arXiv subjects

Ma. T. García-Díaz

Publications and source records attributed to Ma. T. García-Díaz.

14 recordsLinked to original sources

arXiv2026

1RXS J174320.1-042953: another polar with a red-shifted absorption component in emission line wings

We present the results of a spectroscopic and multi-band photometric study of the magnetic cataclysmic variable 1RXS J174320.1-042953. Multi-band photometry confirms a periodic modulation with an orbital period of $P_{\rm orb}=0.0864 \pm 0.0001$ days. Using the estimated secondary mass of $\sim0.15\,\mathrm{M_\odot}$ and, the X-ray-based white dwarf mass of $\sim0.75\,\mathrm{M_\odot}$, we obtain values of $q\sim0.2$ and a system inclination of $47^\circ\pm10^\circ$. The optical spectra of 1RXS J174320.1-042953 are dominated by strong, complex, asymmetric, and highly variable single-peaked emission lines of the Balmer series, \ion{He}{i}, and \ion{He}{ii}, which are characteristic of polar-type magnetic cataclysmic variables. Doppler tomography reveals no evidence of a Keplerian accretion disc, supporting the classification of the system as a polar. The H$β$ and \ion{He}{ii} emission lines can be decomposed into at least two distinct components. The low-velocity components have semi-amplitudes of approximately 170 km s$^{-1}$ (H$β$) and 147 km s$^{-1}$ (\ion{He}{ii}), while the high-velocity components reach about 317 km s$^{-1}$ and 460 km s$^{-1}$, respectively. The low-velocity component is likely associated with the irradiated side of the secondary star facing the white dwarf and/or the vicinity of the L$_1$ point, whereas the high-velocity component is related to the accretion-stream structure. A redshifted absorption component in the emission-line wings is detected at orbital phases near $ϕ\approx 0.0$, reaching velocities up to $\sim1400$ km s$^{-1}$ and likely produced by accretion-stream material crossing the line of sight.

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arXiv2025

Kinematics and physical structure of Ou 5: A bipolar planetary nebula with extreme abundance discrepancy and an eclipsing binary core

We present new deep imaging and high-resolution spectroscopy of the extreme-abundance-discrepancy planetary nebula Ou 5, together with photoionization modelling aimed at probing its unusual thermal and chemical structure. The nebula exhibits a nested bipolar morphology, including inner and outer shells, faint outer lobes, and polar knots. Remarkably, all these components share a dynamical age of order 10,000 yr. Thermal broadening of the H alpha line relative to heavier ions implies a hydrogen temperature 3000 K to 6000 K, in contrast to the ~ 10,000 K derived from collisionally excited line diagnostics. This provides independent support for the presence of at least two distinct temperature/metallicity phases, as previously proposed to explain extreme abundance discrepancies. Photoionization models with sinusoidally varying metallicity successfully reproduce the observed nebular spectrum and morphology. A mixture of fluctuations with both extreme and moderate metallicity contrasts is required to simultaneously fit the O II and the [O III] observations. The nebular He II emission demands a hotter and more luminous central star than previously inferred, consistent with a ~ 0.58 solar mass post-AGB progenitor evolving toward a CO white dwarf. Ou 5 thus reinforces the link between close-binary nuclei and extreme abundance discrepancies, and provides a valuable benchmark for understanding how common-envelope ejections give rise to the thermal and abundance inhomogeneities observed in planetary nebulae.

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arXiv2023

On the nature of the continuum reverberation of X-ray/UV and optical emission of IRAS 09149-6206

We present the results of a continuum reverberation mapping study of the radio-quiet Seyfert 1 galaxy IRAS 09149-6206. The analysis was performed using X-ray, UV and optical observations made with the {\em Swift} telescope between January and December 2017. The time delays between different light curves were measured using three different algorithms: PyI$^2$CCF, PyROA and JAVELIN. Our results show that the time delays increase with wavelength after $τ\propto λ^{4/3}$, as predicted for a geometrically thin and optically thick accretion disc, but only after accounting for significant diffuse continuum emission from the broad line region. However, the measured size of the accretion disc can be up to five times larger than that predicted by standard theory. To our surprise, the strong increase in soft X-ray fluxes is delayed by about 15 days compared to the optical UV fluctuations, which challenges the prediction of the lamp-post model. Our analysis of the X-ray variability reveals the presence of a non-variable spectral component at 0.3-6.0 keV along with variable excess emission at 2.0-3.0 keV, which could be partly related to relativistic reflection in the inner region of the accretion disc. IRAS 09149-6206 joins the list of objects for which the traditional lamp-post model cannot explain the observed time delays. A scenario that incorporates other geometric considerations into the lamp-post model, e.g. an extended corona along a scattering source, might be better suited to explain the observed long time delays

astro-ph.HE↗

arXiv2022

Revisiting the Continuum Reverberation Lags in the AGN PKS 0558-504

We present a revised analysis of the photometric reverberation mapping campaign of the narrow-line Seyfert 1 galaxy PKS 0558-504 carried out with the Swift Observatory during 2008--2010. Previously, Gliozzi et al.\ found using the Discrete Correlation Function (DCF) method that the short-wavelength continuum variations lagged behind variations at longer wavelengths, the opposite of the trend expected for thermal reprocessing of X-rays by the accretion disc, and they interpreted their results as evidence against the reprocessing model. We carried out new DCF measurements that demonstrate that the inverted lag-wavelength relationship found by Gliozzi et al.\ resulted from their having interchanged the order of the driving and responding light curves when measuring the lags. To determine the inter-band lags and uncertainties more accurately, we carried out new measurements with four independent methods. These give consistent results showing time delays increasing as a function of wavelength, as expected for the disc reprocessing scenario. The slope of the re-analysed delay spectrum appears to be roughly compatible with the predicted $τ\propto λ^{4/3}$ relationship for reprocessing by an optically thick and geometrically thin accretion disc, although the data points exhibit a large scatter about the fitted power-law trend.

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arXiv2021

The five axes of the Turtle: symmetry and asymmetry in NGC 6210

We carry out a comprehensive kinematic and morphological study of the asymmetrical planetary nebula: NGC 6210, known as the Turtle. The nebula's spectacularly chaotic appearance has led to proposals that it was shaped by mass transfer in a triple star system. We study the three-dimensional structure and kinematics of its shells, lobes, knots, and haloes by combining radial velocity mapping from multiple long-slit spectra with proper motion measurements from multi-epoch imaging. We find that the nebula has five distinct ejection axes. The first is the axis of the bipolar, wind-blown inner shell, while the second is the axis of the lop-sided, elliptical, fainter, but more massive intermediate shell. A further two axes are bipolar flows that form the point symmetric, high-ionization outer lobes, all with inclinations close to the plane of the sky. The final axis, which is inclined close to the line of sight, traces collimated outflows of low-ionization knots. We detect major changes in outflow directions during the planetary nebula phase, starting at or before the initial ionization of the nebula 3500 years ago. Most notably, the majority of redshifted low-ionization knots have kinematic ages greater than 2000 years, whereas the majority of blueshifted knots have ages younger than 2000 years. Such a sudden and permanent 180-degree flip in the ejection axis at a relatively late stage in the nebular evolution is a challenge to models of planetary nebula formation and shaping.

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arXiv2019

From outburst to quiescence: spectroscopic evolution of V1838 Aql imbedded in a bow-shock nebula

We analyse new optical spectroscopic, direct-image and X-ray observations of the recently discovered a high proper motion cataclysmic variable V1838 Aql. The data were obtained during its 2013 superoutburst and its subsequent quiescent state. An extended emission around the source was observed up to 30 days after the peak of the superoutburst, interpreted it as a bow--shock formed by a quasi-continuous outflow from the source in quiescence. The head of the bow--shock is coincident with the high--proper motion vector of the source ($v_{\perp}=123\pm5$ km s$^{-1}$) at a distance of $d=202\pm7$ pc. The object was detected as a weak X-ray source ($0.015\pm0.002$ counts s$^{-1}$) in the plateau of the superoutburst, and its flux lowered by two times in quiescence (0.007$\pm$0.002 counts s$^{-1}$). Spectroscopic observations in quiescence we confirmed the orbital period value $P_{\rm{orb}}=0.0545\pm 0.0026$ days, consistent with early-superhump estimates, and the following orbital parameters: $γ= -21\pm3$ km s$^{-1}$ and $K_1 = 53\pm3$ km s$^{-1}$. The white dwarf is revealed as the system approaches quiescence, which enables us to infer the effective temperature of the primary $T_{eff}=11,600\pm400$K. The donor temperature is estimated $\lesssim 2200$K and suggestive of a system approaching the period minimum. Doppler maps in quiescence show the presence of the hot spot in HeI line at the expected accretion disc-stream shock position and an unusual structure of the accretion disc in H$α$.

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arXiv2018

The Owl and other strigiform nebulae: multipolar cavities within a filled shell

We present the results of long-slit echelle spectroscopy and deep narrow-band imaging of the Owl Nebula (NGC 3587), obtained at the \textit{Observatorio Astronómico Nacional, San Pedro Mártir}. These data allow us to construct an iso-velocity data cube and develop a 3-D morpho-kinematic model. We find that, instead of the previously assumed bipolar dumbbell shape, the inner cavity consists of multi-polar fingers within an overall tripolar structure. We identify three additional planetary nebulae that show very similar morphologies and kinematics to the Owl, and propose that these constitute a new class of \textit{strigiform} (owl-like) nebulae. Common characteristics of the strigiform nebulae include a double-shell (thin outside thick) structure, low-luminosity and high-gravity central stars, the absence of a present-day stellar wind, and asymmetric inner cavities, visible in both optical and mid-infrared emission lines, that show no evidence for surrounding bright rims. The origin of the cavities is unclear, but they may constitute relics of an earlier stage of evolution when the stellar wind was active.

astro-ph.GA↗

arXiv2014

Internal Proper-Motions in the Eskimo Nebula

We present measurements of internal proper motions at more than five hundred positions of NGC 2392, the Eskimo Nebula, based on images acquired with WFPC2 on board the Hubble Space Telescope at two epochs separated by 7.695 years. Comparison of the two observations shows clearly the expansion of the nebula. We measured the amplitude and direction of the motion of local structures in the nebula by determining their relative shift during that interval. In order to assess the potential uncertainties in the determination of proper motions in this object, and in general, the measurements were performed using two different methods, used previously in the literature. We compare the results from the two methods, and to perform the scientific analysis of the results we choose one, the cross-correlation method, as the more reliable. We go on to perform a "criss-cross" mapping analysis on the proper motion vectors which helps in the interpretation of the velocity pattern. Combining our results on the proper motions with radial velocity measurements obtained from high resolution spectroscopic observations, and employing an existing 3D model, we estimate the distance to the nebula as 1300 pc.

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arXiv2014

A spectroscopic and photometric study of the planetary nebulae Kn 61 and Pa 5

We present the first morpho-kinematical analysis of the planetary nebulae Kn 61 and Pa 5 and explore the nature of their central stars. Our analysis is based on high resolution and medium resolution spectroscopic observations, deep narrow-band imaging, and integral photometry. This material allows us to identify the morphological components and study their kinematics. The direct images and spectra indicate an absence of the characteristic [N II] and [S II] emission lines in both nebulae. The nebular spectrum of Kn 61 suggests an hydrogen deficient planetary nebula and the stellar spectrum of the central star reveals a hydrogen deficient PG 1159-type star. The [O III] position velocity diagram reveals that Kn 61 is a closed, empty, spherical shell with a thin border and a filamentary surface expanding at 67.6 km s$^{-1}$, and the shell is currently not expanding isotropically. We derived a kinematic age of $\sim$ 1.6$\times$10$^4$ yrs for an assumed distance of 4 kpc. A photometric period of $\sim$ 5.7($\pm$0.4) days has been detected for Kn 61, indicating presence of a possible binary system at its core. A possible link between filamentary, spherical shells and PG 1159-type stars is noted. The morphology of Pa 5 is dominated by an equatorial toroid and faint polar extensions. The equatorial region of this planetary nebula is expanding at 45.2 kms$^{-1}$. The stellar spectrum corresponds to a very hot star and is dominated by a steep blue rising continuum and He II, Balmer and Ca II photospheric lines.

astro-ph.SR↗

arXiv2012

A Detailed Morpho-Kinematic Model of the Eskimo, NGC 2392. A Unifying View with the Cat's Eye and Saturn Planetary Nebulae

The 3-D and kinematic structure of the Eskimo nebula, NGC 2392, has been notoriously difficult to interpret in detail given its complex morphology, multiple kinematic components and its nearly pole-on orientation along the line of sight. We present a comprehensive, spatially resolved, high resolution, long-slit spectroscopic mapping of the Eskimo planetary nebula. The data consist of 21 spatially resolved, long-slit echelle spectra tightly spaced over the Eskimo and along its bipolar jets. This data set allows us to construct a velocity-resolved [NII] channel map of the nebula with a resolution of 10 km/s that disentangles the different kinematic components of the nebula. The spectroscopic information is combined with HST images to construct a detailed three dimensional morpho-kinematic model of the Eskimo using the code SHAPE. With this model we demonstrate that the Eskimo is a close analog to the Saturn and the Cat's Eye nebulae, but rotated 90 degrees to the line of sight. Furthermore, we show that the main characteristics of our model apply to the general properties of the group of elliptical planetary nebulae with ansae or FLIERS, once the orientation is considered. We conclude that these kind of nebulae belongs to a class with a complex common evolutionary sequence of events.

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arXiv2012

Morpho-kinematic analysis of the point-symmetric, bipolar planetary nebulae Hb 5 and K 3-17, a pathway to poly-polarity

The kinematics of the bipolar planetary nebulae Hb~5 and K 3-17 are investigated in detail by means of a comprehensive set of spatially resolved high spectral resolution, long-slit spectra. Both objects share particularly interesting characteristics, such as a complex filamentary, rosette-type nucleus, axial point-symmetry and very fast bipolar outflows. The kinematic information of Hb~5 is combined with {\it HST} imagery to construct a detailed 3D model of the nebula using the code SHAPE. The model shows that the large scale lobes are growing in a non-homologous way. The filamentary loops in the core are proven to actually be secondary lobes emerging from what appears to be a randomly punctured, dense, gaseous core and the material that forms the point symmetric structure flows within the lobes with a distinct kinematic pattern and its interaction with the lobes has had a shaping effect on them. Hb~5 and K~3-17 may represent a class of fast evolving planetary nebulae that will develop poly-polar characteristics once the nebular core evolves and expands.

astro-ph.GA↗

arXiv2012

The filamentary Multi-Polar Planetary Nebula NGC 5189

We present a set of optical and infrared images combined with long-slit, medium and high dispersion spectra of the southern planetary nebula (PN) NGC 5189. The complex morphology of this PN is puzzling and has not been studied in detail so far. Our investigation reveals the presence of a new dense and cold infrared torus (alongside the optical one) which probably generated one of the two optically seen bipolar outflows and which might be responsible for the twisted appearance of the optical torus via an interaction process. The high-resolution MES-AAT spectra clearly show the presence of filamentary and knotty structures as well as three expanding bubbles. Our findings therefore suggest that NGC 5189 is a quadrupolar nebula with multiple sets of symmetrical condensations in which the interaction of outflows has determined the complex morphology.

astro-ph.SR↗

arXiv2009

The outflows and 3D structure of NGC 6337, a planetary nebula with a close binary nucleus

NGC 6337 is a member of the rare group of planetary nebulae where a close binary nucleus has been identified. The nebula's morphology and emission line profiles are both unusual, particularly the latter. We present a thorough mapping of spatially resolved, long-slit echelle spectra obtained over the nebula that allows a detailed characterization of its complex kinematics. This information, together with narrow band imagery is used to produce a three dimensional model of the nebula using the code SHAPE. The 3-D model yields a slowly expanding toroid with large density fluctuations in its periphery that are observed as cometary knots. A system of bipolar expanding caps of low ionization are located outside the toroid. In addition, an extended high velocity and tenuous bipolar collimated outflow is found emerging from the core and sharply bending in opposite directions, a behavior that cannot be accounted for by pure magnetic launching and collimation unless the source of the outflow is precessing or rotating, as could be expected from a close binary nucleus.

astro-ph.SR↗

arXiv2008

Velocity Structure in the Orion Nebula. II. Emission Line Atlas of Partially Ionized to Fully Ionized Gas

We present an atlas of three-dimensional (position-position-velocity) spectra of the Orion Nebula in optical emission lines from a variety of different ionization stages: [O I] 6300, [S II] 6716,6731, [N II] 6584, [S III] 6312, H alpha 6563, and [O III] 5007. These transitions provide point to point information about the physical structure and kinematics of the nebula at an effective resolution of 3'' x 2'' x 10 km/s, clearly showing the large scale behavior of the ionized gas and the presence of localized phenomena such as Herbig-Haro outflows. As an example application of the atlas, we present a statistical analysis of the widths of the H alpha, [O III], and [N II] lines that permits a determination of the mean electron temperature in the nebula of (9200 +/- 400) K. We also find, in contradiction to previous claims, that the non-thermal line broadening is not significantly different between recombination lines and collisional lines.

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