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4 results on '"Valeev, A.F."'

1. Superfast line profiles variability in spectra of OBA stars

Author

Kholtygin, A.F., Moiseeva, A.V., Valeev, A.F., Kostenkov, A.E., Tsiopa, O.A., Yakunin, I.A., Fabrika, S.N., Burlak, M.A., Ikonnikova, N.P., Kurdoyakova, M.S., and Ryspaeva, E.B.

Subjects
Line profile variations, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Spectra, OBA stars, Stars, Astrophysics::Galaxy Astrophysics
Abstract

We present new results of our Large Project for revealing the superfast line profile variations (sfLPVs) in spectra of bright OBA stars. The regular variations of the line profiles with periods ranging from a few hours to days in spectra of all massive OBA stars are well known. Recent observations of the A0 supergiant HD92207 using FORS2 spectrograph in spectropolarimetric mode mounted on the 8-m VLT telescope showed moderate line profile variations of various lines on a time-scale of minutes. Such short time-scale LPVs were also detected in our spectral time series for HD 93521 (O9.5III), rho Leo (B1Iab), alpha2 CVn (A0VpSiEu), gamma UMi and other stars obtained with the multi-mode focal reducer SCORPIO at the 6-meter telescope (Northern Caucasus, Russia). Both regular LPVs with periods from 1 to 90 minutes and non-regular LPVs with amplitudes of 1-2% of the continuum level were detected. Our spectral observations of rho Leo at the 1.25-m telescopes of Crimean Astronomical Station of the Sternberg Astronomical Institute (Russia) also lets to detection of sfLPVs in spectra of rho Leo. The presence of the short-term spectral variability in massive OBA stars, which are (at least partly) suggested to be the progenitors of Type II supernova, was not studied in the past and can be crucial for the current theoretical understanding of the supernova physics and for modeling the stellar evolution. We plan to increase the number of telescopes used for observations of OBA stars with ultra-high temporal resolution.

Published
2021
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2. GRB 161219B/SN 2016jca: a powerful stellar collapse

Author

Independent Research Fund Denmark, Instrument Center for Danish Astrophysics, Leverhulme Trust, Istituto Nazionale di Astrofisica, National Science Foundation (US), Ministerio de Economía y Competitividad (España), European Commission, National Aeronautics and Space Administration (US), Russian Science Foundation, Villum Fonden, Ashall, Chris, Mazzali, Paolo A., Pian, E., Woosley, S.E., Palazzi, E., Prentice, S.J., Kobayashi, S., Holmbo, S., Levan, A., Perley, D., Stritzinger, Maximilian, Bufano, F., Filippenko, Alexei V., Melandri, A., Oates, S., Rossi, A., Selsing, J., Zheng, W., Castro-Tirado, Alberto J., Chincarini, G., D'Avanzo, P., De Pasquale, M., Emery, S., Fruchter, Andrew S., Hurley, K., Moller, P., Nomoto, K., Tanaka, M., Valeev, A.F., Independent Research Fund Denmark, Instrument Center for Danish Astrophysics, Leverhulme Trust, Istituto Nazionale di Astrofisica, National Science Foundation (US), Ministerio de Economía y Competitividad (España), European Commission, National Aeronautics and Space Administration (US), Russian Science Foundation, Villum Fonden, Ashall, Chris, Mazzali, Paolo A., Pian, E., Woosley, S.E., Palazzi, E., Prentice, S.J., Kobayashi, S., Holmbo, S., Levan, A., Perley, D., Stritzinger, Maximilian, Bufano, F., Filippenko, Alexei V., Melandri, A., Oates, S., Rossi, A., Selsing, J., Zheng, W., Castro-Tirado, Alberto J., Chincarini, G., D'Avanzo, P., De Pasquale, M., Emery, S., Fruchter, Andrew S., Hurley, K., Moller, P., Nomoto, K., Tanaka, M., and Valeev, A.F.

Abstract

We report observations and analysis of the nearby gamma-ray burst GRB 161219B (redshift z = 0.1475) and the associated Type Ic supernova (SN) 2016jca. GRB 161219B had an isotropic gamma-ray energy of ∼1.6 × 10 erg. Its afterglow is likely refreshed at an epoch preceding the first photometric points (0.6 d), which slows down the decay rates. Combined analysis of the SN light curve and multiwavelength observations of the afterglow suggest that the GRB jet was broad during the afterglow phase (full opening angle ∼42° ± 3°). Our spectral series shows broad absorption lines typical of GRB supernovae (SNe), which testify to the presence of material with velocities up to ∼0.25c. The spectrum at 3.73 d allows for the very early identification of an SN associated with a GRB. Reproducing it requires a large photospheric velocity (35000 ± 7000 km s). The kinetic energy of the SN is estimated through models to be E≈4 × 10 erg in spherical symmetry. The ejected mass in the explosion was M≈6.5 ± 1.5 M⊙, much less than that of other GRB-SNe, demonstrating diversity among these events. The total amount of Ni in the explosion was 0.27 ± 0.05 M⊙. The observed spectra require the presence of freshly synthesized Ni at the highest velocities, at least three times more than a standard GRB-SN. We also find evidence for a decreasing Ni abundance as a function of decreasing velocity. This suggests that SN 2016jca was a highly aspherical explosion viewed close to on-axis, powered by a compact remnant. Applying a typical correction for asymmetry, the energy of SN 2016jca was ∼(1-3) × 10 erg, confirming that most of the energy produced by GRB-SNe goes into the kinetic energy of the SN ejecta.© 2019 The Author(s).

Published
2019

3. Unveiling the enigma of ATLAS17aeu

Author

Ministerio de Ciencia e Innovación (España), European Commission, Russian Science Foundation, Villum Fonden, Istituto Nazionale di Astrofisica, Melandri, A., Rossi, A., Benetti, S., D'Elia, V., Piranomonte, S., Palazzi, E., Levan, A.J., Branchesi, M., Castro-Tirado, Alberto J., D'Avanzo, P., Hu, Y.D., Raimondo, G., Tanvir, N.R., Tomasella, L., Amati, L., Campana, S., Carini, R., Covino, Stefano, Cusano, F., Dadina, M., Della Valle, M., Fan, X., Garnavich, P., Grado, A., Greco, G., Hjorth, Jens, Lyman, J. D., Masetti, N., O'Brien, P., Pian, E., Perego, A., Salvaterra, R., Stella, L., Stratta, G., Yang, S., Di Paola, A., Caballero-García, María Dolores, Fruchter, Andrew S., Giunta, A., Longo, F., Pinamonti, M., Sokolov, Vladimir V., Testa, V., Valeev, A.F., Brocato, E., Ministerio de Ciencia e Innovación (España), European Commission, Russian Science Foundation, Villum Fonden, Istituto Nazionale di Astrofisica, Melandri, A., Rossi, A., Benetti, S., D'Elia, V., Piranomonte, S., Palazzi, E., Levan, A.J., Branchesi, M., Castro-Tirado, Alberto J., D'Avanzo, P., Hu, Y.D., Raimondo, G., Tanvir, N.R., Tomasella, L., Amati, L., Campana, S., Carini, R., Covino, Stefano, Cusano, F., Dadina, M., Della Valle, M., Fan, X., Garnavich, P., Grado, A., Greco, G., Hjorth, Jens, Lyman, J. D., Masetti, N., O'Brien, P., Pian, E., Perego, A., Salvaterra, R., Stella, L., Stratta, G., Yang, S., Di Paola, A., Caballero-García, María Dolores, Fruchter, Andrew S., Giunta, A., Longo, F., Pinamonti, M., Sokolov, Vladimir V., Testa, V., Valeev, A.F., and Brocato, E.

Abstract

Aims. The unusual transient ATLAS17aeu was serendipitously detected within the sky localisation of the gravitational wave trigger GW 170104. The importance of a possible association with gravitational waves coming from a binary black hole merger led to an extensive follow-up campaign, with the aim of assessing a possible connection with GW 170104. Methods. With several telescopes, we carried out both photometric and spectroscopic observations of ATLAS17aeu, for several epochs, between ∼3 and ∼230 days after the first detection. Results. We studied in detail the temporal and spectroscopic properties of ATLAS17aeu and its host galaxy. Although at low significance and not conclusive, we found similarities to the spectral features of a broad-line supernova superposed onto an otherwise typical long-GRB afterglow. Based on analysis of the optical light curve, spectrum, and host galaxy spectral energy distribution, we conclude that the redshift of the source is probably z 0.5 ±0.2. Conclusions. While the redshift range we have determined is marginally compatible with that of the gravitational wave event, the presence of a supernova component and the consistency of this transient with the E-E correlation support the conclusion that ATLAS17aeu was associated with the long gamma-ray burst GRB 170105A. This rules out the association of the GRB 170105A/ATLAS17aeu transient with the gravitational wave event GW 170104, which was due to a binary black hole merger.© 2019 ESO.

Published
2019

4. M31N 2008-12a - The Remarkable Recurrent Nova in M31: Panchromatic Observations of the 2015 Eruption

Author

Darnley, M.J., Henze, M., Bode, M.F., Hachisu, I., Hernanz, M., Hornoch, K., Hounsell, R., Kato, M., Ness, J.-U., Osborne, J.P., Page, K.L., Ribeiro, V.A.R.M., Rodríguez-Gil, P., Shafter, A.W., Shara, M.M., Steele, I.A., Williams, S.C., Arai, A., Arcavi, I., Barsukova, E.A., Boumis, P., Chen, T., Fabrika, S., Figueira, J., Gao, X., Gehrels, N., Godon, P., Goranskij, V.P., Harman, D.J., Hartmann, D.H., Hosseinzadeh, G., Horst, J.C., Itagaki, K., José, J., Kabashima, F., Kaur, A., Kawai, N., Kennea, J.A., Kiyota, S., Kučáková, H., Lau, K.M., Maehara, H., Naito, H., Nakajima, K., Nishiyama, K, O'Brien, T.J., Quimby, R., Sala, G., Sano, Y., Sion, E.M., Valeev, A.F., Watanabe, F., Watanabe, M., Williams, B.F., Xu, Z., Darnley, M.J., Henze, M., Bode, M.F., Hachisu, I., Hernanz, M., Hornoch, K., Hounsell, R., Kato, M., Ness, J.-U., Osborne, J.P., Page, K.L., Ribeiro, V.A.R.M., Rodríguez-Gil, P., Shafter, A.W., Shara, M.M., Steele, I.A., Williams, S.C., Arai, A., Arcavi, I., Barsukova, E.A., Boumis, P., Chen, T., Fabrika, S., Figueira, J., Gao, X., Gehrels, N., Godon, P., Goranskij, V.P., Harman, D.J., Hartmann, D.H., Hosseinzadeh, G., Horst, J.C., Itagaki, K., José, J., Kabashima, F., Kaur, A., Kawai, N., Kennea, J.A., Kiyota, S., Kučáková, H., Lau, K.M., Maehara, H., Naito, H., Nakajima, K., Nishiyama, K, O'Brien, T.J., Quimby, R., Sala, G., Sano, Y., Sion, E.M., Valeev, A.F., Watanabe, F., Watanabe, M., Williams, B.F., and Xu, Z.

Abstract

Contains fulltext : 164095.pdf (preprint version ) (Open Access)

Published
2016

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