arXiv subjects

Kamil Hornoch

Publications and source records attributed to Kamil Hornoch.

25 records · Page 2Linked to original sources

arXiv2021

Properties of Alpha Monocerotid meteors from the observation of the 2019 outburst in the Czech Republic

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.

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arXiv2018

(3200) Phaethon: Bulk density from Yarkovsky drift detection

The recent close approach of the NEA (3200) Phaethon offered a rare opportunity to obtain high-quality observational data. We used the newly obtained optical light curves to improve the spin and shape model of Phaethon and to determine its surface physical properties derived by thermophysical modeling. We also used the available astrometric observations of Phaethon, including those obtained by the Arecibo radar and the Gaia spacecraft, to constrain the secular drift of the orbital semimajor axis. This constraint allowed us to estimate the bulk density by assuming that the drift is dominated by the Yarkovsky effect. We used the convex inversion model to derive the 3D shape model of Phaethon, and a detailed numerical approach for an accurate analysis of the Yarkovsky effect. We obtained a unique solution for Phaethon's pole orientation at $(318,-47)^{\circ}$ ecliptic longitude and latitude (uncertainty of $5^{\circ}$), and confirm the previously reported thermophysical properties ($D=5.1\pm0.2$ km, $Γ=600\pm200$ SI). Phaethon has a top-like shape with possible north-south asymmetry. The characteristic size of the regolith grains is 1-2 cm. The orbit analysis reveals a secular drift of the semimajor axis of $-(6.9\pm1.9)\times 10^{-4}$ au Myr$^{-1}$. With the derived volume-equivalent size of 5.1~km, the bulk density $ρ$ is $1.67\pm0.47$ g cm$^{-3}$. If the size is slightly larger $\sim5.7$ km, as suggested by radar data, $ρ$ would decrease to $1.48\pm0.42$ g cm$^{-3}$. We further investigated the suggestion that Phaethon may be in a cluster with asteroids (155140) 2005 UD and (225416) 1999 YC that was formed by rotational fission of a critically spinning parent body. Phaethon's $ρ$ is consistent with typical values for large ($>100$ km) C-complex asteroids and supports its association with asteroid (2) Pallas. These findings render a cometary origin unlikely for Phaethon.

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arXiv2017

CzeV - The Czech Variable Star Catalogue

We present the first release of the Czech Variable star catalogue that currently contains 1228 stars whose variability was discovered by 60 Czech observers. The catalogue contains confirmed variable stars of various types, but also candidates. We give precise coordinates, cross identification with other catalogues, information about constellation, variability type, brightness, light elements, name of the discoverer and year of discovery. In eighty-eight percent of stars the variability type is estimated, for more than 60 % of the stars the light ephemerides are given.

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arXiv2015

The January 2015 outburst of a red nova in M31

M31N 2015-01a (or M31LRN 2015) is a red nova that erupted in January 2015 -- the first event of this kind observed in M31 since 1988. Very few similar events have been confirmed as of 2015. Most of them are considered to be products of stellar mergers. Results of an extensive optical monitoring of the transient in the period January-March 2015 are presented. Eight optical telescopes were used for imaging. Spectra were obtained on BTA, GTC and the Rozhen 2m telescope. We present a highly accurate 70 d lightcurve and astrometry with a 0.05" uncertainty. The color indices reached a minimum 2-3 d before peak brightness and rapidly increased afterwards. The spectral type changed from F5I to F0I in 6 d before the maximum and then to K3I in the next 30 d. The luminosity of the transient was estimated to $8.7^{+3.3}_{-2.2}\times10^{5}L_{\odot}$ during the optical maximum. Both the photometric and the spectroscopic results confirm that the object is a red nova, similar to V838 Monocerotis.

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arXiv2015

Link between the Potentially Hazardous Asteroid (86039) 1999 NC43 and the Chelyabinsk meteoroid tenuous

We explored the statistical and compositional link between Chelyabinsk meteoroid and potentially hazardous asteroid (86039) 1999 NC43 to investigate their proposed relation proposed by Borovička et al. (2013). Using detailed computation we confirm that the orbit of the Chelyabinsk impactor is anomalously close to 1999 NC43. We find about (1-3) x 10-4 likelihood of that to happen by chance. Taking the standpoint that the Chelyabinsk impactor indeed separated from 1999 NC43 by a cratering or rotational fission event, we run a forward probability calculation, which is an independent statistical test. However, we find this scenario is unlikely at the about (10-3 -10-2) level. We also verified compositional link between Chelyabinska and 1999NC43. Mineralogical analysis of Chelyabinsk (LL chondrite) and (8) Flora (the largest member of the presumed LL chondrite parent family) shows that their olivine and pyroxene chemistries are similar to LL chondrites. Similar analysis of 1999 NC43 shows that its olivine and pyroxene chemistries are more similar to L chondrites than LL chondrites (like Chelyabinsk). We also took photometric observations of 1999 NC43 over 54 nights during two apparitions (2000, 2014). The lightcurve of 1999 NC43 resembles simulated lightcurves of tumblers in Short-Axis Mode with the mean wobbling angle 20-30 deg. While, a mechanism of the non-principal axis rotation excitation is unclear, we can rule out the formation of asteroid in disruption of its parent body as a plausible cause, as it is unlikely that the rotation of an asteroid fragment from catastrophic disruption would be nearly completely halted. Considering all these facts, we find the proposed link between the Chelyabinsk meteoroid and the asteroid 1999 NC43 to be unlikely.

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arXiv2014

Spectral, photometric, and dynamic analysis of eight Draconid meteors

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.

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arXiv2011

Spin vector and shape of (6070) Rheinland and their implications

Main belt asteroids (6070) Rheinland and (54827) 2001NQ8 belong to a small population of couples of bodies which reside on very similar heliocentric orbits. Vokrouhlicky & Nesvorny (2008, AJ 136, 280) promoted a term "asteroid pairs", pointing out their common origin within the past tens to hundreds of ky. Previous attempts to reconstruct the initial configuration of Rheinland and 2001NQ8 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 lightcurve 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 deg. The ecliptic longitude of the pole position is not well constrained as yet. The asymmetric behavior of Rheinland's lightcurve 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 $H_R = 13.68\pm 0.05$ and $G = 0.31\pm 0.05$ values of the H-G system. With the characteristic color index $V-R = 0.49\pm 0.05$ for the S-type asteroids, we thus obtain $H = 14.17\pm 0.07$ for the absolute magnitude of (6070) Rheinland. This a significantly larger value than previously obtained from analysis of the 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. Determination of the rotation state of the secondary component, asteroid (54827) 2001NQ8, is the key element in further constraining the age of the pair and its formation process.

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