Here you will find some sections of interest

Sebastian Bruzzone
Research and Theaching Assitant at The University of Western Ontario.
Physics and Astronomy Building Room 134
Meteor Lab phone: +5196612111 ext 87985

Refereed Publications and Participation in International Conferences

Listed below are some publications, oral contributions and posters presented at several conferences, such as Meteoroids 2013 in Poznan, Poland, the XXVII General Assembly of the IAU in Rio, Brazil, Asteoird Comet Meteors conference in Baltimore, USA among others. The topic of this research focuses on the minor bodies of the Solar System. This topic is within the main area of research of the Astronomy Department that includes the dynamics and observation of minor bodies, as well as modeling non-gravitational forces on long and short-term periodic comets. You can download the PDF files, or take a look at them using an embedded viewer from this site with the flexpaper viewer.

  • Albedo and atmospheric constraints of dwarf planet Makemake from a stellar occultation.
    J L Ortiz, B Sicardy, F Braga-Ribas, A Alvarez-Candal, E Lellouch, R Duffard, N Pinilla-Alonso
    , V D Ivanov, S P Littlefair, J I B Camargo, [......]
    Nature 11/2012; 491(7425):566-9.
    Abstract: Pluto and Eris are icy dwarf planets with nearly identical sizes,
    comparable densities and similar surface compositions as revealed by spectroscopic studies.
    Pluto possesses an atmosphere whereas Eris does not; the difference probably
    arises from their differing distances from the Sun, and explains their different albedos. Makemake is
    another icy dwarf planet with a spectrum similar to Eris and Pluto, and is currently at a distance to
    the Sun intermediate between the two. Although Makemake's size (1,420 +/- 60 km) and albedo are roughly known, there has been no constraint on its density and there were expectations that it could have a Pluto-like
    atmosphere. Here we report the results from a stellar occultation by Makemake on 2011 April 23.
    Our preferred solution that fits the occultation chords corresponds to a body with projected
    axes of 1,430 +/- 9 km (1sigma) and 1,502 +/- 45 km, implying a V-band geometric albedo p(V) = 0.77 +/- 0.03. This albedo is larger than that of Pluto, but smaller than that of Eris. The disappearances and reappearances of the
    star were abrupt, showing that Makemake has no global Pluto-like atmosphere at an upper limit of 4-12
    nanobar (1sigma) for the surface pressure, although a localized atmosphere is possible. A density of 1.7 +/- 0.3g/cm(3) is inferred from the data.

  • Size, shape, albedo, density and atmospheric limit of transneptunian object (50000) Quaoar
    from multi-chord stellar occultations. 2013 ApJ 773 26 doi:10.1088/0004-637X/773/1/26
    F. Braga-Ribas, B. Sicardy, J.L. Ortiz, E. Lellouch, G. Tancredi [..]
    Abstract: We present results derived from the first multi-chord stellar occultations by
    the transneptunian object (50000) Quaoar, observed on 4 May 2011 and 17 Febru- ary 2012, and from a single-chord occultation observed on 15 October 2012. If the timing of the five chords obtained in 2011 is correct, then Quaoar possesses topographic features (crater or mountain) that are too
    large for a body of this mass. An alternative model consists in applying time shifts
    to some chords, to ac- count for possible timing errors. Satisfactory elliptical fits
    to the chords are then possible, yielding an equivalent radius Requiv = 555+/-2.5 km
    and geometric visual albedo pV = 0.109 +/- 0.007. Assuming that Quaoar is a Maclaurin
    spheroid with indeterminate polar aspect angle, we derive a true oblateness of = 0.087+0.0268-0.0175
    an equatorial radius of 569+24-17 km and a density of 1.99 +/- 0.46 g/cm(3) . The orientation of our preferred solution in the plane of the sky implies that Quaoar's satellite Weywot cannot have an equatorial
    orbit. Finally, we do not detect any global atmosphere around Quaoar, with an upper limit
    of 21 nbar for a pure methane atmosphere.

  • Stellar Occultations by TNOs: the January 08 2011 by 2003 AZ84 and the May 04 2011 by (50000) Quaoar. European Planetary Science Congress. Between February 2010 and May 2011, our group has observed five stellar occultations by Trans-neptunian Objects (TNOs), giving the size and shape for some of the biggest TNOs: Varuna, Eris, 2003 AZ84, Make- make and Quaoar. Here we present two of them: the January 08 stellar occultation by 2003 AZ84, and the May 04 by Quaoar.
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  • 5088 TANCREDI: ROTATION PERIOD AND PHASE COEFFICIENTS . Tancredi et al. (2011). Minor Planet Bulletin. The main-belt asteroid 5088 Tancredi was observed during a period of 42 days close to the 2009 opposition. The data were collected with a clear filter on 15 different nights. R-magnitudes were calculated using the MPOSC3 Catalog. The observations covered a range of phase angles from 0.35° to 16°. The phase coefficients in the H-G system (R-mag) are: HR = 12.36 HR = 12.36 [12.30, 12.43]; G = 0.058 [–0.036, 0.153], with 95% confidence range presented within the brackets. Based on the low value of G, the asteroid can be tentatively classified as a C-type asteroid. A precise estimate of the rotation period is computed as P = 5.05909 ± 0.00014 h. The amplitude is A = 0.31 mag.
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  • Radar observations of the Daytime Arietid meteor shower by CMOR II. S. Bruzzone, P. Brown, R. Weryk, D. Wong. Meteoroids 2013 Poznan, Poland.
    Here we present the results from two years of radar observations of the Daytime Arietid meteor shower using the upgraded Canadian Meteor Orbit Radar (also called CMOR II) during the years 2012 and 2013. Since its last upgrade in mid 2009, CMOR II has doubled its transmission power to 15 kW, featuring an extended size range with 6 remote stations routinely measuring 5000-6000 meteoroids orbits each day. The aim of this study is to better characterize the Daytime Arietid meteor shower at sizes of approx. 500e-6 m, by measuring the shower radiant position and drift, pre-atmospheric speed, mass index and orbital elements of the Arietids. At the time of the shower peak, CMOR II measures in excess of 500 Daytime Arietid orbits per day, with some 5000 Arietid orbits recorded over the entire active period of the shower in both 2012 and 2013
  • Searh of Low Activity of Asteroids in Cometary Orbits S.Bruzzone et al. XXVII General Assembly of the IAU, 2009.
    The physical distinction between active comets and inactive asteroids is implausible to apply when the number of discovered objects is on the order of several hundred thousands bodies and there are just scant observations of these objects along the orbit. Therefore, Tancredi (2009) has designed a criteria based on parameters associated to the orbital elements, which allows us to rapidly extract, from the large sample of objects initially classified as asteroids, those which share similar orbital characteristics with comets. These objects are known as Asteroids in Cometary Orbits (ACOs). From the 300.000 objects with precise orbital elements discovered so far, we find only ~70 objects to have orbits compatible with Jupiter-family Comets. We are conducting a program to monitor these objects, in particular when they are going through perihelia. We are performing photometrical observations of them with the aim to detect the presence of a faint coma which would indicate a cometary behavior, and the reclassification of the object. None of the objects studied presented evidence of such peculiar activity during our runs and along the period of time that where followed up at Los Molinos Observatory in Uruguay. Here we present the results of the first 6 months of observations of over 10 ACOs.
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  • Lightcurves of Icy Dwarf Planets S. Roland et al, XXVII General Assembly of the IAU, 2009
    We present lightcurve results of 11 Trans-Neptunian Objects (TNOs) obtained in 3 observation runs at El Leoncito (CASLEO), 2.15 m telescope and Cerro Tololo Inter-­American Observatory (CTIO), 1.0 m Yalo telescope. Lightcurve results will help the classification of this Icy "Dwarf Planets" as possible Plutoid objects. 9 targets were selected from an original 39 candidate list, and observed in a total amount of 12 nights spread in September 2007, August and December 2008. We obtained photometric data for (120178) 2003OP32, (145453) 2005RR43, (145452) 2005RN43, (145451) 2005RM43, (47171) 1999TC36, (55637) 2002UX25, (145452) 2005RN43, (120178) 2003OP32, 2002MS4, 2007UK126 and (55565) 2002AW197. Most of the objects present a quasiflat lightcurve (amplitude less than 0.1 mag), denoting a quasi­spherical or oblate shape. We calibrated data with NOAO IRAF and performed differential photometry. In some observation runs, Landolt standard fields L92, L113 and L95 were observed and V­R color index was computed for some objects.
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  • ITOKAWA: A Global Shacken and Fractured Asteroid with Brazilian Nut Effect. G. Tancredi et al, ACM Baltimore, 2008.
    Images from the Hayabusa space mission to asteroid Itokawa, showed a plausible correlation between the size distribution of boulders and rocks and the gravitational potential at the surface of this asteroid. Then, by suggestion of G. Tancredi, a program to compute the gravitational potential of this irregular asteroid was developed using Matlab and data from the space mission. Also the size distribution of rocks, was performed with the help of the SPICE tools. This led to conclude that this rubble pile asteroid owns it shape due a process governed by the Brazilian nut effect.
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''Perhaps the most widespread evil is the Western view of man and nature.
Among us, it is widely believed that man is apart from nature, superior to it;
indeed, evolution is a process to create man and seat him on the apex of the
cosmic pinnacle. He views the earth as a treasury that he can plunder at will.
And, indeed, the behavior of Western people, notably since the advent of the
Industrial Revolution, gives incontrovertible evidence to support this assertion.''
Ian McHarg, 1971

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