High-velocity string of knots in the outburst of the planetary nebula Hb4

Abstract

The bipolar collimated outflows of the Hb4 Planetary Nebula (PN) exhibit an evident decrease in their expansion velocity with respect to the distance from the central star. So far, similar velocity law has also been found in Herbig-Haro objects. The interpretation of this peculiar velocity law and the classification of the outflows is the main focal point of this paper. High dispersion long-slit echelle spectra along with high resolution images from Hubble Space Telescope (HST) are applied in the astronomical code SHAPE in order to reproduce a threedimensional morpho-kinematicalal model for the core and the bipolar outflows. Its central part shows a number of low-ionization filamentary structures (knots and jets) indicative of common-envelope PNe evolution and it is reconstructed assuming a toroidal structure. The high-resolution HST [N II] image of Hb4 unveils the fragmented structure of outflows. The northern and southern outflows are composed by four and three knots, respectively, and each knot moves outwards with its own expansion velocity. They are reconstructed as string of knots rather than jets.This string of knots is formed by ejection events repeated every 200-250 years. Hb4 displays several indirect evidence for a binary central system with a [WR] companion evolved through the common envelopes channel.The observed deceleration of the knots is likely associated with shock collisions between the knots and the interstellar medium or nebular material.1 the astrometric excess noise is lower than 1 which implies a reliable parallax measure, but due to the high fractional parallax error, the inverse parallax does not provide a reliable distance estimate.

Exploring the differences of integrated and spatially resolved analysis using integral field unit data: the case of Abell 14

“…In contrast to IFS, the position of the slit(s) in long-slit spectroscopy is usually selected based on the morphology of the nebula and/or on the position of distinct features, such as low-ionization structures (LISs: knots, jets, and filaments; e.g., Balick et al 1993Balick et al , 1994Derlopa et al 2019) or bipolar outflows (e.g. Guerrero et al 2013;Akras et al 2015;Ramos-Larios et al 2018).…”

Distance mapping applied to four well-known planetary nebulae and a nova shell

“…The waist is observed as a second larger ellipse lying perpendicular to the inner ellipse. A pair of polar caps and polar filaments are also present at the tips of the bubbles, being very bright in low-ionization lines (Gonçalves et al 2001;) and molecular hydrogen lines (Akras et al (2019), submitted). The conjoined bubbles are older and expand with a lower velocity compared to the inner ellipse (Reed et al 1999).…”

Shaping Planetary Nebulae with Jets and the Grazing Envelope Evolution

“…Hb4 (Derlopa et al 2019) A strong binary interaction which involves mass transfer and jet launching takes place shortly after the CEE. Might be mass accretion from a circumbinary disk, as phase 5 in Table 2.…”