Abstract 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 the 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 σ = 0.89 mag about a mean R -band absolute magnitude given by 〈 M R 〉 = −7.57 ± 0.07. 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 days 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 analyzed spectra, trajectories, orbits, light curves, and decelerations of eight Draconid meteors observed from Northern Italy on October 8, 2011. Meteor morphologies of two of the meteors are ...also presented, one of them obtained with a high resolution camera. Meteor radiants agree with theoretical predictions, with a hint that some meteors may belong to the pre-1900 meteoroid trails. The spectra confirm that Draconids have normal chondritic composition of main elements (Mg, Fe, Na). There are, nevertheless, differences in the temporal evolution of Na line emission. The differences are correlated with the shapes of the light curves and the deceleration rates. Our data confirm that Draconids are porous conglomerates of grains, nevertheless, significant differences in the atmospheric fragmentation of cm-sized Draconids were found. Various textures with various resistance to fragmentation exist among Draconid meteoroids and even within single meteoroids.
Abstract
(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 (
λ
= 116.°6,
β
= −53.°6) and (
λ
= 300.°3,
β
= −55.°4), 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
sid
= 5.234246 ± 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 0.04–0.37 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.
► Absolute magnitudes of 583 main-belt and near-Earth asteroids were estimated. ► Bias in catalogued absolute magnitudes for asteroids smaller than about 30km found. ► Albedos of 300 asteroids from ...WISE thermal observations were revised.
We obtained estimates of the Johnson V absolute magnitudes (H) and slope parameters (G) for 583 main-belt and near-Earth asteroids observed at Ondřejov and Table Mountain Observatory from 1978 to 2011. Uncertainties of the absolute magnitudes in our sample are <0.21mag, with a median value of 0.10mag. We compared the H data with absolute magnitude values given in the MPCORB, Pisa AstDyS and JPL Horizons orbit catalogs. We found that while the catalog absolute magnitudes for large asteroids are relatively good on average, showing only little biases smaller than 0.1mag, there is a systematic offset of the catalog values for smaller asteroids that becomes prominent in a range of H greater than ∼10 and is particularly big above H∼12. The mean (Hcatalog−H) value is negative, i.e., the catalog H values are systematically too bright. This systematic negative offset of the catalog values reaches a maximum around H=14 where the mean (Hcatalog−H) is −0.4 to −0.5. We found also smaller correlations of the offset of the catalog H values with taxonomic types and with lightcurve amplitude, up to ∼0.1mag or less. We discuss a few possible observational causes for the observed correlations, but the reason for the large bias of the catalog absolute magnitudes peaking around H=14 is unknown; we suspect that the problem lies in the magnitude estimates reported by asteroid surveys. With our photometric H and G data, we revised the preliminary WISE albedo estimates made by Masiero et al. (Masired, J.R. et al. 2011. Astrophys. J. 741, 68–89) and Mainzer et al. (Mainzer, A. et al. 2011b. Astrophys. J. 743, 156–172) for asteroids in our sample. We found that the mean geometric albedo of Tholen/Bus/DeMeo C/G/B/F/P/D types with sizes of 25–300km is pV=0.057 with the standard deviation (dispersion) of the sample of 0.013 and the mean albedo of S/A/L types with sizes 0.6–200km is 0.197 with the standard deviation of the sample of 0.051. The standard errors of the mean albedos are 0.002 and 0.006, respectively; systematic observational or modeling errors can predominate over the quoted formal errors. There is apparent only a small, marginally significant difference of 0.031±0.011 between the mean albedos of sub-samples of large and small (divided at diameter 25km) S/A/L asteroids, with the smaller ones having a higher albedo. The difference will have to be confirmed and explained; we speculate that it may be either a real size dependence of surface properties of S type asteroids or a small size-dependent bias in the data (e.g., a bias towards higher albedos in the optically-selected sample of asteroids). A trend of the mean of the preliminary WISE albedo estimates increasing with asteroid size decreasing from D∼30 down to ∼5km (for S types) showed in Mainzer et al. (Mainzer, A. et al. 2011a. Astrophys. J. 741, 90–114) appears to be mainly due to the systematic bias in the MPCORB absolute magnitudes that progressively increases with H in the corresponding range H=10–14.
► We performed a long term monitoring of the comet extending far before and after the EPOXI spacecraft encounter. ► The asymmetric photometric behavior is examined and growing and fading Afρ rates ...are determined. ► The periods characterized by short term variability are examined. ► Ten small outbursts have been detected, two suspected. ► The coma asymmetric shape and gradient are examined.
The results of a CARA (Cometary Archive for Afρ) campaign on Comet 103P/Hartley 2 are presented. The main goal was to monitor extensively the comet during the apparition with CCD R and I imaging and photometry, as a support of EPOXI mission.
The Afρ quantity showed a progressively rising ascending branch, followed by an apparent flat maximum that lasted for 2months, from about −10 to +50days from perihelion. In this period, Afρ peaked at around 100cm in R band with strong short term fluctuations between 70 and 140cm. Early signs of activity were detectable well before perihelion (about 80–90days before) and a random variability is also present in the descending branch after perihelion. Three post perihelion data points (between +55 and +61days) from the 1997–1998 apparition show a bit higher Afρ value of our observation and a similar fast variation.
The average Afρ behavior, corrected for the solar phase effect, is strongly asymmetric and shows a more steeper ascending branch, approaching to perihelion.
Morphology and coma asymmetry, as well as the sunward and tailward profiles are examined. An average gradient indicatively between ∼ρ−0.7 and ρ−1 is observed in the inner coma (ρ<2000km). Ten small amplitude outbursts have been detected and two ones were suspected.
The Double Asteroid Redirection Test (DART) spacecraft successfully performed the first test of a kinetic impactor for asteroid deflection by impacting Dimorphos, the secondary of near-Earth binary ...asteroid (65803) Didymos, and changing the orbital period of Dimorphos. A change in orbital period of approximately 7 min was expected if the incident momentum from the DART spacecraft was directly transferred to the asteroid target in a perfectly inelastic collision
, but studies of the probable impact conditions and asteroid properties indicated that a considerable momentum enhancement (β) was possible
. In the years before impact, we used lightcurve observations to accurately determine the pre-impact orbit parameters of Dimorphos with respect to Didymos
. Here we report the change in the orbital period of Dimorphos as a result of the DART kinetic impact to be -33.0 ± 1.0 (3σ) min. Using new Earth-based lightcurve and radar observations, two independent approaches determined identical values for the change in the orbital period. This large orbit period change suggests that ejecta contributed a substantial amount of momentum to the asteroid beyond what the DART spacecraft carried.
ABSTRACT The Andromeda Galaxy recurrent nova M31N 2008-12a had been observed in eruption 10 times, including yearly eruptions from 2008 to 2014. With a measured recurrence period of days (we believe ...the true value to be half of this) and a white dwarf very close to the Chandrasekhar limit, M31N 2008-12a has become the leading pre-explosion supernova type Ia progenitor candidate. Following multi-wavelength follow-up observations of the 2013 and 2014 eruptions, we initiated a campaign to ensure early detection of the predicted 2015 eruption, which triggered ambitious ground- and space-based follow-up programs. In this paper we present the 2015 detection, visible to near-infrared photometry and visible spectroscopy, and ultraviolet and X-ray observations from the Swift observatory. The LCOGT 2 m (Hawaii) discovered the 2015 eruption, estimated to have commenced at August 28.28 0.12 UT. The 2013-2015 eruptions are remarkably similar at all wavelengths. New early spectroscopic observations reveal short-lived emission from material with velocities ∼13,000 km s−1, possibly collimated outflows. Photometric and spectroscopic observations of the eruption provide strong evidence supporting a red giant donor. An apparently stochastic variability during the early supersoft X-ray phase was comparable in amplitude and duration to past eruptions, but the 2013 and 2015 eruptions show evidence of a brief flux dip during this phase. The multi-eruption Swift/XRT spectra show tentative evidence of high-ionization emission lines above a high-temperature continuum. Following Henze et al. (2015a), the updated recurrence period based on all known eruptions is days, and we expect the next eruption of M31N 2008-12a to occur around 2016 mid-September.
Abstract
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.
Abstract
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.
Abstract
V642 Vir is a polar spotted, well-detached, UV Leo-type, low-mass, pre-WUMa (T1 ∼ 4250K, ∼K6V) eclipsing binary. It was observed in 2020 April, May, and June at the Dark Sky Observatory in ...North Carolina, USA with the 0.81 m reflector of Appalachian State University. A total of 88 timings were used in our 22-year period study which included 12 Transiting Exoplanet Survey Satellite (TESS) timings. The
O
−
C
plots show a low-amplitude oscillation of residuals that points to the existence of an orbiting third body, a dwarf of minimum mass, 0.15
M
⊙
in an eccentric orbit (e = 0.41), with an orbital period of 20.07 yr. The odd light curves of V642 Virginis indicate that it has polar spots similar to UV Leo and the recently published V1023 Per. Its present large polar spot region indicates that it must have a strong magnetic field and that it is synchronously rotating. The BVR
c
I
c
simultaneous Wilson–Devinney Program solution gives a detached binary (primary and secondary components are underfilling their respective Roche Lobes, with 76% and 78% fill outs respectively). The cool spot region models near the pole of the primary component (centered at 10° colatitude) and is angled toward the secondary component. Its large radius (68°) and T-fact (T
spot
/T
surface
= 0.69) also attest to the conclusion of the strength of the magnetic field. The small ΔT in the components (∼318 K) and mass ratio near unity (0.9542 ± 0.0005) show that the stars are similar in spectral type (secondary ∼K9V). The inclination is high, ∼86.87 ± 0.04°, yet there is no time of constant light due to the two stars’ essentially equal radii.
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