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L. F. Miranda

Publications and source records attributed to L. F. Miranda.

At least 19 recordsLinked to original sources
arXiv2025

Confirmation and characterization of Galactic planetary nebulae: insights from a spectroscopic study

We present a spectroscopic investigation of 25 objects previously reported as possible Planetary Nebulae (PNe) in recent catalogs to obtain their physical properties and to establish their true nature. We found 11 objects showing intense emission lines, 11 where it was not possible to measure $\mathrm{Hβ}$, and three where no lines are present. We have used diagnostic diagrams to confirm the true PN nature for eight objects. We obtained elemental abundances for three objects whose values are in agreement with the PNe mean values for our Galaxy. Four objects show [N II] $λ$6583 more intense than $\mathrm{Hα}$, and for two of them, this can be explained by the presence of shocks in the gas. Finally, we report angular sizes based on $\mathrm{Hα}$ and [O III] $λ$5007 emission.

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arXiv2025

An attempt to determine the magnetic field configuration in the planetary nebula K 3-35 with ALMA

We examined dust polarisation within the planetary nebula (PN) K 3-35 using the Atacama Large Millimeter/Submillimeter Array (ALMA). This investigation aimed to identify and trace the magnetic field within the PN, as it potentially plays a crucial role in shaping this bipolar nebula. Our findings include a marginal detection of the polarised region and low fractional polarisation (peaking at 1.4%). Assuming a certain level of validity, we observed well-organised dust grains aligned along the equatorial plane of the PN, indicating a magnetic field alignment with the outflows. The limited polarisation detection at submillimeter wavelengths in this PN and others may be attributed to a pronounced optical depth. However, our K 3-35 analysis with the code DUSTY does not seem to support this idea. We also modelled the SED of K3-35, and our best-fit models included a mixture of silicates and amorphous carbon. The grains of amorphous carbon are less susceptible to alignment with the magnetic field, which could, at least partially, explain the observed low polarisation. The models presented in this article should be considered preliminary, and a more advanced approach is needed for a more complete interpretation of the results.

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arXiv2024

Morphokinematical study of the planetary nebula Me2-1: Unveiling its point-symmetric and unusual physical structure

(Abridged) We present narrow-band images in several emission lines, and high- and intermediate-resolution long-slit spectra of Me2-1 to investigate its morphology and 3D structure, its physical parameters and chemical abundances. We identified in Me2-1: an elliptical ring; two elongated, curved structures (caps) that contain three pairs of bright point-symmetric (PS) knots; a shell interior of the ring; and a faint halo or attached shell. The caps are observed in all images, the PS knots only in the low-excitation emission line ones. These structures are also identified in the high-resolution long-slit spectra. The 3D reconstruction shows that Me2-1 consists of a ring seen almost pole-on, and a virtually spherical shell, to which the caps and PS knots are attached. Caps and PS knots most probably trace the sites where high-velocity collimated bipolar outflows, ejected along a wobbling axis, collide with the spherical shell, are slowed down, and remain attached to it. Although the main excitation mechanism in Me2-1 is found to be photoionization, a contribution of shocks in the PS knots is suggested by their emission line ratios. The combination of collimated outflows and a ring with a spherical shell is unusual among planetary nebulae. We speculate that two planets, each with less than one Jupiter mass, could be involved in the formation of Me2-1 if both enter a common envelope evolution during the asymptotic giant branch phase of the progenitor. One planet is tidally disrupted, forming an accretion disk around the central star, from which collimated bipolar outflows are ejected; the other planet survives, causing wobbling of the accretion disk. The derived physical parameters and chemical abundances are similar to those obtained in previous analyses, with the abundances also pointing to a low-mass progenitor of Me2-1.

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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.

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arXiv2021

Herbig Ae/Be stars towards the dark cloud LDN 1667

We report the discovery of a new emission-line object, named SPH4-South = (GAIA EDR3 5616553300192230272), towards the dark cloud LDN 1667. This object came to our attention after inspecting public images that show a faint diffuse nebula a few arcsec southern from SPH4, an emission-line object previously classified as a T Tauri star. We present high-resolution spectra and analyzed JHK photometry of SPH4 and SPH4-South, and new narrow-band and archival broad-band images of these objects. A comparison of the spectra of SPH4 and SPH4-South with high-resolution ones of DG Cir and R Mon, strongly suggests that SPH 4 and SPH4-South are Herbig Ae/Be stars. The classification of SPH4-South is further supported by using a k-NN algorithm to its position in H-K versus J-H color-color diagram. Both stars are detected in the four WISE bands and the WISE colors allow us to classify SPH4 as a Class I and SPH4-South as a Class II source. We also show that the faint nebula is most probably associated with SPH4-South. Using published results on LDN 1667 and the Gaia Early Data Release 3, we conclude that SPH4 is a member of LDN 1667. The case of SPH4-South is not clear because the determination of its distance and proper motion could be affected by the nebulosity around the star, although membership of SPH4-South to LDN 1667 cannot be ruled out.

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arXiv2020

Discovery of a Fast Expanding Shell in the Inside-out Born-Again Planetary Nebula HuBi 1 Through High-Dispersion Integral Field Spectroscopy

HuBi 1 has been proposed to be member of the rare class of born-again planetary nebulae (PNe), i.e., its central star experienced a very late thermal pulse and ejected highly-processed material at high speeds inside the old hydrogen-rich PN. In this letter we present GTC MEGARA integral field spectroscopic observations of the innermost regions of HuBi 1 at high spectral resolution $\simeq16$ km s$^{-1}$ and multi-epoch sub-arcsec images obtained $\simeq 12$ yr apart. The analysis of these data indicates that the inner regions of HuBi 1 were ejected $\simeq200$ yr ago and expand at velocities $\simeq300$ km s$^{-1}$, in excellent agreement with the born-again scenario. The unprecedented tomographic capabilities of the GTC MEGARA high-dispersion observations used here reveal that the ejecta in HuBi 1 has a shell-like structure, in contrast to the disrupted disk and jet morphology of the ejecta in other born-again PNe.

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arXiv2020

Planetary nebulae seen with TESS: Discovery of new binary central star candidates from Cycle 1

It is now clear that binarity plays a crucial role in many aspects of planetary nebulae (PNe), particularly the striking morphologies they exhibit. To date, there are ~60 known bCSPNe. However, both theory and observation indicates that this represents only the tip of the iceberg, with the Galactic PN population hosting orders of magnitude more. We are involved in a search for new bCSPNe to enhance the statistical validation of the key role of binarity in the formation and shaping of PNe. New discoveries of bCSPNe and their characterization carry important implications not only for understanding PN evolution, but also for studying binary evolution and the poorly-understood common-envelope phase. We used data from the TESS satellite to search for variability in the eight CSPNe that belong to the two-minute cadence preselected targets in Cycle 1, with their available pipeline-extracted light curves. We identified strong periodicities and analysed them in the context of the binary scenario.All the CSPNe but one (Abell15) show clear signs of periodic variability in TESS. The cause of this variability can be attributed to different effects, some of them requiring the presence of a companion star. We find simple sinusoidal modulations in several of the systems, compatible with irradiation effects. In addition, two of the central stars (PG1034+001 and NGC5189) also show photometric variations due to ellipsoidal variations and other signs of variability probably caused by star spots or relativistic Doppler-beaming. The case of the well-studied Helix Nebula is of particular interest: here we constructed a series of binary models to explain the modulations we see in the light curve. We find that the variability constrains the possible companion to be very low-mass main-sequence star or sub-stellar object. We also identify, in substantial detail, the individual pulsation frequencies of NGC246.

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arXiv2019

Kinematical Investigation of Possible Fast Collimated Outflows in Twelve Planetary Nebulae

A significant fraction of planetary nebulae (PNe) exhibit collimated outflows, distinct narrow kinematical components with notable velocity shifts with respect to the main nebular shells typically associated with low-ionization compact knots and linear or precessing jet-like features. We present here a spatio-kinematical investigation of a sample of twelve PNe with morphologies in emission lines of low-ionization species suggestive of collimated outflows. Using archival narrow-band images and our own high-dispersion long-slit echelle spectra, we confirm the presence of collimated outflows in Hen 2-429, J 320, M 1-66, M 2-40, M 3-1, and NGC 6210 and possibly in NGC 6741, for which the spatio-kinematical data can also be interpreted as a pair of bipolar lobes. The presence of collimated outflows is rejected in Hen 2-47, Hen 2-115, M 1-26, and M 1-37, but their morphology and kinematics are indicative of the action of supersonic outflows that have not been able to pierce through the nebular envelope. In this sense, M 1-66 appears to have experienced a similar interaction between the outflow and nebular envelope, but, as opposed to these four PNe, the outflow has been able to break through the nebular envelope. It is suggested that the PNe without collimated outflows in our sample are younger or descend from lower mass progenitors than those that exhibit unambiguous collimated outflows.

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arXiv2018

A new look inside Planetary Nebula LoTr 5: A long-period binary with hints of a possible third component

LoTr 5 is a planetary nebula with an unusual long-period binary central star. As far as we know, the pair consists of a rapidly rotating G-type star and a hot star, which is responsible for the ionization of the nebula. The rotation period of the G-type star is 5.95 days and the orbital period of the binary is now known to be $\sim$2700 days, one of the longest in central star of planetary nebulae. The spectrum of the G central star shows a complex H$α$ double-peaked profile which varies with very short time scales, also reported in other central stars of planetary nebulae and whose origin is still unknown. We present new radial velocity observations of the central star which allow us to confirm the orbital period for the long-period binary and discuss the possibility of a third component in the system at $\sim$129 days to the G star. This is complemented with the analysis of archival light curves from SuperWASP, ASAS and OMC. From the spectral fitting of the G-type star, we obtain a effective temperature of $T_{\rm eff}$ = 5410$\pm$250 K and surface gravity of $\log g$ = 2.7$\pm$0.5, consistent with both giant and subgiant stars. We also present a detailed analysis of the H$α$ double-peaked profile and conclude that it does not present correlation with the rotation period and that the presence of an accretion disk via Roche lobe overflow is unlikely.

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arXiv2016

History of the mass ejection in K 4-37: from the AGB to the evolved planetary nebula phase

We present narrow-, broad-band, and WISE archive images, and high- and intermediate-resolution long-slit spectra of K 4-37, a planetary nebula that has never been analyzed in detail. Although K 4-37 appears bipolar, the morphokinematical analysis discloses the existence of three distinct axes and additional particular directions in the object, indicating that K 4-37 is a multi-axis planetary nebula that has probably been shaped by several bipolar outflows at different directions. A 4-6 M$_{\odot}$ main-sequence progenitor is estimated from the derived high nebular He and N abundances, and very high N/O abundance ratio ($\sim$2.32). The general properties are compatible with K 4-37 being a highly evolved planetary nebula located at $\sim$14 kpc. The WISE image at 22 $μ$m reveals K 4-37 to be surrounded by a large ($\sim$13$\times$8 pc$^2$) elliptical detached shell probably related to material ejected from the AGB progenitor. The observed elliptical morphology suggests deformation of an originally spherical AGB shell by the ISM magnetic field or by the influence of a companion. We compare K 4-37 and NGC 6309 and found remarkable similarities in their physical structure but noticeably different chemical abundances that indicate very different progenitor mass. This strongly suggests that, irrespective of the initial mass, their (presumably binary) central stars have shared a very similar mass ejection history.

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arXiv2016

Observations of the planetary nebula RWT 152 with OSIRIS/GTC

RWT 152 is one of the few known planetary nebulae with an sdO central star. We present subarcsecond red tunable filter Halpha imaging and intermediate-resolution, long-slit spectroscopy of RWT 152 obtained with OSIRIS/GTC with the goal of analyzing its properties. The Halpha image reveals a bipolar nebula with a bright equatorial region and multiple bubbles in the main lobes. A faint circular halo surrounds the main nebula. The nebular spectra reveal a very low-excitation nebula with weak emission lines from H^+, He^+, and double-ionized metals, and absence of emission lines from neutral and single-ionized metals, except for an extremely faint [NII]6584 emission line. These spectra may be explained if RWT 152 is a density-bounded planetary nebula. Low nebular chemical abundances of S, O, Ar, N, and Ne are obtained in RWT 152, which, together with the derived high peculiar velocity ($\sim$ 92-131 km s$^{-1}$), indicate that this object is a halo planetary nebula. The available data are consistent with RWT 152 evolving from a low-mass progenitor ($\sim$ 1 M$_{\odot}$) formed in a metal-poor environment.

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arXiv2016

Searching for new yellow symbiotic stars: positive identification of StHa63

Yellow symbiotic stars are useful targets to probe whether mass transfer has happened in these binary systems. However, the number of known yellow symbiotic stars is very scarce. We report spectroscopic observations of five candidate yellow symbiotic stars selected by their position in the 2MASS (J-H) vs. (H-Ks) diagram and included in some emission-line catalogs. Among the five candidates, only StHa63 is identified as a new yellow symbiotic star because of its spectrum and its position in the [TiO]1-[TiO]2 diagram that indicates a K4-K6 spectral type. In addition, the derived electron density (10E8.4 cm-3) and several emission line intensity ratios provide further support for that classification. The other four candidates are rejected as symbiotic stars because three of them actually do not show emission lines and the fourth one shows only Balmer emission lines. We also found that the WISE W3-W4 index clearly separates normal K-giants from yellow symbiotic stars and, therefore, can be used as an additional tool to select candidate yellow symbiotic stars.

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arXiv2015

A search for water maser emission toward obscured post-AGB star and planetary nebula candidates

Water maser emission at 22 GHz is a useful probe to study the transition between the nearly spherical mass-loss in the AGB to a collimated one in the post-AGB phase. In their turn, collimated jets in the post-AGB phase could determine the shape of planetary nebulae (PNe) once photoionization starts. We intend to find new cases of post-AGB stars and PNe with water maser emission, including water fountains or water-maser-emitting PNe. We observed water maser emission in a sample of 133 objects, with a significant fraction being post-AGB and young PN candidate sources with strong obscuration. We detected this emission in 15 of them, of which seven are reported here for the first time. We identified three water fountain candidates: IRAS 17291-2147, with a total velocity spread of ~96 km/s in its water maser components and two sources (IRAS 17021-3109 and IRAS 17348-2906) that show water maser emission outside the velocity range covered by OH masers. We have also identified IRAS 17393-2727 as a possible new water-maser-emitting PN. The detection rate is higher in obscured objects (14%) than in those with optical counterparts (7%), consistent with previous results. Water maser emission seems to be common in objects that are bipolar in the near-IR (43% detection rate). The water maser spectra of water fountain candidates like IRAS 17291-2147 show significantly less maser components than others (e.g., IRAS 18113-2503). We speculate that most post-AGBs may show water maser emission with wide enough velocity spread (> 100 km/s) when observed with enough sensitivity and/or for long enough periods of time. Therefore, it may be necessary to single out a special group of "water fountains", probably defined by their high maser luminosities. We also suggest that the presence of both water and OH masers in a PN is a better tracer of its youth, rather than the presence of just one of these species.

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arXiv2015

Spectral analysis of BD+30$^{\circ}$623, the peculiar binary central star of the planetary nebula NGC 1514

NGC 1514 is a complex planetary nebula with a peculiar binary central star (BD+30$^{\circ}$623) consisting of a cool star and a hot companion. To date, the parameters of the two stars have not been firmly stablished. We present a detailed spectral analysis of BD+30$^{\circ}$623 based on intermediate-resolution CAFOS optical spectra and IUE ultraviolet spectra with the goal of deriving the parameters of the two stars. For this purpose, we used an extensive composite grid of Kurucz and Tübingen NLTE Model-Atmosphere spectra. From the fitting procedure, in terms of the minimum $χ^{2}$ method, the best models obtained correspond to an Horizontal-Branch A0 star with $T_{\rm eff}$ = 9850$\pm$150 K, log g = 3.50$\pm$0.25, and a hot companion with $T_{\rm eff}$ between 80000 K and 95000K and a log g $\simeq$ 5.5. To our knowledge, this is the first time that the parameters of both stars have been determined accurately through a detailed spectroscopic analysis.

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arXiv2014

The first "water fountain" collimated outflow in a planetary nebula

"Water fountains" (WFs) are evolved objects showing high-velocity, collimated jets traced by water maser emission. Most of them are in the post-Asymptotic Giant Branch and they may represent one of the first manifestations of collimated mass loss in evolved stars. We present water maser, carbon monoxide, and mid-infrared spectroscopic data (obtained with the Australia Telescope Compact Array, Herschel Space Observatory, and the Very Large Telescope, respectively) toward IRAS 15103--5754, a possible planetary nebula (PN) with WF characteristics. Carbon monoxide observations show that IRAS 15103-5754 is an evolved object, while the mid-IR spectrum displays unambiguous [NeII] emission, indicating that photoionization has started and thus, its nature as a PN is confirmed. Water maser spectra show several components spreading over a large velocity range ~75 km/s and tracing a collimated jet. This indicates that the object is a WF, the first WF known that has already entered the PN phase. However, the spatial and kinematical distribution of the maser emission in this object are significantly different from those in other WFs. Moreover, the velocity distribution of the maser emission shows a "Hubble-like" flow (higher velocities at larger distances from the central star), consistent with a short-lived, explosive mass-loss event. This velocity pattern is not seen in other WFs (presumably in earlier evolutionary stages). We therefore suggest that we are witnessing a fundamental change of mass-loss processes in WFs, with water masers being pumped by steady jets in post-AGB stars, but tracing explosive/ballistic events as the object enters the PN phase.

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arXiv2014

The physical structure of planetary nebulae around sdO stars: Abell36, DeHt2, and RWT152

We present narrow-band Halpha and [OIII] images, and high-resolution, long-slit spectra of the planetary nebulae (PNe) Abell36, DeHt2, and RWT152 aimed at studying their morphology and internal kinematics. These data are complemented with intermediate-resolution, long-slit spectra to describe the spectral properties of the central stars and nebulae. The morphokinematical analysis shows that Abell36 consists of an inner spheroid and two bright point-symmetric arcs; DeHt2 is elliptical with protruding polar regions and a bright non-equatorial ring; and RWT152 is bipolar. The formation of Abell36 and DeHt2 requires several ejection events including collimated bipolar outflows that probably are younger than and have disrupted the main shell. The nebular spectra of the three PNe show a high excitation and also suggest a possible deficiency in heavy elements in DeHt2 and RWT152. The spectra of the central stars strongly suggest an sdO nature and their association with PNe points out that they have most probably evolved through the asymptotic giant branch. We analyze general properties of the few known sdOs associated to PNe and find that most of them are relatively or very evolved PNe, show complex morphologies, host binary central stars, and are located at relatively high Galactic latitudes.

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arXiv2014

H$_2$O maser emission associated with the planetary nebula IRAS 16333$-$4807

We present simultaneous observations of H$_2$O maser emission and radio continuum at 1.3 cm carried out with the Australia Telescope Compact Array towards two sources, IRAS 16333$-$4807 and IRAS 12405$-$6219, catalogued as planetary nebula (PN) candidates, and where single-dish detections of H$_2$O masers have been previously reported. Our goal was to unambiguously confirm the spatial association of the H$_2$O masers with these two PN candidates. We detected and mapped H$_2$O maser emission in both fields, but only in IRAS 16333$-$4807 the maser emission is spatially associated with the radio continuum emission. The properties of IRAS 16333$-$4807 provide strong support for the PN nature of the object, hereby confirming it as the fifth known case of a H$_2$O maser-emitting PN. This source is bipolar, like the other four known H$_2$O maser-emitting PNe, indicating that these sources might pertain to a usual, but short phase in the evolution of bipolar PNe. In IRAS 12405$-$6219, the H$_2$O maser and radio continuum emission are not associated with each other and, in addition, the available data indicate that this source is an H II region rather than a PN.

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