Main belt asteroids (6070) Rheinland and (54827) 2001 NQ8 belong to a small population of couples of bodies that reside in very similar heliocentric orbits. Vokrouhlicky & Nesvorny promoted the term ...'asteroid pairs,' pointing out their common origin within the past tens to hundreds of kyr. Previous attempts to reconstruct the initial configuration of Rheinland and 2001 NQ8 at the time of their separation have led to the prediction that Rheinland's rotation should be retrograde. Here, we report extensive photometric observations of this asteroid and use the light curve inversion technique to directly determine its rotation state and shape. We confirm the retrograde sense of rotation of Rheinland, with obliquity value constrained to be >=140?. The ecliptic longitude of the pole position is not well constrained as yet. The asymmetric behavior of Rheinland's light curve reflects a sharp, near-planar edge in our convex shape representation of this asteroid. Our calibrated observations in the red filter also allow us to determine HR = 13.68 ? 0.05 and G = 0.31 ? 0.05 values of the H-G system. With the characteristic color index V -- R = 0.49 ? 0.05 for S-type asteroids, we thus obtain H = 14.17 ? 0.07 for the absolute magnitude of (6070) Rheinland. This is a significantly larger value than previously obtained from analysis of astrometric survey observations. We next use the obliquity constraint for Rheinland to eliminate some degree of uncertainty in the past propagation of its orbit. This is because the sign of the past secular change of its semimajor axis due to the Yarkovsky effect is now constrained. The determination of the rotation state of the secondary component, asteroid (54827) 2001 NQ8, is the key element in further constraining the age of the pair and its formation process.
Photometric observations spanning the UV to the near IR during the nine most recent eruptions (2014-2022) of the extragalactic nova M31N 2008-12a are presented and analyzed in order to explore ...whether the lightcurve properties for a given eruption, specifically the peak magnitudes and fade rates, are correlated with the time interval since the previous eruption. No significant correlation between the pre-eruption interval and the rate of decline was found, however it appears that the brightness at the peak of an outburst may be positively correlated with the time interval since the previous eruption.
We report the discovery of a previously unknown eruption of the recurrent nova M31N 2017-01e that took place on 11 January 2012. The earlier eruption was detected by Pan-STARRS and occurred 1847 days ...(5.06 yr) prior to the eruption on 31 January 2017 (M31N 2017-01e). The nova has now been seen to have had a total of four recorded eruptions (M31N 2012-01c, 2017-01e, 2019-09d, and 2022-03d) with a mean time between outbursts of just \(929.5\pm6.8\) days (\(2.545\pm0.019\) yr), the second shortest recurrence time known for any nova. We also show that there is a blue variable source (\(\langle V \rangle = 20.56\pm0.17\), \(B-V\simeq0.045\)), apparently coincident with the position of the nova, that exhibits a 14.3 d periodicity. Possible models of the system are proposed, but none are entirely satisfactory.
It has long been claimed that novae reaching the highest luminosity at the peak of their eruptions appear to fade the fastest from maximum light. The relationship between peak brightness and fade ...rate is known as the Maximum-Magnitude, Rate-of-Decline (MMRD) relation. Lightcurve parameters for the most recent sample of M31 recurrent novae are presented and used to buttress the case that the observed MMRD relation can be explained as a consequence of observational selection effects coupled with expectations from standard nova models.
The results of a two decade long \(R\)-band photometric survey of novae in M31 are presented. From these data, \(R\)-band light curves have been determined for 180 novae with data sufficient for ...estimating peak brightness and subsequent rate of decline. The data show a weak correlation of peak brightness with fade rate consistent with the well-known Maximum Magnitude versus Rate of Decline (MMRD) relation. As generally appreciated for Galactic novae, the large scatter in the MMRD relation precludes its use in determining distances to individual novae. The novae at maximum light are distributed with standard deviation \(\sigma=0.89\) mag about a mean \(R\)-band absolute magnitude given by \(\langle M_R \rangle=-7.57\pm0.07\). The overall M31 luminosity distribution is in excellent agreement with that found for Galactic novae suggesting that the nova populations in M31 and the Galaxy are quite similar. The notion that all novae can be characterized by a standard luminosity 15 d after maximum light (\(M_{15}\)) is also explored. Surprisingly, the distribution of \(M_{15}\) values is characterized by a standard deviation only slightly smaller than that for novae at maximum light and thus offers little promise for precise extragalactic distance determinations. A dozen faint and fast novae that are likely to be previously unidentified recurrent novae have been identified from their position in the MMRD plot and in the \(M_{15}\) distribution.
We observed the predicted outburst of the Alpha Monocerotid (AMO) meteor shower on 2019 November 22 with our modernized video and photographic cameras. Due to the short duration and moderate ...intensity of the outburst, atmospheric trajectories and radiants were obtained for only ten meteors, seven of which included velocities, magnitudes, and orbits. In addition, one incomplete video spectrum was captured. The radiants and orbits were found to be compatible with that of the 1995 outburst. The spectrum confirmed that AMO meteoroids are deficient in sodium. Unlike any other meteor shower, meteor end heights were found to be distributed along a constant level of 90 km for all meteors with magnitudes between +4 and -2 and with atmospheric trajectory lengths up to 40 km. We propose that Alpha Monocerotids were formed from a devolatilized and fragile cometary crust composed from relatively large fundamental grains.
The nova M31N 2023-11f (2023yoa) has been recently identified as the second eruption of a previously recognized nova, M31N 2013-10c, establishing the latter object as the 21st recurrent nova system ...thus far identified in M31. Here we present well sampled \(R\)-band lightcurves of both the 2013 and 2023 eruptions of this system. The photometric evolution of each eruption was quite similar as expected for the same progenitor system. The 2013 and 2023 eruptions each reached peak magnitudes just brighter than \(R\sim16\), with fits to the declining branches of the eruptions yielding times to decline by two magnitudes of \(t_2(R)=5.5\pm1.7\) and \(t_2(R)=3.4\pm1.5\) days, respectively. M31N 2013-10c has an absolute magnitude at peak, \(M_R=-8.8\pm0.2\), making it the most luminous known recurrent nova in M31.
(155140) 2005 UD has a similar orbit to (3200) Phaethon, an active asteroid in a highly eccentric orbit thought to be the source of the Geminid meteor shower. Evidence points to a genetic ...relationship between these two objects, but we have yet to fully understand how 2005 UD and Phaethon could have separated into this associated pair. Presented herein are new observations of 2005 UD from five observatories that were carried out during the 2018, 2019, and 2021 apparitions. We implemented light curve inversion using our new data, as well as dense and sparse archival data from epochs in 2005--2021 to better constrain the rotational period and derive a convex shape model of 2005 UD. We discuss two equally well-fitting pole solutions (\(\lambda = 116.6^{\circ}\), \(\beta = -53.6^{\circ}\)) and (\(\lambda = 300.3^{\circ}\), \(\beta = -55.4^{\circ}\)), the former largely in agreement with previous thermophysical analyses and the latter interesting due to its proximity to Phaethon's pole orientation. We also present a refined sidereal period of \(P_{\text{sid}} = 5.234246 \pm 0.000097\) hr. A search for surface color heterogeneity showed no significant rotational variation. An activity search using the deepest stacked image available of 2005 UD near aphelion did not reveal a coma or tail but allowed modeling of an upper limit of 0.04 to 0.37~kg s\(^{-1}\) for dust production. We then leveraged our spin solutions to help limit the range of formation scenarios and the link to Phaethon in the context of nongravitational forces and timescales associated with the physical evolution of the system.
The M31 recurrent nova M31N 1926-07c has had five recorded eruptions. Well-sampled light curves of the two most recent outbursts, in January of 2020 (M31N 2020-01b) and September 2022 (M31N ...2022-09a), are presented showing that the photometric evolution of the two events were quite similar, with peak magnitudes of \(R=17.2\pm0.1\) and \(R=17.1\pm0.1\), and \(t_2\) times of \(9.7\pm0.9\) and \(8.1\pm0.5\) days for the 2020 and 2022 eruptions, respectively. After considering the dates of the four most recent eruptions (where the cycle count is believed to be known), a mean recurrence interval of \(\langle P_\mathrm{rec}\rangle=2.78\pm0.03\) years is found, establishing that M31N 1926-07c has one of the shortest recurrence times known.
On 26 September 2022, the Double Asteroid Redirection Test (DART) spacecraft impacted Dimorphos, the satellite of binary near-Earth asteroid (65803) Didymos. This demonstrated the efficacy of a ...kinetic impactor for planetary defense by changing the orbital period of Dimorphos by 33 minutes (Thomas et al. 2023). Measuring the period change relied heavily on a coordinated campaign of lightcurve photometry designed to detect mutual events (occultations and eclipses) as a direct probe of the satellite's orbital period. A total of 28 telescopes contributed 224 individual lightcurves during the impact apparition from July 2022 to February 2023. We focus here on decomposable lightcurves, i.e. those from which mutual events could be extracted. We describe our process of lightcurve decomposition and use that to release the full data set for future analysis. We leverage these data to place constraints on the post-impact evolution of ejecta. The measured depths of mutual events relative to models showed that the ejecta became optically thin within the first ~1 day after impact, and then faded with a decay time of about 25 days. The bulk magnitude of the system showed that ejecta no longer contributed measurable brightness enhancement after about 20 days post-impact. This bulk photometric behavior was not well represented by an HG photometric model. An HG1G2 model did fit the data well across a wide range of phase angles. Lastly, we note the presence of an ejecta tail through at least March 2023. Its persistence implied ongoing escape of ejecta from the system many months after DART impact.
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