Optical spectroscopy of X-ray source 1RXS J204455.9-115151
ATel #6588; N. Masetti (INAF/IASF, Bologna), V. Chavushyan, J. Torrealba (INAOE, Puebla) & E. Jimenez-Bailon (UNAM, Mexico City)
on 17 Oct 2014; 08:55 UT
Credential Certification: Nicola Masetti (masetti@iasfbo.inaf.it)
Subjects: Optical, X-ray, Cataclysmic Variable, Transient
Following the discovery (ATel #6306) and multiwavelength follow-up observations (ATels #6312, #6320) of an outburst from the source 1RXS J204455.9-115151, we spectroscopically observed its optical counterpart with the 2.1m telescope of at the San Pedro Martir Observatory of the Observatorio Astronomico Nacional (Mexico).
The observations were acquired using the Boller & Chivens spectrograph equipped with a 300 lines/mm grating, affording a dispersion of 4.5 Angstroms/pixel; with this setup, a 1200s spectrum covering the 3800-8200 Angstroms range was secured starting at 04:23 UT of October 1, 2014.
A preliminary reduction shows the presence of several single-peaked Balmer (up to at least H_epsilon), HeI and HeII emission lines at a redshift consistent with 0, superimposed on a relatively blue continuum. The equivalent widths of H_alpha, H_beta and HeII4686 emissions are
-122 +- 5, -94 +- 5, and -16 +- 3 Angstroms, respectively.
The optical spectral appearance of the counterpart is thus typical of a Galactic Cataclysmic Variable, as suggested in ATels #6312 and #6320. The ratio between the equivalent widths of HeII4686 and H_beta does not support a magnetic nature for the white dwarf accretor (see e.g.
Cropper 1990, Space Sci. Rev., 54, 195).
