Bo Reipurth

University of Hawaiʻi at Mānoa, Honolulu, Hawaii, United States

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Publications (246)815.45 Total impact

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    ABSTRACT: Using the United Kingdom Infrared Telescope on Mauna Kea, we have carried out a new near-infrared J, H, K monitoring survey of almost a square degree of the star-forming Orion Nebula Cluster with observations on 120 nights over three observing seasons, spanning a total of 894 days. We monitored ~15,000 stars down to J=20 using the WFCAM instrument, and have extracted 1203 significantly variable stars from our data. By studying variability in young stellar objects (YSOs) in the H-K, K color-magnitude diagram, we are able to distinguish between physical mechanisms of variability. Many variables show color behavior indicating either dust-extinction or disk/accretion activity, but we find that when monitored for longer periods of time, a number of stars shift between these two variability mechanisms. Further, we show that the intrinsic timescale of disk/accretion variability in young stars is longer than that of dust-extinction variability. We confirm that variability amplitude is statistically correlated with evolutionary class in all bands and colors. Our investigations of these 1203 variables have revealed 73 periodic AA Tau type variables, many large-amplitude and long-period (P > 15 day) YSOs, including three stars showing widely-spaced periodic brightening events consistent with circumbinary disk activity, and four new eclipsing binaries. These phenomena and others indicate the activity of long-term disk/accretion variability processes taking place in young stars. We have made the light curves and associated data for these 1203 variables available online.
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    ABSTRACT: The luminous Class I protostar HBC 494, embedded in the Orion A cloud, is associated with a pair of reflection nebulae, Re50 and Re50N, which appeared sometime between 1955 and 1979. We have found that a dramatic brightening of Re50N has taken place sometime between 2006 and 2014. This could result if the embedded source is undergoing a FUor eruption. However, the near-infrared spectrum shows a featureless very red continuum, in contrast to the strong CO bandhead absorption displayed by FUors. Such heavy veiling, and the high luminosity of the protostar, is indicative of strong accretion but seemingly not in the manner of typical FUors. We favor the alternative explanation that the major brightening of Re50N and the simultaneous fading of Re50 is caused by curtains of obscuring material that cast patterns of illumination and shadows across the surface of the molecular cloud. This is likely occurring as an outflow cavity surrounding the embedded protostar breaks through to the surface of the molecular cloud. Several Herbig-Haro objects are found in the region.
    The Astrophysical Journal 03/2015; 805(1). DOI:10.1088/0004-637X/805/1/54 · 6.28 Impact Factor
  • The Astronomical Journal 03/2015; 149(3):108. DOI:10.1088/0004-6256/149/3/108 · 4.05 Impact Factor
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    Bo Reipurth, Seppo Mikkola
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    ABSTRACT: We have carried out 200,000 N-body simulations of three identical stellar embryos with masses from a Chabrier IMF and embedded in a molecular core. The bodies are initially non-hierarchical and undergo chaotic motions, while accreting using Bondi-Hoyle accretion. The coupling of dynamics and accretion often leads to one or two dominant bodies controlling the center of the cloud core, while banishing the other(s) to the lower-density outskirts, leading to stunted growth. Eventually each system transforms either to a bound hierarchical configuration or breaks apart into separate single and binary components. The orbital motion is followed for 100 Myr. To illustrate the simulations we introduce the 'triple diagnostic diagram', which plots two dimensionless numbers against each other, representing the binary mass ratio and the mass ratio of the third body to the total system mass. Numerous freefloating BD binaries are formed in these simulations. The separation distribution function is in good correspondence with observations, showing a steep rise at close separations, peaking around 13 AU and then declining more gently. Unresolved BD triple systems may appear as wider BD binaries. Mass ratios are strongly peaked towards unity, as observed, but this is partially due to the initial assumptions. Eccentricities gradually increase towards higher values, due to the lack of viscous interactions in the simulations, which would both shrink the orbits and decrease their eccentricities. The main threat to newly born triple systems is internal instabilities, not external perturbations. Dynamical interactions in newborn triple systems of stellar embryos embedded in and accreting from a cloud core naturally form a population of freefloating BD binaries, and this mechanism may constitute a significant pathway for the formation of BD binaries. (Abstract abbreviated).
    The Astronomical Journal 01/2015; 149(4). DOI:10.1088/0004-6256/149/4/145 · 4.05 Impact Factor
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    ABSTRACT: We present new H$\alpha$ and H$\beta$ images of the HH~1/2 system, and we find that the H$\alpha$/H$\beta$ ratio has high values in ridges along the leading edges of the HH~1 bow shock and of the brighter condensations of HH~2. These ridges have H$\alpha$/H$\beta=4\to 6$, which is consistent with collisional excitation from the $n=1$ to the $n=3$ and 4 levels of hydrogen in a gas of temperatures $T=1.5\to 10\times 10^4$~K. This is therefore the first direct proof that the collisional excitation/ionization region of hydrogen right behind Herbig-Haro shock fronts is detected.
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    ABSTRACT: We present observations of near-infrared 2.12 micro-meter molecular hydrogen outflows emerging from 1.1 mm dust continuum clumps in the North America and Pelican Nebula (NAP) complex selected from the Bolocam Galactic Plane Survey (BGPS). Hundreds of individual shocks powered by over 50 outflows from young stars are identified, indicating that the dusty molecular clumps surrounding the NGC 7000 / IC 5070 / W80 HII region are among the most active sites of on-going star formation in the Solar vicinity. A spectacular X-shaped outflow, MHO 3400, emerges from a young star system embedded in a dense clump more than a parsec from the ionization front associated with the Pelican Nebula (IC 5070). Suspected to be a binary, the source drives a pair of outflows with orientations differing by 80 degrees. Each flow exhibits S-shaped symmetry and multiple shocks indicating a pulsed and precessing jet. The `Gulf of Mexico' located south of the North America Nebula (NGC 7000), contains a dense cluster of molecular hydrogen objects (MHOs), Herbig-Haro (HH) objects, and over 300 YSOs, indicating a recent burst of star formation. The largest outflow detected thus far in the North America and Pelican Nebula complex, the 1.6 parsec long MHO 3417 flow, emerges from a 500 Solar mass BGPS clump and may be powered by a forming massive star. Several prominent outflows such as MHO 3427 appear to be powered by highly embedded YSOs only visible at a wavelength > 70 micro-meters. An `activity index' formed by dividing the number of shocks by the mass of the cloud containing their source stars is used to estimate the relative evolutionary states of Bolocam clumps. Outflows can be used as indicators of the evolutionary state of clumps detected in mm and sub-mm dust continuum surveys.
    The Astronomical Journal 09/2014; 148(6). DOI:10.1088/0004-6256/148/6/120 · 4.05 Impact Factor
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    ABSTRACT: We present a deep survey of Halpha emission-line stars in the M42 region using wide-field objective prism films. A total of 1699 Halpha emission-line stars were identified, of which 1025 were previously unknown, within an area of 5.5 x 5.5 degrees centred on the Trapezium Cluster. We present Halpha strength estimates, positions, and JHKs photometry extracted from 2MASS, and comparisons to previous surveys. The spatial distribution of the bulk of the stars follows the molecular cloud as seen in CO and these stars are likely to belong to the very young population of stars associated with the Orion Nebula Cluster. Additionally, there is a scattered population of Halpha emission-line stars distributed all over the region surveyed, which may consist partly of foreground stars associated with the young NGC 1980 cluster, as well as some foreground and background dMe or Be stars. The present catalogue adds a large number of candidate low-mass young stars belonging to the Orion population, selected independently of their infrared excess or X-ray emission.
    Astronomy and Astrophysics 06/2014; 570. DOI:10.1051/0004-6361/201423594 · 4.48 Impact Factor
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    ABSTRACT: We present high angular resolution, high sensitivity 8.46 GHz (3.6 cm) radio continuum observations made toward the core of the HH~92 outflow with the Very Large Array in 2002-2003 and with the Expanded Very Large Array in 2011. We detect a group of three compact sources distributed in a region 2$''$ in extension and discuss their nature. We conclude that one of the objects (VLA 1) is the exciting source of the giant outflow associated with HH~92. In the case of HH~34 we present new 43.3 GHz (7 mm) observations that reveal the presence of a structure associated with the exciting source and elongated perpendicular to the highly collimated optical jet in the region. We propose that this 7 mm source is a circumstellar disk with radius of $\sim$80 AU and mass of $\sim$0.21 $M_\odot$.
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    ABSTRACT: Observations from optical to centimeter wavelengths have demonstrated that multiple systems of two or more bodies is the norm at all stellar evolutionary stages. Multiple systems are widely agreed to result from the collapse and fragmentation of cloud cores, despite the inhibiting influence of magnetic fields. Surveys of Class 0 protostars with mm interferometers have revealed a very high multiplicity frequency of about 2/3, even though there are observational difficulties in resolving close protobinaries, thus supporting the possibility that all stars could be born in multiple systems. Near-infrared adaptive optics observations of Class I protostars show a lower binary frequency relative to the Class 0 phase, a declining trend that continues through the Class II/III stages to the field population. This loss of companions is a natural consequence of dynamical interplay in small multiple systems, leading to ejection of members. We discuss observational consequences of this dynamical evolution, and its influence on circumstellar disks, and we review the evolution of circumbinary disks and their role in defining binary mass ratios. Special attention is paid to eclipsing PMS binaries, which allow for observational tests of evolutionary models of early stellar evolution. Many stars are born in clusters and small groups, and we discuss how interactions in dense stellar environments can significantly alter the distribution of binary separations through dissolution of wider binaries. The binaries and multiples we find in the field are the survivors of these internal and external destructive processes, and we provide a detailed overview of the multiplicity statistics of the field, which form a boundary condition for all models of binary evolution. Finally we discuss various formation mechanisms for massive binaries, and the properties of massive trapezia.
  • Bo Reipurth
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    ABSTRACT: Astronomer who pioneered studies of young stars.
    Nature 11/2013; 503(7477):470. DOI:10.1038/503470a · 42.35 Impact Factor
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    ABSTRACT: HH 222 is a giant shocked region in the L1641 cloud, and is popularly known as the Orion Streamers or "the waterfall" on account of its unusual structure. At the center of these streamers are two infrared sources coincident with a nonthermal radio jet aligned along the principal streamer. The unique morphology of HH 222 has long been associated with this radio jet. However, new infrared images show that the two sources are distant elliptical galaxies, indicating that the radio jet is merely an improbable line-of-sight coincidence. Accurate proper motion measurements of HH 222 reveal that the shock structure is a giant bow shock moving directly away from the well-known, very young, Herbig Be star V380 Ori. The already known Herbig-Haro object HH 35 forms part of this flow. A new Herbig-Haro object, HH 1041, is found precisely in the opposite direction of HH 222 and is likely to form part of a counterflow. The total projected extent of this HH complex is 5.3 pc, making it among the largest HH flows known. A second outflow episode from V380 Ori is identified as a pair of HH objects, HH 1031 to the northwest and the already known HH 130 to the southeast, along an axis that deviates from that of HH 222/HH 1041 by only 3.°7. V380 Ori is a hierarchical quadruple system, including a faint companion of spectral type M5 or M6, which at an age of ~1 Myr corresponds to an object straddling the stellar-to-brown dwarf boundary. We suggest that the HH 222 giant bow shock is a direct result of the dynamical interactions that led to the conversion from an initial non-hierarchical multiple system into a hierarchical configuration. This event occurred no more than 28,000 yr ago, as derived from the proper motions of the HH 222 giant bow shock.
    The Astronomical Journal 11/2013; 146(5):118-. DOI:10.1088/0004-6256/146/5/118 · 4.05 Impact Factor
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    ABSTRACT: We report photometric observations for comet C/2012 S1 ISON obtained immediately after discovery (22 Sep. 2012; r = 6.28 AU) until moving into solar conjunction in mid-June 2013 using the UH2.2m, and Gemini North 8-m telescopes on Mauna Kea, the Lowell 1.8m in Flagstaff, the Calar Alto 1.2m telescope in Spain, and the VYSOS-5 and VYSOS-20 telescopes on Mauna Loa Hawai’i. An additional pre-discovery data point from the Pan STARRS1 survey extends the light curve back to 28 Jan. 2012 (r = 8.4 AU). The images showed similar tail morphology throughout this period, largely because of projection effects. Additional observations at sub-mm wavelengths using the JCMT on 15 nights between 9 March (r = 4.52 AU) and 16 June 2013 (r = 3.35 AU) were used to search for CO J(3-2), CO J(2-1), HCN J(4-3), and HCN J(3-2) rotation lines. No gas was detected, with preliminary upper limits for CO during 14-15 June (r = 3.3 AU) of Q < 6.4 x 10^27 molec/s based on the observations of the CO J(2-1) line. Using these production rates, the Q(H2O) published by Schleicher (2013; IAUC 9254), and the preliminary radius from the HST measurements (J.-Y. Li et al., 2013; STScI-2013-14) we have generated ice sublimation models consistent with the photometric light curve. The inbound light curve is likely controlled by sublimation of CO or CO2; at these distances water is not a strong contributor to the outgassing. Without more sensitive limits on CO, we cannot yet constrain which of these volatiles is controlling the activity. It is clear from the photometric light curve that the fractional active area of the nucleus increased linearly by about a factor of 2 from Jan. 2012 until mid Jan. 2013 (r ~ 5 AU) at which point the activity decreased by 30% by early May 2013. This suggests that a limited supply of volatile material was driving the current activity.
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    ABSTRACT: We report photometric observations for comet C/2012 S1 (ISON) obtained during the time period immediately after discovery (r=6.28 AU) until it moved into solar conjunction in mid-2013 June using the UH2.2m, and Gemini North 8-m telescopes on Mauna Kea, the Lowell 1.8m in Flagstaff, the Calar Alto 1.2m telescope in Spain, the VYSOS-5 telescopes on Mauna Loa Hawaii and data from the CARA network. Additional pre-discovery data from the Pan STARRS1 survey extends the light curve back to 2011 September 30 (r=9.4 AU). The images showed a similar tail morphology due to small micron sized particles throughout 2013. Observations at sub-mm wavelengths using the JCMT on 15 nights between 2013 March 9 (r=4.52 AU) and June 16 (r=3.35 AU) were used to search for CO and HCN rotation lines. No gas was detected, with upper limits for CO ranging between (3.5-4.5)E27 molec/s. Combined with published water production rate estimates we have generated ice sublimation models consistent with the photometric light curve. The inbound light curve is likely controlled by sublimation of CO2. At these distances water is not a strong contributor to the outgassing. We also infer that there was a long slow outburst of activity beginning in late 2011 peaking in mid-2013 January (r~5 AU) at which point the activity decreased again through 2013 June. We suggest that this outburst was driven by CO injecting large water ice grains into the coma. Observations as the comet came out of solar conjunction seem to confi?rm our models.
    The Astrophysical Journal 09/2013; 776(2013-10-03-2). DOI:10.1088/2041-8205/776/2/L20 · 6.28 Impact Factor
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    ABSTRACT: Our general understanding of multiple star and planet formation is primarily based on observations of young multiple systems in low density regions like Tau-Aur and Oph. Since many, if not most, of the stars are born in clusters, observational constraints from young binaries in those environments are fundamental for understanding both the formation of multiple systems and planets in multiple systems throughout the Galaxy. We build upon the largest survey for young binaries in the Orion Nebula Cluster (ONC) which is based on Hubble Space Telescope observations to derive both stellar and circumstellar properties of newborn binary systems in this cluster environment. We present Adaptive Optics spatially-resolved JHKL'-band photometry and K-band R$\sim$\,5000 spectra for a sample of 8 ONC binary systems from this database. We characterize the stellar properties of binary components and obtain a census of protoplanetary disks through K-L' color excess. For a combined sample of ONC binaries including 7 additional systems with NIR spectroscopy from the literature, we derive mass ratio and relative age distributions. We compare the stellar and circumstellar properties of binaries in ONC with those in Tau-Aur and Oph from samples of binaries with stellar properties derived for each component from spectra and/or visual photometry and with a disk census obtained through K-L color excess. The mass ratio distribution of ONC binaries is found to be indistinguishable from that of Tau-Aur and, to some extent, to that of Oph in the separation range 85-560\,AU and for primary mass in the range 0.15 to 0.8\,M$_{\sun}$.A trend toward a lower mass ratio with larger separation is suggested in ONC binaries which is not seen in Tau-Aur binaries.The components of ONC binaries are found to be significantly more coeval than the overall ONC population and as coeval as components of binaries in Tau-Aur and Oph[...]
    Astronomy and Astrophysics 07/2013; 557. DOI:10.1051/0004-6361/201220681 · 4.48 Impact Factor
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    Josh Walawender, Bo Reipurth, John Bally
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    ABSTRACT: We have searched the Lynds 988 dark cloud complex for optical (\ha{} and \sii{}) and near-IR (\mh{} 2.12 $\mu$m) shocks from protostellar outflows. We find 20 new Herbig-Haro objects and 6 new \mh{} shocks (MHO objects), 3 of which are cross detections. Using the morphology in the optical and near-IR, we connect several of these shocks into at least 5 distinct outflow systems and identify their source protostars from catalogs of infrared sources. Two outflows in the cloud, from IRAS 21014+5001 and IRAS 21007+4951, are in excess of 1 pc in length. The IRAS 21007+4951 outflow has carved a large cavity in the cloud through which background stars can be seen. Also, we have found an optical shock which is the counterflow to the previously discovered "northwest outflow" from LkHa 324SE.
    The Astronomical Journal 07/2013; 146(3). DOI:10.1088/0004-6256/146/3/66 · 4.05 Impact Factor
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    ABSTRACT: We present a study of the nearby isolated star forming region B62, a well-defined Bok globule in northern Ophiuchus. On large scales, we identify the H-alpha emission line stars, several of which are associated with compact reflection nebulae, together with two large Herbig-Haro flows, named HH 1000 and HH 1001. On small scales, we focus on the young stellar object IRAS 17130-2053 located near the center of the globule. This embedded Class I source is found to be a binary in our near-infrared images, and drives the bipolar Herbig-Haro flow HH 1000 as well as a molecular outflow. We present new interferometric observations by the Submillimeter Array and study the molecular environment in multiple dense gas tracers with high resolution.
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    ABSTRACT: Multiple systems have long been used to probe the origin and evolution of stars of all masses. Only in the past 10-15 years have such studies been extended to brown dwarfs and the lowest mass stars through binary surveys of both young star forming regions and the older field population. In addition, a groundswell of interest in M dwarfs in recent years has resulted in large, modern datasets for these most common stars in the Galaxy, thereby enabling renewed perspectives on their multiplicity properties. These latest observational results have in turn fueled the many theories competing to explain the formation of low-mass stars and brown dwarfs. This Cool Stars 17 splinter session examined the current state of this field by reviewing results from the numerous observational techniques - radial velocities, astrometry, direct imaging, and synoptic surveys - that have been used to study multiplicity from the earliest embedded protostars to objects in young star forming regions, old and intermediate-age clusters, as well as the more heterogeneous field population.
    Astronomische Nachrichten 02/2013; 334(1-2):36-. DOI:10.1002/asna.201211772 · 1.12 Impact Factor
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    Bo Reipurth, Seppo Mikkola
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    ABSTRACT: The formation of very wide binary systems, such as the α Centauri system with Proxima (also known as α Centauri C) separated from α Centauri (which itself is a close binary A/B) by 15,000 astronomical units (1 au is the distance from Earth to the Sun), challenges current theories of star formation, because their separation can exceed the typical size of a collapsing cloud core. Various hypotheses have been proposed to overcome this problem, including the suggestion that ultrawide binaries result from the dissolution of a star cluster-when a cluster star gravitationally captures another, distant, cluster star. Recent observations have shown that very wide binaries are frequently members of triple systems and that close binaries often have a distant third companion. Here we report N-body simulations of the dynamical evolution of newborn triple systems still embedded in their nascent cloud cores that match observations of very wide systems. We find that although the triple systems are born very compact-and therefore initially are more protected against disruption by passing stars-they can develop extreme hierarchical architectures on timescales of millions of years as one component is dynamically scattered into a very distant orbit. The energy of ejection comes from shrinking the orbits of the other two stars, often making them look from a distance like a single star. Such loosely bound triple systems will therefore appear to be very wide binaries.
    Nature 12/2012; 492(7428). DOI:10.1038/nature11662 · 42.35 Impact Factor
  • John Bally, Josh Walawender, Bo Reipurth
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    ABSTRACT: We report the discovery of new Herbig-Haro shocks in the southeastern portion of the Taurus molecular cloud complex. The embedded protostar IRAS04325+2402, located in the eastern end of the B18 dark cloud in the cloud region known as L1535, drives a parsec-scale outflow with a length of at least 134' (5.5 pc) toward P.A. = 17°/197° making this the largest protostellar outflow found thus far in Taurus. The southern terminus of this flow located about 65' (~2.7 pc) from the IRAS source consists of a large previously discovered shock, HH 434-436. The northern lobe contains three faint shocks with the most distant being HH 696 located 2.8 pc north of the source. Two smaller shocks, HH 699 and HH 703, are found midway between the IRAS source and HH 434-436. HH 703 has a proper motion of 170 ± 30 km s–1 toward P.A. = 195° ± 10°. Additionally, we report the discovery of a dozen new Herbig-Haro objects tracing outflows and protostellar jets in B18 and near IC 2087, at least two of which have also attained parsec-scale dimensions. These observations demonstrate that some low-mass stars forming from the Taurus clouds drive giant flows which can excite shocks in the inter-cloud medium degrees from their sources, providing further evidence for the generation of large-scale mass motions and turbulence by protostellar outflows.
    The Astronomical Journal 10/2012; 144(5):143. DOI:10.1088/0004-6256/144/5/143 · 4.05 Impact Factor

Publication Stats

3k Citations
815.45 Total Impact Points

Institutions

  • 2010–2015
    • University of Hawaiʻi at Mānoa
      • Institute for Astronomy
      Honolulu, Hawaii, United States
  • 2004–2015
    • University of Hawaiʻi at Hilo
      Hilo, Hawaii, United States
    • University of California, Los Angeles
      • Department of Physics and Astronomy
      Los Ángeles, California, United States
  • 2013
    • Universität Stuttgart
      Stuttgart, Baden-Württemberg, Germany
    • NASA
      Вашингтон, West Virginia, United States
  • 2002–2009
    • Honolulu University
      Honolulu, Hawaii, United States
    • The University of Arizona
      • Department of Astronomy
      Tucson, Arizona, United States
  • 2008
    • University of Hawai'i System
      Honolulu, Hawaii, United States
    • Academia Sinica
      T’ai-pei, Taipei, Taiwan
  • 1997–2008
    • University of Colorado at Boulder
      • • Center for Astrophysics and Space Astronomy
      • • Department of Astrophysical and Planetary Sciences
      Boulder, CO, United States
    • The Entomological Society of Ontario
      Canada
  • 2006
    • University of Victoria
      • Department of Physics and Astronomy
      Victoria, British Columbia, Canada
  • 2003
    • University of California, Berkeley
      • Department of Astronomy
      Berkeley, California, United States
  • 1998–1999
    • University of Colorado
      Denver, Colorado, United States
  • 1995–1999
    • Universidad Nacional Autónoma de México
      • Institute of Astronomy
      Ciudad de México, Mexico City, Mexico
  • 1989–1994
    • University of Santiago, Chile
      • Departamento de Economía
      CiudadSantiago, Santiago, Chile
  • 1993
    • University of Washington Seattle
      • Department of Astronomy
      Seattle, Washington, United States
  • 1992
    • Kokugakuin University
      Edo, Tōkyō, Japan