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Earlier reviews of trans-Neptunian light curves reported mean rotation periods of P = 7-8 h (Duffard et al., 2009), and it was also found that the binary trans-Neptunian population rotates slower (Thirouin & Sheppard, 2014), and objects in the cold classical population have larger variability and rotate slower than the non-cold classical TNOs (Benecchi et al., 2013,Thirouin & Sheppard, 2019). While ground-based observations have obvious limitations in detecting long-period light curves the K2 mission of the Kepler Space Telescope allowed long (up to ~80 days), uninterrupted observations of many Solar system objects, including main belt asteroids, Hildas, Jovian trojans, and also the irregular satellites of giant planets. Light curves were also published for a few, selected trans-Neptunian objects based on K2 observations (see Kiss et al., 2020, for a summary). A common outcome of the studies of larger samples, across all dynamical classes, was the identification of an increased number of targets with long rotation periods compared to previous ground-based studies. A similar trend is observed among the data of nearly 10 000 main belt asteroids obtained by the TESS Space Telescope (Pál et al., 2020), and asteroids with long rotation periods were identified in other surveys like the Asteroid Terrestrial-impact Last Alert System (ATLAS), the Zwicky Transient Facility (Erasmus et al., 2021) and the All-Sky Automated Survey for Supernovae (Hanus et al., 2021). We have collected the K2 trans-Neptunian object observations between Campaigns C03 (November 2014 -- February 2015) to C19 (August -- September, 2018), which includes 67 targets. Due to the faintness of our targets the detectability rate of a light curve period is ~57 %, notably lower than in the case of other small body populations, like Hildas or Jovian trojans. We managed to obtain light curve periods with an acceptable confidence for 36 targets; the majority of these cases are new identifications. We were able to give light curve amplitude upper limits for the other 31 targets. Several of the newly detected light curve periods are longer than ~24 h, in many cases close to ~100 h, i.e., slow rotators. There is a very significant difference between the rotation rates of the LCDB and K2 TNO samples (Figs. 1 and 2). The mean LCD spin frequency is 2.71 c/d (8.8 h), while it is 0.87 c/d (27.6 h) in the K2 sample which is more similar to the K2 Hilda and Jovian Trojan spin frequency distrbutions. Thirouin & Sheppard (2019) obtained 9.48±1.53 h and 8.45±0.58 h mean rotation periods for the cold classical and the non-cold classical TNOs. Our mean values for the same dynamical groups (but using different targets) are notably longer: 1.21+1.58-0.63 c/d (19.83 h) and 0.83+1.81-0.23 c/d (P=28.91 h), respectively. The K2 mean frequency is higher than that of the K2 Jovian Trojans and Hildas, but we could not detect the very long period targets that were observed in these other K2 samples. Figure 1: frequency distribution of asteroids. The cyan, magenta, green and blue colours represent the TNOs in the LCDB and Jovian trojans, Hildas and TNOs from K2, respectively. Figure 2: Frequency as a function of absolute magnitude. Big circles with error bars mark the median values standard deviations for the different samples. The horizontal dashed lines mark the spin frequencies of fast, slow, and very slow rotators (Pravec et al., 2002). While there are only three objects with D>500 km in our sample, there are a number of objects -- both with and without detected light curve periods -- that fall in the 300≤D≤500 km transitional zone where asphericity -- hence light curve amplitude -- is expected to drop assuming a single rotating body, assuming main belt composition. Main belt asteroids are already almost extinct in this size range, and so are Centaurs -- for these bodies irregular shapes are expected in most cases. While the general trend is that larger objects have smaller light curve amplitudes among TNOs -- a trend followed both by our sample and the LCDB TNOs -- there are a considerable number of TNOs with high asphericity in the 300≤D≤500 km size range. This contradiction could be resolved if TNOs had higher-than-expected compressive strength and become spherical for sizes larger than their main belt counterparts, and remain 'irregular' in the 300≤D≤500 km range. However, their general low density and high porosity point against this scenario. A notable fraction of contact or semi-contact binary systems in which the members themselves are in hydrostatical equlibrium could produce a population of high-amplitude light curves in this size range (Lacerda et al., 2006, 2014). As some authors pointed out, contact binaries may be very frequent, especially in the plutino population (Thirouin & Sheppard, 2018,2019). The long term stability of such systems against their tidal evolution, however, should be investigated to answer the reliability of this assumption. Finally, spherical (rotationally flattened) bodies with large albedo variegations could also explain the observed amplitudes. While the general expectation in most TNO light curve studies was a double peak light curve, in our sample most light curves were found to be single-peak, after comparing the single-peak and double-peak solutions. Fgiure 3: Light curve amplitude versus the estimated size of the targets in our sample. The region between the vertical dashed lines mark the irregular-to-spherical transition size range in the main belt. Blue and red symbols mark the K2 targets and K2 upper limits, small grey symbols correspond to main belt asteroids. Large gray symbols represent the theoretical maximum light curve amplitudes the of large main belt objects if it was solely caused by the elongated shape of a body with homogeneous albedo.

Extreme debris discs are characterized by unusually strong mid-infrared excess emission, which often proves to be variable. The warm dust in these discs is of transient nature and is likely related to a recent giant collision occurring close to the star in the terrestrial region. Here we present the results of a 877 days long, gap-free photometric monitoring performed by the Spitzer Space Telescope of the recently discovered extreme debris disc around TYC 4209-1322-1. By combining these observations with other time-domain optical and mid-infrared data, we explore the disc variability of the last four decades with particular emphasis on the last 12 yr. During the latter interval the disc showed substantial changes, the most significant was the brightening and subsequent fading between 2014 and 2018 as outlined in WISE data. The Spitzer light curves outline the fading phase and a subsequent new brightening of the disc after 2018, revealing an additional flux modulation with a period of ~39 days on top of the long-term trend. We found that all these variations can be interpreted as the outcome of a giant collision that happened at an orbital radius of ~0.3 au sometime in 2014. Our analysis implies that a collision on a similar scale could have taken place around 2010, too. The fact that the disc was already peculiarly dust rich 40 yr ago, as implied by IRAS data, suggests that these dust production events belong to a chain of large impacts triggered by an earlier even more catastrophic collision., Comment: 18 pages, 12 figures, published in MNRAS

Various properties of Jovian trojan asteroids such as composition, rotation periods, and photometric amplitudes, or the rate of binarity in the population can provide information and constraints on the evolution of the group and of the Solar System itself. Here we present new photometric properties of 45 Jovian trojans from the K2 mission of the Kepler space telescope, and present phase-folded light curves for 44 targets, including (11351) Leucus, one of the targets of the Lucy mission. We extend our sample to 101 asteroids with previous K2 Trojan measurements, then compare their combined amplitude- and frequency distributions to other ground-based and space data. We show that there is a dichotomy in the periods of Trojans with a separation at $\sim 100$ hr. We find that 25% of the sample are slow rotators (P$\geq$30 hr), which excess can be attributed to binary objects. We also show that 32 systems can be classified as potential detached binary systems. Finally, we calculate density and rotation constraints for the asteroids. Both the spin barrier and fits to strengthless ellipsoid models indicate low densities and thus compositions similar to cometary and TNO populations throughout the sample. This supports the scenario of outer Solar System origin for Jovian trojans., Comment: 25 pages, 19 figures, accepted for publication in ApJS

We present our photometric and spectroscopic observations on the peculiar transient AT2018cow. The multi-band photometry covers from peak to $\sim$70 days and the spectroscopy ranges from 5 to $\sim$50 days. The rapid rise ($t_{\mathrm{r}}$$\lesssim$2.9 days), high luminosity ($M_{V,\mathrm{peak}}\sim-$20.8 mag) and fast decline after peak make AT2018cow stand out of any other optical transients. While we find that its light curves show high resemblance to those of type Ibn supernovae. Moreover, the spectral energy distribution remains high temperature of $\sim$14,000 K after $\sim$15 days since discovery. The spectra are featureless in the first 10 days, while some broad emission lines due to H, He, C and O emerge later, with velocity declining from $\sim$14,000 km s$^{-1}$ to $\sim$3000 km s$^{-1}$ at the end of our observations. Narrow and weak He I emission lines emerge in the spectra at $t>$20 days since discovery. These emission lines are reminiscent of the features seen in interacting supernovae like type Ibn and IIn subclasses. We fit the bolometric light curves with a model of circumstellar interaction (CSI) and radioactive decay (RD) of \Ni and find a good fit with ejecta mass $M_{\mathrm{ej}}\sim$3.16 M$_{\odot}$, circumstellar material mass $M_{\mathrm{CSM}}\sim$0.04 M$_{\odot}$, and ejected \Ni mass $M_{^{56}\mathrm{Ni}}\sim$0.23 M$_{\odot}$. The CSM shell might be formed in an eruptive mass ejection of the progenitor star. Furthermore, host environment of AT2018cow implies connection of AT2018cow with massive stars. Combining observational properties and the light curve fitting results, we conclude that AT2018cow might be a peculiar interacting supernova originated from a massive star., Accepted for publication in ApJ

The Kepler space telescope collected continuous photometry of several Jovian Trojan asteroids in the Solar System during its K2 mission. We extracted light curves 43 new targets from K2 Campaigns 11-19 using our own photometric package developed for moving objects in the Kepler images which, together with the 56 asteroids from Campaign 6, brings the total sample size up to 99 asteroids. We calculated rotational frequencies and amplitudes for each object and their distributions, and we derived statistics on the binary fraction and possible compositions of these asteroids. We find and excess of very slow rotators (>100 hours) and a possible dichotomy in the period distribution. When compared to other space-based photometric results, we find that the distribution of Hilda rotation periods detected with K2 shows the same possible dichotomy, but the large sample of main-belt asteroids measured with the TESS space telescope does not. The excess of slow rotators corroborates with an outward origin, with synchronized binaries migrating inwareds from the Kuiper belt, and some of them dissociating along the way, creating very slowly rotating single objects. Both a low critical density limit and comparison with strengthless ellipsoid models indicate that none of the objects exceed the density of icy objects, further strengthening an inward migration scenario. We estimate a binary fraction of at least 21% based on the number of high-amplitude, long-period objects, in agreement with earlier results. Large photometric amplitudes are prevalent over the entire period range, and we cannot fit all objects with a strengtless model in rotational equilibrium. We highlight a few individual objects as well. (99306) 2001 SC101 is the only asteroid observed in to Campaigns, from different sides of the Sun, and we find clear differences in the light curve shape. (13062) Podarkes is the principal body of a proposed small family: we detect a rotation period of 245 hr which puts it into the very slow rotator group. Finally, we present the first continuous light curve of (11351) Leucus, one of the targets of the Lucy spacecraft, and confirm that it also rotates exceedingly slowly, with a period of 445 hr.

This is an open access article distributed under the terms of the Creative Commons CC-BY license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited., Here we present the results of visible range light curve observations of ten Centaurs using the Kepler Space Telescope in the framework of the K2 mission. Well defined periodic light curves are obtained in six cases allowing us to derive rotational periods, a notable increase in the number of Centaurs with known rotational properties. The low amplitude light curves of (471931) 2013 PH44 and (250112) 2002 KY14 can be explained either by albedo variegations, binarity or elongated shape. (353222) 2009 YD7 and (514312) 2016 AE193 could be rotating elongated objects, while 2017 CX33 and 2012 VU85 are the most promising binary candidates due to their slow rotations and higher light curve amplitudes. (463368) 2012 VU85 has the longest rotation period, P = 56.2 h observed among Centaurs. The P > 20 h rotation periods obtained for the two potential binaries underlines the importance of long, uninterrupted time series photometry of solar system targets that can suitably be performed only from spacecraft, like the Kepler in the K2 mission, and the currently running TESS mission. © 2020 The Authors, The research leading to these results has received funding from the European Union 's Horizon 2020 Research and Innovation Programme, under Grant Agreement No. 687378 ; from the K-125015 , PD-116175 , PD-128360 , and GINOP-2.3.2-15-2016-00003 grants of the National Research Development and Innovation Office (NKFIH, Hungary); and from the LP2012-31 and LP2018-7/2019 Lendület grants of the Hungarian Academy of Sciences . L. M. was supported by the Premium Postdoctoral Research Program of the Hungarian Academy of Sciences . The research leading to these results have been supported by the ÚNKP-19-2 New National Excellence Program of the Ministry of Human Capacities , Hungary. Funding for the Kepler and K2 missions are provided by the NASA Science Mission Directorate. The data presented in this paper were obtained from the Mikulski Archive for Space Telescopes (MAST). STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555 . Support for MAST for non-HST data is provided by the NASA Office of Space Science via grant NNX09AF08G and by other grants and contracts. The authors thank the hospitality of the Veszprém Regional Centre of the Hungarian Academy of Sciences (MTA VEAB), where part of this project was carried out. We also indebted to S. Benecchi and an anonymous reviewer for their comments which have helped to improve the paper.

Compared with previous space-borne surveys, the Transiting Exoplanet Survey Satellite (TESS) provides a unique and new approach to observe Solar System objects. While its primary mission avoids the vicinity of the ecliptic plane by approximately six degrees, the scale height of the Solar System debris disk is large enough to place various small body populations in the field-of-view. In this paper we present the first data release of photometric analysis of TESS observations of small Solar System Bodies, focusing on the bright end of the observed main-belt asteroid and Jovian Trojan populations. This data release, named TSSYS-DR1, contains 9912 light curves obtained and extracted in a homogeneous manner, and triples the number of bodies with unambiguous fundamental rotation characteristics, namely where accurate periods and amplitudes are both reported. Our catalogue clearly shows that the number of bodies with long rotation periods are definitely underestimated by all previous ground-based surveys, by at least an order of magnitude., ApJS, in press. Data are available from https://archive.konkoly.hu/pub/tssys/dr1/ (6.36G, in total)

We present a photometric detection of the first brightness dips of the unique variable star KIC 8462852 since the end of the Kepler space mission in 2013 May. Our regular photometric surveillance started in October 2015, and a sequence of dipping began in 2017 May continuing on through the end of 2017, when the star was no longer visible from Earth. We distinguish four main 1-2.5% dips, named "Elsie," "Celeste," "Skara Brae," and "Angkor", which persist on timescales from several days to weeks. Our main results so far are: (i) there are no apparent changes of the stellar spectrum or polarization during the dips; (ii) the multiband photometry of the dips shows differential reddening favoring non-grey extinction. Therefore, our data are inconsistent with dip models that invoke optically thick material, but rather they are in-line with predictions for an occulter consisting primarily of ordinary dust, where much of the material must be optically thin with a size scale <, 19 pages, 8 figures, accepted for publication in ApJL

The nearby SN 2017eaw is a Type II-P (``plateau') supernova showing early-time, moderate CSM interaction. We present a comprehensive study of this SN including the analysis of high-quality optical photometry and spectroscopy covering the very early epochs up to the nebular phase, as well as near-UV and near-infrared spectra, and early-time X-ray and radio data. The combined data of SNe 2017eaw and 2004et allow us to get an improved distance to the host galaxy, NGC 6946, as $D \sim 6.85$ $\pm 0.63$ Mpc; this fits in recent independent results on the distance of the host and disfavors the previously derived (30% shorter) distances based on SN 2004et. From modeling the nebular spectra and the quasi-bolometric light curve, we estimate the progenitor mass and some basic physical parameters for the explosion and the ejecta. Our results agree well with previous reports on a RSG progenitor star with a mass of $\sim15-16$ M$_\odot$. Our estimation on the pre-explosion mass-loss rate ($\dot{M} \sim3 \times 10^{-7} -$ $1\times 10^{-6} M_{\odot}$ yr$^{-1}$) agrees well with previous results based on the opacity of the dust shell enshrouding the progenitor, but it is orders of magnitude lower than previous estimates based on general light-curve modeling of Type II-P SNe. Combining late-time optical and mid-infrared data, a clear excess at 4.5 $\mu$m can be seen, supporting the previous statements on the (moderate) dust formation in the vicinity of SN 2017eaw., Comment: 34 pages, 19 figures, 7 tables; accepted for publication in ApJ

Wang, Qinan, et al., We present the 30 minutes cadence Kepler/K2 light curve of the Type Ia supernova (SN Ia) SN 2018agk, covering approximately one week before explosion, the full rise phase, and the decline until 40 days after peak. We additionally present ground-based observations in multiple bands within the same time range, including the 1 day cadence DECam observations within the first ~5 days after the first light. The Kepler early light curve is fully consistent with a single power-law rise, without evidence of any bump feature. We compare SN 2018agk with a sample of other SNe Ia without early excess flux from the literature. We find that SNe Ia without excess flux have slowly evolving early colors in a narrow range (g ¿ i ¿ ¿0.20 ± 0.20 mag) within the first ~10 days. On the other hand, among SNeIa detected with excess, SN2017cbv and SN2018oh tend to be bluer, while iPTF16abc¿s evolution is similar to normal SNe Ia without excess in g ¿ i. We further compare the Kepler light curve of SN 2018agk with companion-interaction models, and rule out the existence of a typical nondegenerate companion undergoing Roche lobe overflow at viewing angles smaller than 45°., The UCSC transient team is supported in part by NASA/K2 grants 80NSSC18K0303 and 80NSSC19K0113, the Gordon and Betty Moore Foundation, the Heising–Simons Foundation, and by a fellowship from the David and Lucile Packard Foundation to R. J. F. D. O. J. acknowledges support provided by NASA Hubble Fellowship grant HST-HF2-51462.001, which is awarded by the Space Telescope Science Institute, operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555.