Table Of ContentApJ Letters - Updated 2014 Nov 18
PreprinttypesetusingLATEXstyleemulateapjv.5/2/11
SUBLIMATION-DRIVEN ACTIVITY IN MAIN-BELT COMET 313P/GIBBS
Henry H. Hsieh1, Olivier Hainaut2, Bojan Novakovic´3, Bryce Bolin4, Larry Denneau5, Alan
Fitzsimmons6, Nader Haghighipour5, Jan Kleyna5, Rosita Kokotanekova7,8, Pedro Lacerda8, Karen J.
Meech5, Marco Micheli9, Nick Moskovitz10, Eva Schunova5, Colin Snodgrass7, Richard J.
Wainscoat5, Lawrence Wasserman10, Adam Waszczak11
ApJ Letters - Updated 2014 Nov 18
ABSTRACT
Wepresentanobservationalanddynamicalstudyofnewlydiscoveredmain-beltcomet313P/Gibbs.
5
We find that the object is clearly active both in observations obtained in 2014 and in precovery
1
observations obtained in 2003 by the Sloan Digital Sky Survey, strongly suggesting that its activity
0
is sublimation-driven. This conclusion is supported by a photometric analysis showing an increase in
2
the total brightness of the comet over the 2014 observing period, and dust modeling results showing
n that the dust emission persists over at least three months during both active periods, where we find
a startdatesforemissionnolaterthan2003July24±10forthe2003activeperiodand2014July28±10
J for the 2014 active period. From serendipitous observations by the Subaru Telescope in 2004 when
6 the object was apparently inactive, we estimate that the nucleus has an absolute R-band magnitude
1 of H =17.1±0.3, corresponding to an effective nucleus radius of r ∼1.00±0.15 km. The object’s
R e
faintness at that time means we cannot rule out the presence of activity, and so this computed radius
] should be considered an upper limit. We find that 313P’s orbit is intrinsically chaotic, having a
P
Lyapunov time of T = 12000 yr and being located near two 3-body mean-motion resonances with
E l
Jupiter and Saturn, 11J-1S-5A and 10J+12S-7A, yet appears stable over >50 Myr in an apparent
.
h example of stable chaos. We furthermore find that 313P is the second main-belt comet, after P/2012
p T1 (PANSTARRS), to belong to the ∼155 Myr old Lixiaohua asteroid family.
- Subject headings: comets: general — comets: individual (313P/Gibbs) — minor planets, asteroids:
o
general
r
t
s
a
1. INTRODUCTION no spectroscopic evidence of gas emission was detected
[
(Jewittetal.2015). Asof2015January15, 313Phasan
Comet 313P/Gibbs was discovered as P/2014 S4
1 osculating semimajor axis, eccentricity, and inclination
(Gibbs) on 2014 September 24 by A. R. Gibbs using the
v of a=3.156 AU, e=0.242, and i=10.97◦, respectively,
CatalinaSkySurvey’s0.68-mSchmidttelescope. Follow-
3 an orbital period of 5.61 yr, and a Tisserand parameter
upimagesfromtheMt.Lemmon1.5mtelescoperevealed
7 a 20(cid:48)(cid:48) tail and a slightly elliptical coma with a full-width with respect to Jupiter of TJ = 3.132. These orbital el-
8 ements place the object unequivocally within the main
at half-maximum (FWHM) approximately twice that of
3 asteroid belt, making it one of the growing number of
nearby field stars (Gibbs & Sato 2014). Analysis of ob-
0 active asteroids (cf. Jewitt 2012) in the main belt to be
servations by the Hubble Space Telescope (HST), Keck
.
1 I, and the Danish 1.5 m telescope at La Silla indicate discovered in recent years.
0 continuous mass loss between 2014 October 2 and 2014 Active asteroids include main-belt comets (MBCs; cf.
5 Hsieh & Jewitt 2006), which exhibit cometary activity
November 6, inconsistent with an impact event, though
1 duetoicesublimation,anddisruptedasteroids(cf.Hsieh
: et al. 2012a), where dust emission is caused by effects
v [email protected]
i 1Institute of Astronomy and Astrophysics, Academia Sinica, suchasimpactsorrotationaldisruptions. Distinguishing
X P.O.Box23-141,Taipei10617,Taiwan between different sources of activity is crucial for devel-
2European Southern Observatory, Karl-Schwarzschild-Straße oping our understanding of the global properties (e.g.,
r 2,D-85748GarchingbeiMu¨nchen,Germany
a 3DepartmentofAstronomy,FacultyofMathematics,Univer- abundances, spatial distributions, and physical charac-
sityofBelgrade,Studentskitrg16,11000Belgrade,Serbia teristics)ofobjectsexhibitingeachtypeofactivity(e.g.,
4ObservatoiredelaCoˆted’Azur,Boulevarddel’Observatoire, Hsieh et al. 2015).
B.P.4229,06304NiceCedex4,France
Unambiguously determining the source of comet-like
5Institute for Astronomy, University of Hawaii, 2680 Wood-
activity, especially for a recently discovered object, is
lawnDrive,Honolulu,HI96822,USA
6Astrophysics Research Centre, Queens University Belfast, unfortunately not straightforward. Despite detections of
BelfastBT71NN,UnitedKingdom watericefrostonasteroid(24)Themis(Rivkin&Emery
7Planetary and Space Sciences, Department of Physical Sci-
2010; Campins et al. 2010) and water vapor outgassing
ences,TheOpenUniversity,MiltonKeynes,MK76AA,United
Kingdom from (1) Ceres (Ku¨ppers et al. 2014), attempts to di-
8MaxPlanckInstituteforSolarSystemResearch,Justus-von- rectlydetectgasemissionfromactiveasteroidsviaspec-
Liebig-Weg3,37077Go¨ttingen,Germany troscopy (e.g., Jewitt et al. 2009; Licandro et al. 2011;
9ESASSANEOCoordinationCentre,Frascati,RM,Italy
Hsieh et al. 2012a,b,c, 2013; de Val-Borro et al. 2012;
10LowellObservatory,1400W.MarsHillRoad,Flagstaff,AZ
86001,USA O’Rourke et al. 2013) have all been unsuccessful. We
11Division of Geological and Planetary Sciences, California mustuseindirectmethodsinstead,likedustmodelingor
InstituteofTechnology,Pasadena,CA91125
2
photometric monitoring (cf. Hsieh et al. 2012a), to de- radiidependingonthenightlyseeing,wherebackground
termine whether dust emission was long-lived (implying statistics were measured in nearby regions of blank sky,
sublimation-driven emission; e.g., Hsieh et al. 2012b) or avoiding contamination from the comet.
impulsive (implyingimpact-driven ejection; e.g., Steven-
son et al. 2012). As such, unambiguous confirmation 3. RESULTS
of sublimation is difficult to achieve, a situation further 3.1. Photometric Analysis
complicated in cases where multiple mechanisms could
Apparent R-band magnitudes as measured in 5(cid:48)(cid:48) cir-
be at work (e.g., Jewitt et al. 2014a). Recurrent ac-
cularapertures,andequivalentabsolutemagnitudes(as-
tivity near perihelion, such as that observed for MBCs
sumingastandardH,Gphasefunctionwhereweassume
133P/Elst-Pizarro (Hsieh et al. 2004, 2010; Jewitt et al.
G = 0.15), as well as absolute magnitudes correspond-
2014b) and 238P/Read (Hsieh et al. 2011b), is currently
ingtolargerrectangularaperturesencompassingtheen-
considered the most reliable indicator of sublimation-
tire comet, for all observations are listed in Table 1.
driven activity. This behavior is naturally explained by
Both the central and total brightnesses of the comet
thermally-modulatedsublimationandextremelydifficult
decline over the 2003 observing period (which spans a
to explain as a consequence of any physical disruption
true anomaly range of 30.5◦ < ν < 46.7◦), declining
(Hsieh et al. 2012a; Jewitt 2012).
by ∼40% in 59 days. Meanwhile, the comet brightens
2. OBSERVATIONS over the 2014 observing period (−6.5◦ < ν < 24.0◦), in-
creasing in total brightness by ∼150% in 104 days (Fig-
Following 313P’s discovery, weidentifiedpre-discovery
ure 2a). The object’s increasing brightness in 2014 is
images from August 2014 obtained by the 1.8 m Pan-
suggestive of ongoing, sublimation-driven dust produc-
STARRS1 (PS1) survey telescope using PS1 i - and
P1 tion, but is not unambiguous proof of sublimation (cf.
w -band filters (Tonry et al. 2012). We also obtained
P1 Hsieh et al. 2012a). Multi-filter SDSS observations from
follow-up imaging in October and November 2014 us-
2003 show that the comet has approximately solar col-
ing the Large Format Camera (Simcoe et al. 2000) on
ors (g(cid:48) − r(cid:48) = 0.54 ± 0.05, r(cid:48) − i(cid:48) = 0.10 ± 0.05, and
Palomar Observatory’s 5.1 m Hale telescope, the Large
i(cid:48)−z(cid:48) =0.05±0.05; equivalent to B−V =0.71±0.05,
MonolithicImager(Bidaetal.2014)onLowellObserva-
V −R = 0.41±0.05, and R−I = 0.33±0.05) with no
tory’s4.3-mDiscoveryChannelTelescope,a4096×4096
appreciable color differences between the coma and the
Fairchild CCD on the 2.0 m Faulkes Telescope North on
tail, suggesting that the measured colors in both regions
Haleakala, a 2048×2048 Textronix CCD on the Univer-
are dominated by dust. Strong coma during both ac-
sity of Hawaii (UH) 2.2 m telescope on Mauna Kea, and
tive periods prevent any meaningful determination of a
theEuropeanSouthernObservatory(ESO)FaintObject
rotational period or amplitude.
Spectrograph and Camera (Buzzoni et al. 1984) on the
We measure an apparent R-band magnitude of m =
3.58mNewTechnologyTelescope(Program194.C-0207) R
23.3±0.2 for 313P in 2004, when it was apparently in-
operated by ESO at La Silla. SDSS r(cid:48)-band or Kron-
active, while it was at ν = 108.7◦ and at a heliocentric
CousinsR-bandfilters,asspecifiedinTable1,wereused
distance of R = 3.21 AU. This corresponds to an ab-
forallfollow-upobservations. WeusedImageReduction
solute magnitude of H = 17.1 ± 0.2, from which we
and Analysis Facility software (Tody 1986) to perform R
compute an effective nucleus radius of r ∼1.0±0.1 km
standard bias subtraction and flat-field reduction (using e
(assuming a R-band albedo of p = 0.05; cf. Hsieh et
dithered twilight sky images) for all data, except those R
al. 2009), making it a mid-sized MBC (cf. Hsieh et al.
from PS1, which were reduced using the system’s Image
2015). While no coma or tail was visible in this data,
Processing Pipeline (Magnier 2006).
the object’s faintness at the time means that we cannot
Using the Solar System Object Image Search tool
rule out the presence of activity, particularly since ac-
(SSOIS; Gwyn et al. 2012), provided by the Canadian
tivity was detected for MBCs 133P and P/2010 R2 (La
Astronomical Data Centre, we identified precovery ob-
Sagra) as late as ν = 109◦ and ν = 117◦, respectively,
servations obtained in 2003 by the 2.5 m Sloan Digital
when both were at R ∼ 3.25 AU (Kaluna et al. 2011;
SkySurvey(SDSS)telescope(Yorketal.2000;Fukugita
Hsieh 2014). In fact, HST observations indicate 313P’s
et al. 1996; Gunn et al. 1998, 2006; Aihara et al. 2011),
nucleus may be as small as r ∼ 0.5 km (Jewitt et al.
and in 2004 by Suprime-Cam (Miyazaki et al. 2002) on e
2015). As such, the nucleus size calculated here should
the8.2mSubaruTelescope. TheSDSSobservations,ob-
be regarded as an upper limit.
tained in g(cid:48)-, r(cid:48)-, i(cid:48)-, and z(cid:48)-band filters, show a clearly
Using this nucleus size, we can estimate total dust
cometary object with a dust tail extending as much as
massesatdifferenttimes. FollowingHsieh(2014),wefind
∼1 arcmin in the antisolar direction. The object is ex-
a peak total dust mass of M ≈(2.5±1.0)×108 kg and
tremely faint in the Subaru images, obtained using a d
wide-band“W-J-VR”filterencompassingboththeJohn- dust-to-nucleusmassratioofMd/MN ≈(4.5±1.5)×10−5
son V and Cousins R passbands, exhibiting no indica- in 2003 (at ν = 30.5◦) and Md ≈ (3±1)×107 kg and
tions of activity. M /M ≈ (5.5±2.0)×10−6 in 2014 (at ν = 24◦), or
d N
Absolutecalibrationofalldatawasaccomplishedusing a decline in peak total dust mass of ∼ 1 order of mag-
magnitudesoffieldstarswithapproximatelysolarcolors nitude between 2003 and 2014. Additional photometric
from SDSS (Aihara et al. 2011) or PS1 (Schlafly et al. measurements through the end of the 2014-2015 observ-
2012; Tonry et al. 2012; Magnier et al. 2013). Conver- ingwindowwillpermitamoredirectcomparisonof2003
sionofallphotometrytoR-bandwasaccomplishedusing and 2014-2015 activity levels over the same orbital arcs,
transformations derived by Tonry et al. (2012) and by whilemoreaccuratemeasurementsof313P’snucleussize
R. Lupton (http://www.sdss.org/). Comet photome- will improve the accuracy of the dust mass estimates re-
try was performed using circular apertures with varying ported here. However, these current results suggest that
3
Fig. 1.—Orbitalpositionplot(left)andcompositeimages(right)constructedfromobservationsdetailedinTable1,withthe
Sun (black dot) at the center of the orbital position plot, and the orbits of Mercury, Venus, Earth, Mars, 313P, and Jupiter
shown as black lines. Perihelion (P) and aphelion (A) are marked with crosses. Colored points (left panel) and images (right
panel)correspondtoobservationsfrom(a)2003September30,(b)2003October23,(c)2003November28,(d)2014August6,
(e)2014September3,(f)2014October1,(g)2014October30,and(h)2014November18. Anopensquaresymbol(leftpanel)
marksthepositionofobservationsfrom2004September16(imagenotshown). Theobjectisatthecenterofeachimagepanel,
andNorth(N),East(E),theantisolarvector(−(cid:12)),andthenegativeheliocentricvelocityvector(−v)aremarkedwitharrows.
TABLE 1
Observations
UTDate Tel.a Nb tc Filter Rd ∆e αf νg mR(R,∆,α)h mR(1,1,0)i mR,tot(1,1,0)j Active?k
2003June20 Perihelion....................... 2.367 2.604 23.0 0.0 — — — —
2003September30 SDSS 4 216 g(cid:48)r(cid:48)i(cid:48)z(cid:48) 2.434 1.598 16.1 30.5 18.4±0.1 14.6±0.1 13.6±0.1 yes
2003October23 SDSS 4 216 g(cid:48)r(cid:48)i(cid:48)z(cid:48) 2.465 1.512 8.5 37.0 18.2±0.1 14.8±0.1 13.9±0.1 yes
2003October24 SDSS 4 216 g(cid:48)r(cid:48)i(cid:48)z(cid:48) 2.467 1.511 8.3 37.2 18.3±0.1 14.9±0.1 14.1±0.1 yes
2003November28 SDSS 4 216 g(cid:48)r(cid:48)i(cid:48)z(cid:48) 2.525 1.636 12.1 46.7 18.7±0.1 14.9±0.1 14.2±0.1 yes
2004September16 Subaru 2 120 W-J-VR 3.208 3.742 14.1 108.7 23.3±0.2 17.1±0.2 — no
2009January18 Perihelion....................... 2.385 2.977 17.0 0.0 — — — —
2014August29 Perihelion....................... 2.392 1.555 16.9 0.0 — — — —
2014August06 PS1 2 90 wP1 2.395 1.750 22.1 353.5 20.8±0.1 16.6±0.1 16.6±0.1 yes
2014August18 PS1 3 135 iP1 2.392 1.637 19.6 357.0 20.6±0.1 16.6±0.1 16.6±0.1 yes
2014September03 PS1 2 90 wP1 2.392 1.518 15.2 1.8 20.3±0.1 16.7±0.1 16.7±0.1 yes
2014October01 P200 38 1140 r(cid:48) 2.399 1.429 7.7 10.0 19.3±0.1 16.1±0.1 15.8±0.1 yes
2014October13 FTN 2 120 r(cid:48) 2.404 1.444 8.4 13.2 19.4±0.1 16.1±0.1 16.0±0.1 yes
2014October17 DCT 29 2610 r(cid:48) 2.407 1.461 9.6 14.7 19.3±0.1 15.9±0.1 15.6±0.1 yes
2014October22 DCT 2 240 R 2.410 1.484 11.0 16.2 19.6±0.1 16.1±0.1 15.8±0.1 yes
2014October30 UH2.2 5 1500 R 2.416 1.530 13.4 18.5 19.6±0.1 16.0±0.1 15.8±0.1 yes
2014November17 NTT 4 480 r(cid:48) 2.432 1.683 18.4 23.7 20.2±0.1 16.2±0.1 16.0±0.1 yes
2014November18 NTT 3 900 r(cid:48) 2.433 1.694 18.6 24.0 20.6±0.1 16.6±0.1 15.7±0.1 yes
2014December16 UH2.2 R 2.464 2.023 22.7 31.9 yes
2020April15 Perihelion....................... 2.419 3.344 7.8 0.0 — — — —
aTelescope(SDSS:SloanDigitalSkySurvey;PS1: Pan-STARRS1;P200: PalomarHaleTelescope;FTN:FaulkesTelescopeNorth;DCT:
DiscoveryChannelTelescope;UH2.2: UH2.2mtelescope;NTT:NewTechnologyTelescope).
b Numberofexposures.
c Totalintegrationtime,ins.
d Heliocentricdistance,inAU.
e Geocentricdistance,inAU.
f Solarphaseangle(Sun-object-Earth),indegrees.
g Trueanomaly,indegrees.
h MeanapparentR-bandmagnitude,assumingsolarcolors.
i Absolute R-band magnitude (at R=∆=1 AU and α=0◦) as measured with a 5(cid:48).(cid:48)0 aperture, assuming IAU H,G phase-darkening
whereG=0.15.
j AbsoluteR-bandmagnitudeasmeasuredwithrectangularapertureenclosingentirevisibleextentofcomet.
k Isvisibleactivitypresent?
4
Fig. 2.—(a)PlotofabsolutetotalR-bandmagnitudesmeasuredfor313P(includingthetotalobservedfluxfromthenucleus,
coma, and dust tail) from 2003 through 2014. (b) Predicted apparent R-band magnitude of the nucleus of 313P through the
end of the 2016-2017 observing window. Shaded regions mark time periods when the object is not observable from Earth (i.e.,
solar elongation <50◦).
5
there is a significant decline in activity strength after past until the present, where the seeing disk does not
justtwoorbitpassages, perhapsduetoacombinationof allow us determine whether the emission has very re-
mantling of the active area responsible for the observed cently stopped. The envelope of the coma is effectively
activity (cf. Hsieh et al. 2015) and depletion of exposed enclosed by a syndyne representing β (the minimum
max
volatile material. Alternatively, other effects (e.g., out- particle size) and a synchrone representing t (the
ej,min
bursts or pole orientation evolution) could be responsi- earliest ejection time), such that all the visible dust has
ble, and as such, monitoring of future active episodes is β < β and was ejected at t > t . The values
max ej ej,min
highlyencouragedtoconstrainpossiblecausesfortheob- ofβ andt themselvesrepresentlowerandupper
max ej,min
served decline in activity strength. Generally speaking, limits, respectively, since observations with higher S/N
however, 313P’s activity levels in both 2003 and 2014 could reveal fainter surface brightness features, thus ex-
are comparable to those of other MBCs both in terms tending the envelope of the observed coma and tail.
ofpeaktotaldustmassesandpeakdust-to-nucleusmass In Figure 3, we overplot syndynes (black lines) repre-
ratios (cf. Hsieh 2014). sentingparticlessizesrangingfromβ =0.005toβ =0.03
Our nucleus size estimate also permits us to predict (a∼30−200 µm) and synchrones (red lines) represent-
the comet’s brightness in the absence of activity (or at ing ejection times from t = −10 days to t = −130
ej ej
least at the level of activity exhibited in 2004) in the days (with respect to the time of observations) on im-
future (Figure 2b). Observed magnitudes fainter than ages from Figure 1. We find good agreement among our
predicted will indicate that the nucleus smaller than es- modelsofindividualobservationsindicatingβ ≥0.03
max
timatedhere(implyingthatresidualactivitywaspresent (equivalent to particles tens of microns in radius, and
in 2004), while magnitudes brighter than predicted will larger), and emission start times of no later than 2003
indicate the presence of activity. July 24±10 (ν (cid:46) 10◦ ± 3◦) for the 2003 activity, and
no later than 2014 July 28±10 (ν (cid:46) 351◦ ±3◦) for the
3.2. Morphological Analysis
2014activity,i.e.,withactivitypersistingfor>3months
Highly variable morphology was observed for 313P in each time. We find no evidence of significant changes
both 2003 and 2014. The projected orientation of the (i.e., outbursts or quiescent periods) in the intensity of
dusttailintheskyrotatescounterclockwiseduringboth the activity or in the dust particle size distribution over
activeperiods,eachtimelaggingslightlybehindthesim- the emission period.
ilarlyrotating antisolar vector (asprojectedon thesky),
3.3. Dynamical Analysis
exhibiting strong similarities to the morphological evo-
lution of P/La Sagra in 2010 (Hsieh et al. 2012c). For To ascertain some of 313P’s basic dynami-
P/La Sagra, two dust tails (one oriented in the antiso- cal properties, we first numerically propagate
lar direction, and another aligned with the object’s or- its orbit for 10 Myr using the Orbit9 integrator
bit plane) were observed late in its observed active pe- (http://hamilton.dm.unipi.it/astdys/), accounting
riod (Hsieh et al. 2012c). This distinctive morphology for the four outer planets (Jupiter to Neptune). We
was also observed for 288P (Hsieh et al. 2012b) and was calculate proper orbital elements of ap = 3.15204 AU,
interpreted to indicate long-lived dust emission, since ep = 0.20560, and ip = 10.30◦, and a Lyapunov time of
the antisolar dust tail indicated the presence of small, Tl =12000 yr. This short Tl indicates that 313P’s orbit
fast-moving dust particles that must have been recently is intrinsically chaotic, perhaps due to the proximity
emitted, while the orbit-plane-aligned dust tail corre- of two 3-body mean motion resonances (MMRs) with
sponded to large, slow-moving particles that must have Jupiter and Saturn, 11J-1S-5A and 10J+12S-7A. These
been ejected much longer ago. Only one tail has been tworesonancesarerelativelyweak,buthaveoverlapping
observed for 313P to date, but if the observed activity zonesofinfluenceforep >0.15, formingahighlychaotic
is in fact sublimation-driven, further observations could zone around 313P.
eventually reveal the development of a second dust tail. Next, we extend our integrations to 50 Myr, aiming to
To quantitatively analyze 313P’s dust morphology, we betterunderstand313P’slong-termdynamicalbehavior.
perform a Finson & Probstein (1968) numerical dust We find that the object’s orbital elements remain nearly
modeling analysis. In this formalism, dust grains are constant over even this longer integration period (Fig-
released with zero velocity from the nucleus some time ure 4a). Thus, despite residing in a chaotic region of the
inthepast,andtheirpositioniscomputedatthetimeof asteroidbelt, theorbitof313Pappearsrelativelystable.
observations,accountingforsolargravityandsolarradia- Such behavior has also been observed for other asteroids
tionpressure. Arangeofejectiontimesandparticlesizes in high-order MMRs (Tsiganis et al. 2002), illustrating
are considered, where particle sizes are parametrized us- a phenomenon known as stable chaos (Milani & Nobili
ing the ratio of solar radiation pressure to solar gravity, 1992).
β, where 1/β gives approximate particle radii, a, in mi- We also search for an associated dynamical family to
crons. The locus of the present positions of all particles checkwhether313Pmayhaveoriginatedinarecentfrag-
withacommonejectiontimeiscalledasynchrone,while mentation event like 133P and 288P (Nesvorny´ et al.
the locus of the present positions of all particles with a 2008; Novakovi´c et al. 2012). Employing the hierarchi-
common β is a syndyne. calclusteringmethod(Zappal`aetal.1990), wefindthat
On each image, no gap is observed between the dust 313P is associated with the ∼155 Myr old Lixiaohua as-
tail and the nucleus, implying either that (1) a contin- teroid family (Figure 4b; Novakovi´c et al. 2010), joining
uumofdustgrainsizesuptoverylargegrainsispresent, the family at the low cut-off velocity of d ∼ 20 m s−1,
where in practice, the seeing disk prevents us from set- making it the second MBC in this family after P/2012
ting an upper limit to the grain size, or (2) there has T1 (Hsieh et al. 2013). All Lixiaohua members, includ-
been continued emission of dust from some time in the ing 313P, have similarly chaotic orbits (Novakovi´c et al.
6
Fig. 3.—Syndynes(blacklines)andsynchrones(redlines)overplottedondatafrom(a)2003September30,(b)2003October
23, (c) 2003 November 28, (d) 2014 October 1, (e) 2014 October 30, and (f) 2014 November 18, where β =0.03 syndynes and
t =−10 day synchrones are the upper-most or left-most black and red lines, respectively, in each panel.
ej
Fig. 4.— (a) Evolution of mean semimajor axis (top) and mean eccentricity (bottom) of 313P over 50 Myr from numerical
integrations. (b) Plots of proper semimajor axis versus proper eccentricity (top) and sine of proper inclination (bottom) for
Lixiaohuafamilymembers(blackdots)andMBCs313P(blueXsymbol)andP/2012T1(greenXsymbol). Verticalredshaded
regions mark the 11J-1S-5A and 10J+12S-7A MMRs.
2010), and as such, 313P’s Lixiaohua family association lisional excavation of subsurface ice (Hsieh et al. 2004;
should be considered as reliable as those of other mem- Capriaetal.2012, e.g.,), consistentwiththeconclusions
bers,despitethechaoticityofitsorbitinferredhere. Un- of Jewitt et al. (2015).
fortunately, as in the case of P/2012 T1, any search for Preliminary results from numerical dynamical model-
associations with younger families will be complicated ingindicatethatsomemain-beltobjectswithmoderately
by the high number density of asteroids in this region large eccentricities and inclinations similar to those of
of orbital element space, as well as the region’s intrinsic 313P, particularly those near mean-motion resonances,
chaoticity. may be temporarily-captured JFC-like interlopers, even
if they have T (cid:29) 3 (Hsieh & Haghighipour 2014).
J
4. DISCUSSION Therefore, while our integrations of 313P itself indicate
that it is moderately stable, and thus possibly native to
After133P(Hsiehetal.2004,2010;Jewittetal.2014b)
the main belt, we caution that its dynamical origin can-
and 238P (Hsieh et al. 2011b), 313P is now the third
not be considered absolutely certain.
MBC observed to exhibit recurrent activity. We con-
Continued observations of 313P are encouraged until
clude from this evidence, along with photometric and
March 2015 (the end of the 2014-2015 observing win-
dust modeling results presented here, that 313P’s activ-
dow; Figure 2) to continue monitoring its photomet-
ity is likely sublimation-driven, perhaps due to the col-
7
ric and morphological evolution. From September 2015 scopes, Lowell Observatory’s Discovery Channel Tele-
to May 2016, 313P will have a true anomaly range of scope, the University of Hawaii 2.2 m telescope, ESO’s
93◦ <ν <135◦, and may provide opportunities to char- La Silla Observatory (PID 194.C-0207), and the Cana-
acterize its inactive nucleus. However, given aforemen- dian Astronomy Data Centre operated by the National
tioned examples of MBCs remaining active over simi- Research Council of Canada and the Canadian Space
lar true anomaly ranges (Section 3.1), observations from Agency. SDSS (http://www.sdss.org/) is funded by
November 2016 to July 2017 (154◦ < ν < 184◦), may the Alfred P. Sloan Foundation, the Participating In-
provemorereliablefornucleuscharacterizationpurposes. stitutions, NSF, the U.S. Department of Energy Office
The heretofore unrecognized existence of clearly of Science, NASA, the Japanese Monbukagakusho, the
cometary images of 313P in SDSS data, despite at least Max Planck Society, and the Higher Education Funding
one dedicated effort to search for active comets in that Council for England, and managed by the Astrophysical
data (Solontoi et al. 2010), suggests that renewed ef- Research Consortium for the Participating Institutions.
forts to search for MBCs (and comets in general) in The Pan-STARRS1 Surveys were made possible by the
SDSS data, taking advantage of recent reprocessing of Institute for Astronomy, the University of Hawaii, the
thatdataincludingimprovedblendedsourcediscrimina- Pan-STARRS Project Office, the Max-Planck Society,
tion(Solontoi2014,privatecommunication),couldprove theMaxPlanckInstituteforAstronomy,Heidelbergand
fruitful. SearchesforMBCsinotherdataarchives, espe- the Max Planck Institute for Extraterrestrial Physics,
cially those obtained by large telescopes or with signifi- Garching, Johns Hopkins University, Durham Univer-
cant sky coverage, could be similarly productive. sity, the University of Edinburgh, the Queen’s Univer-
sity Belfast, the Harvard-Smithsonian Center for Astro-
physics, the Las Cumbres Observatory Global Telescope
HHH and NH acknowledge support from the NASA
Network Incorporated, the National Central University
Planetary Astronomy program (Grant NNX14AJ38G).
of Taiwan, the Space Telescope Science Institute, the
KJM and JK acknowledge support from the NASA
PlanetaryScienceDivisionoftheNASAScienceMission
Astrobiology Institute under Cooperative Agreement
Directorate(GrantNNX08AR22G),theNationalScience
NNA09DA77A issued through the Office of Space Sci-
Foundation(GrantAST-1238877), andtheUniversityof
ence. BN is supported by the Ministry of Science of
Maryland. We thank the PS1 Builders and operations
Serbia, Project 176011. This research utilized Palo-
staff for PS1’s construction and operation, and access to
mar Observatory’s Hale Telescope, the Las Cumbres
PS1 data.
Observatory Global Telescope Network’s Faulkes Tele-
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