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Lightcurve analysis of the asteroid 9021 Fagus observed at the Bulgarian National Astronomical Observatory Rozhen during two apparitions in 2013 and 2017 are presented. This asteroid was observed in 2013 accidentally in the field of view in which our long-term target asteroid 901 Brunsia was positioned. A search of the Asteroid Lightcurve Database (Warner et al. 2009) did not find any previously reported results for the rotation period of 9021 Fagus. Unfortunately two nights observations in 2013 showed that the rotation period could be only approximately assumed. The observations during two neighbouring nights in 2017 March 20 and 21 revealed the period of $5.065 pm 0.002$ h with amplitude of $0.73pm0.02$ mag. Obtained lightcurves in combination with other observational techniques, as well as with data gathered from future space mission will contribute to the enlargement of the database for rotational characteristics of the asteroids.
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Lightcurve of the asteroid 3634 Iwan observed at the Bulgarian National Astronomical Observatory Rozhen in 2017 is presented. The asteroid was observed only one night, on 22 March 2017 accidentally in the field of view in which our target for shape modeling asteroid 289 Nenetta was positioned. The Asteroid Lightcurve Database (LCDB; Warner et al. 2009) did not contain any previously reported results for 3634 Iwan. If we accept that the ligtcurve of the asteroid is typical with two maxima and minima, a single night observations covers the whole rotational cycle. The lightcurve plotted by MPO Canopus provides a best fit to synodic period of $4.72pm 0.06$ h with amplitude of $0.15pm 0.02$ mag. Our assessment is that for the uniqueness of the period solution we need longer observational span which will reveal the number of extrema of the lightcurve and confirm the quality code U=3.
We measure the rotation periods of 19 stars in the {it Kepler} transiting planetary systems, $P_{rm rot, astero}$ from asteroseismology and $P_{rm rot, phot}$ from photometric variation of their lightcurve. Two stars exhibit two clear peaks in the Lomb-Scargle periodogram, neither of which agrees with the seismic rotation period. Other four systems do not show any clear peak, whose stellar rotation period is impossible to estimate reliably from the photometric variation; their stellar equators may be significantly inclined with respect to the planetary orbital plane. For the remaining 13 systems, $P_{rm rot, astero}$ and $P_{rm rot, phot}$ agree within 30%. Interestingly, three out of the 13 systems are in the spin-orbit resonant state in which $P_{rm orb, b}/P_{rm rot, astero} approx 1$ with $P_{rm orb, b}$ being the orbital period of the inner-most planet of each system. The corresponding chance probability is ($0.2$-$4.7$) % based on the photometric rotation period data for 464 {it Kepler} transiting planetary systems. While further analysis of stars with reliable rotation periods is required to examine the statistical significance, the spin-orbit resonance between the star and planets, if confirmed, have important implications for the star-planet tidal interaction, in addition to the origin of the spin-orbit (mis-)alignment of transiting planetary systems.
The Palomar Transient Factory (PTF) is a synoptic survey designed to explore the transient and variable sky in a wide variety of cadences. We use PTF observations of fields that were observed multiple times (>=10) per night, for several nights, to find asteroids, construct their lightcurves and measure their rotation periods. Here we describe the pipeline we use to achieve these goals and present the results from the first four (overlapping) PTF fields analyzed as part of this program. These fields, which cover an area of 21 deg^2, were observed on four nights with a cadence of ~20 min. Our pipeline was able to detect 624 asteroids, of which 145 (~20%) were previously unknown. We present high quality rotation periods for 88 main-belt asteroids and possible period or lower limit on the period for an additional 85 asteroids. For the remaining 451 asteroids, we present lower limits on their photometric amplitudes. Three of the asteroids have lightcurves that are characteristic of binary asteroids. We estimate that implementing our search for all existing high-cadence PTF data will provide rotation periods for about 10,000 asteroids mainly in the magnitude range ~14 to ~20.
A new asteroid rotation period survey have been carried out by using the Palomar Transient Factory (PTF). Twelve consecutive PTF fields, which covered an area of 87 deg$^2$ in the ecliptic plane, were observed in $R$ band with a cadence of $sim$20 min during February 15--18, 2013. We detected 2500 known asteroids with a diameter range of 0.5 km $leq D leq$ 200 km. Of these, 313 objects had highly reliable rotation periods and exhibited the spin barrier at $sim2$ hours. In contrast to the flat spin rate distribution of the asteroids with 3 km $leq D leq$ 15 km shown by Pravec et al. (2008), our results deviated somewhat from a Maxwellian distribution and showed a decrease at the spin rate greater than 5 rev/day. One super-fast-rotator candidate and two possible binary asteroids were also found in this work.
We perform a search for dormant comets, asteroidal objects of cometary origin, in the near-Earth asteroid (NEA) population based on dynamical and physical considerations. Our study is based on albedos derived within the ExploreNEOs program and is extended by adding data from NEOWISE and the Akari asteroid catalog. We use a statistical approach to identify asteroids on orbits that resemble those of short-period near-Earth comets using the Tisserand parameter with respect to Jupiter, the aphelion distance, and the minimum orbital intersection distance with respect to Jupiter. From the sample of NEAs on comet-like orbits, we select those with a geometric albedo $p_V leq 0.064$ as dormant comet candidates, and find that only $sim$50% of NEAs on comet-like orbits also have comet-like albedos. We identify a total of 23 NEAs from our sample that are likely to be dormant short-period near-Earth comets and, based on a de-biasing procedure applied to the cryogenic NEOWISE survey, estimate both magnitude-limited and size-limited fractions of the NEA population that are dormant short-period comets. We find that 0.3-3.3% of the NEA population with $H leq 21$, and $9^{+2}_{-5}$% of the population with diameters $d geq 1$ km, are dormant short-period near-Earth comets.
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