Title: Exploring the nature of new main-belt comets with the 10.4m GTC telescope: (300163) 2006 VW139 Authors: J. Licandro, F. Moreno, J. de León, G. P. Tozzi, L. M. Lara, A. Cabrera-Lavers
We aim to study the dust ejected by main-belt comet (MBC) (300163) 2006 VW139 to obtain information on the ejection mechanism and the spectral properties of the object, to see if they are compatible with those of "normal" comets. Images in the g and r band and a low-resolution spectrum in the 0.35-0.9 micron region were obtained with the GTC telescope (La Palma, Spain). Images were analysed to produce a colour map and derive a lower limit of the absolute magnitude. A Monte Carlo (MC) scattering model was used to derive dust properties such as mass loss rates and ejection velocities as a function of time. The spectrum was compared to that of MBC 133P/Elst-Pizarro and used to search for CN emission. The spectrum of 2006 VW139 is typical of a C-class asteroid, with a spectral slope S=0.5±1.0%/1000A. It is similar to the spectrum of 133P and other MBCs. No CN emission is detected. A CN production rate upper limit of 3.76e23 1/s is derived. The MBC present a narrow almost linear tail that extends up to 40.000 km in the anti-solar direction and more than 80.000 km in the direction of the object's orbital plane. The colour of the tail is slightly redder than the Sun (S=3 to 6%/1000A). The MC dust tail model derived the mass loss rates and ejection velocity as a function of time, and the results show that the activity onset occurs shortly after perihelion, and lasts about 100 days; the total ejected mass is about 2e6 kg. The spectrum of VW139 suggests that it is not a "normal" comet. It is typical of the other observed MBCs. Even if no CN emission is detected, the more likely activation mechanism is water-ice sublimation. Like other well studied MBCs, VW139 is likely a primitive C-class asteroid that has a water-ice subsurface depth reservoir that has recently been exposed to sunlight or to temperatures that produce enough heat to sublime the ice.
Title: P/2006 VW139: A Main-Belt Comet Born in an Asteroid Collision? Authors: Bojan Novakovic, Henry H. Hsieh, Alberto Cellino
In this paper we apply different methods to examine the possibility that a small group of 24 asteroids dynamically linked to main-belt comet P/2006 VW139, recently discovered by the Pan-STARRS1 survey telescope, shares a common physical origin. By applying the Hierarchical Clustering and Backward Integration methods, we find strong evidence that 11 of these asteroids form a sub-group which likely originated in a recent collision event, and that this group includes P/2006 VW139. The objects not found to be part of the 11-member sub-group, which we designate as the P/2006 VW139 family, were either found to be dynamically unstable, or these are likely interlopers which should be expected due to the close proximity of the Themis family. As we demonstrated, statistical significance of P/2006 VW139 family is >99 per cent. We determine the age of the family to be 7.5 ±0.3 Myr, and estimate the diameter of the parent body to be about 11 km. Results show that the family is produced by an impact which can be best characterised as a transition from catastrophic to cratering regime. The dynamical environment of this family is studied as well, including the identification of the most influential mean motion and secular resonances in the region. Our findings make P/2006 VW139 now the second main-belt comet to be dynamically associated with a young asteroid family, a fact with important implications for the origin and activation mechanism of such objects.
Title: Discovery of Main-Belt Comet P/2006 VW139 by Pan-STARRS1 Authors: Henry H. Hsieh, Bin Yang, Nader Haghighipour, Heather M. Kaluna, Alan Fitzsimmons, Larry Denneau, Bojan Novakovic, Robert Jedicke, Richard J. Wainscoat, James D. Armstrong, Samuel R. Duddy, Stephen C. Lowry, Chadwick A. Trujillo, Marco Micheli, Jacqueline V. Keane, Laurie Urban, Timm Riesen, Karen J. Meech, Shinsuke Abe, Yu-Chi Cheng, Wen-Ping Chen, Mikael Granvik, Tommy Grav, Wing-Huen Ip, Daisuke Kinoshíta, Jan Kleyna, Pedro Lacerda, Tim Lister, Andrea Milani, David J. Tholen, Peter Veres, Carey M. Lisse, Michael S. Kelley, Yanga R. Fernandez, Bhuwan C. Bhatt, Devendra K. Sahu, Nick Kaiser, K. C. Chambers, Klaus W. Hodapp, Eugene A. Magnier, Paul A. Price, John L. Tonry
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 (~ 10") antisolar dust tail and a longer (~ 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 ~ 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.
The apparent main belt asteroid (300163) 2006 VW139 was found to have a cometary nature by H. Hsieh, R. Wainscoat & D. Larry (PS1 telescope).
The orbital elements of the comet indicate a perihelion passage on the 18th July, 2011, at a distance of ~2.4 AU from the Sun, and an orbital period of ~ 5.33 years.