N. M. Piskunov - Uppsala

N. M. Piskunov
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N. M. Piskunov

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Solar and Stellar Astrophysics (22)
Nuclear Experiment (19)
High Energy Physics - Experiment (9)
Instrumentation and Methods for Astrophysics (9)
Earth and Planetary Astrophysics (4)
Cosmology and Nongalactic Astrophysics (1)
High Energy Physics - Phenomenology (1)

Publications Authored By N. M. Piskunov

Exclusive measurements of the quasi-free $pn \to pp\pi^-$ and $pp \to pp\pi^0$ reactions have been performed by means of $pd$ collisions at $T_p$ = 1.2 GeV using the WASA detector setup at COSY. Total and differential cross sections have been obtained covering the energy region $T_p = 0. Read More

The search for 4He-eta bound states was performed with the WASA-at-COSY facility via the measurement of the excitation function for the dd->3He n pi0 and dd->3He p pi- processes. The beam momentum was varied continuously between 2.127 GeV/c and 2. Read More

Using the production reactions $pd\to {}^3\mbox{He}\,\omega$ and $pp\to pp\omega$, the Dalitz plot distribution for the $\omega \to \pi^+ \pi^- \pi^0$ decay is studied with the WASA detector at COSY, based on a combined data sample of $ (4.408\pm 0.042) \times 10^4$ events. Read More

The first generation of E-ELT instruments will include an optical-infrared High Resolution Spectrograph, conventionally indicated as EELT-HIRES, which will be capable of providing unique breakthroughs in the fields of exoplanets, star and planet formation, physics and evolution of stars and galaxies, cosmology and fundamental physics. A 2-year long phase A study for EELT-HIRES has just started and will be performed by a consortium composed of institutes and organisations from Brazil, Chile, Denmark, France, Germany, Italy, Poland, Portugal, Spain, Sweden, Switzerland and United Kingdom. In this paper we describe the science goals and the preliminary technical concept for EELT-HIRES which will be developed during the phase A, as well as its planned development and consortium organisation during the study. Read More

We present a description of a new instrument development, HARPS3, planned to be installed on an upgraded and roboticized Isaac Newton Telescope by end-2018. HARPS3 will be a high resolution (R = 115,000) echelle spectrograph with a wavelength range from 380-690 nm. It is being built as part of the Terra Hunting Experiment - a future 10 year radial velocity measurement programme to discover Earth-like exoplanets. Read More

We present a catalog of uniformly determined stellar properties and abundances for 1626 F, G, and K stars using an automated spectral synthesis modeling procedure. All stars were observed using the HIRES spectrograph at Keck Observatory. Our procedure used a single line list to fit model spectra to observations of all stars to determine effective temperature, surface gravity, metallicity, projected rotational velocity, and the abundances of 15 elements (C, N, O, Na, Mg, Al, Si, Ca, Ti, V, Cr, Mn, Fe, Ni, & Y). Read More

Context. The Spectroscopy Made Easy (SME) package has become a popular tool for analyzing stellar spectra, often in connection with large surveys or exoplanet research. SME has evolved significantly since it was first described in 1996, but many of the original caveats and potholes still haunt users. Read More

Various theoretical calculations based on QCD or hadronic interactions predict that in addition to the recently observed dibaryon resonance $d^*(2380)$ with $I(J^P) = 0(3^+)$ there should also exist a dibaryon resonance with mirrored quantum numbers $I(J^P) = 3(0^+)$. We report here on a search for such a $NN$-decoupled state in data on the $pp \to pp\pi^+\pi^+\pi^-\pi^-$ reaction. Since no clear-cut evidence has been found, we give upper limits for the production cross section of such a resonance in the mass range 2280 - 2500 MeV. Read More

We report on a high-statistics measurement of the most basic double pionic fusion reaction $\vec{n}p \to d\pi^0\pi^0$ over the energy region of the $d^*(2380)$ resonance by use of a polarized deuteron beam and observing the double fusion reaction in the quasifree scattering mode. The measurements were performed with the WASA detector setup at COSY. The data reveal substantial analyzing powers and confirm conclusions about the $d^*$ resonance obtained from unpolarized measurements. Read More

We performed extensive tests of the accuracy of atmospheric parameter determination for FGK stars based on the spectrum fitting procedure Spectroscopy Made Easy (SME). Our stellar sample consists of 13 objects, including the Sun, in the temperature range 5000--6600~K and metallicity range -1.4 -- +0. Read More

The WASA-at-COSY experiment has collected $3\times10^{7}$ events with $\eta$-mesons produced via the reaction $pd\rightarrow{^{3}\textrm{He}}\eta$ at $\textrm{T} = 1.0 \textrm{GeV}$. Using this data set, we evaluate the branching ratios of the decays $\eta\to\pi^{+}\pi^{-}\gamma$, $\eta\to e^{+}e^{-}\gamma$, $\eta\to\pi^{+}\pi^{-}e^{+}e^{-}$ and $\eta\to e^{+}e^{-}e^{+}e^{-}$. Read More

We propose a method for observing transiting exoplanets with near-infrared high-resolution spectrometers. We aim to create a robust data analysis method for recovering atmospheric transmission spectra from transiting exoplanets over a wide wavelength range in the near infrared. By using an inverse method approach, combined with stellar models and telluric transmission spectra, the method recovers the transiting exoplanet's atmospheric transmittance at high precision over a wide wavelength range. Read More

We study the spot distribution on the surface of LQ~Hya during the observing seasons October 1998 -- November 2002. We look for persistent active longitudes, trends in the level of spot activity and compare to photometric data, specifically to the derived time epochs of the lightcurve minima. We apply the Doppler Imaging technique on photospheric spectral lines using an inversion code to retrieve images of the surface temperature. Read More

We demonstrate a new procedure to derive accurate and precise surface gravities from high resolution spectra without the use of external constraints. Our analysis utilizes Spectroscopy Made Easy (SME) with robust spectral line constraints and uses an iterative process to mitigate degeneracies in the fitting process. We adopt an updated radiative transfer code, a new treatment for neutral perturber broadening, a line list with multiple gravity constraints and separate fitting for global stellar properties and abundance determinations. Read More

Authors: Giovanna Tinetti, Pierre Drossart, Paul Eccleston, Paul Hartogh, Kate Isaak, Martin Linder, Christophe Lovis, Giusi Micela, Marc Ollivier, Ludovic Puig, Ignasi Ribas, Ignas Snellen, Bruce Swinyard. France Allard, Joanna Barstow, James Cho, Athena Coustenis, Charles Cockell, Alexandre Correia, Leen Decin, Remco de Kok, Pieter Deroo, Therese Encrenaz, Francois Forget, Alistair Glasse, Caitlin Griffith, Tristan Guillot, Tommi Koskinen, Helmut Lammer, Jeremy Leconte, Pierre Maxted, Ingo Mueller-Wodarg, Richard Nelson, Chris North, Enric Pallé, Isabella Pagano, Guseppe Piccioni, David Pinfield, Franck Selsis, Alessandro Sozzetti, Lars Stixrude, Jonathan Tennyson, Diego Turrini, Mariarosa Zapatero-Osorio. Jean-Philippe Beaulieu, Denis Grodent, Manuel Guedel, David Luz, Hans Ulrik Nørgaard-Nielsen, Tom Ray, Hans Rickman, Avri Selig, Mark Swain. Marek Banaszkiewicz, Mike Barlow, Neil Bowles, Graziella Branduardi-Raymont, Vincent Coudé du Foresto, Jean-Claude Gerard, Laurent Gizon, Allan Hornstrup, Christopher Jarchow, Franz Kerschbaum, Géza Kovacs, Pierre-Olivier Lagage, Tanya Lim, Mercedes Lopez-Morales, Giuseppe Malaguti, Emanuele Pace, Enzo Pascale, Bart Vandenbussche, Gillian Wright, Gonzalo Ramos Zapata. Alberto Adriani, Ruymán Azzollini, Ana Balado, Ian Bryson, Raymond Burston, Josep Colomé, Vincent Coudé du Foresto, Martin Crook, Anna Di Giorgio, Matt Griffin, Ruud Hoogeveen, Roland Ottensamer, Ranah Irshad, Kevin Middleton, Gianluca Morgante, Frederic Pinsard, Mirek Rataj, Jean-Michel Reess, Giorgio Savini, Jan-Rutger Schrader, Richard Stamper, Berend Winter. L. Abe, M. Abreu, N. Achilleos, P. Ade, V. Adybekian, L. Affer, C. Agnor, M. Agundez, C. Alard, J. Alcala, C. Allende Prieto, F. J. Alonso Floriano, F. Altieri, C. A. Alvarez Iglesias, P. Amado, A. Andersen, A. Aylward, C. Baffa, G. Bakos, P. Ballerini, M. Banaszkiewicz, R. J. Barber, D. Barrado, E. J. Barton, V. Batista, G. Bellucci, J. A. Belmonte Avilés, D. Berry, B. Bézard, D. Biondi, M. Błęcka, I. Boisse, B. Bonfond, P. Bordé, P. Börner, H. Bouy, L. Brown, L. Buchhave, J. Budaj, A. Bulgarelli, M. Burleigh, A. Cabral, M. T. Capria, A. Cassan, C. Cavarroc, C. Cecchi-Pestellini, R. Cerulli, J. Chadney, S. Chamberlain, S. Charnoz, N. Christian Jessen, A. Ciaravella, A. Claret, R. Claudi, A. Coates, R. Cole, A. Collura, D. Cordier, E. Covino, C. Danielski, M. Damasso, H. J. Deeg, E. Delgado-Mena, C. Del Vecchio, O. Demangeon, A. De Sio, J. De Wit, M. Dobrijévic, P. Doel, C. Dominic, E. Dorfi, S. Eales, C. Eiroa, M. Espinoza Contreras, M. Esposito, V. Eymet, N. Fabrizio, M. Fernández, B. Femenía Castella, P. Figueira, G. Filacchione, L. Fletcher, M. Focardi, S. Fossey, P. Fouqué, J. Frith, M. Galand, L. Gambicorti, P. Gaulme, R. J. García López, A. Garcia-Piquer, W. Gear, J. -C. Gerard, L. Gesa, E. Giani, F. Gianotti, M. Gillon, E. Giro, M. Giuranna, H. Gomez, I. Gomez-Leal, J. Gonzalez Hernandez, B. González Merino, R. Graczyk, D. Grassi, J. Guardia, P. Guio, J. Gustin, P. Hargrave, J. Haigh, E. Hébrard, U. Heiter, R. L. Heredero, E. Herrero, F. Hersant, D. Heyrovsky, M. Hollis, B. Hubert, R. Hueso, G. Israelian, N. Iro, P. Irwin, S. Jacquemoud, G. Jones, H. Jones, K. Justtanont, T. Kehoe, F. Kerschbaum, E. Kerins, P. Kervella, D. Kipping, T. Koskinen, N. Krupp, O. Lahav, B. Laken, N. Lanza, E. Lellouch, G. Leto, J. Licandro Goldaracena, C. Lithgow-Bertelloni, S. J. Liu, U. Lo Cicero, N. Lodieu, P. Lognonné, M. Lopez-Puertas, M. A. Lopez-Valverde, I. Lundgaard Rasmussen, A. Luntzer, P. Machado, C. MacTavish, A. Maggio, J. -P. Maillard, W. Magnes, J. Maldonado, U. Mall, J. -B. Marquette, P. Mauskopf, F. Massi, A. -S. Maurin, A. Medvedev, C. Michaut, P. Miles-Paez, M. Montalto, P. Montañés Rodríguez, M. Monteiro, D. Montes, H. Morais, J. C. Morales, M. Morales-Calderón, G. Morello, A. Moro Martín, J. Moses, A. Moya Bedon, F. Murgas Alcaino, E. Oliva, G. Orton, F. Palla, M. Pancrazzi, E. Pantin, V. Parmentier, H. Parviainen, K. Y. Peña Ramírez, J. Peralta, S. Perez-Hoyos, R. Petrov, S. Pezzuto, R. Pietrzak, E. Pilat-Lohinger, N. Piskunov, R. Prinja, L. Prisinzano, I. Polichtchouk, E. Poretti, A. Radioti, A. A. Ramos, T. Rank-Lüftinger, P. Read, K. Readorn, R. Rebolo López, J. Rebordão, M. Rengel, L. Rezac, M. Rocchetto, F. Rodler, V. J. Sánchez Béjar, A. Sanchez Lavega, E. Sanromá, N. Santos, J. Sanz Forcada, G. Scandariato, F. -X. Schmider, A. Scholz, S. Scuderi, J. Sethenadh, S. Shore, A. Showman, B. Sicardy, P. Sitek, A. Smith, L. Soret, S. Sousa, A. Stiepen, M. Stolarski, G. Strazzulla, H. M Tabernero, P. Tanga, M. Tecsa, J. Temple, L. Terenzi, M. Tessenyi, L. Testi, S. Thompson, H. Thrastarson, B. W. Tingley, M. Trifoglio, J. Martín Torres, A. Tozzi, D. Turrini, R. Varley, F. Vakili, M. de Val-Borro, M. L. Valdivieso, O. Venot, E. Villaver, S. Vinatier, S. Viti, I. Waldmann, D. Waltham, D. Ward-Thompson, R. Waters, C. Watkins, D. Watson, P. Wawer, A. Wawrzaszk, G. White, T. Widemann, W. Winek, T. Wiśniowski, R. Yelle, Y. Yung, S. N. Yurchenko

The discovery of almost 2000 exoplanets has revealed an unexpectedly diverse planet population. Observations to date have shown that our Solar System is certainly not representative of the general population of planets in our Milky Way. The key science questions that urgently need addressing are therefore: What are exoplanets made of? Why are planets as they are? What causes the exceptional diversity observed as compared to the Solar System? EChO (Exoplanet Characterisation Observatory) has been designed as a dedicated survey mission for transit and eclipse spectroscopy capable of observing a large and diverse planet sample within its four-year mission lifetime. Read More


The detection of exoplanets using any method is prone to confusion due to the intrinsic variability of the host star. We investigate the effect of cool starspots on the detectability of the exoplanets around solar-like stars using the radial velocity method. For investigating this activity-caused "jitter" we calculate synthetic spectra using radiative transfer, known stellar atomic and molecular lines, different surface spot configurations, and an added planetary signal. Read More

Exoplanet science is booming. In 20 years our knowledge has expanded considerably, from the first discovery of a Hot Jupiter, to the detection of a large population of Neptunes and super-Earths, to the first steps toward the characterization of exoplanet atmospheres. Between today and 2025, the field will evolve at an even faster pace with the advent of several space-based transit search missions, ground-based spectrographs, high-contrast imaging facilities, and the James Webb Space Telescope. Read More

Intermediate-mass, magnetic chemically peculiar (Ap) stars provide a unique opportunity to study the topology of stellar magnetic fields in detail and to investigate magnetically driven processes of spot formation. Here we aim to derive the surface magnetic field geometry and chemical abundance distributions for the extraordinary Ap star HD 75049. This object hosts a surface field of ~30 kG, one of the strongest known for any non-degenerate star. Read More

Aims: We present a magnetic Doppler imaging study from all Stokes parameters of the cool, chemically peculiar star HD 24712. This is the very first such analysis performed at a resolving power exceeding 10^5. Methods: The analysis is performed on the basis of phase-resolved observations of line profiles in all four Stokes parameters obtained with the HARPSpol instrument attached at the 3. Read More

Exclusive measurements of the quasi-free $np \to np\pi^0\pi^0$ reaction have been performed by means of $dp$ collisions at $T_d$ = 2.27 GeV using the WASA detector setup at COSY. Total and differential cross sections have been obtained covering the energy region $\sqrt s$ = (2. Read More

Exclusive and kinematically complete measurements of the double pionic fusion to $^3$He have been performed in the energy region of the so-called ABC effect, which denotes a pronounced low-mass enhancement in the $\pi\pi$-invariant mass spectrum. The experiments were carried out with the WASA detector setup at COSY. Similar to the observations in the basic $pn \to d \pi^0\pi^0$ reaction and in the $dd \to ^4$He$\pi^0\pi^0$ reaction, the data reveal a correlation between the ABC effect and a resonance-like energy dependence in the total cross section. Read More

Authors: P. Adlarson1, W. Augustyniak2, W. Bardan3, M. Bashkanov4, F. S. Bergmann5, M. Berłowski6, H. Bhatt7, M. Büscher8, H. Calén9, I. Ciepał10, H. Clement11, D. Coderre12, E. Czerwiński13, K. Demmich14, E. Doroshkevich15, R. Engels16, A. Erven17, W. Erven18, W. Eyrich19, P. Fedorets20, K. Föhl21, K. Fransson22, F. Goldenbaum23, P. Goslawski24, A. Goswami25, K. Grigoryev26, C. --O. Gullström27, F. Hauenstein28, L. Heijkenskjöld29, V. Hejny30, M. Hodana31, B. Höistad32, N. Hüsken33, A. Jany34, B. R. Jany35, L. Jarczyk36, T. Johansson37, B. Kamys38, G. Kemmerling39, F. A. Khan40, A. Khoukaz41, D. A. Kirillov42, S. Kistryn43, H. Kleines44, B. Kłos45, M. Krapp46, W. Krzemień47, P. Kulessa48, A. Kupść49, K. Lalwani50, D. Lersch51, B. Lorentz52, A. Magiera53, R. Maier54, P. Marciniewski55, B. Mariański56, M. Mikirtychiants57, H. --P. Morsch58, P. Moskal59, H. Ohm60, I. Ozerianska61, E. Perez del Rio62, N. M. Piskunov63, P. Podkopał64, D. Prasuhn65, A. Pricking66, D. Pszczel67, K. Pysz68, A. Pyszniak69, C. F. Redmer70, J. Ritman71, A. Roy72, Z. Rudy73, S. Sawant74, S. Schadmand75, T. Sefzick76, V. Serdyuk77, R. Siudak78, T. Skorodko79, M. Skurzok80, J. Smyrski81, V. Sopov82, R. Stassen83, J. Stepaniak84, E. Stephan85, G. Sterzenbach86, H. Stockhorst87, H. Ströher88, A. Szczurek89, A. Täschner90, A. Trzciński91, R. Varma92, G. J. Wagner93, M. Wolke94, A. Wrońska95, P. Wüstner96, P. Wurm97, A. Yamamoto98, L. Yurev99, J. Zabierowski100, M. J. Zieliński101, A. Zink102, J. Złomańczuk103, P. {Ż}uprański104, M. {Ż}urek105, R. L. Workman106, W. J. Briscoe107, I. I. Strakovsky108
Affiliations: 1WASA-at-COSY Collaboration, 2WASA-at-COSY Collaboration, 3WASA-at-COSY Collaboration, 4WASA-at-COSY Collaboration, 5WASA-at-COSY Collaboration, 6WASA-at-COSY Collaboration, 7WASA-at-COSY Collaboration, 8WASA-at-COSY Collaboration, 9WASA-at-COSY Collaboration, 10WASA-at-COSY Collaboration, 11WASA-at-COSY Collaboration, 12WASA-at-COSY Collaboration, 13WASA-at-COSY Collaboration, 14WASA-at-COSY Collaboration, 15WASA-at-COSY Collaboration, 16WASA-at-COSY Collaboration, 17WASA-at-COSY Collaboration, 18WASA-at-COSY Collaboration, 19WASA-at-COSY Collaboration, 20WASA-at-COSY Collaboration, 21WASA-at-COSY Collaboration, 22WASA-at-COSY Collaboration, 23WASA-at-COSY Collaboration, 24WASA-at-COSY Collaboration, 25WASA-at-COSY Collaboration, 26WASA-at-COSY Collaboration, 27WASA-at-COSY Collaboration, 28WASA-at-COSY Collaboration, 29WASA-at-COSY Collaboration, 30WASA-at-COSY Collaboration, 31WASA-at-COSY Collaboration, 32WASA-at-COSY Collaboration, 33WASA-at-COSY Collaboration, 34WASA-at-COSY Collaboration, 35WASA-at-COSY Collaboration, 36WASA-at-COSY Collaboration, 37WASA-at-COSY Collaboration, 38WASA-at-COSY Collaboration, 39WASA-at-COSY Collaboration, 40WASA-at-COSY Collaboration, 41WASA-at-COSY Collaboration, 42WASA-at-COSY Collaboration, 43WASA-at-COSY Collaboration, 44WASA-at-COSY Collaboration, 45WASA-at-COSY Collaboration, 46WASA-at-COSY Collaboration, 47WASA-at-COSY Collaboration, 48WASA-at-COSY Collaboration, 49WASA-at-COSY Collaboration, 50WASA-at-COSY Collaboration, 51WASA-at-COSY Collaboration, 52WASA-at-COSY Collaboration, 53WASA-at-COSY Collaboration, 54WASA-at-COSY Collaboration, 55WASA-at-COSY Collaboration, 56WASA-at-COSY Collaboration, 57WASA-at-COSY Collaboration, 58WASA-at-COSY Collaboration, 59WASA-at-COSY Collaboration, 60WASA-at-COSY Collaboration, 61WASA-at-COSY Collaboration, 62WASA-at-COSY Collaboration, 63WASA-at-COSY Collaboration, 64WASA-at-COSY Collaboration, 65WASA-at-COSY Collaboration, 66WASA-at-COSY Collaboration, 67WASA-at-COSY Collaboration, 68WASA-at-COSY Collaboration, 69WASA-at-COSY Collaboration, 70WASA-at-COSY Collaboration, 71WASA-at-COSY Collaboration, 72WASA-at-COSY Collaboration, 73WASA-at-COSY Collaboration, 74WASA-at-COSY Collaboration, 75WASA-at-COSY Collaboration, 76WASA-at-COSY Collaboration, 77WASA-at-COSY Collaboration, 78WASA-at-COSY Collaboration, 79WASA-at-COSY Collaboration, 80WASA-at-COSY Collaboration, 81WASA-at-COSY Collaboration, 82WASA-at-COSY Collaboration, 83WASA-at-COSY Collaboration, 84WASA-at-COSY Collaboration, 85WASA-at-COSY Collaboration, 86WASA-at-COSY Collaboration, 87WASA-at-COSY Collaboration, 88WASA-at-COSY Collaboration, 89WASA-at-COSY Collaboration, 90WASA-at-COSY Collaboration, 91WASA-at-COSY Collaboration, 92WASA-at-COSY Collaboration, 93WASA-at-COSY Collaboration, 94WASA-at-COSY Collaboration, 95WASA-at-COSY Collaboration, 96WASA-at-COSY Collaboration, 97WASA-at-COSY Collaboration, 98WASA-at-COSY Collaboration, 99WASA-at-COSY Collaboration, 100WASA-at-COSY Collaboration, 101WASA-at-COSY Collaboration, 102WASA-at-COSY Collaboration, 103WASA-at-COSY Collaboration, 104WASA-at-COSY Collaboration, 105WASA-at-COSY Collaboration, 106SAID Data Analysis Center, 107SAID Data Analysis Center, 108SAID Data Analysis Center

New data on quasifree polarized neutron-proton scattering, in the region of the recently observed $d^*$ resonance structure, have been obtained by exclusive and kinematically complete high-statistics measurements with WASA at COSY. This paper details the determination of the beam polarization, checks of the quasifree character of the scattering process, on all obtained $A_y$ angular distributions and on the new partial-wave analysis, which includes the new data producing a resonance pole in the $^3D_3$-$^3G_3$ coupled partial waves at ($2380\pm10 - i40\pm5$) MeV -- in accordance with the $d^*$ dibaryon resonance hypothesis. The effect of the new partial-wave solution on the description of total and differential cross section data as well as specific combinations of spin-correlation and spin-transfer observables available from COSY-ANKE measurements at $T_d$ = 2. Read More

Magnetic Doppler imaging from four Stokes parameter observations has uncovered a new level of complexity of stellar magnetic fields previously not known. This new information is of interest to the evolution and structure of magnetic fields of intermediate and high-mass stars. Recently, we performed magnetic Doppler imaging study of the chemically peculiar star HD 24712 using phase-resolved spectropolarimetric observations of line-profiles in all four Stokes parameters. Read More

CRIRES, the ESO high resolution infrared spectrometer, is a unique instrument which allows astronomers to access a parameter space which up to now was largely uncharted. In its current setup, it consists of a single-order spectrograph providing long-slit, single-order spectroscopy with resolving power up to R=100,000 over a quite narrow spectral range. This has resulted in sub-optimal efficiency and use of telescope time for all the scientific programs requiring broad spectral coverage of compact objects (e. Read More

Charge symmetry breaking (CSB) observables are a suitable experimental tool to examine effects induced by quark masses on the nuclear level. Previous high precision data from TRIUMF and IUCF are currently used to develop a consistent description of CSB within the framework of chiral perturbation theory. In this work the experimental studies on the reaction dd->4He{\pi}0 have been extended towards higher excess energies in order to provide information on the contribution of p-waves in the final state. Read More


Dalitz plot distribution of the $\eta\to\pi^+\pi^-\pi^0$ decay is determined using a data sample of $1.2\cdot 10^7$ $\eta$ mesons from $pd\to ^3\textrm{He}\eta$ reaction at 1 GeV collected by the WASA detector at COSY. Read More

Exclusive and kinematically complete high-statistics measurements of quasifree polarized $\vec{n}p$ scattering have been performed in the energy region of the narrow resonance structure $d^*$ with $I(J^P) = 0(3^+)$, $M \approx$ 2380 MeV/$c^2$ and $\Gamma \approx$ 70 MeV observed recently in the double-pionic fusion channels $pn \to d\pi^0\pi^0$ and $pn \to d\pi^+\pi^-$. The experiment was carried out with the WASA detector setup at COSY having a polarized deuteron beam impinged on the hydrogen pellet target and utilizing the quasifree process $\vec{d}p \to np + p_{spectator}$. That way the $np$ analyzing power $A_y$ was measured over a large angular range. Read More


We present new data for angular distributions and on the cross section ratio of the p + d -> 3He + eta reaction at excess energies of Q = 48.8 MeV and Q = 59.8 MeV. Read More

Based on detailed spectral synthesis we carry out quantitative measurements of the strength and complexity of surface magnetic fields in the four well-known M-dwarfs GJ 388, GJ 729, GJ 285, and GJ 406 populating the mass regime around the boundary between partially and fully convective stars. Very high resolution R=100000, high signal-to-noise (up to 400) near-infrared Stokes I spectra were obtained with CRIRES at ESO's Very Large Telescope covering regions of the FeH Wing-Ford transitions at 1mum. The field distributions in all four stars are characterized by three distinct groups of field components, the data are neither consistent with a smooth distribution of different field strengths, nor with one average field strength covering the full star. Read More

Current knowledge about stellar magnetic fields relies almost entirely on circular polarization observations. Few objects have been observed in all four Stokes parameters. The magnetic Ap star HD 24712 (DO Eri, HR 1217) was recently observed in the Stokes IQUV parameters with the HARPSpol instrument at the 3. Read More

Our current knowledge about the stellar magnetic fields relies almost entirely on the circular polarization observations. Very few objects have been observed so far in all four Stokes parameters. The magnetic Ap star HD24712 (DO Eri, HR1217) was recently observed in the Stokes IQUV parameters with the HARPSpol instrument at the 3. Read More


Exclusive measurements of the quasi-free $pn \to pp\pi^0\pi^-$ reaction have been performed by means of $pd$ collisions at $T_p$ = 1.2 GeV using the WASA detector setup at COSY. Total and differential cross sections have been obtained covering the energy region $\sqrt s$ = (2. Read More

High-resolution spectropolarimetric observations provide simultaneous information about stellar magnetic field topologies and three-dimensional distributions of chemical elements. Here we present analysis of a unique full Stokes vector spectropolarimetric data set, acquired for the cool magnetic Ap star HD 24712. The goal of our work is to examine circular and linear polarization signatures inside spectral lines and to study variation of the stellar spectrum and magnetic observables as a function of rotational phase. Read More

Several recent spectrophotometric studies failed to detect significant global magnetic fields in late-B HgMn chemically peculiar stars, but some investigations have suggested the presence of strong unstructured or tangled fields in these objects. We used detailed spectrum synthesis analysis to search for evidence of tangled magnetic fields in high-quality observed spectra of 8 slowly rotating HgMn stars and one normal late-B star. We also evaluated recent sporadic detections of weak longitudinal magnetic fields in HgMn stars based on the moment technique. Read More


An exclusive measurement of the dd -> 3He n \pi 0 reaction was carried at a beam momentum of p = 1.2 GeV/c using the WASA-at-COSY facility. For the first time data on the total cross section as well as differential distributions were obtained. Read More


The presently world largest data sample of pi0 --> gamma e+e- decays containing nearly 5E5 events was collected using the WASA detector at COSY. A search for a dark photon U produced in the pi0 --> gamma U --> gamma e+e- decay from the pp-->pp\pi^0 reaction was carried out. An upper limit on the square of the U-gamma mixing strength parameter epsilon^2 of 5e-6 at 90% CL was obtained for the mass range 20 MeV Read More

In atmospheres of magnetic main-sequence stars, the diffusion of chemical elements leads to a number of observed anomalies, such as abundance spots across the stellar surface. The aim of this study was to derive a detailed picture of the surface abundance distribution of the magnetic chemically peculiar star HD 3980. Based on high-resolution, phase-resolved spectroscopic observations of the magnetic A-type star HD 3980, the inhomogeneous surface distribution of 13 chemical elements (Li, O, Si, Ca, Cr, Mn, Fe, La, Ce, Pr, Nd, Eu, and Gd) has been reconstructed. Read More

Stellar activity signatures such as spots and plage can significantly limit the search for extrasolar planets. Current models of activity-induced radial velocity (RV) signals focused on the impact of temperature contrast in spots predicting the signal to diminish toward longer wavelengths. On the other hand, the relative importance of the Zeeman effect on RV measurements should grow with wavelength, because the Zeeman displacement itself grows with \lambda, and because a magnetic and cool spot contributes more to the total flux at longer wavelengths. Read More

We present high spectral resolution ($R\approx108,000$) Stokes $V$ polarimetry of the Classical T Tauri stars (CTTSs) GQ Lup and TW Hya obtained with the polarimetric upgrade to the HARPS spectrometer on the ESO 3.6 m telescope. We present data on both photospheric lines and emission lines, concentrating our discussion on the polarization properties of the \ion{He}{1} emission lines at 5876 \AA\ and 6678 \AA. Read More

We present two new accurate and efficient method to compute the formal solution of the polarized radiative transfer equation. In this work, the source function and the absorption matrix are approximated using quadratic and cubic Bezier spline interpolants. These schemes provide 2nd and 3rd order approximation respectively and don't suffer from erratic behavior of the polynomial approximation (overshooting). Read More

The relativley large spread in the derived metallicities ([Fe/H]) of M dwarfs shows that various approaches have not yet converged to consistency. The presence of strong molecular features, and incomplete line lists for the corresponding molecules have made metallicity determinations of M dwarfs difficult. Furthermore, the faint M dwarfs require long exposure times for a signal-to-noise ratio sufficient for a detailed spectroscopic abundance analysis. Read More

Mercury-manganese (HgMn) stars have been considered as non-magnetic and non-variable chemically peculiar (CP) stars for a long time. However, recent discoveries of the variability in spectral line profiles have suggested an inhomogeneous surface distribution of chemical elements in some HgMn stars. From the studies of other CP stars it is known that magnetic field plays a key role in the formation of surface spots. Read More

Chemically peculiar stars of the mercury-manganese (HgMn) type represent a new class of spotted late-B stars, in which evolving surface chemical inhomogeneities are apparently unrelated to the presence of strong magnetic fields but are produced by some hitherto unknown astrophysical mechanism. The goal of this study is to perform a detailed line profile variability analysis and carry out a sensitive magnetic field search for one of the brightest HgMn stars - mu Lep. We acquired a set of very high-quality intensity and polarization spectra of mu Lep with the HARPSpol polarimeter. Read More

We present new data for the polarization observables of the final state proton in the $^{1}H(\vec{\gamma},\vec{p})\pi^{0}$ reaction. These data can be used to test predictions based on hadron helicity conservation (HHC) and perturbative QCD (pQCD). These data have both small statistical and systematic uncertainties, and were obtained with beam energies between 1. Read More

Close M-dwarf binaries and higher multiples allow the investigation of rotational evolution and mean magnetic flux unbiased from scatter in inclination angle and age since the orientation of the spin axis of the components is most likely parallel and the individual systems are coeval. Systems composed of an early (M0.0 -- M4. Read More

Authors: P. Adlarson, C. Adolph, W. Augustyniak, W. Bardan, M. Bashkanov, T. Bednarski, F. S. Bergmann, M. Berłowski, H. Bhatt, K. -T. Brinkmann, M. Büscher, H. Calén, H. Clement, D. Coderre, E. Czerwiński, E. Doroshkevich, R. Engels, W. Erven, W. Eyrich, P. Fedorets, K. Föhl, K. Fransson, F. Goldenbaum, P. Goslawski, K. Grigoryev, C. -O. Gullström, C. Hanhart, L. Heijkenskjöld, J. Heimlich, V. Hejny, F. Hinterberger, M. Hodana, B. Höistad, M. Jacewicz, A. Jany, B. R. Jany, L. Jarczyk, T. Johansson, B. Kamys, G. Kemmerling, O. Khakimova, A. Khoukaz, S. Kistryn, J. Klaja, H. Kleines, B. Kłos, F. Kren, W. Krzemień, P. Kulessa, A. Kupść, K. Lalwani, S. Leupold, B. Lorentz, A. Magiera, R. Maier, B. Mariański, P. Marciniewski, U. -G. Meißner, M. Mikirtychiants, H. -P. Morsch, P. Moskal, B. K. Nandi, S. Niedźwiecki, H. Ohm, A. Passfeld, C. Pauly, E. Perez del Rio, T. Petri, Y. Petukhov, N. Piskunov, P. Pluciński, P. Podkopał, A. Povtoreyko, D. Prasuhn, A. Pricking, K. Pysz, A. Pyszniak, T. Rausmann, C. F. Redmer, J. Ritman, A. Roy, Z. Rudy, S. Sawant, S. Schadmand, A. Schmidt, T. Sefzick, V. Serdyuk, N. Shah, M. Siemaszko, R. Siudak, T. Skorodko, M. Skurzok, J. Smyrski, V. Sopov, R. Stassen, J. Stepaniak, G. Sterzenbach, H. Stockhorst, F. Stollenwerk, A. Szczurek, A. Täschner, C. Terschlüsen, T. Tolba, A. Trzciński, R. Varma, P. Vlasov, G. J. Wagner, W. Węglorz, A. Winnemöller, A. Wirzba, M. Wolke, A. Wrońska, P. Wüstner, P. Wurm, X. Yuan, L. Yurev, J. Zabierowski, C. Zheng, M. J. Zieliński, W. Zipper, J. Złomańczuk, P. Żuprański

An exclusive measurement of the decay eta --> pi+ pi- gamma has been performed at the WASA facility at COSY. The eta mesons were produced in the fusion reaction pd --> 3He X at a proton beam momentum of 1.7 GeV/c. Read More


The reaction pp->pppi0pi0 has been investigated at a beam energy of 1.4 GeV using the WASA-at-COSY facility. The total cross section is found to be (324 +- 21_systematic +- 58_normalization) mub. Read More

Aims. We study the spot activity of II Peg during the years 2004-2010 to determine long- and short-term changes in the magnetic activity. In a previous study, we detected a persistent active longitude, as well as major changes in the spot configuration occurring on a timescale of shorter than a year. Read More

Galaxies are believed to be the main providers of Lyman continuum (LyC) photons during the early phases of the cosmic reionization. Little is known however, when it comes to escape fractions and the mechanisms behind the leakage. To learn more one may look at local objects, but so far only one low-z galaxy has shown any sign of emitting LyC radiation. Read More

The reaction pp -> K^+ + (Lambda p) has been measured at T_p = 1.953 GeV and \Theta = 0 deg with a high missing mass resolution in order to study the Lambda p final state interaction. Narrow S = -1 resonances predicted by bag model calculations are not visible in the missing mass spectrum. Read More