M. A. Guerrero

Macquarie University, Sydney, New South Wales, Australia

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Publications (103)221.55 Total impact

  • J. A. Toalá · M. A. Guerrero · Y. -H. Chu · S. J. Arthur · R. A. Gruendl ·
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    ABSTRACT: We discuss our most recent findings on the diffuse X-ray emission from Wolf-Rayet (WR) nebulae. The best-quality X-ray observations of these objects are those performed by XMM-Newton and Chandra towards S308, NGC2359, and NGC6888. Even though these three WR nebulae might have different formation scenarios, they all share similar characteristics: i) the main plasma temperatures of the X-ray-emitting gas is found to be $T$=[1-2]$\times$10$^{6}$ K, ii) the diffuse X-ray emission is confined inside the [O III] shell, and iii) their X-ray luminosities and electron densities in the 0.3-2.0~keV energy range are $L_\mathrm{X}\approx$10$^{33}$-10$^{34}$~erg~s$^{-1}$ and $n_\mathrm{e}\approx$0.1-1~cm$^{-3}$, respectively. These properties and the nebular-like abundances of the hot gas suggest mixing and/or thermal conduction is taking an important role reducing the temperature of the hot bubble.
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    ABSTRACT: The last part of SpS5 dealt with the circumstellar environment. Structures are indeed found around several types of massive stars, such as blue and red supergiants, as well as WRs and LBVs. As shown in the last years, the potential of IR for their study is twofold: first, IR can help discover many previously unknown nebulae, leading to the identification of new massive stars as their progenitors; second, IR can help characterize the nebular features. Current and new IR facilities thus pave the way to a better understanding of the feedback from massive stars.
    Proceedings of the International Astronomical Union 08/2015; 10(H16):429-438. DOI:10.1017/S174392131401179X
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    ABSTRACT: 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.
    Astronomy and Astrophysics 04/2015; 578. DOI:10.1051/0004-6361/201526009 · 4.38 Impact Factor
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    J. A. Toalá · M. A. Guerrero · G. Ramos-Larios · V. Guzmán ·
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    ABSTRACT: We present a morphological study of nebulae around Wolf-Rayet (WR) stars using archival narrow-band optical and Wide-field Infrared Survey Explorer (WISE) infrared images. The comparison among WISE images in different bands and optical images proves to be a very efficient procedure to identify the nebular emission from WR nebulae, and to disentangle it from that of the ISM material along the line of sight. In particular, WR nebulae are clearly detected in the WISE W4 band at 22 $\mu$m. Analysis of available mid-IR Spitzer spectra shows that the emission in this band is dominated by thermal emission from dust spatially coincident with the thin nebular shell or most likely with the leading edge of the nebula. The WR nebulae in our sample present different morphologies that we classified into well defined WR bubbles (bubble ${\cal B}$-type nebulae), clumpy and/or disrupted shells (clumpy/disrupted ${\cal C}$-type nebulae), and material mixed with the diffuse medium (mixed ${\cal M}$-type nebulae). The variety of morphologies presented by WR nebulae shows a loose correlation with the central star spectral type, implying that the nebular and stellar evolutions are not simple and may proceed according to different sequences and time-lapses. We report the discovery of an obscured shell around WR35 only detected in the infrared.
    Astronomy and Astrophysics 03/2015; 578. DOI:10.1051/0004-6361/201525706 · 4.38 Impact Factor
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    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 02/2015; 800(1). DOI:10.1088/0004-637X/800/1/8 · 5.99 Impact Factor
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    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.
    The Astrophysical Journal 11/2014; 799(1). DOI:10.1088/0004-637X/799/1/67 · 5.99 Impact Factor
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    M. A. Guerrero · J. A. Toalá · Y. -H. Chu · R. A. Gruendl ·
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    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; 574. DOI:10.1051/0004-6361/201424995 · 4.38 Impact Factor
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    J. A. Toalá · M. A. Guerrero · Y. -H. Chu · R. A. Gruendl ·
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    ABSTRACT: A recent XMM–Newton observation 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 reanalysed 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 T1 = 2 × 106 K and T2 = 5.7 × 107 K are required. The estimated X-ray luminosity in the 0.3–2.0 keV energy range is LX = 2 × 1033 erg s−1. The averaged rms electron density of the X-ray-emitting gas (ne ≲ 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). DOI:10.1093/mnras/stu2163 · 5.11 Impact Factor
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    ABSTRACT: Originally published in: 2014MNRAS.443.3388S. List and characteristics of 159 new true, likely and possible extended PNe discovered in the framework of IPHAS. Also listed is the basic information for the spectroscopic follow-up (1 data file).
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    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). DOI:10.1088/0004-637X/794/2/99 · 5.99 Impact Factor
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    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 Isaac Newton Telescope Photometric Hα 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, multiwavelength imaging data base, 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 Anticentre, 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). DOI:10.1093/mnras/stu1404 · 5.11 Impact Factor
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    ABSTRACT: The onset of asymmetry in planetary nebulae (PNe) occurs during the short transition between the end of the asymptotic giant branch (AGB) phase and the beginning of the PN phase. Sources in this transition phase are compact and emit intensely in infrared wavelengths, making high spatial resolution observations in the infrared mandatory to investigate the shaping process of PNe. Interferometric VLTI IR observations have revealed compelling evidence of disks at the cores of PNe, but the limited sensitivity, strong observational constraints, and limited spatial coverage place severe limits on a universal use of this technique. Inspired by the successful detection of proto-planetary disks using spectro-astrometric observations, we apply this technique here for the first time to search for subarcsecond structures in PNe. Our exploratory study using CRyogenic high-resolution Infra-Red Echelle Spectrograph (CRIRES) commissioning data of the proto-PN IRAS 17516-2525 and the young PN SwSt 1 has revealed small-sized structures after the spectro-astrometric analysis of the two sources. In IRAS 17516-2525, the spectro-astrometric signal has a size of only 12+/-5mas, as detected in the Br gamma line, whereas the structures found in SwSt 1 have sizes of 230 +/- 29 mas in the [Fe III] line and 130 +/- 21 mas in the Br gamma line. The spectroscopic observations required to perform spectro-astrometry of sources in the transition towards the PN phase are less time-consuming and much more sensitive than VLTI IR observations. The results presented here open a new window in the search for the small-sized collimating agents that shape the complex morphologies of extremely axisymmetric PNe.
    Astronomy and Astrophysics 06/2014; 566:A133. DOI:10.1051/0004-6361/201322564 · 4.38 Impact Factor
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    ABSTRACT: Following a vast search for extended Planetary Nebulae (PNe) in the Galactic Plane using IPHAS, we present the first release of the "IPHAS Catalogue of Extended Nebulae". The catalogue in its current version contains more than one hundred spectroscopically identified PNe distributed from the Galactic Center to the Galactic Anticenter. These new "IPHAS PNe" are generally more evolved and show lower surface brightness than most of the already detected PNe but they are comparable to the southern "MASH PNe". In this poster we present the catalogue and its main entries as well as statistics based on the principal PNe properties.
    Asymmetrical Planetary Nebulae VI Conference, 4-8 November, 2013. Edited by C. Morisset, G. Delgado-Inglada and S. Torres-Peimbert; 04/2014
  • G. Ramos-Larios · E. Santamaría · A. Marquez-Lugo · M. A. Guerrero · L. Sabin ·
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    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.
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    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.
  • M. Blanco Cárdenas · H. U. Käufl · M. A. Guerrero · L. F. Miranda ·
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    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.
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    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.
  • G. Rubio · R. Vázquez · G. Ramos-Larios · M. A. Guerrero · L. Olguín · H. Mata ·
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    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.
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    ABSTRACT: We describe the late spectral variability and flux evolution of TDF Sw J1644+57, a Tidal Disruption Flare which left the typical potential trend proportional to $t^{-5/3}$ in 2012, maintaining a quiescent flux until nowadays. Sixteen X-ray observations of ESA satellite \emph{XMM-Newton} have been used in this study, including the one performed on 17$^{\rm th}$July, 2013. A search for optical emission in BOOTES/CASANDRA database has been performed too. Late X-ray fluxes show that the source flux decline does not follow the expected TDF trend at the time of the last \emph{XMM-Newton} observation. Moreover, the spectra fitting parameters, in particular the neutral hydrogen column density, N$_{\rm H}$, and the power-law index, $\Gamma$, indicate that the source darkening has diminished and that the spectral shape has flattened with time. The disruption of the star could have come to an end. Nevertheless, a quiescent X-ray flux continues. Evidence for a quiescent X-ray flux is presented.
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    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-. DOI:10.1051/epjconf/20136101003

Publication Stats

533 Citations
221.55 Total Impact Points


  • 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
  • 2012
    • Rochester Institute of Technology
      Rochester, New York, United States
  • 2005-2009
    • Spanish National Research Council
      • Andalusian Astrophysics Institute
      Madrid, Madrid, Spain
  • 2003-2004
    • Bureau of Materials & Physical Research
      Springfield, Illinois, United States
  • 2002-2003
    • University of Illinois, Urbana-Champaign
      • Department of Astronomy
      Urbana, IL, United States