Video data, posted to YouTube channel "Cabrillo Astro"
How to report a CBET discovery
This is a bright event, with good rank, and high probability of getting good data from inside the predicted shadow. Karl von Ahnen and I are both inside the path. Kirk will be out of town and not doing this one. However, this event is near the 97% moon, at only 9 degrees away - the sky will be bright. I would not go more than 2x setting, and maybe even 1x setting if the star is bright enough. Minimizing sky noise will be good. Probably 2x is best, as my guess.
W band (my nomenclature) is the "Watec 910hx band" magnitude. This turns out, from photometric calibrations by Hristo, to be very close to the "r" magnitude, which I've used at the title pre-event prediction which this page was meant initially to be. Indeed, after discovering Pavlov's transformation formulae, the W magnitude is the same.
Alt=42, Az=88 in the East. Target star and asteroid are about 1/3 of the way from the Plieades to the Hyades star clusters, above the rising moon.
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I was the only observer. I observed from Cabrillo College Observatory, 15 ft from the door to the Dome building. The target was bright and easy to follow at 2x, so I disconnected the external monitor to slightly improve the video signal to the camcorder, and just watched it on the flip-out screen of the camcorder. This would eliminate noise caused by a splitting of the video signal. Earlier tests I did in 2024 showed the resulting noise from having the external monitor in parallel with the camcorder, the rise was so small as to be negligible. Now, Kirk Bender has shown that the video signal voltage did drop to the camcorder when the external monitor was connected. However that lowered voltage is auto-raised inside the camcorder. Nevertheless, for this event, it's a non-issue as the external monitor was disconnected during the recording.
W. Longitude 121 55 26.87"
N. Latitude 36 59 33.71"
Altitude 216 ft
Target star= TYC 1814-01633-1
| name | V | g | R | r | source |
| TYC 1814-01633-1 | 11.35 | 10.94 | -- | OWc | |
| 11.46 | 11.64 | 11.345 | C2A | ||
Julian Date of occultation timings: 2460631.70132
The UCAC4 catalog description and photometric (B,V,g,r,i) sources are given here. The r band is from the APASS photometric database (AAVSO Photometric All-Sky Survey)
R band center= 658nm Width = 138nm
r band center=?
r band in APASS seems to be Sloan Digitial Sky Survey r band. But what I see in the reference for Sloan is instead labelled as r' band in: https://amostech.com/TechnicalPapers/2018/Poster/Castro.pdf . No r-r' or R-r' transformation graphs are given. I conclude it's best to look at UCAC4 in V , B, and r for target as well as the other stars, to stay consistent in bands between the reference stars and target.
I will refer to the magnitude system of the unfilter Watec 910hx as "W" magnitudes, which will be useful for deciding the observability with our gear, for all occultations, but here it will especially be useful in assessing the depth of the observed Martschmidt occultations. I will transform the B and V magnitudes of the reference stars into W magnitudes and report magnitudes and magnitude drops in "W" magnitudes. How to find the W magnitude? This link was sent to me and is quite useful...
From Hristo Pavlov and his associated camera tabular calibration data and especially this, for the Watec 910hx, shows:
V - W = + 0.315 * (B-V) + ZeroPoint +/- 0.10, where W = "instrumental magnitude for Watec 910hx" in my own nomenclature.
So, solving for W gives
W = V - 0.315(B-V) - Zero point (note: zero points cancel out if only concerned with magnitude differences, as we are here; in occultation drops, and so can be neglected).
The table, based on the "Analysis #5" photometry below, has the resulting W magnitudes calculated from the C2A tabular V and B-V values, gotten by left-clicking on the different stars in C2A. I use a zero point=0 since the zero point cancels out for finding magnitude differences.
| Name | V | B-V | r | Avg Counts |
Watec 910hx =W Mag |
W Mag Drop from Target |
| Target | 11.46 | 0.473 | 11.34 | 517 | 11.31 | 0.00 |
| Ref1 | 10.03 | 0.815 | 9.95 | 9.77 | -- | |
| Ref4 | 12.47 | 1.326 | 11.99 | 256 | 12.05 | 0.74 |
| Ref5 | 13.09 | 1.611 | 12.08 | 155 | 12.58 | 1.27 |
| Ref6 | 11.73 | 0.698 | 11.49 | 460 | 11.51 | 0.27 |
| Ref7 | 12.32 | 0.719 | 12.09 | 274 | 12.09 | 0.78 |
| Ref8 | 12.65 | 1.141 | 12.24 | 219 | 12.29 | 0.98 |
| Ref9 | 13.01 | 0.856 | 12.71 | 140 | 12.74 | 1.43 |
| Ref10 | 13.084 | 1.024 | 12.71 | 115 | 12.76 | 1.45 |
| Ref11 | 13.30 | 0.79 | 13.03 | 87 | 13.05 | 1.74 |
| Occ 1 | -- | -- | -- | 80 | ~13.1 | 1.8 |
| Occ 2 | -- | -- | -- | 80 | ~13,1 | 1.8 |
| no-star1 (sky) | -- | -- | -- | 0* / 80* |
* The average counts level for the 'sky' (= label "no-star") for the entire recording was zero, but during the actual 2 seconds centered on the occultation, was ~80 counts, the same as the bottoms of the occultations.
The asteroid itself is listed in OW cloud with a magnitude (band not given) of 17.0. If "no-star" (sky) has counts=0, as the new PyMovie 4.0.9 now corrects to, and as is shown in the PyMovie light curves, then a drop of 11.31 to 17.0 = 5.7 magnitudes or .0052 x 517 unocculted targets counts = 3 counts. Clearly the occultation limiting magnitude doesn't reach this far down. From the table above, the magnitude of the bottom of the light curves is about W=13.1, so I appears that from 13th to 17th magnitude and below, is beyond the limiting magnitude of 13, and is lost in the noise. Some light curve bottom points do reach to zero, but might be caused by Fresnel diffraction or just noise.
A 444 frame stack (Fourier finder) from PyMovie. The vertical banding was later removed in deriving the light curves in Analysis #5 below using the median filter capability in PyMovie. Star ID's key is from C2A at right. |
Finder chart for the reference stars, from C2A. The UCAC4 catalog numbers, and the V and r magnitudes are given. |
Note that except for the very red star Ref5, the W magnitude is within 0.1 mag of the r magnitude. This will be useful in giving the W magnitude in the future on my website planning pages, as the r magnitude is available for nearly all UCAC4 stars. However, here, "r" magnitudes are not needed or used in the analysis.
Hristo's table also gives another calibration for W magnitudes, using IR bands:
K - InstrumentalMag = - 3.004 * (J-K) + ZeroLevel +/- 0.12
So W = K+3.004(J-K) + zero level (but, we don't have K magnitudes given for ref stars in C2A, only Ks magnitudes, so I've not used this to find W magnitudes)
The observing site temperature was in the high 30's F, as there was frost on the wooden tables, and this was at 8:30pm. Frost warnings were indeed issued by the local Monterey Bay weather people. The cold probably helped reduce thermal noise in the camera. Even though the target was only 9 degrees from the 97% moon, the 2x setting and clean skies made for a background sky that was clearly well below the target star and other fainter stars. I set gamma=1.0 to maximize visibililty of any partial drop, and since I did not need to brighten the dark end of the sky pixel levels histogram. That histogram is shown below.
My visual impression as I watched, was that I had a double occultation.. I live commented "Eyeah!" on the first D, and then was taken aback by seeing it reappear after 0.3s and then immediately disappear again for about 0.3s. I took some Dark video to accompany this tape if it is valuable for other astronomers to do their own reductions. I had to wait a few more days to get a clear twilight sky and take flat field video, at the same focus and optics. After this flat field video, I then did a cleaning of the Watec chip (air blower only) and removed the few dust motes seen on the Martschmidt video captures seen here. None of the dust motes were over stars used in the reductions, however.
I used PyMovie, and static circular 4 px aperture masks. I used the two bright stars on either side of the target as my reference stars. The upper one remained w/o saturated pixels, while the lower ref2 star did have saturated pixels and was not used as a reference, but only as the second tracking star. For this first run, I did not use median filtering in either rows or columns.
MagDrop report: percentDrop: 76.5
magDrop: 1.572 +/- 0.258 (0.95 ci)
DNR: 3.78
D time: [04:49:53.3336]
D: 0.6800 containment intervals: {+/- 0.0080} seconds
D: 0.9500 containment intervals: {+/- 0.0197} seconds
D: 0.9973 containment intervals: {+/- 0.0402} seconds
R time: [04:49:53.6536]
R: 0.6800 containment intervals: {+/- 0.0080} seconds
R: 0.9500 containment intervals: {+/- 0.0197} seconds
R: 0.9973 containment intervals: {+/- 0.0402} seconds
Duration (R - D): 0.3200 seconds
Duration: 0.6800 containment intervals: {+/- 0.0115} seconds
Duration: 0.9500 containment intervals: {+/- 0.0257} seconds
Duration: 0.9973 containment intervals: {+/- 0.0452} seconds
MagDrop report: percentDrop: 86.1
magDrop: 2.144 +/- 0.736 (0.95 ci)
DNR: 4.25
D time: [04:49:54.2736]
D: 0.6800 containment intervals: {+/- 0.0089} seconds
D: 0.9500 containment intervals: {+/- 0.0223} seconds
D: 0.9973 containment intervals: {+/- 0.0439} seconds
R time: [04:49:54.6302]
R: 0.6800 containment intervals: {+/- 0.0089} seconds
R: 0.9500 containment intervals: {+/- 0.0223} seconds
R: 0.9973 containment intervals: {+/- 0.0439} seconds
Duration (R - D): 0.3566 seconds
Duration: 0.6800 containment intervals: {+/- 0.0128} seconds
Duration: 0.9500 containment intervals: {+/- 0.0287} seconds
Duration: 0.9973 containment intervals: {+/- 0.0521} seconds
Since clipped low end histogram of sky pixel values is not an issue for this occultation, due to the bright sky only 9 degrees from a 97% moon, then the magnitude and % brightness drops can be taken as not affected by this issue. Nominal 76% and 86% light loss for the two occultations, taken from the PyOTE log files and copy/pasted above.
Target star is in the red box in the center of the frame, flanked by the two tracking and reference stars. Note that the 2nd reference star just above the numerals on the right side, is unusable as a reference star because it has saturated pixels. The ref1 star upper left of the target did not have saturated pixels. |
PyMovie composite of light curves. Target star is in gold |
Is the slight and very extended dip in brightness beginning just before the middle of the recording, well after the occultations, due to the target being in the dark vertical bar discussed below? |
A clear double occultation in the raw .avi "signal". The drop is to "zero" (=no-star level), but the question is really, was this corresponding to a deep enough level to rule out the double event being due to a binary star and not a binary asteroid? The fact the event happened only 9 degrees from a 97% moon, albeit in very clean skies, means the limiting magnitude vs sky brightness was not immediately obvious. |
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PyOTE D and R confidence intervals for the first occultation. |
False Positive (FP) test for the first occultation |
PyOTE D and R confidence intervals for the second occultation. |
False Positive (FP) test for the second occultation |
The histogram of tone values and default range. In the images below, I've tightened the limits to help show the stars better. But the point of this image is that despite the IRE=0 hardwired into the PAL Watec camera, the complete range of sky values is is not clipped at the low end, as can happen in much darker skies and short integrations. |
First question: Was one of the occultations due to a dust mote or to bad pixels? Here, on the extreme left side frame in the image table below, is the Fourier Finder image for a stack of 111 frames in PyMovie (about 4 seconds of stacking), and also a screen capture of the chip 1 second after the occultation, to show the relative positions of the target and reference stars. I've used this to then locate where to put an "x" for the target at the time of the occultation on the 111 frame finder image. The tracking was good, with very little drift during the full recording of the event. The vertical banding that seems characteristic of my camera is evident, but the intensity contrast of the pixel brightness variations was highly amplified in these images below. You can see how I've taken the actual dynamic range and compressed it severely for the sake of ID'ing fainter stars, by looking at the pixel value histogram plotted vertically on the right side of the image. You can also see that for this bright-sky event, the IRE=0 issue is not relevant. No offsetting of the "no-star" level due to clipped values at the low end, as often happens in dark skies and/or short integrations events. Also, the later versions of PyMovie have fixed this problem.
A 111 frame Fourier stack , from the beginning of the recording |
A 25 frame stack just before the start of the 1st occultation |
A 12 frame stack just after the first occultation ended |
A 12 frame stack just before the first occultation began |
A 12 frame stack just after the 2nd occultation ended. |
Conclusions: The target remained in the evenly lit columns area to the left of the prominent vertical dark bar until over 25 seconds after the occultations, when it was then affected. That is likely the cause of the light curve slight but extended dip seen in the full duration light curve of the target, Also, the occultation events and ref stars were not affected by bad pixel clusters or the dust motes at far right.
I used TME aperture masks on a larger range of stars, including fainter stars, and also 3 "no-star" apertures in different spots near the target. The goal is to find if both mag drops are significantly and clearly deeper than stars whose brightness is less than half the brightness of the target, and also above the brightness of 3 different "no-star" static circular 4px apertures. If yes, this would make a very strong case that the double dip was due to a binary asteroid and not a binary star. I think such a case is made, below.
PyMovie screen capture, with apertures shown. |
The calibrated (using ref1) light curve of the target, together with ref5's light curve. Ref5 has V=13.09, r=12.08. So W=12.58. So ref5 is 34% of the target star's brightness in the Watec band. This star is quite a bit redder than the target star, and than the Ref7 and Ref8 star's shown at right, and which have similar color to the target. |
Target, ref7, and no-star1 light curves. Ref7 is V=13.03, r=12.63, so W=12.09. So ref7 is 49% of the target star's brightness. Ref7's light is clearly above that of the empty sky, and the empty sky is, inside the occultations, virtually identical in level with the target's brightness. The color of this star is V-r = 0.4, vs. target star's color of V-r=0.1.. |
Target and Ref8. Ref8 is V=12.65, r=12.24 so W=12.29. So Ref8 is 40% of the target's brightness. The color is 0.4 again. The star is clearly above the depth of the target's occultations, making the occultations at a level below 38% for both events. |
Target and Ref9. Ref9 is V=13.01, r=12.71 W=12.74. So Ref9 is 27% of the target's W brightness. The color is V-r=0.3, a bit closer to the target star's color of V-r=0.1. The star is slightly but consistently above the depth of the target's occultations, making the occultations at a level at or below 27% of un-occulted brightness for both drop events. Inconsistent with causation by a binary star. |
The first occultation's solution in PyOTE. The DNR is deeper, and the occultation is longer and looks to be more reasonable than the placement of the D in the first analysis. The timing looks centered on the drop steep trend and not at the very bottom this time. |
The false positive test is also stronger, which however it to be expected if the event is longer. |
The second occultation solution is almost identical to the 1st analysis version. |
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magDrop report: percentDrop: 82.1 magDrop: 1.867 +/- 0.485 (0.95 ci)
DNR: 4.48
D time: [04:49:53.2411]
D: 0.6800 containment intervals: {+/- 0.0084} seconds
D: 0.9500 containment intervals: {+/- 0.0202} seconds
D: 0.9973 containment intervals: {+/- 0.0407} seconds
R time: [04:49:53.6536]
R: 0.6800 containment intervals: {+/- 0.0084} seconds
R: 0.9500 containment intervals: {+/- 0.0202} seconds
R: 0.9973 containment intervals: {+/- 0.0407} seconds
Duration (R - D): 0.4125 seconds
Duration: 0.6800 containment intervals: {+/- 0.0123} seconds
Duration: 0.9500 containment intervals: {+/- 0.0276} seconds
Duration: 0.9973 containment intervals: {+/- 0.0486} seconds
magDrop report: percentDrop: 85.1 magDrop: 2.067 +/- 0.681 (0.95 ci)
DNR: 4.64
D time: [04:49:54.2713]
D: 0.6800 containment intervals: {+/- 0.0081} seconds
D: 0.9500 containment intervals: {+/- 0.0209} seconds
D: 0.9973 containment intervals: {+/- 0.0391} seconds
R time: [04:49:54.6284]
R: 0.6800 containment intervals: {+/- 0.0081} seconds
R: 0.9500 containment intervals: {+/- 0.0209} seconds
R: 0.9973 containment intervals: {+/- 0.0391} seconds
Duration (R - D): 0.3571 seconds
Duration: 0.6800 containment intervals: {+/- 0.0122} seconds
Duration: 0.9500 containment intervals: {+/- 0.0272} seconds
Duration: 0.9973 containment intervals: {+/- 0.0476} seconds
The TME solution light curves above are seen to have deeper and better DNR's than analysis #1 with static circular apertures. This adds to the confidence in the binary asteroid interpretation. The duration of the first event is also now longer than in the first analysis with circular 4px apertures. Mark Simpson also felt that tighter 2.4px apertures were better, and that would go with the TME also being better, so that is consistent. For a drop to W magnitude ~16.6, the light loss should be 99%, but within the scatter during these short occultations, the measured 93% and 96% light loss is consistent. However, I believe the best analysis will be one which includes circular apertures that are tight, and also that include both horizontal and vertical median filtering. That analysis is below. Indeed, the timing accuracies are improved below.
What is needed to make a best-case here, is to use the newly calculated (not estimated) (Hristo Pavlov's formula) W magnitudes for a range of faint reference stars and show their light curves relative to the occultation bottoms, and also "no-star"= sky. I use circular apertures of 3.0 px size, based on curve of growth under the seeing and sky brightness. I use the median filtering both horizontal and vertical. Also, to do a 'Fourier Finder' just including the first occultation duration period (it'll be noisy) and compare what it sees of the target vs. the fainter W stars.
A 999 frame Fourier Finder. Now, we see the stars are trailed, and the vertical banding is not. So it does seem that the vertical banding is inherent in the column pixel sensitivities. And, Fourier finders should be confined to durations less than significant star trails. Another feature I see is that the pixel-to-pixel variance rapidly damps out as you raise the number of frames in the Finder. This suggests that the "speckled" noise is mostly due to read out and Poisson and other moment to moment noise sources and that the pixels themselves are (at least vertically) pretty consistent in their sensitivities. |
A stack of 444 frames; Fourier Finder with the "horizontal median filter" option checked, but Median filtering does not happen in Fourier frames in this version of PyMovie. |
A stack of 444 frames; Fourier Finder with the "vertical median filter" option checked (but on Fourer finders the median filter is not applied, so the vertical banding is still visible. It is not present on the live frame-to-frame as the analysis proceeds). The source of the banding is believed, according to Tony George (private comm.) to be due to differences in the individual amplifiers for each pixel column. Each column has its own amplifier and they are not perfectly the same, it seems. |
All ref stars and target on one plot. Individual reference stars follow in this table and below table; all raw PyMovie photometry. |
The 'no-star1' light curve points center pretty well on zero, as hoped. Raw brightnesses uncalibrated to any constant reference star are what are given in the PyMovie light curves on this table row and the one below. |
ref1, brighter than target at W=9.77, was used as the calibration star for the light curve of the target |
Ref4, fainter than target by 0.74 mag, half the brightness. |
Ref5, W=12.58 or 1.27 mag fainter than target, centers above zero but getting close to the limiting magnitude detectable |
Ref6 only 0.2 mag fainter than target, used for tracking |
Ref 7, W=12.09 or 0.78 mag fainter than target. |
Ref 8, W=12.29 or 0.98 fainter than target. |
Ref 9, W=12.74 or 1.43 mag fainter than target, at counter = 140, while the bottom of the target light curve and sky both were about level=80 counts. |
Ref 10, W=12.76 or 1.45 mag fainter than target, centers about level=120 counts |
Ref 11, W=13.05, centers about level 90, indistinguishable from the 80 counnts of the sky and the bottom of the two occultations. W=13.0 was judged to be the limiting magnitude detectable. |
Raw light curve of the target |
Zoomed in. Both occultation bottoms were slightly above zero but so was the empty sky counts, by the same amount during the seconds around the occultations. |
PyMovie screen capture, with contrast bar adjusted to maximize contrast of a single frame |
PyOTE reduction. The red points to the right of the occultation in the target star, were the 'metric interval'. Minimizing the scatter in these points was achieved by optimal smoothing of the brighter reference star (green). |
False positive test on the first occultation. Passed solidly |
False positive test on the 2nd occultation. Passed solidly |
PyOTE solution for the first occultation, with 1-sigma error bars shown |
And PyOTE solution for the 2nd occultation. |
Calibrated light curve of the double occultation, with the light of ref4 star shown clearly above the depths of both occultations. Ref 4 turns out, was exactly 1/2 the brightness of the unocculted target, and shows that both occultations were deeper than half the brightness lost. This rules out a double star cause for the two occultations. |
Yellow points are Ref5, only 0.2 mag fainter than target. |
Calibrated target with ref8 at W=12.29, or 0.98 magnitudes or 40% of full target brightness. Ref8 was still above the bottoms of the occultations, although approaching noise level |
Target with ref9 at W=12.74, still on average above the bottoms of the occultations. |
Target with ref10, aat W=12.76, with average counts values near time of occultations shown. Ref10 is above the occultation bottoms but not by much. |
magDrop report: percentDrop: 83.9 magDrop: 1.981 +/- 0.431 (0.95 ci)
DNR: 4.13
D time: [04:49:53.2381]
D: 0.6800 containment intervals: {+/- 0.0077} seconds
D: 0.9500 containment intervals: {+/- 0.0196} seconds
D: 0.9973 containment intervals: {+/- 0.0392} seconds
R time: [04:49:53.6536]
R: 0.6800 containment intervals: {+/- 0.0077} seconds
R: 0.9500 containment intervals: {+/- 0.0196} seconds
R: 0.9973 containment intervals: {+/- 0.0392} seconds
Duration (R - D): 0.4155 seconds
Duration: 0.6800 containment intervals: {+/- 0.0116} seconds
Duration: 0.9500 containment intervals: {+/- 0.0258} seconds
Duration: 0.9973 containment intervals: {+/- 0.0468} seconds
magDrop report: percentDrop: 87.4 magDrop: 2.246 +/- 0.596 (0.95 ci)
DNR: 4.30
D time: [04:49:54.2708]
D: 0.6800 containment intervals: {+/- 0.0074} seconds
D: 0.9500 containment intervals: {+/- 0.0180} seconds
D: 0.9973 containment intervals: {+/- 0.0379} seconds
R time: [04:49:54.6038]
R: 0.6800 containment intervals: {+/- 0.0074} seconds
R: 0.9500 containment intervals: {+/- 0.0180} seconds
R: 0.9973 containment intervals: {+/- 0.0379} seconds
Duration (R - D): 0.3330 seconds
Duration: 0.6800 containment intervals: {+/- 0.0108} seconds
Duration: 0.9500 containment intervals: {+/- 0.0245} seconds
Duration: 0.9973 containment intervals: {+/- 0.0435} seconds
Minimum major axis corresponds to assuming a circular orbit. OWc says the orbital motion of the assumed single asteroid in RA was 38.6 arcsec/hr and in Dec was 4.77 arcsec/hr. Sqrt of sum of squares says velocity is 38.90 "/hr or 38900 mas/hr or 10.81 mas/sec, which is a combination of the asteroid orbital velocity vector and the Earth orbital velocity vector. However, that does not address the speed of the asteroid around each other. For a stationary asteroid center of mass, or a stationary single asteroid and all the velocity considered in the companion, then the transverse velocity of one asteroid relative to the other is what counts. The eclipse lasted 2.0 hr = .0863 of the orbital period. If the components were spherical and equal sized in order to account for the 0.75 magnitude drop of JFG's light curve, and if the albedo assumed was correct, then the sum of the sky-plane areas of two components must be the same as the assumed single asteroid, whose diameter of 5.7 km gives sky plane area = 25.5 km^2. So each component gave a sky plane area of 12.75 km^2 or radius 2.02 km or diameter of 4.04 km. But, for equal mass'd and equal size objects, one object is moving in opposite velocity and direction to the other. So, it only take 1/2 as long as an eclipse if one object is stationary and the other moving with all the speed. But wait; what about the speed of the rotating and revolving Earth? Rotation is only 1/2 km/sec, but orbital speed is 30 km/sec, but in a direction such that only about 25 km/sec is transverse to the direction to the asteroid. But this is still rather faster than the asteroid itself. In the frame of the orbiting asteroid pair,
Wait.... the duration of the eclipse depends too on the velocity of the observer, not just the velocity of one object relative to the other in the frame attached to the center of mass of the asteroid pair. The velocity of the observer is high compared to the velocities in the orbits. But, wait... the lever arm of that high velocity in shortening or lengthening the eclipses is also rather enormous. So... don't think the differing position of the Earth during the 2 hr eclipse matters. The eclipse duration is really almost entirely the result of the binary asteroid internal orbiting motion.
So, 4.04 km traversed in 2hr which was .0863 of the circumference of the orbit. So the circumference of the orbit it 4.04/.0863 = 46.8 km so the diameter of the orbit is 46.8/pi = 14.9 km under that assumption, so Semi major axis would be 1/2 of that or 7.45 km as the minimum but under the assumptions which are unconfirmed.
More reliably, the minimum major axis must be 10.7 km because that is the separation between centers of the components on the sky plane from the occultation. So the semi-major axis would be a minimum of 5.45 km. I've decided the uncertain calculation based on the eclipses should just be left out of the CBET.
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Dave Gault: Produced a sky plane of this event, assuming my chord went across the middle of two spherical objects. And, Mark Simpson did an independent analysis of the photometry using his own set of stars, several in common with my own. He used static circular apertures, and arrives at the same conclusions: The binary star hypothesis is essentially ruled out, in his judgement, mine, Mark Simpson's, and Jean-Francois'.
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Dave Gault generated this using my Analysis #1 timings and assuming my chord went across the center of both objects. |
Revised Dave Gault sky plane, using the TME aperture timings, and again assuming my chord went across the centers of both objects. On the sky plane, the components' centers are 10.67 km apart. This must then be the minimum possible major axis. |
Mark Simpson: Took my .avi file and did his own analysis using static circular apertures, and got good confirmation of my own analysis: The .csv in particular, you’ll need to enter your timing manually when loaded. Sorry, but I use Astrid and I’m not familiar with the craziness of OCR, camera delays and entering those, at least not enough to be confident of your setup, so I just played it safe and entered the first time in the first time field in the video and the same for the last frame.
But I see nothing wrong with your data, or analysis (assuming you’ve correctly entered the OCR and delays), so I used your times for SkyPlane plot as they are valid. Also my DNR came out similar to yours, but I settled on a mask radius was 2.4, as it was slightly better (but that’s not really that relevant here). Your data was consistent in the drops over reasonable mask sizes, which is also further confirmation what you are seeing is real when noise is high. I used Reference3 to normalize a bit (just because there was a bit of variance) and smoothing of 10 periods (but I probably didn’t need to normalize, it didn’t hurt by doing it anyway in this case).
For the reference stars, timing doesn’t matter at all, so primarily I was just interested in excluding the binary star hypothesis. Once that’s excluded, then you’ve poven it’s a binary asteroid.
Hope that makes sense. Please write a paper on it, nice catch and it should be out there.
David Dunham notes: Congratulations on this discovery! (10430) Martschmidt is in neither the Johnstone archive of binary asteroids nor is it one of the GAIAMOONS (from Gaia astrometry) object, so there are no previous hints of duplicity. There are no observations of any occultations by this asteroid, in the latest Occult asteroidal occultation observations database. For GAIAMOONS, you can check for them in the attached plain-text file (can open with Notepad) Gaia_Binaries.dat whose format is explained in the attached ReadMe.txt file. The next step now is to alert the best observers of asteroid rotational lightcurves; for a high-numbered relatively small asteroid like this, there is probably little or no photometric information. Of course, this asteroid was not on my radar when I generated the predictions of occultations by special main-belt asteroids a few months ago, so I’ll make a new Occult run to find events in the future through the end of 2025.
Scott Young comments: According to the Light Curve Database, (10430 Martschmidt) has a photometric period of 15.577h (somewhat uncertain, uncertainty code "2" out of 3) and a maximum amplitude of 0.6mag. A bit faint for my scope, but I will see if I can get one of the iTelescope scopes onto it this week and see what we can see.
Jean-Francois Gout: Last night (=Nov 19 local Mississippi time), I managed to get 5 hours of photometry data on (10430) Martschmidt. After a mostly flat lightcurve, there was a sudden drop in brightness. The observing session ended due to the asteroid reaching 30 degrees altitude) before the end of the brightness recovery. I'm attaching the data as a csv file and also a screenshot of the lightcurve. We will need more observations to confirm the presence of mutual events (eclipses and transits), but this is promising. I'll keep looking at this asteroid in the upcoming nights. Weather forecast calls for clear sky here in Mississippi, but the wind might cause some trouble for the fairly long (3 minutes) exposures that I need to get a descent SNR on this object. Observations from Europe/Asia would be especially valuable to complement my own observations.
RN: My comment here - if Jean-Francois' light curve drop is matched by another drop (one a transit, one an eclipse), and if the drops in light are Algol-eclipse-like, rather than gradual e.g. such as perhaps sine waves, this indeed argues they are mutual eclipses and not albedo or shadowing changes, which should highly likely be more gradual. The new data from Matthieu clinches the case this is a binary asteroid, the period is most 23.2 hrs, but 1/2 that or 11.6 hrs can't be entirely ruled out yet. If 23.2 hrs then Mattheiu's data show a secondary eclipse halfway between the primary eclipses seen by Jean-Francois, see below. Cabrillo College Observatory's 12" f/6.3 with SBIG ST2000xcm may be able to reach this magnitude as well, but we have had cloudy skies so far (as of Nov 30). Student Bernard H from Astro 9ABC is also doing photometry on the asteroid itself.
Nov 20 UT, JF Gout's first 5 hours of photometry from his telescope in Mississippi. Cut short by limits. |
Here is more photometry data from JF Gout, showing 3 apparent eclipses. The eclipses are spaced 23.2 hrs apart. But is there a secondary eclipse hidden in the unseen portion? |
Matthieu Conjat succeeded in getting a long series of data that ended just as Gout's began. The eclipse at the beginning of Mattheiu's data (in red, at left) has an eclipse profile looking a bit different and is 11.60 hr or 0.5x23.2 hrs before Gout's data. The eclipse narrowness and shape make this highly inconsistent with an albedo or self-shadowing effect; these have classic Algol type eclipse shapes of nearly identical sized components. An 11.6 hr period would require a highly elliptical orbit sufficient to miss a secondary eclipse. This would be very unusual and the most likely conclusion is a 23.2 hr period.
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The final Analysis #5 IOTA reports and log file were sent to Norm at IOTA on Jan 17, 2025. The CBET announcement was sent Sunday Jan 11 but needs some minor revisions before resubmitting soon.
Jan 27 - Petr Pravec's minor suggestions have been incorporated, and the revised CBET (labelled ...."final2") have just been sent off to Dan Green, co-authors, and all on the original review report.
Feb 3 - my student Bernard Hyuk has also been doing asteroid photometry and captured most of an eclipse of depth 0.6 magnitudes during early December 2024, indicating the alignment of the satellite orbital plane was still well aligned with the direction to Earth even 3 weeks after the eclipses above.
Feb 10 - additional clarifications requested by Dan Green, being sent, and also some clarifying added to this website page as well.
