From outburst to quiescence: spectroscopic evolution of V1838 Aql imbedded in a bow-shock nebula

We analyse new optical spectroscopic, direct-image and X-ray observations of the recently discovered a high-proper motion cataclysmic variable V1838 Aql. The data were obtained during its 2013 superoutburst and its subsequent quiescent state. An extended emission around the source was observed up to 30 d after the peak of the superoutburst, interpreted it as a bow shock formed by a quasi-continuous outflow from the source in quiescence. The head of the bow shock is coincident with the high-proper motion vector of the source (v⊥ = 123 ± 5 km s−1) at a distance of d = 202 ± 7 pc. The object was detected as a weak X-ray source (0.015 ± 0.002 counts s−1) in the plateau of the superoutburst and its flux lowered by two times in quiescence (0.007 ± 0.002 counts s−1). Spectroscopic observations in quiescence we confirmed the orbital period value Porb = 0.0545 ± 0.0026 d, consistent with early-superhump estimates, and the following orbital parameters: γ = −21 ± 3 km s−1 and K1 = 53 ± 3 km s−1. The white dwarf is revealed as the system approaches quiescence, which enables us to infer the effective temperature of the primary Teff = 11 600 ± 400 K. The donor temperature is estimated 2200K and suggestive of a system approaching the period minimum. Doppler maps in quiescence show the presence of the hotspot in He I line at the expected accretion disc-stream shock position and an unusual structure of the accretion disc in Hα.The authors are indebted to Universidad Nacional Autonoma de Mexico (UNAM)/DGAPA for financial support via PAPIIT projects IN111713, IN122409, IN100617, IN102517, IN102617, IN108316, and IN114917. JVHS is supported by a Vidi grant awarded to N. Degenaar by the Netherlands Organization for Scientific Research (NWO) and acknowledges travel support from DGAPA/UNAM. JE acknowledges support from an LKBF travel grant to visit the Anton Panekoek Institute. VN acknowledges the financial support from the visitor and mobility program of the Finnish Centre for Astronomy with ESO (FINCA), funded by the Academy of Finland grant No. 306531. GT acknowledges Consejo Nacional de Ciencia y Tecnologia (CONACyT) grant 166376. E. de la F. wishes to thank CGCI-Universidad de Guadalajara staff for mobility support. VS thanks Deutsche Forschungsgemeinschaft (DFG) for financial support (grant WE 1312/51-1). His work was also funded by the subsidy allocated to Kazan Federal University for the state assignment in the sphere of scientific activities (3.9780.2017/8.9). We thank Tom Marsh for the use of MOLLY. We acknowledge with thanks the variable star observations from the AAVSO International Data base contributed by observers worldwide and used in this research. We acknowledge the use of public data from the Swift data archive. This research made use of ASTROPY, a community-developed core PYTHON package for Astronomy (Astropy Collaboration et al. 2013), MATPLOTLIB (Hunter 2007) and APLPY (Robitaille & Bressert 2012). Based (partly) on observations made with the Gran Telescopio Canarias (GTC), installed in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias in the island of La Palma (GTC7-16AMEX). Partly based on observations made with the Nordic Optical Telescope, operated by the Nordic Optical Telescope Scientific Association at the Observatorio del Roque de los Muchachos, La Palma, Spain, of the Instituto de Astrofisica de Canarias. The data presented here were obtained in part with ALFOSC, which is provided by the Instituto de Astrofisica de Andalucia (IAA) under a joint agreement with the University of Copenhagen and NOTSA. The results presented in this paper are based on observations collected at the European Southern Observatory under programme ID 0100.D0932. We thank the day and night-time support staff at the OANSPM for facilitating and helping obtain our observations. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. We thank J. van den Eijnden for help on Swift's DDT proposal