RX J0806.3+1527 According to astro-ph/0203043, RX J0806.3+1527 is identified with a variable emission-line object with a pulse period of 321 s. The object is interpreted as a double-degenerate (AM CVn-type) cataclysmic variable. Since this object is not reddened as in V407 Vul, further monitoring is strongly encouraged to check long-term variation. See astro-ph for the indentification chart. If the object undergoes an outburst in future, the object will become the top-priority target for time-resolved CCD photometry. Paper: astro-ph/0203043 From: (Giallo) Israel <gianluca@ulysses.mporzio.astro.it> Date: Mon, 4 Mar 2002 18:37:54 GMT (115kb) Title: RXJ0806.3+1527: a double degenerate binary with the shortest known orbital period (321s) Authors: G.L. Israel, W. Hummel, S. Covino, S. Campana, I. Appenzeller, W. Gassler, K.-H. Mantel, G. Marconi, C.W. Mauche, U. Munari, I. Negueruela, H. Nicklas, G. Rupprecht, R.L. Smart, O. Stahl, L. Stella Comments: Accepted for publication on A&A Letters \\ We carried out optical observations of the field of the X-ray pulsator RXJ0806.3+1527. A blue V=21.1 star was found to be the only object consistent with the X-ray position. VLT FORS spectra revealed a blue continuum with no intrinsic absorption lines. Broad (v~1500 km/s), low equivalent width (about -1/-6A) emission lines from the HeII Pickering series were clearly detected. B, V and R time-resolved photometry revealed the presence of about 15% pulsations at the 321s X-ray period, confirming the identification. These findings, together with the period stability and absence of any additional modulation in the 1min-5hr period range, argue in favour of the orbital interpretation of the 321s pulsations. The most likely scenario is thus that RXJ0806.3+1527 is a double degenerate system of the AM CVn class. This would make RXJ0806.3+1527 the shortest orbital period binary currently known and one of the best candidates for gravitational wave detection. \\ ( http://arXiv.org/abs/astro-ph/0203043 , 115kb)