Photometry of distant active comet C/2010 S1 (LINEAR)
We present the results of photometric observations of a dynamically new comet C/2010 S1 (LINEAR), conducted on June 18, 2012. The comet demonstrated a considerable level of physical activity at a heliocentric distance of 6.3 AU. The brightness, measured under a phase angle of 8.9 degrees, was equal...
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| Цитувати: | Photometry of distant active comet C/2010 S1 (LINEAR) / O. Shubina, I. Kulyk, P. Korsun, Ya. Romanjuk // Advances in Astronomy and Space Physics. — 2014. — Т. 4., вип. 1-2. — С. 38-41. — Бібліогр.: 15 назв. — англ. |
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irk-123456789-1198092017-06-10T03:03:15Z Photometry of distant active comet C/2010 S1 (LINEAR) Shubina, O. Kulyk, I. Korsun, P. Romanjuk, Ya. We present the results of photometric observations of a dynamically new comet C/2010 S1 (LINEAR), conducted on June 18, 2012. The comet demonstrated a considerable level of physical activity at a heliocentric distance of 6.3 AU. The brightness, measured under a phase angle of 8.9 degrees, was equal to 14.55ᵐ±0.06ᵐ and 14.21ᵐ±0.04ᵐ in V- and R-bands, respectively. The brightness distribution over the coma was found to be inversely proportional to the projected onto the sky plane nucleocentric distance, with a slope of approximately −1. Therefore, the calculated Af ρ parameter, approximately 8400 cm and 8200 cm for V and R filters, respectively, was used to estimate the dust production rate. Assuming a steady outflow of dust particles from the nucleus, the dust production rate was estimated to be between 20 and 60 kg/s, depending on the assumed value of the grain's albedo. The V-R colour index obtained from the near-nucleus region of the coma is in agreement with the solar V-R colour index, and does not indicate significant reddening of the re ected solar radiation in the spectral region of 540-683 nm. Remove selected 2014 Article Photometry of distant active comet C/2010 S1 (LINEAR) / O. Shubina, I. Kulyk, P. Korsun, Ya. Romanjuk // Advances in Astronomy and Space Physics. — 2014. — Т. 4., вип. 1-2. — С. 38-41. — Бібліогр.: 15 назв. — англ. 2227-1481 DOI: 10.17721/2227-1481.4.38-41 http://dspace.nbuv.gov.ua/handle/123456789/119809 en Advances in Astronomy and Space Physics Головна астрономічна обсерваторія НАН України |
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We present the results of photometric observations of a dynamically new comet C/2010 S1 (LINEAR), conducted on June 18, 2012. The comet demonstrated a considerable level of physical activity at a heliocentric distance of 6.3 AU. The brightness, measured under a phase angle of 8.9 degrees, was equal to 14.55ᵐ±0.06ᵐ and 14.21ᵐ±0.04ᵐ in V- and R-bands, respectively. The brightness distribution over the coma was found to be inversely proportional to the projected onto the sky plane nucleocentric distance, with a slope of approximately −1. Therefore, the calculated Af ρ parameter, approximately 8400 cm and 8200 cm for V and R filters, respectively, was used to estimate the dust
production rate. Assuming a steady outflow of dust particles from the nucleus, the dust production rate was estimated to be between 20 and 60 kg/s, depending on the assumed value of the grain's albedo. The V-R colour index obtained from the near-nucleus region of the coma is in agreement with the solar V-R colour index, and does not indicate significant reddening of the re ected solar radiation in the spectral region of 540-683 nm.
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Shubina, O. Kulyk, I. Korsun, P. Romanjuk, Ya. |
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Shubina, O. Kulyk, I. Korsun, P. Romanjuk, Ya. Photometry of distant active comet C/2010 S1 (LINEAR) Advances in Astronomy and Space Physics |
| author_facet |
Shubina, O. Kulyk, I. Korsun, P. Romanjuk, Ya. |
| author_sort |
Shubina, O. |
| title |
Photometry of distant active comet C/2010 S1 (LINEAR) |
| title_short |
Photometry of distant active comet C/2010 S1 (LINEAR) |
| title_full |
Photometry of distant active comet C/2010 S1 (LINEAR) |
| title_fullStr |
Photometry of distant active comet C/2010 S1 (LINEAR) |
| title_full_unstemmed |
Photometry of distant active comet C/2010 S1 (LINEAR) |
| title_sort |
photometry of distant active comet c/2010 s1 (linear) |
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Головна астрономічна обсерваторія НАН України |
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2014 |
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http://dspace.nbuv.gov.ua/handle/123456789/119809 |
| citation_txt |
Photometry of distant active comet C/2010 S1 (LINEAR) / O. Shubina, I. Kulyk, P. Korsun, Ya. Romanjuk // Advances in Astronomy and Space Physics. — 2014. — Т. 4., вип. 1-2. — С. 38-41. — Бібліогр.: 15 назв. — англ. |
| series |
Advances in Astronomy and Space Physics |
| work_keys_str_mv |
AT shubinao photometryofdistantactivecometc2010s1linear AT kulyki photometryofdistantactivecometc2010s1linear AT korsunp photometryofdistantactivecometc2010s1linear AT romanjukya photometryofdistantactivecometc2010s1linear |
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2025-07-08T16:38:48Z |
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2025-07-08T16:38:48Z |
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1837097527981113344 |
| fulltext |
Photometry of distant active comet C/2010 S1 (LINEAR)
O. Shubina1∗, I. Kulyk2, P.Korsun2, Ya.Romanjuk2
Advances in Astronomy and Space Physics, 4, 38-41 (2014)
© O. Shubina, I. Kulyk, P.Korsun, Ya.Romanjuk, 2014
1Faculty of Physics, Taras Shevchenko National University of Kyiv, Glushkova ave. 4, Kyiv 03127, Ukraine
2Main Astronomical Observatory of the NAS of Ukraine, Akademika Zabolotnoho Str. 27, Kyiv 03680, Ukraine
We present the results of photometric observations of a dynamically new comet C/2010 S1 (LINEAR), conducted
on June 18, 2012. The comet demonstrated a considerable level of physical activity at a heliocentric distance of
6.3AU. The brightness, measured under a phase angle of 8.9 degrees, was equal to 14.55m±0.06m and 14.21m±0.04m
in V- and R-bands, respectively. The brightness distribution over the coma was found to be inversely proportional to
the projected onto the sky plane nucleocentric distance, with a slope of approximately −1. Therefore, the calculated
Afρ parameter, approximately 8400 cm and 8200 cm for V and R �lters, respectively, was used to estimate the dust
production rate. Assuming a steady out�ow of dust particles from the nucleus, the dust production rate was
estimated to be between 20 and 60 kg/s, depending on the assumed value of the grain's albedo. The V�R colour
index obtained from the near-nucleus region of the coma is in agreement with the solar V�R colour index, and does
not indicate signi�cant reddening of the re�ected solar radiation in the spectral region of 540�683 nm.
Key words: comets: individual: C/2010 S1, photometry, dust production
introduction
Small bodies from the outskirts of the Solar Sys-
tem are considered to be relatively unmodi�ed rem-
nants of the early stage of the solar system forma-
tion. Therefore, they can retain information about
the abundance of volatile materials in comet progen-
itors, as well as the local temperature conditions at
the stage of their origin. Being scattered in the inner
region of the Solar System, some cometary nuclei be-
come relatively active at heliocentric distances larger
than 4 AU. Di�erent physical mechanisms, which can
trigger physical activity at such large heliocentric
distances, are widely discussed, however the prob-
lem is still unresolved [9, 11, 12]. The monitoring
of dynamically new comets at large heliocentric dis-
tances can reveal various patterns of development of
the comets' activities, and provide data for study-
ing the brightness evolution and dust composition of
their comae [9]. Furthermore, this is also a means to
discriminate between di�erent physical mechanisms
triggering and sustaining the comet's activity.
Comet C/2010 S1 is a dynamically new comet
which was discovered on September 23, 2010 by
the LINEAR team as an asteroid-like object of ap-
proximately 18m. Follow-up observations revealed a
bright coma and faint tail. Having a perihelion at
5.89AU, the comet moved beyond the zone where
the water ice sublimation can be signi�cant, there-
fore it provided an opportunity to monitor its dis-
tant activity over a large segment of its orbit. In the
present work we have studied the properties of the
comet based on photometric observations collected
when C/2010 S1 was at a heliocentric distance of
6.35AU and at a distance of 6.53AU from the Earth.
The objective here was to investigate the morphology
of the cometary atmosphere, estimate the dust pro-
duction rate of the cometary nucleus, and calculate
B�V colour of the innermost region of the cometary
coma.
observations
The observations were conducted on June 18,
2012 at the observation station of Taras Shevchenko
National University of Kyiv located at village Lis-
nyky. The total brightness of the comet was approx-
imately 15m. Several parameters of the comet's orbit
such as a perihelion distance (q), an orbital inclina-
tion (i) and a moment of the perihelion passage (T ),
as well as geometric circumstances for a mean UT
moment of the observations (a heliocentric distance,
r, geocentric distance, ∆, and phase angle, α), are
presented in Table 1. The 14-inch Kyiv Internet tele-
scope Celestron 1400XTL was used for the observa-
tions. The CCD ST8XML receiver has 1530×1020
pixels with a pixel size of 9×9µm. Since 2×2 bin-
ning was applied during the observations, one pixel
corresponded to 0.95′′/pix and the full �eld of the
camera was approximately 12′×8′. The images were
obtained through broadband V and R �lters centred
at 0.543 and 0.676µm with half-widths (FWHM) of
0.090 and 0.160, respectively. Fifteen images in the
V-band and �fteen images in the R-band with ex-
posure time of 40 s were acquired during the night.
Airmasses varied from 1.26 to 1.31. The images of
∗belkalenaastronom@gmail.com
38
Advances in Astronomy and Space Physics O. Shubina, I. Kulyk, P.Korsun, Ya.Romanjuk
SA110 were obtained for absolute calibration of the
comet images [7]. The sequence of �ve images was
observed with the exposure time of 40 s under the air-
mass of 1.5. There were no complementary observa-
tions of the standard stars to calculate the extinction
coe�cients, therefore the standard extinction coe�-
cients for V- and R-bands were used [2]. The twilight
sky was observed for the �at�eld correction.
data processing
The photometric processing of the data com-
prised three steps: standard photometric reductions,
preliminary processing of the comet images, and
photometric measurements of the comet images and
standard star images. The standard reductions,
which were applied on both the comet images and
the standard star images, included bias subtraction,
corrections with dark frames, and a �at �eld normal-
ization procedure.
Pre-processing of the images with the comet con-
sisted of cleaning of the images from bright stars lo-
cated close to the cometary coma, subtracting the
background signal, shifting all the images to the
same centre and stacking them together to obtain
a resultant image. In order to clean the area in the
vicinity of the comet, the images of the nearby bright
stars were carefully replaces with the surrounding
background signal. Then the background level was
calculated and removed, images were shifted and
stacked together. Median procedure between stacked
images was applied to increase the signal-to-noise ra-
tio. A sequence of apertures of di�erent sizes was
applied to perform photometric measurements of the
comet image and retrieve the brightness pro�le. The
largest aperture was equal to 45 pixels and corre-
sponded to a distance of 225000 km in the projec-
tion on the sky plane at the geocentric distance of the
comet. The raw and �nal images of comet C/2010 S1
are depicted in Fig. 1 and Fig. 2, respectively.
Fig. 3 represents the total �ux in the measured
units (ADU) integrated along radius-vectors of dif-
ferent lengths for each position angle (the position
angle is measured from the North direction counter-
clockwise, thus through the East). The lengths of
the radius-vectors are represented as a legend in the
�gure. The �gure shows that the comet image has
the elongated coma extending along the radius vec-
tor directed to the position angle of approximately
80◦ (i. e., to the Sun). The several enhancements
are seen in the �gure. Growth of the signal around
140◦ is likely due to the faint background stars, which
were di�cult to remove because they were partly em-
bedded in the coma. The scatter around the back-
ground level in a segment of the position angles be-
tween 220◦ and 320◦ is caused by remnants of the
bright star (see Fig. 1). In order to check if the en-
hancements between 0◦�180◦ are caused by radiation
pressure acting on released grains, or possibly it is
an anti-tail, we built the brightness distribution over
the coma with Monte Carlo model [6]. The model
image, which was made in the cometocentric coor-
dinate system, proved that the elongated coma was
indeed directed opposite to the Sun direction. The
model image being projected on the sky plane coin-
cided well with the observed one.
In order to make the absolute calibration of the
measured �ux from the comet, the frames with
SA110 �eld were processed: the background sig-
nal was removed afterward photometric measure-
ments with the aperture of 12 pixels, which cor-
responded approximately to 3×FWHM, were per-
formed for each standard star belonging to SA110
�eld.
C/2010 S1 (LINEAR)
30 arcsec E
N
Fig. 1: The raw image of comet C/2010 S1. North, East,
the sun ward direction, and the scale bar are indicated.
C/2010 S1 (LINEAR)
30 arcsec E
N
Fig. 2: The �nal cleaned median-combined image of
comet C/2010 S1. North, East, the Sun ward direction,
and the scale bar are indicated.
39
Advances in Astronomy and Space Physics O. Shubina, I. Kulyk, P.Korsun, Ya.Romanjuk
Fig. 3: The total count integrated along the radius vector
(from 9 to 45 pixels) for each position angle from 0◦ to
360◦. The position angle starts at North and increases in
the counterclockwise direction through the East.
In order to calculate the apparent magnitude of
the comet at the given wavelength and for the given
aperture size, the following standard equation was
used:
mcom = 2.5 log
(
Ncom
Nstr
)
+mstr − kλ∆M
here, Ncom is the total count from the comet image
for the given aperture size per 1 second, Nstr is the
total count from the star image per 1 second, kλ is
the main extinction coe�cient for the given wave-
length, ∆M is the di�erence between the comet and
star airmasses.
The brightness of the comet evaluated with the
aperture size of 12 pixels is equal to 14.55m ± 0.06m
and 14.21m±0.04m for V- and R-bands, respectively.
The colour index CIV−R equals 0.34m±0.07m. This
value is consistent with the di�erence between the so-
lar magnitudes at the wavelengths corresponding to
the e�ective wavelengths of V and R �lters (−26.76
and −27.10, respectively). It points out that there
is no signi�cant reddening of the re�ected solar ra-
diation in the spectral region of 540�683 nm.
Afρ parameter and
the dust production rate
Since the cometary spectra did not reveal molec-
ular emissions seen above the re�ected solar con-
tinuum, it was possible to use the images obtained
through the wide V and R �lters for the analy-
sis of the cometary dust environment. Vorontsov-
Veliaminov [13] and then Konopleva [4] proved that
surface brightness of a comet atmosphere varies as
∼ ρ−1 at the sky-plane, provided that both the dust
production rate of a nucleus and the velocities of
ejected particles are constant. C/2010 S1 surface
brightness pro�le was examined within the range of
the radius vectors corresponding to the projected
distances between 40000 and 200000 km in the sky
plane. The slopes of −0.98± 0.02 and −1.12± 0.03
were extracted for the V and R colour bands respec-
tively. Therefore, the Afρ technique was used as a
measure of the dust production rate of the cometary
nucleus [1]. The Afρ parameter is widely used in
order to compare the data obtained at di�erent ob-
serving sites, epochs, and under the di�erent viewing
geometries. A'Hearn et al. [1] provided the de�ni-
tion of the Af as a product of grain's albedo, A,
and a �lling factor, f . The latter is the ratio of
particle total cross section to the projected �eld of
view. A simple steady-state coma model is implied
for the de�nition of the Afρ technique, therefore the
constant dust production rate from a nucleus and
constant velocities of ejected particles are expected.
Under this condition the product of Af and ρ (the
projection of the �eld of view on the sky plane) is
aperture-independent and can be used to derive the
dust production and to compare the activity level of
di�erent comets. The following equation is widely
used for the calculation of the Afρ parameter:
Afρ =
(
4r2∆2100.4(m�−mR)
)
/ρ. (1)
Here, the Afρ value is expressed in cm; ∆ is the
comet geocentric distance expressed in cm; r is the
comet heliocentric distance, expressed in AU; ρ is
the aperture size projected in to the sky plane at
the comet geocentric distance and expressed in cm;
m� and mR are the apparent magnitudes of the Sun
and the comet for the given �lter. Calculated values
of Afρ equal to 8400 ± 600 cm and 8200 ± 1000 cm
for V and R �lters, respectively. The errors were
estimated by the di�erentiation of the equation (1)
taking into account the uncertainties of the comet
and solar magnitudes. The measured magnitudes of
the comet were not reduced to 0◦ phase angle, that
means that estimated with Eq. (1) Afρ correspond
to the speci�c phase angle of 8.9◦.
The Afρ was used to estimate the dust produc-
tion rate of the cometary nucleus following the ap-
proach presented in Weiler et al. [14]. In order to cal-
culate the dust production rate, several assumptions
about dust particles populating the coma should be
made. Adopting parameters, such as out�ow veloci-
ties of particles, their optical properties, and the size
frequency distribution of particles, we took into ac-
count the discussion recently given by Fink and Ru-
bin [3], as well as the results of modelling of dust en-
vironment of some distant comets with Monte Carlo
model [5, 6]. We assumed that dust particles in co-
mae of distant comets are large enough: the mini-
mum and maximum radii of dust were set at 5 and
103 µm respectively. The calculation was made for
the di�erent values of particle's Bond albedo: 0.1,
0.2, and 0.3. The high albedo of the dust parti-
cles populated the coma can be justi�ed by the pres-
ence of icy grains and is consistent with recently re-
40
Advances in Astronomy and Space Physics O. Shubina, I. Kulyk, P.Korsun, Ya.Romanjuk
Table 1: Some orbital parameters of C/2010 S1 and geometric conditions of the observations.
Date of Orbital parameters Geometric conditions
observations, UT q, AU i, degrees T r, AU ∆, AU α, degrees
2012 June 18.95943 5.89 125.3 2013/05/20.3 6.35 6.53 8.90
ported results of near-infrared spectroscopy of the
comet [15]. The author found the presence of 1.5
and 2.0 micron absorption features in the spectrum
of the comet likely due to amorphous water ice at a
heliocentric distance of 5.9AU [15]. The phase func-
tion was adopted in a form of 10−0.4×β×α, indepen-
dent on the grain size. This expression was chosen
because the observations were conducted under low
phase angle α of 8.9◦, which is close to backscatter-
ing direction. The phase coe�cient, β, was assumed
to be equal to 0.04. The normalized size frequency
distribution function f(a) = a−n was used with a
power index n equal to −4.0. The equation for dust
density was taken from Newburn and Spinrad [10].
The expression for expansion velocities of grain par-
ticles was taken from Korsun et al. [6] in a form of
v(a) ∼ r−0.5× a−0.5, which provides the range of ve-
locities between 2−15m/s for the particle sizes fallen
in the interval of 1000�10µm. Estimated values of
the dust mass production rates of the cometary nu-
cleus do not di�er much for the two colour bands and
equal to about 60 kg/s, 30 kg/s, and 20 kg/s assum-
ing the grain albedo of 0.1, 0.2, and 0.3, respectively.
brief conclusions
The results of the analysis of the photometric ob-
servations of distant comet C/2010 S1 (LINEAR)
are presented. The observations were obtained at
the observation station of Taras Shevchenko Na-
tional University of Kyiv located at village Lisnyky.
The orbital characteristics of the comet point out
that it belongs to the class of dynamically new
comets, which are genetically connected to the Oort
cometary cloud. Although a perihelion of the comet
orbit was at the distance of 5.89AU and, therefore,
the comet moved beyond the water ice sublimation
zone, its bright coma and faint tail had been already
seen at the discovery. The results presented in our
work con�rm the high level of physical activity of
C/2010 S1.
The distribution of the integrated �ux from the
cometary image over the position angle shows the
elongated coma, up to approximately 30 px (approx-
imately 140000 km in the sky plan projection) and
directed to the position angle of about 80◦.
The Afρ parameter calculated within the aper-
ture size of 12 pixels (∼ 11′′) equals to 8400±600 cm
and 8200± 1000 cm for V and R �lters, respectively.
The dust production rate of the cometary nucleus
was estimated based on the Afρ parameter. It falls
into the interval between 20 and 60 kg/s depending
on the adopted grain albedo. The dust production
rate of C/2010 S1 is probably considerably lower
than the dust production rates of comets C/1995 O1
Hale-Bopp and C/2007 D1 (LINEAR). Both comets
demonstrated very high activity having dust produc-
tion rates about 1000 kg/s at the same large helio-
centric distances [8, 9, 14].
The colour-index, CIV−R, of C/2010 S1 amounts
to 0.34m ± 0.07m that is comparable with the solar
colour index. It means that no signi�cant redden-
ing of the re�ected solar radiation by the near nu-
clear part of the coma was detected in the interval
of 540− 683nm.
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