arXiv subjects

P. Boumis

Publications and source records attributed to P. Boumis.

At least 19 recordsLinked to original sources

arXiv2025

Dissecting NGC 3132: Tracing the mass-loss history of the southern ring planetary nebula

Central to our understanding of stellar evolution and its impact on processes in our Galaxy and across the Universe is the study of mass loss. While the general framework is well established, recent JWST observations of objects like NGC 3132 have revealed intricate nebular structures, suggesting complex mass-loss processes likely driven by multiple star system at its core. These findings pose new challenges for the currently available investigation tools. The primary goal of this study is the first detailed comparison of the physical properties and chemical composition obtained for NGC 3132, based on the latest detailed 3D model and observations from MUSE, JWST and Spitzer. We evaluate the reliability of the traditional empirical method and photoionization model for abundances estimations, both based on the same available high-quality, spatially resolved observations. We find that the model and empirical method yield consistent results for the integrated total properties such as Te, ne and chemical abundances. However, when applied to simulated observations from the model, the empirical method fails to recover the model input abundances, providing only an approximate estimate. This discrepancy arises in part from the loss of information when summing fluxes over regions which have complex ionisation structures. This discrepancy in the case of oxygen has been estimated to be up to 35%. Moreover, the latest IR data reveal a spatial correlation between H2, c(Hb) as well as the [8.0]/[4.5] IRAC ratio. Finally, new clumps are discovered in [Ni II] 7378 \AA, [Fe II] 8617 \AA and [Fe III] 5270 \AA emission lines.

astro-ph.GA↗

arXiv2025

Nickel- and iron-rich clumps in planetary nebulae: New discoveries and emission-line diagnostics

Integral field spectroscopy (IFS) offers a distinct advantage for studying extended sources by enabling spatially resolved emission maps for several emission lines without the need for specific filters. This study conducts a detailed analysis of iron and nickel emission lines in 12 planetary nebulae (PNe) using integral field unit (IFU) data from MUSE to provide insights into their formation and evolution mechanisms. New diagnostic line ratios, combined with machine-learning algorithms, were used to distinguish excitation mechanisms such as shock and photoionization. Electron densities and elemental abundances were estimated using different atomic data through the PyNeb package. The contribution of fluorescent excitation of nickel lines was also examined. A total of 16 iron- and nickel-rich clumps are detected in seven out of 12 PNe. New clumps are discovered in NGC 3132 and IC 4406. The most prominent lines are [Fe II] 8617 Angstrom and [Ni II] 7378 Angstrom. Both emission lines are observed emanating directly from the low-ionization structures (LIS) of NGC 3242, NGC 7009, and NGC 6153, as well as from clumps in NGC 6369 and Tc 1. Their abundances are found to be below solar values, indicating that a fraction of Fe and Ni remains depleted in dust grains. The depletion factors exhibit a strong correlation over a wide range. A machine-learning approach allows us to classify ten out of 16 clumps as shock-excited and to establish a new shock/photoionization selection criterion: log([Ni II] 7378 Angstrom / H-alpha) and log([Fe II] 8617 Angstrom / H-alpha) greater than -2.20.

astro-ph.SR↗

arXiv2025

Integral field spectroscopy of the planetary nebula NGC 3242 and the puzzling nature of its low ionization structures

The physico-chemical properties of the planetary nebula (PN) NGC 3242 are investigated in both 1D and 2D, using Integral Field Unit (IFU) data. This PN has a complex morphology with multiple shells and contains a pair of structures with a lower degree of ionization compared to the main nebular components. These structures are known as low ionization structures (LISs), and their origin is still a mystery. With the capabilities provided by IFU spectroscopy, we aim to gain a better understanding of the behavior of nebular properties in the LISs. Data from the Multi Unit Spectroscopic Explorer (MUSE) at the Very Large Telescope (VLT) were used in order to perform a spatially resolved physico-chemical analysis of NGC 3242 both in 2D, through the analysis of emission line maps, and in 1D, simulating long-slit spectroscopy, with pseudo-slits. Through the deeper investigation of MUSE data, we detect new structures perpendicular to the pair of LISs of NGC 3242, which are mainly seen in the light of [S III] and [N II]. In addition, two arc-like structures are revealed. Moreover, an inner jet-like structure is found through its [Fe III] emission. The interaction of the jet with the rim may be related to the formation of knots and blobs. The higher value of Te, is estimated from the [S III] diagnostic lines, followed by Te ([N II]), Te(H I) and finally Te (He I). In all cases, Te is higher at the inner nebular structures. Regarding electron density, ne, is lower at the LISs, while an increase is observed at the nebular rim. Diagnostic diagrams confirm that NGC 3242 is a highly ionized nebula. Moreover, the MUSE data unveiled for the first time in this PN, the atomic line [C I] {\lambda}8727, primarily emitted from the LISs. This finding suggests that these structures may consist of a molecular core surrounded by neutral and ionized gas

astro-ph.SR↗

arXiv2024

Episodic mass loss in the very luminous red supergiant [W60] B90 in the Large Magellanic Cloud

This study delves into [W60] B90, one of the most luminous and extreme Red Supergiants (RSGs) in the Large Magellanic Cloud (LMC), aiming to search for evidence of episodic mass loss. Our discovery of a bar-like nebular structure at 1 pc, reminiscent of the bar around Betelgeuse, raised the question of whether [W60] B90 also has a bow shock. We collected and analyzed proper motion data from Gaia, as well as new multi-epoch spectroscopic and imaging data, and archival time-series photometry in the optical and mid-infrared. We found [W60] B90 to be a walkaway star, with a supersonic peculiar velocity in the direction of the bar. We detected shocked emission between the bar and the star, based on the [S II]/H$\alpha$ > 0.4 criterion, providing strong evidence for a bow shock. The 30-year optical light curve revealed semi-regular variability, showing three similar dimming events with $\Delta V \sim 1$ mag, a recurrence of $\sim$12 yr, and a rise time of 400 d. We found the mid-IR light curve to vary by 0.51 mag and 0.37 mag in the WISE1 and WISE2 bands, respectively, and by 0.42 mag and 0.25 mag during the last dimming event. During this event, optical spectroscopy revealed spectral variability (M3I to M4I), a correlation between the $T_{\rm eff}$ and the brightness, increased extinction, and, after the minimum, spectral features incompatible with the models. We also found a difference of >300 K between the $T_{\rm eff}$ measured from the TiO bands in the optical and the atomic lines from our $J$-band spectroscopy. We inferred that [W60] B90 is a more massive analog of Betelgeuse in the LMC and the first extragalactic single RSG with a suspected bow shock. Its high luminosity $\log(L/L_{\odot})=5.32$, mass-loss rate, and mid-IR variability compared to other RSGs in the LMC, indicate that it is in an unstable evolutionary state undergoing episodes of mass loss.

astro-ph.SR↗

arXiv2023

Multi-band analyses of the bright GRB 230812B and the associated SN2023pel

GRB~230812B is a bright and relatively nearby ($z =0.36$) long gamma-ray burst (GRB) that has generated significant interest in the community and has thus been observed over the entire electromagnetic spectrum. We report over 80 observations in X-ray, ultraviolet, optical, infrared, and sub-millimeter bands from the GRANDMA (Global Rapid Advanced Network for Multi-messenger Addicts) network of observatories and from observational partners. Adding complementary data from the literature, we then derive essential physical parameters associated with the ejecta and external properties (i.e. the geometry and environment) of the GRB and compare with other analyses of this event. We spectroscopically confirm the presence of an associated supernova, SN2023pel, and we derive a photospheric expansion velocity of v $\sim$ 17$\times10^3$ km s$^{-1}$. We analyze the photometric data first using empirical fits of the flux and then with full Bayesian Inference. We again strongly establish the presence of a supernova in the data, with a maximum (pseudo-)bolometric luminosity of $5.75 \times 10^{42}$ erg/s, at $15.76^{+0.81}_{-1.21}$ days (in the observer frame) after the trigger, with a half-max time width of 22.0 days. We compare these values with those of SN1998bw, SN2006aj, and SN2013dx. Our best-fit model favours a very low density environment ($\log_{10}({n_{\rm ISM}/{\rm cm}^{-3}}) = -2.38^{+1.45}_{-1.60}$) and small values for the jet's core angle $\theta_{\rm core} = 1.54^{+1.02}_{-0.81} \ \rm{deg}$ and viewing angle $\theta_{\rm obs} = 0.76^{+1.29}_{-0.76} \ \rm{deg}$. GRB 230812B is thus one of the best observed afterglows with a distinctive supernova bump.

astro-ph.HE↗

arXiv2023

Detection of optical emission from the supernova remnant G7.7-3.7

We present the first optical study of the supernova remnant (SNR) G7.7-3.7, with the aim of determining its evolutionary phase since it has been suggested to be the remnant of SN 386 AD. We obtained narrow-band images in the filters H$\alpha$ + [NII], H$\beta$, [OIII], [SII] that revealed faint optical emission in the southern region of the SNR consisting of two filaments elongated in the east-west direction aligned with the X-ray emitting region of the remnant. The filaments were seen in H$\alpha$ + [NII], [OIII] images and marginally in the [SII] images, with a non-detection in H$\beta$. Long-slit spectroscopy of three regions along one filament revealed large ratios of [SII] / H$\alpha$ = (1.6-2.5), consistent with that expected for a shock-heated SNR. The [SII] doublet ratio observed in two of the regions implies an upper limit for the electron density of the gas, with estimates falling below 400 cm$^{-3}$ and 600 cm$^{-3}$ in the respective areas. We discuss potential physical mechanisms that formed the observed optical filaments and we suggest that most likely they resulted by a collision of the SNR with a dense circumstellar shell lying at the southern region of the remnant.

astro-ph.GA↗

arXiv2023

Planetary nebulae hosting accreting white dwarfs: A possible solution for the mysterious cut-off of Planetary Nebula Luminosity Function?

Many binary companions to the central stars of planetary nebulae (PNe) are found to be inflated, perhaps indicating that accretion onto the central star might occur during the PN phase. The discovery of a handful of nova eruptions and supersoft X-ray sources inside PNe supports this hypothesis. In this paper, we investigate the impact that hosting a steadily-accreting WD would have on the properties and evolution of a PN. By pairing the published accreting nuclear-burning WD models with radiation transfer simulations, we extract the time evolution of the emission line spectra and ionization properties of a PN that surrounds a 0.6$\rm M_{\odot}$ steadily nuclear-burning WD as a function of the mass accretion rate. We find that accreting WDs are able to form very extended, high excitation, [O III]-bright PNe, which are characterised by high nebular electron temperatures. Their properties remain almost invariant with time and their visibility time can be much longer compared to PNe powered by single WDs. We discuss the implications of our findings in explaining specific characteristics observed in PNe. Finally, we examine how accreting WDs affect the planetary nebula luminosity function (PNLF) by covering WD masses in the range of 0.5-0.8$\rm M_{\odot}$ and for various accretion rates within the steady accretion regime. We find that for all but the lowest accretion rates, the [O III]-luminosities are almost constant and clustered very close to the PNLF cut-off value. Our results suggest that mass-accreting WDs in interacting binaries might play a role in understanding the invariant cut-off of the PNLF.

astro-ph.SR↗

arXiv2022

Discovery of an optical cocoon tail behind the runaway HD 185806

Studies on the circumstellar structures around evolved stars provide vital information on the evolution of the parent star and the properties of the local interstellar medium. In this work, we present the discovery and characterization of an optical cocoon tail behind the star HD 185806. The cocoon apex emission is puzzling, as it is detected in the infrared but shows no signal in the optical wavelength. The H-alpha and [OIII] fluxes of the nebular structure vary from 2.7 to 8.5x10^{-12} erg s^{-1} cm^ {-2} and from 0.9 to 7.0x10^{-13} erg s^{-1} cm^{-2}, respectively. Through high-resolution spectroscopy, we derive the spectral type of the star, construct the position-velocity diagrams of the cocoon tail for the H-alpha, [OIII] and [NII] emission lines, and determine its velocity in the range of -100 to 40 km s ^{-1} . Furthermore, we use SED fitting and MESA evolutionary models adopting a distance of 900 pc, and classify HD 185806 as a 1.3 M star, in the transition phase between the RGB and early AGB stages. Finally, we study the morpho-kinematic structure of the cocoon tail using the astronomical software SHAPE. An ellipsoidal structure, with an inclination of 19 degrees with respect to the plane of sky is found to better reproduce the observed cocoon tail of HD 185806.

astro-ph.SR↗

arXiv2022

Host galaxy magnitude of OJ 287 from its colours at minimum light

OJ 287 is a BL Lacertae type quasar in which the active galactic nucleus (AGN) outshines the host galaxy by an order of magnitude. The only exception to this may be at minimum light when the AGN activity is so low that the host galaxy may make quite a considerable contribution to the photometric intensity of the source. Such a dip or a fade in the intensity of OJ 287 occurred in November 2017, when its brightness was about 1.75 magnitudes lower than the recent mean level. We compare the observations of this fade with similar fades in OJ 287 observed earlier in 1989, 1999, and 2010. It appears that there is a relatively strong reddening of the B$-$V colours of OJ 287 when its V-band brightness drops below magnitude 17. Similar changes are also seen V$-$R, V$-$I, and R$-$I colours during these deep fades. These data support the conclusion that the total magnitude of the host galaxy is $V=18.0 \pm 0.3$, corresponding to $M_{K}=-26.5 \pm 0.3$ in the K-band. This is in agreement with the results, obtained using the integrated surface brightness method, from recent surface photometry of the host. These results should encourage us to use the colour separation method also in other host galaxies with strongly variable AGN nuclei. In the case of OJ 287, both the host galaxy and its central black hole are among the biggest known, and its position in the black hole mass-galaxy mass diagram lies close to the mean correlation.

astro-ph.GA↗

arXiv2022

Linking the properties of accreting white dwarfs with the ionization state of their ambient medium

Steadily accreting white dwarfs (WDs) are efficient sources of ionization and thus, are able to create extended ionized nebulae in their vicinity. These nebulae represent ideal tools for the detection of accreting WDs, given that in most cases the source itself is faint. In this work, we combine radiation transfer simulations with known H and He accreting WD models, providing for the first time the ionization state and the emission line spectra of the formed nebulae as a function of the WD mass, the accretion rate and the chemical composition of the accreted material. We find that the nebular optical line fluxes and radial extent vary strongly with the WD's accretion properties, peaking in systems with WD masses of 0.8 - 1.2 $\rm~M_{\odot}$. Projecting our results on the 'BPT' diagnostic diagrams, we show that accreting WDs nebulae possess characteristics distinct from those of H II-like regions, while they share similar line ratios with the galactic low-ionization emission-line regions. Finally, we compare our results to the relevant constraints imposed by the lack of ionized nebulae in the vicinity of supersoft X-ray sources (SSSs) and Type Ia supernova remnants - sources which are related to steadily accreting WDs. The large discrepancies uncovered by our comparison rule out any steadily accreting WD as a potential progenitor of the studied remnants and additionally require the ambient medium around the SSSs to be less dense than 0.2 $\rm~cm^{-3}$. We discuss possible alternatives that could bridge the incompatibility between the theoretical expectations and the relevant observations.

astro-ph.SR↗

arXiv2022

Spectroscopic Analysis Tool for intEgraL fieLd unIt daTacubEs (satellite): Case studies of NGC 7009 and NGC 6778 with MUSE

Integral field spectroscopy (IFS) provides a unique capability to spectroscopically study extended sources over a 2D field of view, but it also requires new techniques and tools. In this paper, we present an automatic code, Spectroscopic Analysis Tool for intEgraL fieLd unIt daTacubEs, SATELLITE, designed to fully explore such capability in the characterization of extended objects, such as planetary nebulae, H II regions, galaxies, etc. SATELLITE carries out 1D and 2D spectroscopic analysis through a number of pseudo-slits that simulate slit spectrometry, as well as emission line imaging. The 1D analysis permits direct comparison of the integral field unit (IFU) data with previous studies based on long-slit spectroscopy, while the 2D analysis allows the exploration of physical properties in both spatial directions. Interstellar extinction, electron temperatures and densities, ionic abundances from collisionally excited lines, total elemental abundances and ionization correction factors are computed employing the Pyneb package. A Monte Carlo approach is implemented in the code to compute the uncertainties for all the physical parameters. SATELLITE provides a powerful tool to extract physical information from IFS observations in an automatic and user configurable way. The capabilities and performance of SATELLITE are demonstrated by means of a comparison between the results obtained from the Multi Unit Spectroscopic Explorer (MUSE) data of the planetary nebula NGC 7009 with the results obtained from long-slit and IFU data available in the literature. The SATELLITE characterization of NGC 6778 based on MUSE data is also presented.

astro-ph.SR↗

arXiv2022

Deep optical study of the mixed-morphology supernova remnant G 132.7+1.3 (HB3)

We present optical ccd images of the large supernova remnant (SNR) G132.7$+$1.3 (HB3) covering its full extent for the first time, in the emission lines of H$\alpha+$[N II], [S II] and [O III], where new and known filamentary and diffuse structures are detected. These observations are supplemented by new low-resolution long-slit spectra and higher-resolution images in the same emission lines. Both the flux-calibrated images and spectra confirm that the optical emission originates from shock-heated gas since the [S II]/H$\alpha$ $>$ 0.4. Our findings are also consistent with the recently developed emission line ratio diagnostics for distinguishing SNRs from H II regions. A multi-wavelength comparison among our optical data and relevant observations in radio, X-rays, $\gamma$-rays and CO bands, provided additional evidence on the interaction of HB3 with the surrounding clouds and clarified the borders of the SNR and the adjacent cloud. We discuss the supernova (SN) properties and evolution that led to the current observables of HB3 and we show that the remnant has most likely passed at the pressure driven snowplow phase. The estimated SN energy was found to be $\left(3.7 \pm 1.5\right) \times 10^{51}$ erg and the current SNR age $\left(5.1 \pm 2.1\right) \times 10^4$ yrs. We present an alternative scenario according to which the SNR evolved in the wind bubble cavity excavated by the progenitor star and currently is interacting with its density walls. We show that the overall mixed morphology properties of HB3 can be explained if the SN resulted by a Wolf-Rayet progenitor star with mass $\sim 34 \rm~M_{\rm\odot}$.

astro-ph.GA↗

arXiv2021

First deep images catalogue of extended IPHAS PNe

We present the first instalment of a deep imaging catalogue containing 58 True, Likely and Possible extended PNe detected with the Isaac Newton Telescope Photometric H$\alpha$ Survey (IPHAS). The three narrow-band filters in the emission lines of H$\alpha$, [N II] $\lambda$6584 \r{A} and [O III] $\lambda$5007 \r{A} used for this purpose allowed us to improve our description of the morphology and dimensions of the nebulae. In some cases even the nature of the source has been reassessed. We were then able to unveil new macro-and micro-structures, which will without a doubt contribute to a more accurate analysis of these PNe. It has been also possible to perform a primary classification of the targets based on their ionization level. A Deep Learning classification tool has also been tested. We expect that all the PNe from the IPHAS catalogue of new extended planetary nebulae will ultimately be part of this deep H$\alpha$, [N II] and [O III] imaging catalogue.

astro-ph.SR↗

arXiv2021

The Supernova Remnant Populations of the galaxies NGC 45, NGC 55, NGC 1313, NGC 7793: Luminosity and Excitation Functions

We present a systematic study of the Supernova Remnant (SNR) populations in the nearby galaxies NGC 45, NGC 55, NGC 1313, and NGC 7793 based on deep Ha and [S II] imaging. We find 42 candidate and 54 possible candidate SNRs based on the [S II] / Ha > 0.4 criterion, 84 of which are new identifications. We derive the Ha and the joint [S II]-Ha luminosity functions after accounting for incompleteness effects. We find that the Ha luminosity function of the overall sample is described with a skewed Gaussian with a mean equal to log(LHa / 10^(36) erg s^(-1)) = 0.07 and m(log(LHa / 10^(36) erg s^(-1)))) = 0.58. The joint [S II]-Ha function is parameterized by a skewed Gaussian along the log([S II] / 10^(36) erg s^(-1)) = 0.88 x log(LHa / 10^(36) erg s^(-1)) - 0.06 line and a truncated Gaussian with m(log(L[S II] / 10^(36))) = 0.024 and s(log(L[S II] / 10^(36))) = 0.14, on its vertical direction. We also define the excitation function as the number density of SNRs as a function of their [S II]/Ha ratios. This function is represented by a truncated Gaussian with a mean at -0.014. We find a sub-linear [S II]-Ha relation indicating lower excitation for the more luminous objects.

astro-ph.GA↗

arXiv2021

3D MHD astrospheres: applications to IRC-10414 and Betelgeuse

A significative fraction of all massive stars in the Milky Way move supersonically through their local interstellar medium (ISM), producing bow shock nebulae by wind-ISM interaction. The stability of these observed astrospheres around cool massive stars challenges precedent two-dimensional (magneto-)hydrodynamical simulations of their surroundings. We present three-dimensional magneto-hydrodynamical (3D MHD) simulations of the circumstellar medium of runaway M-type red supergiant stars moving with velocity v_star= 50 km/s. We treat the stellar wind with a Parker spiral and assume a 7 microG magnetisation of the ISM. Our free parameter is the angle theta_mag between ISM flow and magnetisation, taken to 0, 45 and 90 degrees. It is found that simulation dimension, coordinate systems and grid effects can greatly affect the development of the modelled astrospheres. Nevertheless, as soon as the ISM flow and magnetisation directions differs by more than a few degrees (theta_mag>5 degree), the bow shock is stabilised, most clumpiness and ragged structures vanishing. The complex shape of the bowshocks induce important projection effects, e.g. at optical Ha line, producing complex of astrospheric morphologies. We speculate that those effects are also at work around earlier-type massive stars, which would explain their diversity of their observed arc-like nebula around runaway OB stars. Our 3D MHD models are fitting well observations of the astrospheres of several runaway red supergiant stars. The results interpret the smoothed astrosphere of IRC-10414 and Betelgeuse aOri) are stabilised by an organised, non-parallel ambient magnetic field. Our findings suggest that IRC-10414 is currently in a steady state of its evolution, and that Betelgeuse's bar is of interstellar origin.

astro-ph.SR↗

arXiv2021

The reactivation of water maser emission in the planetary nebula IRAS 18061--2505 through a born-again episode

Water maser emitting planetary nebulae (H$_2$O-PNe) are believed to be among the youngest PNe. We present new optical narrow- and broad-band images, intermediate- and high-resolution long-slit spectra, and archival optical images of the H$_2$O-PN IRAS 18061--2505. It appears a pinched-waist bipolar PN consisting of knotty lobes with some point-symmetric regions, a bow-shock near the tip of each lobe, and a very compact inner nebula where five components are identified in the spectra by their kinematic and emission properties. The water masers most probably reside in an oxygen-rich ring tracing the equatorial region of the bipolar lobes. These two structures probably result from common envelope evolution plus several bipolar and non-bipolar collimated outflows that have distorted the lobes. The bow-shocks could be related to a previous phase to that of common envelope. The inner nebula may be attributed to a late or very late thermal pulse that occurred before 1951.6 when it was not detectable in the POSSI-Blue image. Chemical abundances and other properties favour a 3--4 M$_{\odot}$ progenitor, although if the common envelope phase accelerated the evolution of the central star, masses <1.5 M$_{\odot}$ cannot be discarded. The age of the bipolar lobes is incompatible with the existence of water masers in IRAS 18061--2505, which may have been lately reactivated through shocks in the oxygen-rich ring, that are generated by the thermal pulse, implying that this PN is not extremely young. We discuss H$_2$O-PNe and possibly related objects in the light of our results for IRAS 18061--2505.

astro-ph.GA↗

arXiv2020

"Ears" formation in Supernova Remnants: Overhearing an interaction history with bipolar circumstellar structures

A characteristic feature that is frequently met in nearby supernova remnants (SNRs) is the existence of two antisymmetric, local protrusions that are projected as two "ears" in the morphology of the nebula. In this work, we present a novel scenario for the "ear" formation process according to which the two lobes are formed through the interaction of the SNR with a bipolar circumstellar medium (CSM) that was surrounding the explosion center. We conduct two dimensional hydrodynamic simulations and we show that the SNR shock breakout from the bipolar CSM triggers the inflation of two opposite protrusions at the equator of the remnant that retain their size and shape for several hundreds up to a few thousand years of the SNR evolution. We run a set of models by varying the supernova (SN) and CSM properties and we demonstrate that the extracted results reveal a good agreement with the observables, regarding the "ears" sizes, lifespan, morphology and kinematics. We discuss the plausibility of our model in nature and we suggest that the most likely progenitors of the "ear-carrying" SNRs are the Luminous Blue Variables or the Red/Yellow Supergiants for the SNRs resulted by core collapse SN events and the symbiotic binaries or the planetary nebulae for the remnants formed by Type Ia SNe. Finally, we compare our model with other "ear" formation models of the literature and we show that there are distinctive differences among them, concerning the "ears" orientation and the phase in which the "ear" formation process occurs.

astro-ph.SR↗

arXiv2020

Two New Nova Shells associated with V4362 Sagittarii and DO Aquilae

A classical nova is an eruption on the surface of a white dwarf in an accreting binary system. The material ejected from the white dwarf surface generally forms an axisymmetric shell. The shaping mechanisms of nova shells are probes of the processes that take place at energy scales between planetary nebulae and supernova remnants. We report on the discovery of nova shells surrounding the post-nova systems V4362 Sagittarii (1994) and more limited observations of DO Aquilae (1925). Distance measurements of 0.5p/m1.4 kpc for V4362 Sgr and 6.7 p/m 3.5 kpc -0.2 for DO Aql are found based on the expansion parallax method. The growth rates are measured to be 0.07``/year for DO Aql and 0.32``/year for V4362 Sgr. A preliminary investigation into the ionisation structure of the nova shell associated with V4362 Sgr is presented. The observed ionisation structure of nova shells depends strongly on their morphology and the orientation of the central component towards the observer. X-ray, IR and UV observations as well as optical integral field unit spectroscopy are required to better understand these interesting objects.

astro-ph.SR↗