The nature of the Stingray nebula from radio observations (original) (raw)
Related papers
Monthly Notices of the Royal Astronomical Society, 2015
We provide radio spectral properties at high frequencies (1≤ν (GHz) ≤ 20) for 65 planetary nebulae in the Australia Telescope 20 GHz (AT20G) survey, identified from our list of sources that show flat-spectrum (α > −0.5) and are well resolved at 0.15 arcsec angular size scale. We show that this method very effectively identifies thermal sources like planetary nebulae (and H II regions). In our analysis of the radio spectra of a subset of 37 planetary nebulae, we find no clear evidence of either the excess flux in the optically thin region proposed in the literature, or non-thermal emission. Using a combination of radio spectra, radio interferometric technique and infrared spectra from Wide-field Infrared Survey Explorer, we provide an effective method of identifying further candidates and we list a total of six new planetary nebulae that require follow-up. Together with the list of planetary nebula candidates and the planetary nebulae from the AT20G survey presented in this paper, we provide radio spectra for a complete radio flux limited sample of planetary nebulae at |b| > 1.5 deg in the Southern hemisphere at 20 GHz.
From pre- to young planetary nebulae: radio continuum variability
Monthly Notices of the Royal Astronomical Society, 2011
Searching for variability, we have observed a sample of hot post-asymptotic giant branch stars and young planetary nebula candidates with the Very Large Array at 4.8, 8.4 and 22.4 GHz. The sources had been previously detected in the radio continuum, which is a proof that the central stars have started ionizing their circumstellar envelopes, and an increase in radio flux with time can be expected as a result of the progression of the ionization front. Such a behaviour has been found in IRAS 18062+2410, whose radio modelling has allowed us to determine that its ionized mass has increased from 10 −4 to 3.3 × 10 −4 M in 8 yr and its envelope has become optically thin at lower frequencies. Different temporal behaviours have been found for three other sources. IRAS 17423−1755 has shown a possibly periodic pattern and an inversion of its radio spectral index, as expected from a varying stellar wind. We estimate that the radio flux arises from a very compact region around the central star (∼10 15 cm) with an electron density of 2 × 10 6 cm −3. IRAS 22568+6141 and IRAS 17516−2525 have decreased their radio flux densities by about 10 per cent per year over 4 yr. While a linear increase in the flux density with time points to the progression of the ionization front in the envelope, decreases as well as quasi-periodic patterns may indicate the presence of unstable stellar winds/jets or thick dusty envelopes absorbing ionizing photons.
Radio characteristics of the very young Planetary Nebulae SAO244567
arXiv preprint astro-ph/0310288, 2003
The radio emission from the youngest known Planetary nebula, SAO 244567, has been mapped at 20,13, 6, 3.6 and 1.2 cm by using the Australian Telescope Compact Array (ATCA). These observations constitute the first detailed radio study of this very interesting object, as they allow us to obtain, for the first time, the radio morphology of the source and to compute the radio spectrum up to 18 752 MHz.
The rapid evolution of the exciting star of the Stingray nebula
Astronomy & Astrophysics, 2014
Context. SAO 244567, the exciting star of the Stingray nebula, is rapidly evolving. Previous analyses suggested that it has heated up from an effective temperature of about 21 kK in 1971 to over 50 kK in the 1990s. Canonical post-asymptotic giant branch evolution suggests a relatively high mass while previous analyses indicate a low-mass star. Aims. A comprehensive model-atmosphere analysis of UV and optical spectra taken during 1988-2006 should reveal the detailed temporal evolution of its atmospheric parameters and provide explanations for the unusually fast evolution. Methods. Fitting line profiles from static and expanding non-LTE model atmospheres to the observed spectra allowed us to study the temporal change of effective temperature, surface gravity, mass-loss rate, and terminal wind velocity. In addition, we determined the chemical composition of the atmosphere. Results. We find that the central star has steadily increased its effective temperature from 38 kK in 1988 to a peak value of 60 kK in 2002. During the same time, the star was contracting, as concluded from an increase in surface gravity from log g = 4.8 to 6.0 and a drop in luminosity. Simultaneously, the mass-loss rate declined from log(Ṁ/M yr −1) = −9.0 to −11.6 and the terminal wind velocity increased from v ∞ = 1800 km s −1 to 2800 km s −1. Since around 2002, the star stopped heating and has cooled down again to 55 kK by 2006. It has a largely solar surface composition with the exception of slightly subsolar carbon, phosphorus, and sulfur. The results are discussed by considering different evolutionary scenarios. Conclusions. The position of SAO 244567 in the log T eff-log g plane places the star in the region of sdO stars. By comparison with stellar-evolution calculations, we confirm that SAO 244567 must be a low-mass star (M < 0.55 M). However, the slow evolution of the respective stellar evolutionary models is in strong contrast to the observed fast evolution and the young planetary nebula with a kinematical age of only about 1000 years. We speculate that the star could be a late He-shell flash object. Alternatively, it could be the outcome of close-binary evolution. Then SAO 244567 would be a low-mass (0.354 M) helium pre-white dwarf after the common-envelope phase, during which the planetary nebula was ejected.
The Astrophysical Journal, 2005
We present a new planetary nebula, first identified in images from the Australia Telescope Compact Array, although not recognized at that time. Recent observations with the Spitzer Space Telescope during the GLIMPSE Legacy program have rediscovered the object. The highresolution radio and infrared images enable the identification of the central star or its wind, the recognition of the radio emission as thermal, and the probable presence of polycylic aromatic hydrocarbons in and around the source. These lead to the conclusion that G313.3+00.3 is a planetary nebula. This object is of particular interest because it was discovered solely through radio and mid-infrared imaging, without any optical (or near-infrared) confirmation, and acts as a proof of concept for the discovery of many more highly extinguished planetary nebulae. G313.3+00.3 is well-resolved by both the instruments with which it was identified, and suffers extreme reddening due to its location in the Scutum-Crux spiral arm.
New models for the rapid evolution of the central star of the Stingray Nebula
MNRAS PREPRINT , 2021
We present stellar evolution calculations from the Asymptotic Giant Branch (AGB) to the Planetary Nebula (PN) phase for models of initial mass 1.2 M⊙ and 2.0 M⊙ that experience a Late Thermal Pulse (LTP), a helium shell flash that occurs following the AGB and causes a rapid looping evolution between the AGB and PN phase. We use these models to make comparisons to the central star of the Stingray Nebula, V839 Ara (SAO 244567). The central star has been observed to be rapidly evolving (heating) over the last 50 to 60 years and rapidly dimming over the past 20-30 years. It has been reported to belong to the youngest known planetary nebula, now rapidly fading in brightness. In this paper we show that the observed timescales, sudden dimming, and increasing Log(g), can all be explained by LTP models of a specific variety. We provide a possible explanation for the nebular ionization, the 1980's sudden mass loss episode, the sudden decline in mass loss, and the nebular recombination and fading.
The Fall of the Youngest Planetary Nebula, Hen3-1357
arXiv: Solar and Stellar Astrophysics, 2020
The Stingray Nebula, aka Hen3-1357, went undetected until 1990 when bright nebular lines and radio emission were unexpectedly discovered. We report changes in shape and rapid and secular decreases in its nebular emission-line fluxes based on well calibrated images obtained by the Hubble Space Telescope in 1996, 2000, and 2016. Hen3-1357 is now a "recombination nebula".
Optical observations of southern planetary nebula candidates
Astronomy and Astrophysics Supplement Series, 1996
We present Hα+[N ii] images and low resolution spectra of 16 IRAS-selected, southern planetary nebula candidates previously detected in the radio continuum. The Hα+[N ii] images are presented as finding charts. Contour plots are shown for the resolved planetary nebulae. From these images mean optical angular diameters were determined. Optical spectra show that these IRAS-selected and radio detected planetary nebula candidates are indeed planetary nebulae. The values for their extinction coefficient is generally very high. More than half of the planetary nebulae seem to be of low excitation, having central stars with an effective temperature of probably ∼ 60 000 K or less.