arXiv subjects

Chadwick A. Trujillo

Publications and source records attributed to Chadwick A. Trujillo.

36 records · Page 2Linked to original sources

arXiv2021

Physical Characterization of Main-Belt Comet (248370) 2005 QN173

We report results from new and archival observations of the newly discovered active asteroid (248370) 2005 QN_137, which has been determined to be a likely main-belt comet based on a subsequent discovery that it is recurrently active near perihelion. From archival data analysis, we estimate g'-, r'-, i'-, and z'-band absolute magnitudes for the nucleus of H_g=16.62+/-0.13, H_r=16.12+/-0.10, H_i=16.05+/-0.11, and H_z=15.93+/-0.08, corresponding to nucleus colors of g'-r'=0.50+/-0.16, r'-i'=0.07+/-0.15, and i'-z'=0.12+/-0.14, an equivalent V-band absolute magnitude of H_V=16.32+/-0.08, and a nucleus radius of r_n=1.6+/-0.2 km (using a V-band albedo of p_V=0.054+/-0.012). Meanwhile, we find mean near-nucleus coma colors when 248370 was active of g'-r'=0.47+/-0.03, r'-i'=0.10+/-0.04, and i'-z'=0.05+/-0.05, and similar mean dust tail colors, suggesting that no significant gas coma is present. We find approximate ratios between the scattering cross-sections of near-nucleus dust (within 5000 km of the nucleus) and the nucleus of A_d/A_n=0.7+/-0.3 on 2016 July 22, and 1.8<A_d/A_n<2.9 in 2021 July and August. During the 2021 observation period, the coma declined in intrinsic brightness by ~0.35 mag (or ~25%) in 37 days, while the surface brightness of the dust tail remained effectively constant over the same period. Constraints derived from the sunward extent of the coma suggest that terminal velocities of ejected dust grains are extremely slow (~1 m/s for 1 micron particles), indicating that the observed dust emission may have been aided by rapid rotation of the nucleus lowering the effective escape velocity.

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arXiv2021

Outer Solar System Perihelion Gap Formation Through Interactions with a Hypothetical Distant Giant Planet

Among the outer solar system minor planet orbits there is an observed gap in perihelion between roughly 50 and 65 au at eccentricities $e\gtrsim0.65$. Through a suite of observational simulations, we show that the gap arises from two separate populations, the Extreme Trans-Neptunian Objects (ETNOs; perihelia $q\gtrsim40$ au and semimajor axes $a\gtrsim150$ au) and the Inner Oort Cloud objects (IOCs; $q\gtrsim65$ au and $a\gtrsim250$ au), and is very unlikely to result from a realistic single, continuous distribution of objects. We also explore the connection between the perihelion gap and a hypothetical distant giant planet, often referred to as Planet 9 or Planet X, using dynamical simulations. Some simulations containing Planet X produce the ETNOs, the IOCs, and the perihelion gap from a simple Kuiper-Belt-like initial particle distribution over the age of the solar system. The gap forms as particles scattered to high eccentricity by Neptune are captured into secular resonances with Planet X where they cross the gap and oscillate in perihelion and eccentricity over hundreds of kiloyears. Many of these objects reach a minimum perihelia in their oscillation cycle within the IOC region increasing the mean residence time of the IOC region by a factor of approximately five over the gap region. Our findings imply that, in the presence of a massive external perturber, objects within the perihelion gap will be discovered, but that they will be only $\sim20$% as numerous as the nearby IOC population ($65$ au $\lesssim q \lesssim 100$ au).

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arXiv2021

(6478) Gault: Physical characterization of an active main-belt asteroid

In December 2018, the main-belt asteroid (6478)~Gault was reported to display activity. Gault is an asteroid belonging to the Phocaea dynamical family and was not previously known to be active, nor was any other member of the Phocaea family. In this work we present the results of photometric and spectroscopic observations that commenced soon after the discovery of activity. We obtained observations over two apparitions to monitor its activity, rotation period, composition, and possible non-gravitational orbital evolution. We find that Gault has a rotation period of $P = 2.4929 \pm 0.0003$ hours with a lightcurve amplitude of $0.06$ magnitude. This short rotation period close to the spin barrier limit is consistent with Gault having a density no smaller than $ρ= 1.85$~g/cm$^3$ and its activity being triggered by the YORP spin-up mechanism. Analysis of the Gault phase curve over phase angles ranging from $0.4^{\circ}$ to $23.6^{\circ}$ provides an absolute magnitude of $H = 14.81 \pm 0.04$, $G1=0.25 \pm 0.07$, and $G2= 0.38 \pm 0.04$. Model fits to the phase curve find the surface regolith grain size constrained between 100-500 $\rmμ$m. Using relations between the phase curve and albedo we determine that the geometrical albedo of Gault is $p_{\rm v} = 0.26 \pm 0.05$ corresponding to an equivalent diameter of $D = 2.8^{+0.4}_{-0.2}$ km. Our spectroscopic observations are all consistent with an ordinary chondrite-like composition (S, or Q-type in the Bus-DeMeo taxonomic classification). A search through archival photographic plate surveys found previously unidentified detections of Gault dating back to 1957 and 1958. Only the latter had been digitized, which we measured to nearly double the observation arc of Gault. Finally, we did not find any signal of activity during the 2020 apparition or non-gravitational effects on its orbit.

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arXiv2021

The Reactivation of Main-Belt Comet 259P/Garradd (P/2008 R1)

We present observations of main-belt comet 259P/Garradd from four months prior to its 2017 perihelion passage to five months after perihelion using the Gemini North and South telescopes. The object was confirmed to be active during this period, placing it among seven MBCs confirmed to have recurrent activity. We find an average net pre-perihelion dust production rate for 259P in 2017 of dM/dt = 4.6+/-0.2 kg/s (assuming grain densities of rho = 2500 kg/m^3 and a mean effective particle size of a_d = 2 mm) and a best-fit start date of detectable activity of 2017 April 22+/-1, when the object was at a heliocentric distance of r_h = 1.96-/+0.03 au and a true anomaly of nu = 313.9+/-0.4 deg. We estimate the effective active fraction of 259P's surface area to be from f_act ~ 7x10^-3 to f_act ~ 6x10^-2 (corresponding to effective active areas of A_act ~ 8x10^3 m^2 to A_act ~ 7x10^4 m^2) at the start of its 2017 active period. A comparison of estimated total dust masses measured for 259P in 2008 and 2017 shows no evidence of changes in activity strength between the two active apparitions. The heliocentric distance of 259P's activity onset point is much smaller than those of other MBCs, suggesting that its ice reservoirs may be located at greater depths than on MBCs farther from the Sun, increasing the time needed for a solar irradiation-driven thermal wave to reach subsurface ice. We suggest that deeper ice on 259P could be a result of more rapid ice depletion caused by the object's closer proximity to the Sun compared to other MBCs.

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arXiv2020

Cometary Activity Discovered on a Distant Centaur: A Non-Aqueous Sublimation Mechanism

Centaurs are minor planets thought to have originated in the outer Solar System region known as the Kuiper Belt. Active Centaurs enigmatically display comet-like features (e.g., tails, comae) even though they orbit in the gas giant region where it is too cold for water to readily sublimate. Only 18 active Centaurs have been identified since 1927 and, consequently, the underlying activity mechanism(s) have remained largely unknown up to this point. Here we report the discovery of activity emanating from Centaur 2014 OG392, based on archival images we uncovered plus our own new observational evidence acquired with the Dark Energy Camera (Cerro Tololo Inter-American Observatory Blanco 4 m telescope), the Inamori-Magellan Areal Camera & Spectrograph (Las Campanas Observatory 6.5 m Walter Baade Telescope) and the Large Monolithic Imager (Lowell Observatory 4.3 m Discovery Channel Telescope). We detect a coma as far as 400,000 km from 2014 OG392, and our novel analysis of sublimation processes and dynamical lifetime suggest carbon dioxide and/or ammonia are the most likely candidates for causing activity on this and other active Centaurs. We find 2014 OG392 is optically red, but CO2 and NH3 are spectrally neutral in this wavelength regime so the reddening agent is as yet unidentified.

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arXiv2019

Six Years of Sustained Activity from Active Asteroid (6478) Gault

We present archival observations demonstrating that main belt asteroid (6478) Gault has an extensive history of comet-like activity. Outbursts have taken place during multiple epochs since 2013 and at distances extending as far as 2.68 au, nearly aphelion. (6478) Gault is a member of the predominately S-type (i.e., volatile-poor) Phocaea family; no other main belt object of this type has ever shown more than a single activity outburst. Furthermore, our data suggest that this is the longest duration of activity caused by a body spinning near the rotational breakup barrier. If activity is indeed unrelated to volatiles, as appears to be the case, (6478) Gault represents a new class of object, perpetually active due to rotational spin-up.

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arXiv2018

The 2016 Reactivations of Main-Belt Comets 238P/Read and 288P/(300163) 2006 VW139

We report observations of the reactivations of main-belt comets 238P/Read and 288P/(300163) 2006 VW139, that also track the evolution of each object's activity over several months in 2016 and 2017. We additionally identify and analyze archival SDSS data showing 288P to be active in 2000, meaning that both 238P and 288P have now each been confirmed to be active near perihelion on three separate occasions. From data obtained of 288P from 2012-2015 when it appeared inactive, we find best-fit R-band H,G phase function parameters of H_R=16.80+/-0.12 mag and G_R=0.18+/-0.11, corresponding to effective component radii of r_c=0.80+/-0.04 km, assuming a binary system with equally-sized components. Fitting linear functions to ejected dust masses inferred for 238P and 288P soon after their observed reactivations in 2016, we find an initial average net dust production rate of 0.7+/-0.3 kg/s and a best-fit start date of 2016 March 11 (when the object was at a true anomaly of -63 deg) for 238P, and an initial average net dust production rate of 5.6+/-0.7 kg/s and a best-fit start date of 2016 August 5 (when the object was at a true anomaly of -27 deg) for 288P. Applying similar analyses to archival data, we find similar start points for previous active episodes for both objects, suggesting that minimal mantle growth or ice recession occurred between the active episodes in question. Some changes in dust production rates between active episodes are detected, however. More detailed dust modeling is suggested to further clarify the process of activity evolution in main-belt comets.

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arXiv2018

SAFARI: Searching Asteroids For Activity Revealing Indicators

Active asteroids behave dynamically like asteroids but display comet-like comae. These objects are poorly understood, with only about 30 identified to date. We have conducted one of the deepest systematic searches for asteroid activity by making use of deep images from the Dark Energy Camera (DECam) ideally suited to the task. We looked for activity indicators amongst 11,703 unique asteroids extracted from 35,640 images. We detected three previously-identified active asteroids ((62412), (1) Ceres and (779) Nina), though only (62412) showed signs of activity. Our activity occurrence rate of 1 in 11,703 is consistent with the prevailing 1 in 10,000 activity occurrence rate estimate. Our proof of concept demonstrates 1) our novel informatics approach can locate active asteroids and 2) DECam data are well-suited to the search for active asteroids.

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arXiv2018

The Reactivation and Nucleus Characterization of Main-Belt Comet 358P/PANSTARRS (P/2012 T1)

We present observations of main-belt comet 358P/PANSTARRS (P/2012 T1) obtained using the Gemini South telescope from 2017 July to 2017 December, as the object approached perihelion for the first time since its discovery. We find best-fit IAU phase function parameters of H_R=19.5+/-0.2 mag and G_R=-0.22+/-0.13 for the nucleus, corresponding to an effective radius of r_N=0.32+/-0.03 km (assuming an albedo of p_R=0.05). The object appears significantly brighter (by >1 mag) than expected starting in 2017 November, while a faint dust tail oriented approximately in the antisolar direction is also observed on 2017 December 18. We conclude that 358P has become active again for the first time since its previously observed active period in 2012-2013. These observations make 358P the seventh main-belt comet candidate confirmed to exhibit recurrent activity near perihelion with intervening inactivity away from perihelion, strongly indicating that its activity is sublimation-driven. Fitting a linear function to the ejected dust masses inferred for 358P in 2017 when it is apparently active, we find an average net dust production rate of 2.0+/-0.6 kg/s (assuming a mean effective particle radius of 1 mm) and an estimated activity start date of 2017 November 8+/-4 when the object was at a true anomaly of 316+/-1 deg and a heliocentric distance of R=2.54 AU. Insufficient data is currently available to ascertain whether activity strength has changed between the object's 2012-2013 and 2017 active periods. Further observations are therefore highly encouraged during the object's upcoming observing window (2018 August through 2019 May).

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arXiv2014

Search for the Return of Activity in Active Asteroid 176P/LINEAR

We present the results of a search for the reactivation of active asteroid 176P/LINEAR during its 2011 perihelion passage using deep optical observations obtained before, during, and after that perihelion passage. Deep composite images of 176P constructed from data obtained between June 2011 and December 2011 show no visible signs of activity, while photometric measurements of the object during this period also show no significant brightness enhancements similar to that observed for 176P between November 2005 and December 2005 when it was previously observed to be active. An azimuthal search for dust emission likewise reveals no evidence for directed emission (i.e., a tail, as was previously observed for 176P), while a one-dimensional surface brightness profile analysis shows no indication of a spherically symmetric coma at any time in 2011. We conclude that 176P did not in fact exhibit activity in 2011, at least not on the level on which it exhibited activity in 2005, and suggest that this could be due to the devolatization or mantling of the active site responsible for its activity in 2005.

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arXiv2012

Discovery of Main-Belt Comet P/2006 VW139 by Pan-STARRS1

Main belt asteroid (300163) 2006 VW139 (later designated P/2006 VW139) was discovered to exhibit comet-like activity by the Pan-STARRS1 survey telescope using automated point-spread-function analyses performed by PS1's Moving Object Processing System. Deep follow-up observations show both a short (\sim 10") antisolar dust tail and a longer (\sim 60") dust trail aligned with the object's orbit plane, similar to the morphology observed for another main-belt comet, P/2010 R2 (La Sagra), and other well-established comets, implying the action of a long-lived, sublimation-driven emission event. Photometry showing the brightness of the near-nucleus coma remaining constant over \sim 30 days provides further evidence for this object's cometary nature, suggesting it is in fact a main-belt comet, and not a disrupted asteroid. A spectroscopic search for CN emission was unsuccessful, though we find an upper limit CN production rate of Q_CN < 1.3x10^24 mol/s, from which we infer a water production rate of Q_H2O < 10^26 mol/s. We also find an approximately linear optical spectral slope of 7.2%/1000A, similar to other cometary dust comae. Numerical simulations indicate that P/2006 VW139 is dynamically stable for > 100 Myr, while a search for a potential asteroid family around the object reveals a cluster of 24 asteroids within a cutoff distance of 68 m/s. At 70 m/s, this cluster merges with the Themis family, suggesting that it could be similar to the Beagle family to which another main-belt comet, 133P/Elst-Pizarro, belongs.

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arXiv2011

A Photometric System for Detection of Water and Methane Ices on Kuiper Belt Objects

We present a new near-infrared photometric system for detection of water ice and methane ice in the solar system. The system consists of two medium-band filters in the K-band region of the near-infrared, which are sensitive to water ice and methane ice, plus continuum observations in the J-band and Y-band. The primary purpose of this system is to distinguish between three basic types of Kuiper Belt Objects (KBOs) --- those rich in water ice, those rich in methane ice, and those with little absorbance. In this work, we present proof-of-concept observations of 51 KBOs using our filter system, 21 of which have never been observed in the near-IR spectroscopically. We show that our custom photometric system is consistent with previous spectroscopic observations while reducing telescope observing time by a factor of 3. We use our filters to identify Haumea collisional family members, which are thought to be collisional remnants of a much larger body and are characterized by large fractions of water ice on their surfaces. We add 2009 YE7 to the Haumea collisional family based on our water ice band observations(J-H2O = -1.03 +/- 0.27) which indicate a high amount of water ice absorption, our calculated proper orbital elements, and the neutral optical colors we measured, V-R = 0.38 +/- 0.04, which are all consistent with the rest of the Haumea family. We identify several objects dynamically similar to Haumea as being distinct from the Haumea family as they do not have water ice on their surfaces. In addition, we find that only the largest KBOs have methane ice, and we find that Haumea itself has significantly less water ice absorption than the smaller Haumea family members. We find no evidence for other families in the Kuiper Belt.

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arXiv2010

The Size Distribution of the Neptune Trojans and the Missing Intermediate Sized Planetesimals

We present an ultra-deep survey for Neptune Trojans using the Subaru 8.2-m and Magellan 6.5-m telescopes. The survey reached a 50% detection efficiency in the R-band at 25.7 magnitudes and covered 49 square degrees of sky. This depth corresponds to Neptune Trojans that are about 16 km in radius (assuming an albedo of 0.05). A paucity of smaller Neptune Trojans (radii < 45 km) compared to larger ones was found. The brightest Neptune Trojans appear to follow a steep power-law slope (q = 5+-1) similar to the brightest objects in the other known stable reservoirs such as the Kuiper Belt, Jupiter Trojans and main belt asteroids. We find a roll-over for the Neptune Trojans that occurs around a radii of r=45+-10 km (23.5+-0.3 mags), which is also very similar to the other stable reservoirs. All the observed stable regions in the the solar system show evidence for Missing Intermediate Sized Planetesimals (MISPs). This indicates a primordial and not collisional origin, which suggests planetesimal formation proceeded directly from small to large objects. The scarcity of intermediate and smaller sized Neptune Trojans may limit them as being a strong source for the short period comets.

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arXiv2009

A Survey for Satellites of Venus

We present a systematic survey for satellites of Venus using the Baade-Magellan 6.5 meter telescope and IMACS wide-field CCD imager at Las Campanas observatory in Chile. In the outer portions of the Hill sphere the search was sensitive to a limiting red magnitude of about 20.4, which corresponds to satellites with radii of a few hundred meters when assuming an albedo of 0.1. In the very inner portions of the Hill sphere scattered light from Venus limited the detection to satellites of about a kilometer or larger. Although several main belt asteroids were found, no satellites (moons) of Venus were detected.

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arXiv2005

Near Infrared Surface Properties of the Two Intrinsically Brightest Minor Planets (90377) Sedna and (90482) Orcus

We present low resolution K band spectra taken at the Gemini 8 meter telescope of (90377) Sedna and (90482) Orcus (provisional designations 2003 VB12 and 2004 DW, respectively), currently the two minor planets with the greatest absolute magnitudes (i.e. the two most reflective minor planets). We place crude limits on the surface composition of these two bodies using a Hapke model for a wide variety of assumed albedos. The unusual minor planet (90377) Sedna was discovered on November 14, 2003 UT at roughly 90 AU with 1.6 times the heliocentric distance and perihelion distance of any other bound minor planet. It is the first solar system object discovered between the Kuiper Belt and the Oort Cloud, and may represent a transition population between the two. The reflectance spectrum of (90377) Sedna appears largely featureless at the current signal-to-noise ratio, suggesting a surface likely to be highly processed by cosmic rays. For large grain models (100 micron to 1 cm) we find that (90377) Sedna must have less than 70% surface fraction of water ice and less than 60% surface fraction of methane ice to 3 sigma confidence. Minor planet (90482) Orcus shows strong water ice absorption corresponding to less than 50% surface fraction for grain models 25 micron and larger. Orcus cannot have more than 30% of its surface covered by large (100 mm to 1 cm) methane grains to 3 sigma confidence.

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arXiv2002

A Correlation Between Inclination and Color in the Classical Kuiper Belt

We have measured broadband optical BVR photometry of 24 Classical and Scattered Kuiper belt objects (KBOs), approximately doubling the published sample of colors for these classes of objects. We find a statistically significant correlation between object color and inclination in the Classical Kuiper belt using our data. The color and inclination correlation increases in significance after the inclusion of additional data points culled from all published works. Apparently, this color and inclination correlation has not been more widely reported because the Plutinos show no such correlation, and thus have been a major contaminant in previous samples. The color and inclination correlation excludes simple origins of color diversity, such as the presence of a coloring agent without regard to dynamical effects. Unfortunately, our current knowledge of the Kuiper belt precludes us from understanding whether the color and inclination trend is due to environmental factors, such as collisional resurfacing, or primordial population effects. A perihelion and color correlation is also evident, although this appears to be a spurious correlation induced by sampling bias, as perihelion and inclination are correlated in the observed sample of KBOs.

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arXiv2001

Large Bodies in the Kuiper Belt

We present a survey for bright Kuiper Belt Objects (KBOs) and Centaurs, conducted at the Kitt Peak National Observatory (KPNO) 0.9 m telescope with the KPNO 8k Mosaic CCD. The survey imaged 164 sq deg near opposition to a limiting red magnitude of 21.1. Three bright KBOs and one Centaur were found, the brightest KBO having red magnitude 19.7, about 700 km in diameter assuming a dark Centaur-like 4% albedo. We estimate the power-law differential size distribution of the Classical KBOs to have index q = 4.2 (+0.4)(-0.3), with the total number of Classical KBOs with diameters larger than 100 km equal to 4.7 (+1.6)(-1.0) x 10^4. Additionally, we find that if there is a maximum object size in the Kuiper Belt, it must be larger than 1000 km in diameter. By extending our model to larger size bodies, we estimate that 30 (+16)(-12) Charon-sized and 3.2 (+2.8)(-1.7) Pluto-sized Classical KBOs remain undiscovered.

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arXiv2001

Properties of the Trans-Neptunian Belt: Statistics From the CFHT Survey

We present the results of a wide-field survey designed to measure the size, inclination, and radial distributions of Kuiper Belt Objects (KBOs). The survey found 86 KBOs in 73 square degrees observed to limiting red magnitude 23.7 using the Canada-France-Hawaii Telescope and the 12k x 8k CCD Mosaic camera. For the first time, both ecliptic and off-ecliptic fields were examined to more accurately constrain the inclination distribution of the KBOs. The survey data were processed using an automatic moving object detection algorithm, allowing a careful characterization of the biases involved. In this work, we quantify fundamental parameters of the Classical KBOs (CKBOs), the most numerous objects found in our sample, using the new data and a maximum likelihood simulation. Deriving results from our best-fit model, we find that the size distribution follows a differential power law with exponent q = 4.0 (+0.6)(-0.5) (1 sigma, or 68.27% confidence). In addition, the CKBOs inhabit a very thick disk consistent with a Gaussian distribution of inclinations with a Half-Width of i(1/2) = 20 (+6)(-4) deg (1 sigma). We estimate that there are N = 3.8 (+2.0)(-1.5) x 10^4 (1 sigma) CKBOs larger than 100 km in diameter. We also find compelling evidence for an outer edge to the CKBOs at heliocentric distance R = 50 AU.

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