11 research outputs found
Initial Characterization of Active Transitioning Centaur, P/2019 LD2 (ATLAS), Using Hubble, Spitzer, ZTF, Keck, Apache Point Observatory, and GROWTH Visible and Infrared Imaging and Spectroscopy
We present visible and mid-infrared imagery and photometry of temporary Jovian co-orbital comet P/2019 LD2 taken with Hubble Space Telescope/Wide Field Camera 3 (HST/WFC3), Spitzer Space Telescope/Infrared Array Camera (Spitzer/IRAC), and the GROWTH telescope network, visible spectroscopy from Keck/Low-Resolution Imaging Spectrometer (LRIS), and archival Zwicky Transient Facility observations taken between 2019 April and 2020 August. Our observations indicate that the nucleus of LD2 has a radius between 0.2 and 1.8 km assuming a 0.08 albedo and a coma dominated by âŒ100 ÎŒm-scale dust ejected at âŒ1 m sâ1 speeds with a âŒ1âČ jet pointing in the southwest direction. LD2 experienced a total dust mass loss of âŒ108 kg at a loss rate of âŒ6 kg sâ1 with AfÏ/cross section varying between âŒ85 cm/125 km2 and âŒ200 cm/310 km2 from 2019 April 9 to 2019 November 8. If the increase in AfÏ/cross section remained constant, it implies LD2's activity began âŒ2018 November when within 4.8 au of the Sun, implying the onset of H2O sublimation. We measure CO/CO2 gas production of âČ1027 mol sâ1/âČ1026 mol sâ1 from our 4.5 ÎŒm Spitzer observations; gâr = 0.59 ± 0.03, râi = 0.18 ± 0.05, and iâz = 0.01 ± 0.07 from GROWTH observations; and H2O gas production of âČ80 kg sâ1 scaling from our estimated C2 production of mol sâ1 from Keck/LRIS spectroscopy. We determine that the long-term orbit of LD2 is similar to Jupiter-family comets having close encounters with Jupiter within âŒ0.5 Hill radius in the last âŒ3 y and within 0.8 Hill radius in âŒ9 y. Additionally, 78.8% of our orbital clones are ejected from the solar system within 1 Ă 106 yr, having a dynamical half-life of 3.4 Ă 105 yr
The Remarkable Spin-down and Ultra-fast Outflows of the Highly-Pulsed Supersoft Source of Nova Hercules 2021
Nova Her 2021 (V1674 Her), which erupted on 2021 June 12, reached naked-eye brightness and has been detected from radio to -rays. An extremely fast optical decline of 2 magnitudes in 1.2 days and strong Ne lines imply a high-mass white dwarf. The optical pre-outburst detection of a 501.42s oscillation suggests a magnetic white dwarf. This is the first time that an oscillation of this magnitude has been detected in a classical nova prior to outburst. We report X-ray outburst observations from {\it Swift} and {\it Chandra} which uniquely show: (1) a very strong modulation of super-soft X-rays at a different period from reported optical periods; (2) strong pulse profile variations and the possible presence of period variations of the order of 0.1-0.3s; and (3) rich grating spectra that vary with modulation phase and show P Cygni-type emission lines with two dominant blue-shifted absorption components at and 9000 km s indicating expansion velocities up to 11000 km s. X-ray oscillations most likely arise from inhomogeneous photospheric emission related to the magnetic field. Period differences between reported pre- and post-outburst optical observations, if not due to other period drift mechanisms, suggest a large ejected mass for such a fast nova, in the range -. A difference between the period found in the {\it Chandra} data and a reported contemporaneous post-outburst optical period, as well as the presence of period drifts, could be due to weakly non-rigid photospheric rotation