@article{1cd15deaafd54a73ad371e85cd0fb344,
title = "IGR J19552+0044: A new asynchronous short period polar: Filling the gap between intermediate and ordinary polars",
abstract = "Context. Based on XMM-Newton X-ray observations IGR J19552+0044 appears to be either a pre-polar or an asynchronous polar. Aims. We conducted follow-up optical observations to identify the sources and periods of variability precisely and to classify this X-ray source correctly. Methods. Extensive multicolor photometric and medium- to high-resolution spectroscopy observations were performed and period search codes were applied to sort out the complex variability of the object. Results. We found firm evidence of discording spectroscopic (81.29 ± 0.01 m) and photometric (83.599 ± 0.002 m) periods that we ascribe to the white dwarf (WD) spin period and binary orbital period, respectively. This confirms that IGR J19552+0044 is an asynchronous polar. Wavelength dependent variability and its continuously changing shape point at a cyclotron emission from a magnetic WD with a relatively low magnetic field below 20 MG. Conclusions. The difference between the WD spin period and the binary orbital period proves that IGR J19552+0044 is a polar with the largest known degree of asynchronism (0.97 or 3%).",
keywords = "Accretion, accretion disks, Binaries: close, Stars: magnetic field",
author = "G. Tovmassian and D. Gonz{\'a}lez-Buitrago and J. Thorstensen and E. Kotze and H. Breytenbach and A. Schwope and F. Bernardini and Zharikov, {S. V.} and Hernandez, {M. S.} and Buckley, {D. A.H.} and {De Miguel}, E. and Hambsch, {F. J.} and G. Myers and W. Goff and D. Cejudo and D. Starkey and T. Campbell and J. Ulowetz and W. Stein and P. Nelson and Reichart, {D. E.} and Haislip, {J. B.} and Ivarsen, {K. M.} and Lacluyze, {A. P.} and Moore, {J. P.} and Miroshnichenko, {A. S.}",
note = "Funding Information: Acknowledgements. G.T. and S.Z. acknowledge PAPIIT grants IN108316/IN-100617 and CONACyT grants 166376; 151858 and CAR 208512 for resources provided toward this research. J.T. acknowledges the NSF grant AST-1008217. Funding Information: G.T. and S.Z. acknowledge PAPIIT grants IN108316/IN-100617 and CONACyT grants 166376; 151858 and CAR 208512 for resources provided toward this research. J.T. acknowledges the NSF grant AST-1008217. Funding Information: 2 IRAF is distributed by the National Optical Astronomy Observatories, which are operated by the Association of Universities for Research in Astronomy, Inc., under cooperative agreement with the National Science Foundation. Publisher Copyright: {\textcopyright} ESO, 2017.",
year = "2017",
month = dec,
day = "1",
doi = "10.1051/0004-6361/201731323",
language = "English (US)",
volume = "608",
journal = "Astronomy and Astrophysics",
issn = "0004-6361",
publisher = "EDP Sciences",
}