and Astronomy, Monash University, VIC 3800, Australia 8Istituto NaZionale di Astrofisica - Osservatorio Astronomico di Arcetri, Largo Enrico Fermi, 5, 50125, Firenze, Italy 9School of Science, The University of New South Wales, Canberra, ACT 2600, Australia Neutron-star mergers were recently confirmed as sites of rapid-neutron-capture (r-process) nucleosynthesis1–3. However, in Galactic chemical evolution models, neutron-star mergers alone cannot reproduce the observed element abundance patterns of extremely metal-poor stars, which indicates the existence of other sites of r-process nucleosynthesis4–6. These sites may be investigated by studying the element abundance patterns of chemically primitive stars in the halo of the Milky Way, because these objects retain the nucleosynthetic signatures of the earliest generation of stars7–13. -
Luminous Blue Variables
Review Luminous Blue Variables Kerstin Weis 1* and Dominik J. Bomans 1,2,3 1 Astronomical Institute, Faculty for Physics and Astronomy, Ruhr University Bochum, 44801 Bochum, Germany 2 Department Plasmas with Complex Interactions, Ruhr University Bochum, 44801 Bochum, Germany 3 Ruhr Astroparticle and Plasma Physics (RAPP) Center, 44801 Bochum, Germany Received: 29 October 2019; Accepted: 18 February 2020; Published: 29 February 2020 Abstract: Luminous Blue Variables are massive evolved stars, here we introduce this outstanding class of objects. Described are the specific characteristics, the evolutionary state and what they are connected to other phases and types of massive stars. Our current knowledge of LBVs is limited by the fact that in comparison to other stellar classes and phases only a few “true” LBVs are known. This results from the lack of a unique, fast and always reliable identification scheme for LBVs. It literally takes time to get a true classification of a LBV. In addition the short duration of the LBV phase makes it even harder to catch and identify a star as LBV. We summarize here what is known so far, give an overview of the LBV population and the list of LBV host galaxies. LBV are clearly an important and still not fully understood phase in the live of (very) massive stars, especially due to the large and time variable mass loss during the LBV phase. We like to emphasize again the problem how to clearly identify LBV and that there are more than just one type of LBVs: The giant eruption LBVs or h Car analogs and the S Dor cycle LBVs. -
Formation and Evolution of Stars
Journal of Physical Science and Application 11 (1) (2021) 1-11 doi: 10.17265/2159-5348/2021.01.001 D DAVID PUBLISHING Formation and Evolution of Stars Cuixiang Zhong Department of Physics, Jiangxi Normal University, Nanchang, China Abstract: The evolution of stars is one of the most important problems in astrophysics. However, the existing theories of stellar evolution fail to reveal the real mechanism of star formation, and thus fail to correctly reveal the mechanisms and laws of star growth, aging, death and resurrection. Therefore, by studying the formation process of satellites, planets and stars, the author can reveal the mechanisms and laws of star formation and evolution: as the star spins rapidly and its planets go round and round, a series of cyclones can form all over the star. These cyclones not only ignite thermonuclear reactions in the star, but also continuously absorb hydrogen and other interstellar material in space to maintain thermonuclear reactions in the star. But, with the increase of star mass, if the magnetic attraction of the stellar cyclone grows large enough that the star engulfs the innermost planet scattering cyclones through the magnetic attraction of the cyclone, the stellar mass will increase significantly, the stellar atmosphere will thicken significantly, the internal temperature of the star will increase greatly, and the huge energy will be released, causing the star to suddenly expand and become a red giant. When the red giant burns the swallowed planet, its internal temperature will gradually decrease, and the helium fusion will stop. At this time, the central gravity of the star cannot be balanced by the radiation pressure generated by the hydrogen or helium fusion, and the inner star will contract. -
Curriculum Vitae Thomas Matheson
Curriculum Vitae Thomas Matheson Address: NSF's National Optical-Infrared Astronomy Research Laboratory Community Science and Data Center 950 North Cherry Avenue Tucson, AZ 85719, USA Telephone: (520) 318{8517 Fax: (520) 318{8360 e-mail: [email protected] WWW: http://www.noao.edu/noao/staff/matheson/ Education: University of California, Berkeley, Berkeley, CA Department of Astronomy Ph.D. received June 2000 M.A. received June 1992 PhD Thesis Topic: The Spectral Characteristics of Stripped-Envelope Supernovae Thesis Advisor: Professor Alexei V. Filippenko Harvard University, Cambridge, MA Department of Astronomy & Astrophysics and Physics A.B. magna cum laude, received June 1989 Senior Thesis Topic: Transients in the Solar Transition Region Thesis Advisor: Professor Robert W. Noyes Employment: NSF's National Optical-Infrared Astronomy Research Laboratory (The Former National Optical Astronomy Observatory) Community Science and Data Center Head of Time-Domain Services 2017 { present Astronomer 2018 { present Associate Astronomer 2009 { 2018 (Tenure, 2011) Assistant Astronomer 2004 { 2009 Harvard-Smithsonian Center for Astrophysics Optical and Infrared Division Post-doctoral fellow 2000 { 2004 University of California, Berkeley Department of Astronomy Research Assistant 1991 { 2000 Harvard-Smithsonian Center for Astrophysics Solar and Stellar Physics Division Research Assistant 1989 { 1990 Thomas Matheson|Curriculum Vitae Teaching: Harvard University, Department of Astronomy, Teaching Assistant 2001, 2003 University of California, Berkeley, -
POSTERS SESSION I: Atmospheres of Massive Stars
Abstracts of Posters 25 POSTERS (Grouped by sessions in alphabetical order by first author) SESSION I: Atmospheres of Massive Stars I-1. Pulsational Seeding of Structure in a Line-Driven Stellar Wind Nurdan Anilmis & Stan Owocki, University of Delaware Massive stars often exhibit signatures of radial or non-radial pulsation, and in principal these can play a key role in seeding structure in their radiatively driven stellar wind. We have been carrying out time-dependent hydrodynamical simulations of such winds with time-variable surface brightness and lower boundary condi- tions that are intended to mimic the forms expected from stellar pulsation. We present sample results for a strong radial pulsation, using also an SEI (Sobolev with Exact Integration) line-transfer code to derive characteristic line-profile signatures of the resulting wind structure. Future work will compare these with observed signatures in a variety of specific stars known to be radial and non-radial pulsators. I-2. Wind and Photospheric Variability in Late-B Supergiants Matt Austin, University College London (UCL); Nevyana Markova, National Astronomical Observatory, Bulgaria; Raman Prinja, UCL There is currently a growing realisation that the time-variable properties of massive stars can have a funda- mental influence in the determination of key parameters. Specifically, the fact that the winds may be highly clumped and structured can lead to significant downward revision in the mass-loss rates of OB stars. While wind clumping is generally well studied in O-type stars, it is by contrast poorly understood in B stars. In this study we present the analysis of optical data of the B8 Iae star HD 199478. -
Nature, 451, 802, 2008
Vol 451 | 14 February 2008 | doi:10.1038/nature06602 LETTERS Discovery of the progenitor of the type Ia supernova 2007on Rasmus Voss1,2 & Gijs Nelemans3 Type Ia supernovae are exploding stars that are used to measure On 2007 November 5, supernova SN2007on was found in the the accelerated expansion of the Universe1,2 and are responsible for outskirts of the elliptical galaxy NGC 140419. Optical spectra of the most of the iron ever produced3. Although there is general agree- supernova20 showed that the supernova was of type Ia. The position ment that the exploding star is a white dwarf in a binary system, of the supernova, at RA 5 03 h 38 m 50.9 s, dec. 5235u 349 300 the exact configuration and trigger of the explosion is unclear4, (J2000), is about 700 from the core of the host, corresponding to which could hamper their use for precision cosmology. Two fam- 8 kpc for a distance of 20 Mpc to NGC 140421. Observations by the ilies of progenitor models have been proposed. In the first, a white SWIFT mission on November 11 detected the supernova in the dwarf accretes material from a companion until it exceeds the optical/ultraviolet monitor but not in the X-ray telescope22. We ana- Chandrasekhar mass, collapses and explodes5,6. Alternatively, lysed the SWIFT data and determined the position of the supernova two white dwarfs merge, again causing catastrophic collapse and as RA 5 03 h 38 m 50.98 s, dec. 5235u 349 31.00 (J2000), with uncer- an explosion7,8. It has hitherto been impossible to determine if tainty of 10 (Fig. -
Iptf14hls: a Unique Long-Lived Supernova from a Rare Ex- Plosion Channel
iPTF14hls: A unique long-lived supernova from a rare ex- plosion channel I. Arcavi1;2, et al. 1Las Cumbres Observatory Global Telescope Network, Santa Barbara, CA 93117, USA. 2Kavli Institute for Theoretical Physics, University of California, Santa Barbara, CA 93106, USA. 1 Most hydrogen-rich massive stars end their lives in catastrophic explosions known as Type 2 IIP supernovae, which maintain a roughly constant luminosity for ≈100 days and then de- 3 cline. This behavior is well explained as emission from a shocked and expanding hydrogen- 56 4 rich red supergiant envelope, powered at late times by the decay of radioactive Ni produced 1, 2, 3 5 in the explosion . As the ejected mass expands and cools it becomes transparent from the 6 outside inwards, and decreasing expansion velocities are observed as the inner slower-moving 7 material is revealed. Here we present iPTF14hls, a nearby supernova with spectral features 8 identical to those of Type IIP events, but remaining luminous for over 600 days with at least 9 five distinct peaks in its light curve and expansion velocities that remain nearly constant in 10 time. Unlike other long-lived supernovae, iPTF14hls shows no signs of interaction with cir- 11 cumstellar material. Such behavior has never been seen before for any type of supernova 12 and it challenges all existing explosion models. Some of the properties of iPTF14hls can be 13 explained by the formation of a long-lived central power source such as the spindown of a 4, 5, 6 7, 8 14 highly magentized neutron star or fallback accretion onto a black hole . -
A Magnetar Model for the Hydrogen-Rich Super-Luminous Supernova Iptf14hls Luc Dessart
A&A 610, L10 (2018) https://doi.org/10.1051/0004-6361/201732402 Astronomy & © ESO 2018 Astrophysics LETTER TO THE EDITOR A magnetar model for the hydrogen-rich super-luminous supernova iPTF14hls Luc Dessart Unidad Mixta Internacional Franco-Chilena de Astronomía (CNRS, UMI 3386), Departamento de Astronomía, Universidad de Chile, Camino El Observatorio 1515, Las Condes, Santiago, Chile e-mail: [email protected] Received 2 December 2017 / Accepted 14 January 2018 ABSTRACT Transient surveys have recently revealed the existence of H-rich super-luminous supernovae (SLSN; e.g., iPTF14hls, OGLE-SN14-073) that are characterized by an exceptionally high time-integrated bolometric luminosity, a sustained blue optical color, and Doppler- broadened H I lines at all times. Here, I investigate the effect that a magnetar (with an initial rotational energy of 4 × 1050 erg and 13 field strength of 7 × 10 G) would have on the properties of a typical Type II supernova (SN) ejecta (mass of 13.35 M , kinetic 51 56 energy of 1:32 × 10 erg, 0.077 M of Ni) produced by the terminal explosion of an H-rich blue supergiant star. I present a non-local thermodynamic equilibrium time-dependent radiative transfer simulation of the resulting photometric and spectroscopic evolution from 1 d until 600 d after explosion. With the magnetar power, the model luminosity and brightness are enhanced, the ejecta is hotter and more ionized everywhere, and the spectrum formation region is much more extended. This magnetar-powered SN ejecta reproduces most of the observed properties of SLSN iPTF14hls, including the sustained brightness of −18 mag in the R band, the blue optical color, and the broad H I lines for 600 d. -
A Blast Wave from the 1843 Eruption of Eta Carinae
1 A Blast Wave from the 1843 Eruption of Eta Carinae Nathan Smith* *Astronomy Department, University of California, 601 Campbell Hall, Berkeley, CA 94720-3411 Very massive stars shed much of their mass in violent precursor eruptions [1] as luminous blue variables (LBVs) [2] before reaching their most likely end as supernovae, but the cause of LBV eruptions is unknown. The 19th century eruption of Eta Carinae, the prototype of these events [3], ejected about 12 solar masses at speeds of 650 km/s, with a kinetic energy of almost 1050ergs[4]. Some faster material with speeds up to 1000-2000 km/s had previously been reported [5,6,7,8] but its full distribution was unknown. Here I report observations of much faster material with speeds up to 3500-6000 km/s, reaching farther from the star than the fastest material in earlier reports [5]. This fast material roughly doubles the kinetic energy of the 19th century event, and suggests that it released a blast wave now propagating ahead of the massive ejecta. Thus, Eta Carinae’s outer shell now mimics a low-energy supernova remnant. The eruption has usually been discussed in terms of an extreme wind driven by the star’s luminosity [2,3,9,10], but fast material reported here suggests that it was powered by a deep-seated explosion rivalling a supernova, perhaps triggered by the pulsational pair instability[11]. This may alter interpretations of similar events seen in other galaxies. Eta Carinae [3] is the most luminous and the best studied among LBVs [1,2]. -
Massive Stellar Mergers As Precursors of Hydrogen-Rich Pulsational Pair Instability Supernovae
UvA-DARE (Digital Academic Repository) Massive Stellar Mergers as Precursors of Hydrogen-rich Pulsational Pair Instability Supernovae Vigna-Gómez, A.; Justham, S.; Mandel, I.; de Mink, S.E.; Podsiadlowski, P. DOI 10.3847/2041-8213/ab1bdf Publication date 2019 Document Version Final published version Published in Astrophysical Journal Letters Link to publication Citation for published version (APA): Vigna-Gómez, A., Justham, S., Mandel, I., de Mink, S. E., & Podsiadlowski, P. (2019). Massive Stellar Mergers as Precursors of Hydrogen-rich Pulsational Pair Instability Supernovae. Astrophysical Journal Letters, 876(2), [L29]. https://doi.org/10.3847/2041- 8213/ab1bdf General rights It is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulations If you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: https://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. UvA-DARE is a service provided by the library of the University of Amsterdam (https://dare.uva.nl) Download date:29 Sep 2021 The Astrophysical Journal Letters, 876:L29 (6pp), 2019 May 10 https://doi.org/10.3847/2041-8213/ab1bdf © 2019. -
11. Dead Stars
Astronomy 110: SURVEY OF ASTRONOMY 11. Dead Stars 1. White Dwarfs and Supernovae 2. Neutron Stars & Black Holes Low-mass stars fight gravity to a standstill by becoming white dwarfs — degenerate spheres of ashes left over from nuclear burning. If they gain too much mass, however, these ashes can re-ignite, producing a titanic explosion. High-mass stars may make a last stand as neutron stars — degenerate spheres of neutrons. But at slightly higher masses, gravity triumphs and the result is a black hole — an object with a gravitational field so strong that not even light can escape. 1. WHITE DWARFS AND SUPERNOVAE a. Properties of White Dwarfs b. White Dwarfs in Binary Systems c. Supernovae and Remnants White Dwarfs in a Globular Cluster Hubble Space Telescope Finds Stellar Graveyard The Companion of Sirius Sirius weaves in its path; has a companion (Bessel 1844). 1800 1810 1820 1830 1840 1850 1860 1870 “Father, Sirius is a double star!” (Clark 1862). P = 50 yr, a = 19.6 au a3 = M + M ≃ 3 M⊙ P2 A B MA = 2 M⊙, MB = 1 M⊙ Why is the Companion So Faint? LB ≈ 0.0001 LA Because it’s so small! DB = 12000 km < D⊕ ≃ 6 3 ρB 2 × 10 g/cm The Dog Star, Sirius, and its Tiny Companion Origin and Nature A white dwarf is the degenerate carbon/oxygen core left after a double-shell red giant ejects its outer layers. Degeneracy Pressure Electrons are both particles and waves. h λ = The wavelength λ of an electron is me v e Rules for electrons in a box: 1.