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A Whole Earth Telescope campaign on the pulsating subdwarf B binary system PG 1336-018 (NY Vir)

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A Whole Earth Telescope campaign on the pulsating subdwarf B binary system PG 1336-018 (NY Vir)

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Título A Whole Earth Telescope campaign on the pulsating subdwarf B binary system PG 1336-018 (NY Vir)
Autor Kilkenny, Dave
Reed, M. D.
O'Donoghue, Darragh
Kawaler, Steven D.
Mukadam, Anjum Shagufta
Kleinman, Scot James
Nitta, Atsuko
Metcalfe, Travis S.
Provencal, Judith L.
Watson, Todd K.
Sullivan, Denis J.
Sullivan, Terry
Shobbrook, Robert R.
Jiang, Xiaojun
Joshi, Santosh
Ashoka, B.N.
Seetha, S.
Leibowitz, Elia M.
Ibbetson, Peter A.
Mendelson, Haim
Meistas, Edmundas G.
Kalytis, Romualdas
Alisauskas, Darius
Martinez, Peter
Van Wyk, Francois
Stobie, Robert S.
Marang, Fred
Zola, Staszek
Krzesinski, Jerzy
Ogloza, Waldemar
Moskalik, Pawel
Silvotti, Roberto
Piccioni, Adalberto
Vauclair, Gérard
Dolez, Noël
Chevreton, Michel
Dreizler, Stefan
Schuh, Sonja L.
Deetjen, Jochen L.
Solheim, Jan-Eric
Gonzalez Perez, Jose Miguel
Ulla, Ana
Ostensen, Roy
Manteiga, Minia
Suarez, Olga
Burleigh, Matt
Kepler, Souza Oliveira
Kanaan Neto, Antonio Nemer
Giovannini Junior, Odilon
Abstract We present results from a multisite (‘Whole Earth Telescope’) photometric campaign on PG 1336−018, the close eclipsing binary system containing a pulsating subdwarf B (sdB) star. The main part of the campaign (1999 April) resulted in ~172 h of observations, representing a coverage of about 47 per cent, and additional data were obtained outside the core campaign. Periodogram analysis shows that the light variations are dominated by three frequencies near 5757, 5585 and 5369 μHz (~174, 179 and 186s, respectively), although many frequencies are present, particularly in the range 5000–6000 μHz (~200–170 s). We identify, with some confidence, 28 frequencies down to a semi-amplitude of 0.0005 in fractional intensity (equivalent to about 0.5 mmag). It is clear that the pulsation frequencies of PG 1336−018 have changed substantially since the 1996 discovery observations were made, and that amplitude changes occur, at least in the dominant three frequencies, on relatively short time-scales (of the order of a day). On the assumption that the pulsating star is phase-locked in the binary system, we have searched for rotational splitting of frequencies near the orbital and half of the orbital period, but the results are confused by aliasing at those frequencies (due to the data gaps caused by the eclipses). A preliminary model qualitatively matches the distribution of frequencies in PG 1336−018, with some good individual correspondences, but cannot be considered adequate because geometric cancellation should hide some of the modes which are apparently detected. Analysis of the pulsations during eclipse recovers three of the strongest modes, but the limited eclipse data – which can, at best, be only about 9 per cent of the total – do not allow mode identification at this stage. Simulations indicate that an overall coverage of about 80 per cent would be required for this to be viable. An attempt was made to determine phase shifts in the pulsation frequencies as a way of directly measuring the size of the binary orbit, but the uncertainties in the method are comparable to the light travel time across the orbit (probably less than a second).
Contido em Monthly notices of the Royal Astronomical Society. Oxford. Vol. 345, no. 3 (Nov. 2003), p. 834-846
Assunto Estrelas
Fotometria astronômica
Fotometria estelar
Pulsacoes estelares
[en] Stars: individual: PG 1336−018
[en] Stars: oscillations
[en] Stars: variables: other
Origem Estrangeiro
Tipo Artigo de periódico
URI http://hdl.handle.net/10183/89981
Arquivos Descrição Formato
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