VLT VIMOS integral field spectroscopy of the nova remnant FH Ser

¹ Instituto de Astrofísica de Andalucía, IAA-CSIC, Glorieta de la Astronomía S/N, Granada 18008, Spain
² Instituto de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, Morelia 58089, Mich., Mexico
³ Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo, Rua do Matão 1226, São Paulo 05508-900, Brazil
⁴ Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Ciudad de México 04510, Mexico
⁵ Centro de Estudios de Física del Cosmos de Aragón, Unidad Asociada al CSIC, Plaza San Juan 1, Teruel 44001, Spain

^★ Corresponding author; mar@iaa.es

Received: 25 October 2024
Accepted: 27 December 2024

Abstract

Context. The source FH Ser experienced a slow classical nova outburst in February 1970 that was the first ever observed at UV, optical, and IR wavelengths. Its nova remnant is elliptical and has multiple knots. A peculiar ring-like filament lies along its minor axis.

Aims. We investigate here the true 3D spatio-kinematical structure of FH Ser to assess the effects of early shaping and to assess its mass and kinetic energy.

Methods. We obtained integral field spectroscopic observations made with the Very Large Telescope (VLT) VIsible MultiObject Spectrograph (VIMOS) of FH Ser. The data cube was analyzed using 3D visualizations that revealed different structural components. A simple geometrical model was compared to the 3D data cube to determine the spatio-kinematic properties of FH Ser.

Results. FH Ser consists of a tilted prolate ellipsoidal shell that is most prominent in Hα, and of a ring-like structure that is most prominent in [N II]. The ellipsoidal shell has equatorial and polar velocities of ≃505 and ≈630 km s⁻¹, respectively, and its major axis is tilted by ≃52° with respect to the line of sight. The inclination angle of the symmetry axis of the ring is similar, that is, it can be described as an equatorial belt of the main ellipsoidal shell. FHSer has an ionized mass of 2.6 × 10⁻⁴ M_⊙, with a kinetic energy of 1.6 × 10⁴⁵ erg.

Conclusions. The two different structural components in FH Ser with a similar orientation can be linked to a density enhancement along a plane, most likely the orbital plane at the time of the nova event. The acquisition of integral field spectroscopic observations of nova remnants is mostly required to separate different structural components and to assess their 3D physical structure.