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M Chadid and J Vernin and G Preston and C Zalian and C Pouzenc and L Abe and A Agabi and E Aristidi and LY Liu and D, . (2014). First Detection of Multi-shocks in RR Lyrae Stars from Antarctica: A Possible Explanation of the
. Astron. J. (N. Y.), 148(5), 88–.
Abstract: We present the first detection of multi-shocks propagating through the atmosphere of the Blazhko star S Arae using uninterrupted, accurate optical photometric data collected during one polar night, 150 days from Antarctica at Dome C, with the Photometer AntarctIca eXtinction (PAIX). We acquired 89,736 CCD frames during 323 pulsation cycles and 3 Blazhko cycles. We detected two new light curve properties in the PAIX light curve, ${jump}$ and ${rump}$, which we associated with two new post-maximum shock waves ShPM1 and ShPM2. ${jump}$, lump, ${rump}$, bump, and hump are induced by five shock waves, with different amplitudes and origins, ShPM1, ShPM, ShPM2, ShPM3, and the main shock ShH + He. Correlations between the length of rise time and light amplitude and ShPM3 are monotonous during three Blazhko cycles, but the pulsation curve is double peaked. We discuss the physical mechanisms driving the modulation of these quantities. Finally, we hypothesize that the origin of the Blazhko effect is a dynamical interaction between a multi-shock structure and an outflowing wind in a coronal structure.
Programme: 1096
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Korbinian Sager, Christian Boehm, Laura Ermert, Lion Krischer, Andreas Fichtner. (2020). Global-Scale Full-Waveform Ambient Noise Inversion (Vol. 125).
Abstract: We present the first application of full-waveform ambient noise inversion to observed correlation functions that jointly constrains 3-D Earth structure and heterogeneous noise sources. For this, we model and interpret ambient noise correlations as recordings of correlation wavefields, which completely eliminates the limiting assumptions of Green's function retrieval, such as equipartitioning and homogeneous random noise sources. Our method accounts for seismic wave propagation physics in 3-D heterogeneous and attenuating media and also for the heterogeneous and nonstationary nature of the ambient noise field. Designed as a proof of concept, the study considers long periods from 100 to 300 s, thus focusing on the Earth's hum. Treating correlations as self-consistent observables allows us to make separate measurements on the causal and acausal branches of correlation functions, without any need to choose one of them or form the average. We validate our approach by assessing the quality of the obtained models and by comparing them to previous studies. This work is a step toward the establishment of full-waveform ambient noise inversion as a tomographic technique with the goal to go beyond ambient noise tomography based on Green's function retrieval.
Keywords: computational seismology full-waveform inversion global tomography interferometry seismic noise
Programme: 133
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Faith Hawthorn, Daniel Bayliss, Thomas G Wilson, Andrea Bonfanti, Vardan Adibekyan, Yann Alibert, Sérgio G Sousa, Karen A Collins, Edward M Bryant, Ares Osborn, David J Armstrong, Lyu Abe, Jack S Acton, Brett C Addison, Karim Agabi, Roi Alonso, Douglas R Alves, Guillem Anglada-Escudé, Tamas Bárczy, Thomas Barclay, David Barrado, Susana C C Barros, Wolfgang Baumjohann, Philippe Bendjoya, Willy Benz, Allyson Bieryla, Xavier Bonfils, François Bouchy, Alexis Brandeker, Christopher Broeg, David J A Brown, Matthew R Burleigh, Marco Buttu, Juan Cabrera, Douglas A Caldwell, Sarah L Casewell, David Charbonneau, Sébastian Charnoz, Ryan Cloutier, Andrew Collier Cameron, Kevin I Collins, Dennis M Conti, Nicolas Crouzet, Szilárd Czismadia, Melvyn B Davies, Magali Deleuil, Elisa Delgado-Mena, Laetitia Delrez, Olivier D S Demangeon, Brice-Olivier Demory, Georgina Dransfield, Xavier Dumusque, Jo Ann Egger, David Ehrenreich, Philipp Eigmüller, Anders Erickson, Zahra Essack, Andrea Fortier, Luca Fossati, Malcolm Fridlund, Maximilian N Günther, Manuel Güdel, Davide Gandolfi, Harvey Gillard, Michaël Gillon, Crystal Gnilka, Michael R Goad, Robert F Goeke, Tristan Guillot, Andreas Hadjigeorghiou, Coel Hellier, Beth A Henderson, Kevin Heng, Matthew J Hooton, Keith Horne, Steve B Howell, Sergio Hoyer, Jonathan M Irwin, James S Jenkins, Jon M Jenkins, Eric L N Jensen, Stephen R Kane, Alicia Kendall, John F Kielkopf, Laszlo L Kiss, Gaia Lacedelli, Jacques Laskar, David W Latham, Alain Lecavalier des Etangs, Adrien Leleu, Monika Lendl, Jorge Lillo-Box, Christophe Lovis, Djamel Mékarnia, Bob Massey, Tamzin Masters, Pierre F L Maxted, Valerio Nascimbeni, Louise D Nielsen, Sean M O’Brien, Göran Olofsson, Hugh P Osborn, Isabella Pagano, Enric Pallé, Carina M Persson, Giampaolo Piotto, Peter Plavchan, Don Pollacco, Didier Queloz, Roberto Ragazzoni, Heike Rauer, Ignasi Ribas, George Ricker, Damien Ségransan, Sébastien Salmon, Alexandre Santerne, Nuno C Santos, Gaetano Scandariato, François-Xavier Schmider, Richard P Schwarz, Sara Seager, Avi Shporer, Attila E Simon, Alexis M S Smith, Gregor Srdoc, Manfred Steller, Olga Suarez, Gyula M Szabó, Johanna Teske, Nicolas Thomas, Rosanna H Tilbrook, Amaury H M J Triaud, Stéphane Udry, Valérie Van Grootel, Nicholas Walton, Sharon X Wang, Peter J Wheatley, Joshua N Winn, Robert A Wittenmyer, Hui Zhang. (2023). TOI-836: A super-Earth and mini-Neptune transiting a nearby K-dwarf (Vol. 520).
Abstract: We present the discovery of two exoplanets transiting TOI-836 (TIC 440887364) using data from TESS Sector 11 and Sector 38. TOI-836 is a bright (T = 8.5 mag), high proper motion (∼200 mas yr−1), low metallicity ([Fe/H]≈−0.28) K-dwarf with a mass of 0.68 ± 0.05 M⊙ and a radius of 0.67 ± 0.01 R⊙. We obtain photometric follow-up observations with a variety of facilities, and we use these data sets to determine that the inner planet, TOI-836 b, is a 1.70 ± 0.07 R⊕ super-Earth in a 3.82-d orbit, placing it directly within the so-called ‘radius valley’. The outer planet, TOI-836 c, is a 2.59 ± 0.09 R⊕ mini-Neptune in an 8.60-d orbit. Radial velocity measurements reveal that TOI-836 b has a mass of 4.5 ± 0.9 M⊕, while TOI-836 c has a mass of 9.6 ± 2.6 M⊕. Photometric observations show Transit Timing Variations (TTVs) on the order of 20 min for TOI-836 c, although there are no detectable TTVs for TOI-836 b. The TTVs of planet TOI-836 c may be caused by an undetected exterior planet.
Programme: 1066
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Noah Vowell, Joseph E. Rodriguez, Samuel N. Quinn, George Zhou, Andrew Vanderburg, Andrew W. Mann, Matthew J. Hooton, Keivan G. Stassun, Saburo Howard, Allyson Bieryla, David W. Latham, Steve B. Howell, Tristan Guillot, Carl Ziegler, Karen A. Collins, Theron W. Carmichael, Jon M. Jenkins, Avi Shporer, Lyu ABE, Philippe Bendjoya, Jonathan L. Bush, Marco Buttu, Kevin I. Collins, Jason D. Eastman, Matthew J. Fields, Thomas Gasparetto, Maximilian N. Günther, Veselin B. Kostov, Adam L. Kraus, Kathryn V. Lester, Alan M. Levine, Colin Littlefield, Wenceslas Marie-Sainte, Djamel Mékarnia, Hugh P. Osborn, David Rapetti, George R. Ricker, S. Seager, Ramotholo Sefako, Gregor Srdoc, Olga Suarez, Guillermo Torres, Amaury H. M. J. Triaud, R. Vanderspek, Joshua N. Winn. (2023). HIP 33609 b: An Eccentric Brown Dwarf Transiting a V = 7.3 Rapidly Rotating B Star (Vol. 165).
Abstract: We present the discovery and characterization of HIP 33609 b, a transiting warm brown dwarf orbiting a late B star, discovered by NASA's Transiting Exoplanet Survey Satellite as TOI-588 b. HIP 33609 b is a large (R b = R J) brown dwarf on a highly eccentric (e = ) orbit with a 39 days period. The host star is a bright (V = 7.3 mag), T eff = 10,400 K star with a mass of M * = M ⊙ and radius of R * = R ⊙, making it the hottest transiting brown dwarf host star discovered to date. We obtained radial velocity measurements from the CHIRON spectrograph confirming the companion's mass of M b = M J as well as the host star's rotation rate ( km s−1). We also present the discovery of a new comoving group of stars, designated as MELANGE-6, and determine that HIP 33609 is a member. We use a combination of rotation periods and isochrone models fit to the cluster members to estimate an age of 150 ± 25 Myr. With a measured mass, radius, and age, HIP 33609 b becomes a benchmark for substellar evolutionary models.
Programme: 1066
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Aristidi E., Agabi K., Fossat E., Azouit M., Martin F., Sadibekova T., Travouillon T., Vernin J. & Ziad A. (2005). Site testing in summer at Dome C, Antarctica. Astronomy & astrophysics, 444(2), 651–659.
Abstract: We present summer site testing results based on DIMM data obtained at Dome C, Antarctica. These data were collected on the bright star Canopus during two 3-months summer campaigns in 2003-2004 and 2004-2005. We performed continuous monitoring of the seeing and the isoplanatic angle in the visible. We found a median seeing of 0.54'' and a median isoplanatic angle of 6.8''. The seeing appears to have a deep minimum around 0.4'' almost every day in late afternoon.
Keywords: site testing
Programme: 908
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Hu X G, Liu L T, Kroner C, Sun H P, . (2009). Observation of the seismic anisotropy effects on free oscillations below 4 mHz
. J. Geophys. Res., 114(B7), B07301–.
Abstract: We present observations of significant fundamental spheroidal-toroidal mode coupling at frequencies below 4 mHz in the early part of vertical component records from seismic stations on near-equatorial source-receiver propagation paths after the 26 December 2004 and 28 March 2005 great Sumatra earthquakes. Since the mixed-type coupling induced by rotational Coriolis force are very weak at these selected equatorial-path stations, we investigate what effects mimic the strong Coriolis effects at frequencies below 4 mHz, suggesting that local azimuthal anisotropy in the upper mantle is the most likely explanation for the strong anomalous coupling we observed. In addition, strong anisotropy coupling observed in the frequency band of 14 mHz is always characterized by anomalous small amplitudes of coupled spheroidal modes on the vertical component of seismograph, suggesting that excitation of quasi-toroidal modes by azimuthal anisotropy associates with geometric nodes of fundamental spheroidal modes.
Keywords: seismic anisotropy, free oscillations of the earth, mixed-type mode coupling, 7255 Surface waves and free oscillations, 7208 Mantle, 7299 General or miscellaneous,
Programme: 133
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Séran E, Godefroy M, Kauristie K, Cerisier J-C, Berthelier J-J, Lester M, Sarri L-E, . (2009). What can we learn from HF signal scattered from a discrete arc?
. Ann. Geophys., 27(5), 1887–1896.
Abstract: We present observations of a discrete southward propagating arc which appeared in the mid-night sector at latitudes equatorward of main substorm activity. The arc observations were made simultaneously by the ALFA (Auroral Light Fine Analysis) optical camera, the SuperDARN-CUTLASS HF radar and the Demeter satellite during a coordinated multi-instrumental campaign conducted at the KEOPS/ESRANGE site in December 2006. The SuperDARN HF signal which is often lost in the regions of strong electron precipitation yields in our case clear backscatter from an isolated arc of weak intensity. Consequently we are able to study arc dynamics, the formation of meso-scale irregularities of the electron density along the arc, compare the arc motion with the convection of surrounding plasma and discuss the contribution of ionospheric ions in the arc erosion and its propagation.
Programme: 312;911
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Léo Bosse, Jean Lilensten, Nicolas Gillet, Sylvain Rochat, Alain Delboulbé, Stephane Curaba, Alain Roux, Yves Magnard, Magnar G. Johnsen, Unni-Pia Løvhaug, Pierre-Olivier Amblard, Nicolas Le Bihan, Maxime Nabon, Hanane Marif, Frédérique Auriol, Camille Noûs. (2020). On the nightglow polarisation for space weather exploration (Vol. 10).
Abstract: We present here observations of the polarisation of four auroral lines in the auroral oval and in the polar cusp using a new ground polarimeter called Petit Cru. Our results confirm the already known polarisation of the red line, and show for the first time that the three other lines observed here (namely 557.7 nm, 391.4 nm and 427.8 nm) are polarised as well up to a few percent. We show that in several circumstances, this polarisation is linked to the local magnetic activity and to the state of the ionosphere through the electron density measured with EISCAT. However, we also show that the contribution of light pollution from nearby cities via scattering can not be ignored and can play an important role in polarisation measurements. This series of observations questions the geophysical origin of the polarisation. It also leaves open its relation to the magnetic field orientation and to the state of both the upper atmosphere and the troposphere.
Keywords: polarisation / aurora
Programme: 1026
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Laurel Kaye, Shreyas Vissapragada, Maximilian N Günther, Suzanne Aigrain, Thomas Mikal-Evans, Eric L N Jensen, Hannu Parviainen, Francisco J Pozuelos, Lyu Abe, Jack S Acton, Abdelkrim Agabi, Douglas R Alves, David R Anderson, David J Armstrong, Khalid Barkaoui, Oscar Barragán, Björn Benneke, Patricia T Boyd, Rafael Brahm, Ivan Bruni, Edward M Bryant, Matthew R Burleigh, Sarah L Casewell, David Ciardi, Ryan Cloutier, Karen A Collins, Kevin I Collins, Dennis M Conti, Ian J M Crossfield, Nicolas Crouzet, Tansu Daylan, Diana Dragomir, Georgina Dransfield, Daniel Fabrycky, Michael Fausnaugh, Gábor Fuűrész, Tianjun Gan, Samuel Gill, Michaël Gillon, Michael R Goad, Varoujan Gorjian, Michael Greklek-McKeon, Natalia Guerrero, Tristan Guillot, Emmanuël Jehin, J S Jenkins, Monika Lendl, Jacob Kamler, Stephen R Kane, John F Kielkopf, Michelle Kunimoto, Wenceslas Marie-Sainte, James McCormac, Djamel Mékarnia, Farisa Y Morales, Maximiliano Moyano, Enric Palle, Vivien Parmentier, Howard M Relles, François-Xavier Schmider, Richard P Schwarz, S Seager, Alexis M S Smith, Thiam-Guan Tan, Jake Taylor, Amaury H M J Triaud, Joseph D Twicken, Stephane Udry, J I Vines, Gavin Wang, Peter J Wheatley, Joshua N Winn. (2021). Transit timings variations in the three-planet system: TOI-270 (Vol. 510).
Abstract: We present ground- and space-based photometric observations of TOI-270 (L231-32), a system of three transiting planets consisting of one super-Earth and two sub-Neptunes discovered by TESS around a bright (K-mag = 8.25) M3V dwarf. The planets orbit near low-order mean-motion resonances (5:3 and 2:1) and are thus expected to exhibit large transit timing variations (TTVs). Following an extensive observing campaign using eight different observatories between 2018 and 2020, we now report a clear detection of TTVs for planets c and d, with amplitudes of ∼10 min and a super-period of ∼3 yr, as well as significantly refined estimates of the radii and mean orbital periods of all three planets. Dynamical modelling of the TTVs alone puts strong constraints on the mass ratio of planets c and d and on their eccentricities. When incorporating recently published constraints from radial velocity observations, we obtain masses of $M{\mathrm{b}}=1.48\pm 0.18\, M\oplus$, $M{\mathrm{c}}=6.20\pm 0.31\, M\oplus$, and $M{\mathrm{d}}=4.20\pm 0.16\, M\oplus$ for planets b, c, and d, respectively. We also detect small but significant eccentricities for all three planets : eb = 0.0167 ± 0.0084, ec = 0.0044 ± 0.0006, and ed = 0.0066 ± 0.0020. Our findings imply an Earth-like rocky composition for the inner planet, and Earth-like cores with an additional He/H2O atmosphere for the outer two. TOI-270 is now one of the best constrained systems of small transiting planets, and it remains an excellent target for atmospheric characterization.
Programme: 1066
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Maggi A., Tape C., Chen M., Chao D. & Tromp J. (2009). An automated data-window selection algorithm for adjoint tomography. Geophysical journal international, 178, 257–281.
Abstract: We present FLEXWIN, an open source algorithm for the automated selection of time windows on pairs of observed and synthetic seismograms. The algorithm was designed specifically to accommodate synthetic seismograms produced from 3-D wavefield simulations, which capture complex phases that do not necessarily exist in 1-D simulations or traditional traveltime curves. Relying on signal processing tools and several user-tuned parameters, the algorithm is able to include these new phases and to maximize the number of measurements made on each seismic record, while avoiding seismic noise. Our motivation is to use the algorithm for iterative tomographic inversions, in which the synthetic seismograms change from one iteration to the next. Hence, automation is needed to handle the volume of measurements and to allow for an increasing number of windows at each model iteration. The algorithm is sufficiently flexible to be adapted to many tomographic applications and seismological scenarios, including those based on synthetics generated from 1-D models. We illustrate the algorithm using data sets from three distinct regions: the entire globe, the Japan subduction zone, and southern California.
Programme: 133;906
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