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Re: 2008 TC3 rotation period

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  • Alan W Harris
    We have received a set of photometric data taken by Marek Kozubal and Ronald Dantowitz at the Clay Center Observatory, Dexter School, MA, spanning about 2
    Message 1 of 9 , Oct 7, 2008
      We have received a set of photometric data taken by Marek Kozubal and
      Ronald Dantowitz at the Clay Center Observatory, Dexter School, MA,
      spanning about 2 hours. In addition to a dramatic trend of about 2.5
      magnitudes brightening, the data show a very clear periodicity of about 0.9
      magnitude amplitude and a simple period of 49 seconds, or a double period
      of 98 seconds. Thus Richard's analysis is just about right, within his
      stated error estimate. After de-trending the data and examining a longer
      time series, it appears that the variation is not simply periodic, but
      instead the object appears to be in a non-principal axis spin state, or
      "tumbling". There are a few other tumbling super-fast rotators, so this is
      not a unique case. It will take a bit more time for a careful analysis,
      since aspect is changing as fast as the brightness, so there may need to be
      a "de-trending" of the time series applied as well.

      Alan Harris and Brian Warner


      At 05:26 PM 10/7/2008, RICHARD MILES wrote:
      >Gustavo,
      >
      >A most excellent animation.
      >
      >Folk might want to watch the object flashing brighter and fainter.
      >It appears to do this 26 times in a periodic fashion.
      >
      > From the field shown, I estimate the sequence lasts some 1380 seconds.
      >If the variations are due to rotational modulation of the light, the object
      >must therefore rotate every 106 +/-8 seconds or so.
      >That would make it the 4th fastest rotator that we know of amongst the
      >asteroid community!

      *******************************************************************
      Alan W. Harris
      Senior Research Scientist
      Space Science Institute
      4603 Orange Knoll Ave. Phone: 818-790-8291
      La Canada, CA 91011-3364 email: awharris@...
      *******************************************************************
    • Juan Antonio Henríquez Santana
      Great animation Gustavo, you know :-) Saludos Juan A. Henríquez http://atlante.org.es 2008/10/8 RICHARD MILES ... [Non-text
      Message 2 of 9 , Oct 7, 2008
        Great animation Gustavo, you know :-)

        Saludos
        Juan A. Henríquez
        http://atlante.org.es



        2008/10/8 RICHARD MILES <rmiles.btee@...>

        > Gustavo,
        >
        > A most excellent animation.
        >
        > Folk might want to watch the object flashing brighter and fainter.
        > It appears to do this 26 times in a periodic fashion.
        >
        > From the field shown, I estimate the sequence lasts some 1380 seconds.
        > If the variations are due to rotational modulation of the light, the object
        >
        > must therefore rotate every 106 +/-8 seconds or so.
        > That would make it the 4th fastest rotator that we know of amongst the
        > asteroid community!
        >
        > Regards,
        > Richard
        >
        > ----- Original Message -----
        > From: "gustavo_muler" <gustavomuler@...<gustavomuler%40telefonica.net>
        > >
        > To: <mpml@yahoogroups.com <mpml%40yahoogroups.com>>
        > Sent: Tuesday, October 07, 2008 11:55 PM
        > Subject: {MPML} small video from the 2008 TC3
        >
        > > the video...
        > >
        > > http://www.youtube.com/watch?v=lveXdIWuHL8
        > >
        > > shots of 3 seconds, 200 exposures.
        > >
        > > regards to all.
        > >
        > > congratulations for the interesting informations and following up.
        > >
        > > gustavo.
        > >
        > >
        > >
        > > ------------------------------------
        > >
        > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        > >
        > > Posts to this list or information found within may be freely used, with
        > > the stipulation that MPML and the originating author are cited as the
        > > source of the information.Yahoo! Groups Links
        > >
        > >
        > >
        >
        >
        >


        [Non-text portions of this message have been removed]
      • RICHARD MILES
        Alan and Brian, Good work. I had earlier corresponded with Stanislav Korotkiy, who sent me some images since I could see periodicity in his trailed images,
        Message 3 of 9 , Oct 7, 2008
          Alan and Brian,

          Good work.

          I had earlier corresponded with Stanislav Korotkiy, who sent me some images
          since I could see periodicity in his trailed images, which he shared with us
          yesterday.

          I told Stanislav that I thought it was exhibiting a 100-sec rotation period
          but I knew that something was not quite right.
          I then emailed him questioning possible variable transparency of his sky.

          Also noticed on Gustavo's animation that the periodicity was not entirely
          regular, thought it could be a tumbler but then applied Occam's razor to my
          earlier message. I presumed there was some variation in transparency
          creating the appearance of it being a tumbling stone.

          At H=30.4, 2008 TC3 is the most intrinsically faint natural object for which
          a rotational lightcurve has been / will be derived.
          The previous record was 2008 JL24 (H=29.8) which has a rotation period of
          193.86 +/-0.22 seconds.

          Richard Miles


          ----- Original Message -----
          From: "Alan W Harris" <awharris@...>
          To: <mpml@yahoogroups.com>
          Sent: Wednesday, October 08, 2008 12:43 AM
          Subject: {MPML} Re: 2008 TC3 rotation period


          > We have received a set of photometric data taken by Marek Kozubal and
          > Ronald Dantowitz at the Clay Center Observatory, Dexter School, MA,
          > spanning about 2 hours. In addition to a dramatic trend of about 2.5
          > magnitudes brightening, the data show a very clear periodicity of about
          > 0.9
          > magnitude amplitude and a simple period of 49 seconds, or a double period
          > of 98 seconds. Thus Richard's analysis is just about right, within his
          > stated error estimate. After de-trending the data and examining a longer
          > time series, it appears that the variation is not simply periodic, but
          > instead the object appears to be in a non-principal axis spin state, or
          > "tumbling". There are a few other tumbling super-fast rotators, so this
          > is
          > not a unique case. It will take a bit more time for a careful analysis,
          > since aspect is changing as fast as the brightness, so there may need to
          > be
          > a "de-trending" of the time series applied as well.
          >
          > Alan Harris and Brian Warner
          >
          >
          > At 05:26 PM 10/7/2008, RICHARD MILES wrote:
          >>Gustavo,
          >>
          >>A most excellent animation.
          >>
          >>Folk might want to watch the object flashing brighter and fainter.
          >>It appears to do this 26 times in a periodic fashion.
          >>
          >> From the field shown, I estimate the sequence lasts some 1380 seconds.
          >>If the variations are due to rotational modulation of the light, the
          >>object
          >>must therefore rotate every 106 +/-8 seconds or so.
          >>That would make it the 4th fastest rotator that we know of amongst the
          >>asteroid community!
          >
        • Tomasz Kwiatkowski
          ... Hi Richard, Well, setting up records based on H is quite tricky as it is determined with much lower accuracy than the rotation period. So I doubt if the
          Message 4 of 9 , Oct 8, 2008
            On Wed, 8 Oct 2008, RICHARD MILES wrote:

            > At H=30.4, 2008 TC3 is the most intrinsically faint
            > natural object for which a rotational lightcurve has been
            > / will be derived. The previous record was 2008 JL24
            > (H=29.8) which has a rotation period of 193.86 +/-0.22
            > seconds.

            Hi Richard,

            Well, setting up records based on H is quite tricky as it
            is determined with much lower accuracy than the rotation
            period. So I doubt if the race in H would make it into the
            Olympics :-)

            I am not aware of any lightcurve observations of 2008 JL24.
            Did you do them yourself? Also, at H=30.1 (I think the MPC
            value of 29.5 is too low), 2006 RH120 has a rotation period
            of 82.5/165 s.

            Cheers,

            Tomek

            --
            -----------------------------------------------------------------------
            Tomasz Kwiatkowski Poznan Observatory, A.Mickiewicz University
            tkastr@... http://www.astro.amu.edu.pl/Staff/Tkastr/
            -----------------------------------------------------------------------
            A clever person solves a problem. A wise person avoids it. A. Einstein
            -----------------------------------------------------------------------
          • RICHARD MILES
            ... I agree that MPC data is tricky when it comes to photometry but when observing campaigns are conducted on specific objects then the H value is usually
            Message 5 of 9 , Oct 8, 2008
              Tomasz Kwiatkowski wrote:
              > Well, setting up records based on H is quite tricky as it
              > is determined with much lower accuracy than the rotation
              > period. So I doubt if the race in H would make it into the
              > Olympics :-)

              I agree that MPC data is tricky when it comes to photometry but when
              observing campaigns are conducted on specific objects then the H value is
              usually accurate to 0.1 mag or better if observed at relatively low phase
              angle.
              >
              > I am not aware of any lightcurve observations of 2008 JL24.
              > Did you do them yourself? Also, at H=30.1 (I think the MPC
              > value of 29.5 is too low), 2006 RH120 has a rotation period
              > of 82.5/165 s.

              Observations of 2008 JL24 by Peter Birtwhistle, George Faillace, Mike Beer
              (of St. David's College here in the UK) and myself were published in The
              Astronomer, Vol.45, No.531, July 2008. Details are actually - Period =
              193.87+/-0.11 sec, H=29.9, Amplitude=0.7 mag.

              The article also includes results on 2008 HJ (H=25.9) and 2008 JP24
              (H=27.0), the latter being incomplete so no tentative period obtained but it
              may be a tumbler.

              I can send you (and Al Harris) a copy if you so wish. Please correspond
              off-line.
              Cheers,
              Richard
            • ppravec
              Alan has sent me the detrended data obtained by Marek Kozubal and Ron Dantowitz. 2008 TC3 was definitely a tumbler. There is seen strong signal in two
              Message 6 of 9 , Oct 9, 2008
                Alan has sent me the detrended data obtained by Marek Kozubal and Ron
                Dantowitz. 2008 TC3 was definitely a tumbler. There is seen strong
                signal in two frequencies correspoding to periods 0.0269409 and
                0.0136205 h, and in linear combinations of the two frequencies. I
                cannot tell which of the frequencies is a rotation rate and which is
                precession.
                The data fitted with full 2-dimmensional Fourier series of the 4th order:
                http://www.asu.cas.cz/~ppravec/2008tc3.png
                The rms residual is 0.058 mag and residuals show a nearly Gaussian
                distribution, so they are probably due to a photometric noise (rather
                than, e.g., another possible lightcurve component].

                I'm running more analyses of the complex case, so I may write an
                update later.

                Whichever of the two periods is a rotation, the asteroid was one of
                the fastest rotators among asteroids known so far. Two others fastest
                rotators compiled in the Warner&Harris LCDB:
                2000 DO8, P = 0.0217 h, D~4 m
                2000 WH10, P = 0.0222 h, D~10 m
                (Whiteley 2002).
                It is good to have another one in the sample, and especially to know
                that it is a tumbler. Among superfast rotators, tumblers appear on
                any spin rate, suggesting a higher mu*Q (consistent with higher
                rigidity expected for coherent bodies) or younger age than larger,
                cohesionless asteroids (predominating in size range D > 0.2 km). See
                Pravec et al., Icarus 173, 108-131, 2005; Pravec et al., Proceedings
                of the IAU Symposium 236 (Eds.: Milani A., Valsecchi, G.B.,
                Vokrouhlicky, D.) Cambridge Univ. Press, pp. 167-176, 2007.

                Cheers,

                Petr Pravec

                --- In mpml@yahoogroups.com, Alan W Harris <awharris@...> wrote:
                >
                > We have received a set of photometric data taken by Marek Kozubal and
                > Ronald Dantowitz at the Clay Center Observatory, Dexter School, MA,
                > spanning about 2 hours. In addition to a dramatic trend of about 2.5
                > magnitudes brightening, the data show a very clear periodicity of
                about 0.9
                > magnitude amplitude and a simple period of 49 seconds, or a double
                period
                > of 98 seconds. Thus Richard's analysis is just about right, within his
                > stated error estimate. After de-trending the data and examining a
                longer
                > time series, it appears that the variation is not simply periodic, but
                > instead the object appears to be in a non-principal axis spin state, or
                > "tumbling". There are a few other tumbling super-fast rotators, so
                this is
                > not a unique case. It will take a bit more time for a careful
                analysis,
                > since aspect is changing as fast as the brightness, so there may
                need to be
                > a "de-trending" of the time series applied as well.
                >
                > Alan Harris and Brian Warner
                >
                >
                > At 05:26 PM 10/7/2008, RICHARD MILES wrote:
                > >Gustavo,
                > >
                > >A most excellent animation.
                > >
                > >Folk might want to watch the object flashing brighter and fainter.
                > >It appears to do this 26 times in a periodic fashion.
                > >
                > > From the field shown, I estimate the sequence lasts some 1380 seconds.
                > >If the variations are due to rotational modulation of the light,
                the object
                > >must therefore rotate every 106 +/-8 seconds or so.
                > >That would make it the 4th fastest rotator that we know of amongst the
                > >asteroid community!
                >
                > *******************************************************************
                > Alan W. Harris
                > Senior Research Scientist
                > Space Science Institute
                > 4603 Orange Knoll Ave. Phone: 818-790-8291
                > La Canada, CA 91011-3364 email: awharris@...
                > *******************************************************************
                >
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