TY - JOUR
T1 - The Reactivation and Nucleus Characterization of Main-belt Comet 358P/PANSTARRS (P/2012 T1)
AU - Hsieh, Henry H.
AU - Ishiguro, Masateru
AU - Knight, Matthew M.
AU - Micheli, Marco
AU - Moskovitz, Nicholas A.
AU - Sheppard, Scott S.
AU - Trujillo, Chadwick A.
N1 - Funding Information:
H.H.H., M.M.K., N.A.M., and S.S.S. acknowledge support from the NASA Solar System Observations program (Grant NNX16AD68G), while C.A.T. was funded in part through the State of Arizona Technology and Research Initiative Program. We are grateful to J. Chavez, J. Fuentes, G. Gimeno, M. Gomez, A. Lopez, L. Magill, S. Margheim, P. Prado, M. Schwamb, A. Shugart, and E. Wenderoth for assistance in obtaining observations, and to an anonymous reviewer who helped to improve this manuscript. This research made use of Astropy, a community-developed core Python package for astronomy, uncertainties (version 3.0.2), a python package for calculations with uncertainties by Eric O. Lebigot, and scientific software at www.comet-toolbox.com (Vincent 2014). This work also benefited from support by the International Space Science Institute in Bern, Switzerland, through the hosting and provision of financial support for an international team, which was led by C. Snodgrass and included H.H.H. and M.M.K., to discuss the science of MBCs. This work is based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the National Research Council (Canada), CONICYT (Chile), Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina), and Ministério da Ciência, Tecnologia e Inovação (Brazil). Facility: Gemini South (GMOS-S).
Publisher Copyright:
© 2018. The American Astronomical Society. All rights reserved.
PY - 2018/7
Y1 - 2018/7
N2 - We present observations of main-belt comet (MBC) 358P/PANSTARRS (P/2012 T1) obtained using the Gemini South telescope from 2017 July to 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 MBC 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 kg s-1 (assuming a mean effective particle radius of mm) and an estimated activity start date of 2017 November 8 ± 4 when the object was at a true anomaly of ν = 316° ± 1° 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).
AB - We present observations of main-belt comet (MBC) 358P/PANSTARRS (P/2012 T1) obtained using the Gemini South telescope from 2017 July to 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 MBC 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 kg s-1 (assuming a mean effective particle radius of mm) and an estimated activity start date of 2017 November 8 ± 4 when the object was at a true anomaly of ν = 316° ± 1° 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).
KW - comets: general
KW - comets: individual (358P/PANSTARRS)
KW - minor planets, asteroids: general
UR - http://www.scopus.com/inward/record.url?scp=85050003394&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85050003394&partnerID=8YFLogxK
U2 - 10.3847/1538-3881/aac81c
DO - 10.3847/1538-3881/aac81c
M3 - Article
AN - SCOPUS:85050003394
SN - 0004-6256
VL - 156
JO - Astronomical Journal
JF - Astronomical Journal
IS - 1
M1 - 39
ER -