M. A. Guerrero

Macquarie University, Sydney, New South Wales, Australia

Are you M. A. Guerrero?

Claim your profile

Publications (98)217.17 Total impact

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We present X-ray spectral analysis of 20 point-like X-ray sources detected in Chandra Planetary Nebula Survey (ChanPlaNS) observations of 59 planetary nebulae (PNe) in the solar neighborhood. Most of these 20 detections are associated with luminous central stars within relatively young, compact nebulae. The vast majority of these point-like X-ray-emitting sources at PN cores display relatively "hard" ($\geq0.5$~keV) X-ray emission components that are unlikely to be due to photospheric emission from the hot central stars (CSPN). Instead, we demonstrate that these sources are well modeled by optically-thin thermal plasmas. From the plasma properties, we identify two classes of CSPN X-ray emission: (1) high-temperature plasmas with X-ray luminosities, $L_{\rm X}$, that appear uncorrelated with the CSPN bolometric luminosity, $L_{\rm bol}$; and (2) lower-temperature plasmas with $L_{\rm X}/L_{\rm bol}\sim10^{-7}$. We suggest these two classes correspond to the physical processes of magnetically active binary companions and self-shocking stellar winds, respectively. In many cases this conclusion is supported by corroborative multiwavelength evidence for the wind and binary properties of the PN central stars. By thus honing in on the origins of X-ray emission from PN central stars, we enhance the ability of CSPN X-ray sources to constrain models of PN shaping that invoke wind interactions and binarity.
    The Astrophysical Journal 12/2014; 800(1). · 6.28 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: "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.
    12/2014;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We present the XMM-Newton discovery of X-ray emission from the planetary nebula (PN) A78, the second born-again PN detected in X-rays apart from A30. These two PNe share similar spectral and morphological characteristics: They harbor diffuse soft X-ray emission associated with the interaction between the H-poor ejecta and the current fast stellar wind, and a point-like source at the position of the central star (CSPN). We present the spectral analysis of the CSPN, using for the first time a NLTE code for expanding atmospheres which takes line blanketing into account for the UV and optical spectra. The wind abundances are used for the X-ray spectral analysis of the CSPN and the diffuse emission. The X-ray emission from the CSPN in A78 can be modeled by a single C VI emission line, while the X-ray emission from its diffuse component is better described by an optically thin plasma emission model with temperature $kT$=0.088 keV ($T\approx$1.0$\times$10${^6}$ K). We estimate X-ray luminosities in the 0.2--2.0 keV energy band of $L_{\mathrm{X,CSPN}}$=(1.2$\pm$0.3)$\times$10$^{31}$ erg~s$^{-1}$ and $L_{\mathrm{X,DIFF}}$=(9.2$\pm$2.3)$\times$10$^{30}$ erg~s$^{-1}$ for the CSPN and diffuse components, respectively.
    11/2014;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We present an analysis of XMM-Newton Reflection Grating Spectrometer (RGS) observations of the planetary nebula (PN) NGC 6543, rendering it the second PN with high resolution X-ray spectroscopic observations besides BD+30 3639. The observations consist of 26 pointings, of which 14 included RGS observations for a total integration time of 435 ks. Many of these observations, however, were severely affected by high-background levels, and the net useful exposure time is drastically reduced to 25 ks. Only the O VII triplet at 22 \AA\ is unambiguously detected in the RGS spectrum of NGC 6543. We find this spectrum consistent with an optically thin plasma at 0.147 keV (1.7 MK) and nebular abundances. Unlike the case of BD+30 3639, the X-ray emission from NGC 6543 does not reveal overabundances of C and Ne. The results suggest the N/O ratio of the hot plasma is consistent with that of the stellar wind, i.e., lower than the nebular N/O ratio, but this result is not conclusive.
    Astronomy and Astrophysics 10/2014; · 4.48 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A recent XMM-Newton observation (Zhekov 2014) has revealed diffuse X-ray emission inside the nebula NGC 2359 around the Wolf-Rayet star WR 7. Taking advantage of an improved point-source rejection and background subtraction, and a detailed comparison of optical and X-ray morphology, we have reanalyzed these X-ray observations. Our analysis reveals diffuse X-ray emission from a blowout and the presence of emission at energies from 1.0 to 2.0 keV. The X-ray emission from NGC 2359 can be described by an optically-thin plasma emission model, but contrary to previous analysis, we find that the chemical abundances of this plasma are similar to those of the optical nebula, with no magnesium enhancement, and that two components at temperatures T_1=2x10^6 K and T_2=5.7x10^7 K are required. The estimated X-ray luminosity in the 0.3 - 2.0 keV energy range is L_X=2x10^33 erg s^-1. The averaged rms electron density of the X-ray-emitting gas (n_e \lesssim 0.6 cm^-3) reinforces the idea of mixing of material from the outer nebula into the hot bubble.
    Monthly Notices of the Royal Astronomical Society 10/2014; 446(1). · 5.23 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We present results from the most recent set of observations obtained as part of the Chandra X-ray observatory Planetary Nebula Survey (ChanPlaNS), the first comprehensive X-ray survey of planetary nebulae (PNe) in the solar neighborhood (i.e., within ~1.5 kpc of the Sun). The survey is designed to place constraints on the frequency of appearance and range of X-ray spectral characteristics of X-ray-emitting PN central stars and the evolutionary timescales of wind-shock-heated bubbles within PNe. ChanPlaNS began with a combined Cycle 12 and archive Chandra survey of 35 PNe. ChanPlaNS continued via a Chandra Cycle 14 Large Program which targeted all (24) remaining known compact (R_neb <~ 0.4 pc), young PNe that lie within ~1.5 kpc. Results from these Cycle 14 observations include first-time X-ray detections of hot bubbles within NGC 1501, 3918, 6153, and 6369, and point sources in HbDs 1, NGC 6337, and Sp 1. The addition of the Cycle 14 results brings the overall ChanPlaNS diffuse X-ray detection rate to ~27% and the point source detection rate to ~36%. It has become clearer that diffuse X-ray emission is associated with young (<~5x10^3 yr), and likewise compact (R_neb<~0.15 pc), PNe with closed structures and high central electron densities (n_e>~1000 cm^-3), and rarely associated with PNe that show H_2 emission and/or pronounced butterfly structures. Hb 5 is one such exception of a PN with a butterfly structure that hosts diffuse X-ray emission. Additionally, of the five new diffuse X-ray detections, two host [WR]-type CSPNe, NGC 1501 and NGC 6369, supporting the hypothesis that PNe with central stars of [WR]-type are likely to display diffuse X-ray emission.
    The Astrophysical Journal 07/2014; 794(2). · 6.28 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We present the first results of our search for new, extended Planetary Nebulae (PNe) based on careful, systematic, visual scrutiny of the imaging data from the INT Photometric H-alpha Survey of the Northern Galactic Plane (IPHAS). The newly uncovered PNe will help to improve the census of this important population of Galactic objects that serve as key windows into the late stage evolution of low to intermediate mass stars. They will also facilitate study of the faint end of the ensemble Galactic PN luminosity function. The sensitivity and coverage of IPHAS allows PNe to be found in regions of greater extinction in the Galactic Plane and/or those PNe in a more advanced evolutionary state and at larger distances compared to the general Galactic PN population. Using a set of newly revised optical diagnostic diagrams in combination with access to a powerful, new, multi-wavelength imaging database, we have identified 159 true, likely and possible PNe for this first catalogue release. The ability of IPHAS to unveil PNe at low Galactic latitudes and towards the Galactic Anticenter, compared to previous surveys, makes this survey an ideal tool to contribute to the improvement of our knowledge of the whole Galactic PN population
    Monthly Notices of the Royal Astronomical Society 07/2014; 443(4). · 5.23 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The onset of asymmetry in planetary nebulae (PNe) occurs during the
    Astronomy and Astrophysics. 06/2014; 566:A133.
  • [Show abstract] [Hide abstract]
    ABSTRACT: We present new high resolution narrow-band [OIII] λ5007 images, as well as long-slit high resolution echelle spectra of the planetary nebula NGC 6309 at unprecedented detail, comfirming the presence of a halo circumscribing the quadrupolar outflows and discovering two diffuse emission blobs, which seem to be related to collimated ejections from the central star. Radial velocities of these faint blobs are very low, but qualitatively correspond to the radial direction of the quadrupolar lobes. Some possible scenarios are discussed, including collimated outflows from the central star and interaction of wind with field material, among others.
    03/2014;
  • [Show abstract] [Hide abstract]
    ABSTRACT: Many PNe show rings and shells related to the remnants of the circumstellar envelopes of the asymptotic giant branch phase (AGB). After an extensive search in the HST and Spitzer archives we found ring-like structures in several PNe. Following the image analysis described by Corradi et al. (2004), and unsharp masking techniques it was possible to effectively remove the underlying halo emission, enhancing the ring structures. We mention in the results some hypotheses about the origins of these rings.
    03/2014;
  • [Show abstract] [Hide abstract]
    ABSTRACT: We present radio observations of water masers toward the planetary nebula (PN) IRAS 15103-5754 (I15103), obtained during several campaigns at the Australia Telescope Compact Array (ATCA) and the Parkes antenna. I15103 is one of the rare planetary nebulae (PNe) exhibiting water maser emission. The follow-up of water masers is crucial in PNe, since the lifetime expected for this emission is very short, and it might trace the youngest stages of a star in the PN phase. The maser components detected in this source trace a jet with possible precession, which could be shaping its circumstellar envelope. Extraordinarily bright water maser emission reaching 1600 Jy was observed during our last observation campaigns, making I15103 the PN with the most intense water maser emission ever detected. The rapid evolution of its radio continuum emission associated to this unusual water maser activity indicates that this source could be one of the youngest PN known up to now.
    03/2014;
  • [Show abstract] [Hide abstract]
    ABSTRACT: Water masers have been revealed as an important tool to study the jets that shape the circumstellar envelopes of Planetary Nebulae (PNe). Water fountains are evolved objects with water maser components expanding velocities larger than 100 km/s, and they represent one of the first manifestations of axisymmetric jets during the late AGB or post-AGB phases. The unexpected presence of water masers in PNe, and the recent finding of the first PN with water fountain characteristics lead us to propose an evolutionary sequence that could connect the evolved sources presenting this emission. Water masers disappear quickly with the beginning of the photoionisation during the PN phase, but their presence in the disk, in the lobes or tracing jets in these objects can give an estimation of the evolutionary stage of the PN.
    03/2014;
  • [Show abstract] [Hide abstract]
    ABSTRACT: One of the most intriguing issues related with planetary nebulae (PNe) is their shaping process, since the most asymmetrical PNe defy the standard models for the formation of spherical, elliptical or slightly bipolar PNe. To observe the shaping mechanism, the use of high-resolution techniques is mandatory. Interferometric IR observations performed with the VLTI have revealed clear evidences of disks at the core of few PNe, nevertheless the use of the VLTI impose constraints in the sensitivity as well as in the spatial coverage, limiting the targets that can be observed with this technique. On the other hand, CRIRES-VLT high-resolution spectro-astrometry technique have proven its efficiency revealing the existence of protoplanetary disks.The spectro-astrometric observations using CRIRES-VLT are less time consuming and less constrained by the models used to interpret the data than VLTI observations. Inspired by these results and the less complicated spectro-astrometric observations, we have applied for the first time CRIRES-VLT spectro-astrometry to sources in transition to the PN phase to demonstrate the capabilities of this technique in the search of disks and compact structures at the innermost regions of these objects. We have used CRIRES-VLT commissioning data to develop the methodology and the tools to apply spectro-astrometric analysis to the proto-PN IRAS 17516-2525 and the young PN SwSt 1. In previous studies, the morphology of SwSt 1 is barely resolved and remains unresolved for IRAS 17516-252. Our exploratory study has revealed compact structures after the spectro-astrometric analysis. In the case of SwSt 1 we have investigated the line of [Fe III] at 2.145 microns and Br gamma line at 2.160 microns and we have detected small structures ~230 mas and 130 mas, respectively. As for IRAS 17516-252, the spectro-astrometric signature of the Br gamma line suggest the presence of a compact Keplerian-like disk structure of ~12 mas in size. Additionally, we have requested CRIRES-VLT observations devoted solely to spectro-astrometric analysis. We present preliminary results for the Red Rectangle (AFGL 915) in the CO fundamental band at 4.99 microns. We have found the spectro-astrometric signatures of the Keplerian gaseous CO disk detected in previous radio observations, but with smaller size (~100 mas = 35 AU). These CRIRES-VLT high-resolution spectro-astrometric results open a new window in the search of the shaping mechanism of the more complex morphologies of extremely asymmetric PNe.
    03/2014;
  • [Show abstract] [Hide abstract]
    ABSTRACT: We describe the evolution of of Swift J1644+57, whose unique X-ray properties have led several groups to interpret its behavior as corresponding to an extraordinary event of tidal disruption of a star by a supermassive black hole in the nucleus of a (z = 0.3545) galaxy, as derived by GTC. Multiwavelength observations (X-rays, optical, millimetre, centimitre) are proving to be essential to reveal the long term nature of the emission in this source. In particular, we identify for the first time the properties of a forming relativistic jet. In our interpretation of the phenomenon, we leave the still open possibility that it may correspond to the onset of a dormant AGN, but this may only be tested with longer term X-ray, millimetre and centimetre monitoring.
    The European Physical Journal Conferences 12/2013; 61:01003-.
  • [Show abstract] [Hide abstract]
    ABSTRACT: The shaping process of planetary nebulae (PNe) takes place during the short transition from the asymptotic giant branch (AGB) phase to the white dwarf stage. The young PN K 3-35 represents a unique case where a small-sized water maser ring has been linked to the launch of collimated outflows that shape the nebula. The contrasting optical and radio continuum morphologies of K 3-35 indicate that they disclose different structural components that are apparently unconnected. To bridge the gap between optical and radio continuum observations, we present here new broadband and narrowband near-and mid-IR images of K 3-35. These images, and their comparison with optical and radio continuum images, are revealing. The radio continuum and mid-IR images are dominated by a compact source at the core of K 3-35 whose emission gives evidence of very dense ionized material embedded within a dust cocoon. The emission from the core, obscured at optical wavelengths, is faintly detected in the K s band. We suggest that the dust may shield the water molecules at the inner ring from the central star ionizing radiation. The precessing collimated outflows, very prominent in radio continuum, are also detected in mid-IR, very particularly in the [S iv] image. The mid-IR emission from these outflows consist mostly of ionized material, although the broadband filter at 11.85 μm seems to imply that a small amount of dust may be carried out by the outflow. The interactions of these outflows with the nebular shell result in shocks that excite the emission of H 2 as well as low-excitation lines from ionized species, such as [N ii] at the tips of the outflows.
    Astronomy and Astrophysics 10/2013; 561(A81). · 4.48 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We analyze Chandra observations of the Wolf-Rayet (WR) bubble NGC 6888. This WR bubble presents similar spectral and morphological X-ray characteristics to those of S 308, the only other WR bubble also showing X-ray emission. The observed spectrum is soft, peaking at the N VII line emission at 0.5 keV with additional line emission at 0.7 - 0.9 keV and a weak tail of harder emission up to ~1.5 keV. This spectrum can be described by a two-temperature optically thin plasma emission model (T_{1}~1.4x10^{6} K, T_{2}~7.4x10^{6} K). We confirm the results of previous X-ray observations that no noticeable temperature variations are detected in the nebula. The X-ray-emitting plasma is distributed in three apparent morphological components: two caps along the tips of the major axis and an extra contribution toward the northwest blowout not reported in previous analysis of the X-ray emission toward this WR nebula. Using the plasma model fits of the Chandra ACIS spectra for the physical properties of the hot gas and the ROSAT PSPC image to account for the incomplete coverage of Chandra observations, we estimate a luminosity of L_X = (7.7\pm0.1)x10^{33} erg/s for NGC 6888 at a distance of 1.26 kpc. The average rms electron density of the X-ray-emitting gas is >= 0.4 cm^{-3} for a total mass >= 1.2 Msun.
    The Astronomical Journal 10/2013; 147(2). · 4.05 Impact Factor
  • Source
    J. A. Toalá, M. A. Guerrero
    [Show abstract] [Hide abstract]
    ABSTRACT: We present the analysis of XMM-Newton archival observations towards the Wolf-Rayet (WR) bubble around WR16. Despite the closed bubble morphology of this WR nebula, the XMM-Newton observations show no evidence of diffuse emission in its interior as in the similar WR bubbles NGC6888 and S308. We use the present observations to estimate a 3-\sigma upper limit to the X-ray luminosity in the 0.3-1.5 keV energy band equal to 7.4x10^{32} erg s^{-1} for the diffuse emission from the WR nebula, assuming a distance of 2.37 kpc. The WR nebula around WR16 is the fourth observed by the current generation of X-ray satellites and the second not detected. We also examine FUSE spectra to search for nebular O VI absorption lines in the stellar continuum of WR16. The present far-UV data and the lack of measurements of the dynamics of the optical WR bubble do not allow us to confirm the existence of a conductive layer of gas at T~3x10^5 K between the cold nebular gas and the hot gas in its interior. The present observations result in an upper limit of n_e < 0.6 cm^-3 on the electron density of the X-ray emitting material within the nebula.
    Astronomy and Astrophysics 09/2013; · 4.48 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Stars over a wide range of masses and evolutionary stages are nowadays known to emit X-rays. This X-ray emission is a unique probe of the most energetic phenomena occurring in the circumstellar environment of these stars, and provides precious insight on magnetic phenomena or hydrodynamic shocks. Owing to its large collecting area, Athena+ will open up an entirely new window on these phenomena. Indeed, Athena+ will not only allow us to study many more objects with an unprecedented spectral resolution, but will also pioneer the study of the dynamics of these objects via time-resolved high-resolution spectroscopy. In this way, Athena+ will be a unique tool to study accretion processes in TTauri stars, flaring activity in young stars, dynamos in ultra-cool dwarfs, small and large-scale structures in the winds of single massive stars, wind interactions in massive binary systems, hot bubbles in planetary nebula... All these studies will lead to a deeper understanding of yet poorly understood processes which have profound impact in star and planetary system formation as well as in feedback processes on Galactic scale.
    06/2013;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: This White Paper, submitted to the recent ESA call for science themes to define its future large missions, advocates the need for a transformational leap in our understanding of two key questions in astrophysics: 1) How does ordinary matter assemble into the large scale structures that we see today? 2) How do black holes grow and shape the Universe? Hot gas in clusters, groups and the intergalactic medium dominates the baryonic content of the local Universe. To understand the astrophysical processes responsible for the formation and assembly of these large structures, it is necessary to measure their physical properties and evolution. This requires spatially resolved X-ray spectroscopy with a factor 10 increase in both telescope throughput and spatial resolving power compared to currently planned facilities. Feedback from supermassive black holes is an essential ingredient in this process and in most galaxy evolution models, but it is not well understood. X-ray observations can uniquely reveal the mechanisms launching winds close to black holes and determine the coupling of the energy and matter flows on larger scales. Due to the effects of feedback, a complete understanding of galaxy evolution requires knowledge of the obscured growth of supermassive black holes through cosmic time, out to the redshifts where the first galaxies form. X-ray emission is the most reliable way to reveal accreting black holes, but deep survey speed must improve by a factor ~100 over current facilities to perform a full census into the early Universe. The Advanced Telescope for High Energy Astrophysics (Athena+) mission provides the necessary performance (e.g. angular resolution, spectral resolution, survey grasp) to address these questions and revolutionize our understanding of the Hot and Energetic Universe. These capabilities will also provide a powerful observatory to be used in all areas of astrophysics.
    06/2013;
  • [Show abstract] [Hide abstract]
    ABSTRACT: We present the analysis of the hot plasma detected with XMM-Newton and Chandra X-ray observations toward the only two Wolf-Rayet bubbles so far detected: S 308 and NGC 6888. Both nebulae present spectra dominated by soft temperature plasmas of ˜10^{6} K with luminosities of L_{{X}}˜10^{33}-10^{34} erg s^{-1}, but with different X-ray-emitting plasma distribution. In the case of S 308 it presents a limb-brightened morphology, while in the case of NGC 6888, it shows three maxima localized at the Northeast and Southwest caps and another one extending toward the Northwest.
    05/2013;

Publication Stats

467 Citations
217.17 Total Impact Points

Institutions

  • 2014
    • Macquarie University
      Sydney, New South Wales, Australia
    • University of Guadalajara
      • Instituto de Astronomía y Meteorología
      Guadalajara, Jalisco, Mexico
  • 2005–2014
    • Instituto De Astrofisica De Andalucia
      Granata, Andalusia, Spain
  • 2011
    • Rochester Institute of Technology
      • Center for Imaging Science
      Rochester, New York, United States
  • 2005–2009
    • Spanish National Research Council
      • Andalusian Astrophysics Institute
      Madrid, Madrid, Spain
  • 2008
    • The University of Sheffield
      • Department of Physics and Astronomy
      Sheffield, ENG, United Kingdom
  • 2004
    • Bureau of Materials & Physical Research
      Springfield, Illinois, United States
  • 2000–2003
    • University of Illinois, Urbana-Champaign
      • Department of Astronomy
      Urbana, IL, United States
  • 1999
    • Instituto de Astrofísica de Canarias
      San Cristóbal de La Laguna, Canary Islands, Spain