SB2
Session assets
Introduction:
Numerous energetic collisions between asteroids in the inner Solar System have led to the creation of groups of fragments, known as asteroid collisional families. These families populate the Main Belt, each family typically originating from a single parent body that was shattered [1]. The fragments of the same collision form a characteristic V-shape in the plane defined by inverse diameter (1/D) and orbital semimajor axis (a), due to the Yarkovsky effect [2, 3]. It is a thermal force, which cause outward drift to prograde rotating asteroids and inward drift to retrograde. A method for the identification of very old and dispersed asteroid families has been developed [4,5] to search for families by their V-shapes. Such families may be invisible with the Hierarchical Clustering Method (HCM) [6, 7]. So far, six asteroid families have been discovered by using the V-shape method: the Eulalia and New Polana families [8], a low-albedo primordial family [5] with nominal age of about 4 Gyr, Athor family, ~3.0 Gyr-old, Zita family, ~4.5 Gyr-old [9] and an S-complex asteroid family, ~4.3 Gyr-old [10].
Here, we study the spin states of asteroids that belong to the two X-complex asteroid families in the Inner Main Belt, Athor and Zita [9, 11]. Athor family is detectable also with HCM, conversely, the Zita family is not, as its members have dispersed in orbital elements (ghost family, according to [12]).
Methodology:
We used shape models that were retrieved from the literature or databases as well as multi-epoch observational datasets. Dense-in-time photometric data were retrieved from the literature and obtained from “Ancient Asteroids”1, our own observing campaign [13]. Specifically, we obtained 366 new lightcurves for 84 asteroids. Sparse-in-time photometric data were retrieved from sky surveys, namely: ASAS-SN, ATLAS, PTF, ZTF, and space missions, Gaia and TESS. Further data were collected from published asteroid models.
We reduced and calibrated the photometric data following the same methodology of previous works [14, 15, 16] and using different weights for each dataset based on their accuracy [17]. Then we applied the Convex Inversion (CI) method, developed by Kaasalainen et al. [18, 19], for each asteroid from our sample. The CI reveals the spin axis orientation of asteroids, hence their sense of rotation.
Results:
Athor family:
We obtained 31 new asteroid models for Athor family and 9 revised ones. Including the archival models, the spin state is known for 49 members.
Figure 1 shows the spin states of Athor family members distributed in the family's V-shape. We found that the outward side of the family exhibits a statistical predominance of prograde asteroids of 76% and in the inward side retrograde asteroids of 60%. Considering only the family core, the outward side presents similar excess of prograde asteroids (77%) and inward side excess of retrograde asteroids (72%). The Kernel Density Estimation (KDE) visualizes qualitatively the underlying probability distribution for the retrograde and prograde rotators and presents two clear peaks: one for retrograde rotators in the inward side and another for prograde in the outward side.
Zita family:
Concerning the Zita family, we produced 17 new asteroid models and 7 revised. Including the archival models, the spin state is known for 32 members.
Figure 2 shows the spin states of Zita family members distributed in the family's V-shape. We found that the 80% the Zita members in the inward side are retrograde rotators, while the outward side contains same number of prograde and retrograde asteroids. The KDE presents a clear peak for prograde in the outward side, while the maximum for retrograde rotators is around family’s V-shape center.
Conclusions:
The Athor family exhibits a statistical predominance of retrograde asteroids in the inward side and, conversely, predominance of prograde asteroids in the outward side. This result adds evidence that the members are fragments of the same parent body, an EL planetesimal, that was shattered about 3 Gy ago.
The Zita family demonstrates an excess of retrograde asteroids in the inward side, but there is absence of asteroids due to orbital resonances. Conversely, the outward side does not present any predominance with an equal distribution of prograde and retrograde rotators. However, KDE exhibits a clear peak for prograde asteroids in the outward side.
The spin states of these asteroids, derived from observations and modeling, validate the existence of the Athor and Zita families, with the Athor family exhibiting a stronger signature, which is expected as it is younger and more compact. This research provides independent confirmation and characterisation of these very old families, offering tight constraints for our Solar System's evolution models [10, 20].
References:
[1] Zappalà et al. (1984). Icarus, 59(2), 261-285.
[2] Bottke et al. (2006). Annu. Rev. Earth Planet. Sci., 34, 157-191.
[3] Vokrouhlický et al. (2006). Icarus, 182(1), 118-142.
[4] Bolin et al. (2017). Icarus, 282, 290-312.
[5] Delbo et al. (2017). Science, 357(6355), 1026-1029.
[6] Zappalà et al. (1990). Astron.J., 100, 2030-2046.
[7] Zappalà et al. (1995). Icarus, 116(2), 291-314.
[8] Walsh et al. (2013). Icarus, 225(1), 283-297.
[9] Delbo et al. (2019). A&A, 624, A69.
[10] Ferrone et al. (2023). A&A, 676, A5.
[11] Avdellidou et al. (2022). A&A, 665, L9.
[12] Dermott et al. (2021). MNRS, 505(2), 1917-1939.
[13] Athanasopoulos et al. (2021). EPSC2021-355.
[14] Hanuš et al. (2011) A&A, 530, A134.
[15] Hanuš et al. (2013). A&A, 551, A67.
[16] Athanasopoulos et al. (2022). A&A, 666, A116.
[17] Hanuš et al. (2023). A&A, 679, A56.
[18] Kaasalainen et al. (2001). Icarus, 153(1), 24-36.
[19] Kaasalainen et al. (2001). Icarus, 153(1), 37-51.
[20] Avdellidou et al. (2024). Science, eadg8092.
Acknowledgments:
D.A. acknowledges support from the Academy Complex Systems of the Universite Côte d’Azur under the scheme “Programme de visites doctorales". M.D. and C.A. acknowledge support from ANR “ORIGINS” (ANR-18- 647 CE31-0014). The Czech Science Foundation has supported the research of J.H. through grant 22-17783S. N.T. acknowledge support from the Astronomical station Vidojevica and funding from the Ministry of Science, Technological Development and Innovation of the Republic of Serbia (451-03-47/2023-01/ 200002) and by the European Commission through project BELISSIMA (call FP7-REGPOT-2010-5, No. 256772).
1http://users.uoa.gr/~kgaze/ancient_asteroids.html
How to cite: Athanasopoulos, D., Hanuš, J., Avdellidou, C., van Belle, G., Ferrero, A., Bonamico, R., Gazeas, K., Delbo, M., Rivet, J.-P., Apostolovska, G., Todorović, N., Novakovic, B., Vchkova Bebekovska, E., and Romanyuk, Y.: Spin states of X-complex asteroids in the Inner Main Belt confirm the existence of Athor and Zita collisional families., Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-359, https://doi.org/10.5194/epsc2024-359, 2024.
Abstract:
The Gaia data release 3 (DR3) in June 2022 provided precise photometric measurements for over 150,000 asteroids, allowing the derivation of rotation state properties for approximately 8,600 of them. We complemented DR3 data with measurements from the Asteroid Terrestrial-impact Last Alert System (ATLAS), which offers more frequent observations for over 100,000 asteroids, albeit with slightly lower accuracy. By employing a physical model encompassing rotation period, spin axis orientation, and 3D shape, we derived approximately 16,000 unique spin state and shape solutions. This dataset, derived from photometry from two consistent sources, mitigates biases present in previous multi-source datasets. Notably, our analysis revealed a higher proportion of slow rotators, often overlooked due to sampling bias. We investigate several specific collisional families in detail, finding evidence that older families display characteristics indicative of a more evolved population, influenced by YORP spin-down effects. Conversely, young families such as Veritas exhibit largely unevolved spin states due to thermal forces, reflecting the aftermath of the collisions that created them.
Introduction:
Understanding the physical properties of asteroids, including their spin state, shape, albedo, and size, is essential for unraveling their evolutionary history. Various observational techniques have been utilized to derive these properties, with lightcurve inversion methods playing a crucial role in reconstructing asteroid shapes and spin states. Recent advancements in data availability, such as the Gaia data release 3 (DR3) and the Asteroid Terrestrial-impact Last Alert System (ATLAS), offer new opportunities to investigate asteroid properties in greater detail. The YORP effect has emerged as a key factor shaping asteroid spin states within families, highlighting the importance of considering family age in such studies.
Methods:
We combine data from Gaia DR3 and ATLAS to derive physical properties for asteroids, including rotation period, spin axis orientation, and 3D shape. Gaia DR3 provides precise photometric measurements for over 150,000 asteroids, while ATLAS offers more frequent observations for over 100,000 asteroids. Utilizing a physical model, we derive unique spin state and shape solutions for approximately 16,000 asteroids.
Results:
Our analysis reveals a higher proportion of slow rotators in the dataset, challenging previous sampling biases. We investigate specific collisional families, finding evidence that older families exhibit characteristics indicative of a more evolved population, influenced by YORP spin-down effects. Conversely, young families display largely unevolved spin states, reflecting the aftermath of the collisions that created them.
Conclusions:
This study enhances our understanding of asteroid populations and their evolutionary processes. Insights derived from this analysis contribute to the dynamic modeling of the solar system and provide valuable constraints for future studies.
Figure 1: Spin states in two collisional families. The solutions are derived from the latest photometric datasets. The young Veritas family (8 Myr old, Carruba et al. 2017, MNRAS, 469, 4400) comprises asteroids with spin vectors distributed uniformly. In contrast, the old Gefion family (1 Gyr old, Aljbaae et al. 2019, A&A, 622, A39) exhibits a bimodal distribution of spin vectors. Additionally, the prevalence of numerous slow rotators (P > 20 hours) also confirms Gefion's evolved state.
How to cite: Hanus, J. and Durech, J.: Spin State Properties in Young Asteroid Families, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-616, https://doi.org/10.5194/epsc2024-616, 2024.
Introduction:
Determining the physical parameters of asteroids is a complex yet crucial
task in planetary science. Recent advancements in observational techniques and
the availability of vast data have led to the development of numerous analytical
and modelling approaches for parameter determination.
In our research, we focused on studying several main-belt asteroids using
high-quality data. Initially, we modelled visible lightcurves using convex inver-
sion (see [1] and [2]) obtaining precise information on the spin axis and an initial
shape model. Subsequently, we used these results as input for another mod-
elling technique called Convex Inversion Thermophysical Model (CITPM, see
[3]). CITPM optimizes the model based both on lightcurves and thermal data,
providing output such as surface roughness, temperature distribution, thermal
inertia, and asteroid size. Additionally, by fitting the initial models to stellar
occultation observations, we determined asteroid sizes with another recognized
precise method. This revealed a good agreement with the sizes determined by
CITPM, enhancing the credibility of its other output parameters.
Results:
asteroid (527) Euryanthe. The CITPM model for solution 1 and solution 2 are
shown in Figure 1. Due to the mirror-pole ambiguity, we obtain two possible
solutions (see [4]). Some of the parameters derived using the CITPM are given
in Table 1. Additionally, Figure 2 shows a fit of our models of (527) Euryanthe
to a stellar occultation by this asteroid observed on 2019-01-20. The best fit was
obtained for pole solution 2, and the corresponding size was found at 52.7 ± 1.8
km.
Conclusions:
The utilization of quality data has enabled the generation of reliable asteroid
models. Furthermore, the supplementary use of the occultation observation
technique, renowned for its accuracy in determining asteroid sizes, has proven
to be consistent with sizes determined via the CITPM technique. Without such
models as presented above, asteroid sizes tend to be determined with an order
of magnitude poorer accuracy.
References:
How to cite: Choukroun, A., Marciniak, A., and Ďurech, J.: Determining the sizes of selected asteroids with different techniques, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-597, https://doi.org/10.5194/epsc2024-597, 2024.
Introduction
Bilobed objects (contact binaries) appear across the solar system in both asteroid and comet populations. Radar imaging reveals that at least 15% of near-Earth asteroids (NEAs) are contact binaries [1] but bilobed objects have also been detected in the Asteroid Belt and the Kuiper Belt. Notable examples include Itokawa (NEA), Selam (main-belt asteroid), and Arrokoth (trans-Neptunian object). It is currently unknown whether contact binaries form predominantly as two separate objects or are the natural evolution of a single body. Theories for contact binary formation in asteroids include the reaccumulation of fragments resulting from a catastrophic collision [2]. A second possibility is that the two lobes could be formed from a rotational instability as a result of YORP [3]. To date, the sample size of modelled contact binaries stands at thirteen, with only six from the NEA population. We present the model of Apollo group asteroid (388188) 2006 DP14 (henceforth DP14) which demonstrates a contact binary like structure in publicly available radar data from 2014 (Figure 2).
Observations
We collected optical photometry of DP14 during over two nights in 2014, one from a 0.36-m telescope at the Perth Observatory in Australia, and one from the PROMPT1 0.41-m telescope in Cerro Tololo, Chile. We have 9 nights of data from 2022, 5 of which are semi-sparse lightcurves obtained from the Danish 1.54-m telescope on La Silla, while the other 4 are complete lightcurves obtained from the 2.54-m Isaac Newton Telescope on La Palma, Spain. Finally, we have 3 nights of densely populated lightcurves from the Danish telescope from 2023. The INT and 2023 lightcurves were collected in the SDSS-R filter, reduced with standard procedures and calibrated to ATLAS REFCAT-2 stars in the field after PSF photometry. The 2022 data from the Danish telescope was calibrated in the Cousins R system with the Landolt standards with absolute accuracy of 0.01 mag. In our modelling, we also used published data spanning two nights in 2014, collected from a 0.6-m telescope at the CS3-Palmer Divide Station [4].
The radar data used was recorded in 2014 at the Goldstone DSN antenna in the United States and contains two nights of delay-Doppler images and 3 sets of echo power spectra.
Modelling
To model DP14 we first performed convex inversion [5,6] in order to refine the spin-state solution and generate a convex hull of the asteroid's shape. While these results were inconclusive for the rotational pole it allowed us to gain a good estimate of the period (see Figure 1), and allowed us to confirm the rotational pole was in the southern hemisphere when creating our initial conditions for further modelling with radar.
Figure 1: Periodogram of the convex inversion performed on all the lightcurves. It is known from radar imaging that the object is elongated, so although the best solution is a fit for a single-peaked lightcurve, we instead used the two-peaked solution that agreed with Warner (2014) [1] as initial conditions for the radar modelling.
We used the SHAPE modelling software [7] to combine the optical lightcurves with radar echo spectra and delay-Doppler images from 2014 from the Goldstone DSN antenna. We first used a simple single ellipsoid estimation of shape in order to refine the spin-state solution, before moving on to a bi-ellipsoid model. The inherent degeneracy of pole solutions in radar modelling resulted in minima at both the south and north pole but, given the results of the convex inversion and measurement of Yarkovsky effect (negative A2 in the most recent orbital solution) from optical and radar astrometry, we used the southern pole solution. We then switched to a vertex shape model fit in order to refine the shape and allow for better fitting to the narrow neck and the crater visible on the elongated body of the target seen in the delay-Doppler images.
As a preliminary result, we have determined that DP14 has a distinctive narrow neck connecting two lobes of unequal size. Results suggest a period of 5.77 ± 0.05 hours and a rotational pole of approximately β = -80 and λ = 50. The radar model can be seen in Figure 2.
Figure 2: Left column: Delay-Doppler images of DP14 taken with the Goldstone DSN antenna in the United States on 12/02/2014. The second image was taken approximately 50 minutes after the first, with the third another 30 minutes later. Centre column: The simulated delay-Doppler images created from the preliminary model. Right: The plane of sky views of the model with a pink axis representing the rotational pole.
Summary & Conclusion
We have reached a spin-state solution with a rotational pole close to the south pole of the ecliptic, as is observed in the majority of NEAs. Modelling reveals results expected from a visual inspection of the data, with an elongated body with a large crater on its side and smaller more spherical head connected by a narrow neck. The model of DP14 will allow better comparisons to theory based dynamical simulations to investigate its likely origins, while an additional spin-state solution and shape model give vital hints into not only the object's own formation history, but allow us to place the results in the wider context of other similarly shaped solar system objects.
Bibliography
[1] Benner, L. A. M. et al. In Asteroids IV ; University of Arizona Press: 2015, pp 165–182.
[2] Campo Bagatin, A. et al. Icarus 2020, 339, 113603.
[3] Jacobson, S. A. et al. Icarus 2016, 277, 381–394.
[4] Warner, B. D. Minor Planet Bulletin 2014, 41, 157–168
[5] Kaasalainen, M.; Torppa, J. Icarus 2001, 153, 24–36.
[6] Kaasalainen, M.; Torppa, J.; Muinonen, K. Icarus 2001, 153, 37–51.
[7] Magri, C. et al. Icarus 2007, 186, 152–177.
How to cite: Cannon, R., Rożek, A., Snodgrass, C., Brozović, M., Pravec, P., Holc, T., and Robinson, J.: Shape model of contact binary asteroid 2006 DP14 using radar and optical data, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-660, https://doi.org/10.5194/epsc2024-660, 2024.
(385186) 1994 AW1 is a potentially hazardous asteroid, the first near-Earth asteroid suspected to be a binary [1,2] and was selected as the initial target of the DART and HERA mission. 1994 AW1 made a close approach to Earth in July 2015, getting as close as 25 lunar distances on the 15th. This flyby was a great opportunity for observations in photometry [3] and radar.
Continuous wave (CW) and Delay Doppler imaging modes were used, first at Goldstone for the 14-19 July period (0.066-0.070 au), and then by Arecibo for the 20-30 July 2015 (0.075-0.126 au). A range resolution of 150 m was achieved at Goldstone in bistatic configuration with Green Bank Telescope (8560 MHz), while monostatic observation in S-band (2380 MHz, 12.6 cm) at Arecibo were obtained at resolutions of 30 m and 75 m. The rotation period of the primary (2.52 h) and orbital period of the secondary (22 h) derived from optical light curves [4] were confirmed by these observations. The primary is about 800 m in diameter and the secondary is about half of the primary size. A more recent but relatively distant approach (July 8, 2022; 0.11 au) allowed CW spectra to be obtained at Goldstone [5].
We also obtained new light curves in 13-24 January 2023 while it was at V ~16-17 mag. We used the TRAPPIST-South (I40, Chile) and -North (Z53, Morocco) [6] to gather 10 light curves in total. For 4 of them, brightness drops indicate mutual events between 1994 AW1 and its satellite.
We searched for the sidereal rotation period of 1994 AW1 by combining the TRAPPIST data with data from the Ondřejov Observatory 0.65m telescope and the Danish 1.54m telescope, obtained between 2014 and 2023. We used the lightcurve inversion method of [7] and [8] and derived a convex shape model with sidereal period of 2.518586 ± 0.000011 h, a pole orientation of 187° of ecliptic longitude and +67° of ecliptic latitude, and a b/a axis ratio of 0.97.
Figure: Convex shape model of 1994 AW1 derived from lightcurve inversion and viewed along the rotation (z) axis on the left, the x axis (middle) and the y axis (right). The black arrow indicates the rotation axis.
Finally, we combined our radar and optical datasets with SHAPE [9] to perform shape modeling of the primary component. We will present our preliminary non-convex 3D shape model, pole coordinates and system density.
References:
[1] Pravec, P. and Hahn, G. (1997), Icarus, 127.
[2] Mottola, S. et al. (1995), Icarus 117, 62-70.
[3] Warner D. B. (2016), MPB, 43.
[4] Pravec et al. (2006), Icarus, 181, 63-93.
[5] Brozovic, M. et al. (2022) DPS 54.
[6] Jehin, E. et al. (2011), The Messenger 145, 2–6.
[7] Kaasalainen & Torppa (2001), Icarus, 153, 24.
[8] Kaasalainen, M. et al. (2001), Icarus, 153, 37.
[9] Magri, C. et al. (2007), Icarus 186, 152-177.
How to cite: Ferrais, M., Marshall, S., Venditti, F., Devogèle, M., Pravec, P., Scheirich, P., and Jehin, E.: Shape model of the binary NEA (385186) 1994 AW1 from 2015 radar observations and long term lightcurve dataset. , Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-161, https://doi.org/10.5194/epsc2024-161, 2024.
Introduction
Asteroids, as remnants of the early solar system, hold crucial clues about the processes that led to the formation of planets. These small bodies are composed of materials that have remained relatively unchanged since the solar system’s formation, making them valuable targets for scientific study. Near-Earth objects (NEOs), which include both asteroid-like and comet-like bodies whose orbits bring them close to Earth, are particularly important. These objects not only
offer insights into planetary formation but also pose potential threats to Earth due to their proximity and frequent interactions with terrestrial planets. Understanding their composition, distribution, and behavior is essential for both scientific research and planetary defense.
 |
| Fig. 1: Orbital distribution of Near-Earth Objects by type, showing semimajor axis vs. eccentricity (left) and perihelion vs. inclination (right). |
– SkyMapper: Offers a combination of shallow and deep sequences in multiple filters, enhancing the dataset’s depth and breadth.
– Gaia: Contains low-resolution reflectance spectra covering a wide wavelength range, providing crucial spectral data.
– Ground-based Observations: High-resolution spectra from various surveys add to the robustness of the dataset.
Data from these diverse sources were cross-matched and compared to ensure consistency. Systematic biases were identified and corrected to create a homogeneous dataset. Given the fast-moving nature of NEOs, the study re-measured photometry for these objects in the SDSS to address potential biases related to their rapid motion. This step was crucial for ensuring accurate photometric measurements, which are foundational for subsequent analysis.
– Multi-color Classification: Utilized combinations of g, r, i, z colors to classify NEOs with high accuracy.
– Single-color Classification: Applied when only g-r color was available, providing a broader classification into "red" or "blue" objects. This approach, while less precise, ensures that all available data can be utilized.
 |
| Fig. 2: Taxonomic classification of NEOs in the SDSS color space. |
– Photometric and Taxonomic Data: The catalog includes updated photometry for 470 NEOs and taxonomic classifications for 7,401 NEOs (Sergeyev et al., 2023) see Table 1. This extensive dataset forms a solid foundation for further analysis.
– Spectral Slope and Perihelion Dependence: Confirmed the relationship between spectral slope and perihelion among S-type NEOs, suggesting a rejuvenation mechanism linked to thermal fatigue. This finding supports existing theories about the effects of solar radiation on asteroid surfaces (Graves et al., 2019).
– S-type Asteroids: Showed a constant spectral slope for smaller diameters and an increase for larger ones, consistent with previous studies. This trend indicates that space weathering affects asteroids differently based on their size.
 |
| Fig. 3: Running mean of the ratio between the number of Q and S asteroids as a function of perihelion, inclination, and diameter. Shaded areas correspond to the uncertainties considering the Poisson statistic for the Q/S ratio. |
A-types, characterized by olivine-rich compositions, are rare in the main belt but more common among NEOs. The study found a higher fraction of A-types near the orbit of Mars, possibly linked to the Hungaria asteroid family (Devogèle et al., 2019). This distribution pattern provides clues about the dynamical processes that bring these objects into near-Earth space.
Fitzsimmons, A., Khan, M., Küppers, M., Michel, P., & Pravec, P. 2020, in European Planetary Science Congress, EPSC2020–1064
Galluccio, L., Delbo, M., De Angeli, F., et al. 2022, in European Planetary Science Congress, EPSC2022–357
Graves, K. J., Minton, D. A., Molaro, J. L., & Hirabayashi, M. 2019, Icarus, 322, 1
Mahlke, M., Carry, B., & Mattei, P. A. 2022, A&A, 665, A26
Marsset, M., DeMeo, F. E., Burt, B., et al. 2022, AJ, 163, 165
Sergeyev, A. V. & Carry, B. 2021, A&A, 652, A59
Sergeyev, A. V., Carry, B., Marsset, M., et al. 2023, A&A, 679, A148
Sergeyev, A. V., Carry, B., Onken, C. A., et al. 2022, A&A, 658, A109
How to cite: Sergeyev, A. V., Carry, B., Marsset, M., Pravec, P., Perna, D., DeMeo, F. E., Petropoulou, V., Lazzarin, M., La Forgia, F., and Di Pietro, I.: Compositional Diversity and Space Weathering of Near-Earth Objects, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-792, https://doi.org/10.5194/epsc2024-792, 2024.
Jovian Trojan and Hilda asteroids are of particular importance because they provide important constraints for Solar System formation and evolution models. Despite their large number, rotational characteristics are known for a relatively limited sample from ground-based observations. Rotation period and amplitude distributions derived from this sample are strongly affected by ground-based biases, as it was shown by recent studies using data from the K2 mission of the Kepler Space Telescope. An important result of these investigations is that there are a significantly larger number of slow rotators than previously thought. Here we present several week-long, uninterrupted light curves, in many cases spanning over multiple sectors for a large number of Jovian Trojans and Hildas, provided by the TESS mission. Our results are compared with the previous investigations of ground-based observations and K2 measurements, confirming the significance and the presence of slow rotators as it was hinted by earlier studies. We also investigate the difference between the rotational characteristics of the 'red' and 'less red' groups and that of the different collisional families.
Figure 1.:Cleaned light curve, frequency spectrum and folded light curve of the Hilda asteroids (153) Hilda and (197558) 2004 FL122, observed by TESS.
How to cite: Nóra, T., Plachy, E., Bognár, Z., Szakáts, R., Takács, D., Bódi, A., Gábor, M., Pál, A., M. Szabó, G., Molnár, L., Sárneczky, K., Vinkó, J., Szabó, R., Kiss, C., Bartczak, P., and Podlewska-Gaca, E.: Exploring the physical properties of Jupiter Trojans and Hildas with the TESS space telescope, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-100, https://doi.org/10.5194/epsc2024-100, 2024.
1. Introduction
The Yarkovsky effect is a recoil force from the emitted thermal radiation that causes a slow change of asteroids’ orbits [1]. Its evolutionary significance includes spreading asteroid families and delivery of asteroids to the Kirkwood gaps thus re-supplying the population of near-Earth asteroids by the new members from the main belt, whereas its practical applications range from asteroid mass determination to prediction of asteroid hazard. Ordinarily the Yarkovsky effect is either estimated from an oversimplified linearized thermal model of a spherical asteroid or simulated fully numerically. The former path compromises the accuracy, whereas the latter conceals the physics. We choose the middle path between the spherical Scylla and the numerical Charybdis, and create a compromise theory that is simple for understanding and parametric analysis, sufficiently precise for practical use, and thoroughly verified at each step by comparison with numerical simulations.
2. Thermal model
For each surface element of the asteroid express the mean Yarkovsky force FY as
Here, A is the asteroid’s Bond albedo, LΘ is the solar luminosity, S is the area of the surface element, r is the asteroid’s distance from the Sun, c is the speed of light, and p is what we call the dimensionless Yarkovsky pressure. This pressure is computed from the solution of the 1D heat equation under a surface element of a convex asteroid with zero obliquity. Under such assumptions, the solution of the non-dimensional heat equation depends on only two free parameters, namely the latitude ψ of the asteroid surface element and the thermal parameter θ, defined as in [2]. In addition to the commonly used analytic solution of the linearized heat equation valid for θ>>1, we also apply the approach of [3] to construct the opposite approximation θ<<1, and then proceed to the next iteration beyond the formalism of [3]. Then we sew together the two asymptotic solutions valid for the cases θ>>1 and θ<<1, thus obtaining a unified solution approximately valid for all θ:
Figure 1 illustrates this equation as a function of both θ and ψ, whereas Figure 2 compares different analytical and numerical calculations of p.
Figure 1. Dependence of the non-dimensional Yarkovsky pressure p on the thermal parameter θ and the latitude ψ. All the curves in the plot are self-similar.
Figure 2. Comparison of p (ψ=0°) for the two analytic asymptotics, the sewed approximate solution, the numeric simulation, and an analytic fit.
The accuracy of the abovementioned analytic solution can be further improved by adding more free parameters to the expression and fitting them to the numerical solution, resulting in several different analytic fits with the accuracy ~1% each, that are virtually indistinguishable from the numerical simulation, one of them shown in Figure 2. In the left-hand side of Figure 2 we see that the linear thermal model (orange line) widely used for all θ [1] is wrong for θ<<1 (asymptotically by the factor of approximately 2).
3. Integration of the force over the asteroid’s surface
Next, several opportunities arize to integrate the Yarkovsky force over the asteroid surface: to integrate the approximate analytic expression for the force over a spherical or ellipsoidal asteroid, integrate it over a complex shape of a real asteroid, use the precise numerical expression for the Yarkovsky force… We explore all these possibilities, obtaining a set of expressions for the Yarkovsky effect of varying accuracy and complexity. One of such expressions is shown in Figure 3 in comparison with the Yarkovsky effect calculations for real asteroid shapes. It represents the factor f, by which the Yarkovsky effect of a spherical asteroid should be multiplied.
Figure 3. The shape factor f of the Yarkovsky effect plotted as a function of asteroid flattening c/(ab)1/2 and color-coded as a function of the asteroid’s equatorial axes ratio b/a. (With a, b, and c being the asteroid’s axes, longest to shortest.) Different shape datasets are represented with different types of symbols, and the theory for different axes ratios is shown with solid lines of corresponding colors.
4. Conclusion
As a part of a larger problem of improving the accuracy of the expression for the Yarkovsky drift rate, we revised the expression for the Yarkovsky pressure as a function of the thermal parameter and investigated the dependence of the Yarkovsky effect on the asteroid shape. The commonly used linearized thermal model of the Yarkovsky effect differs from our revised expression by the factor of approximately 2 for thermal parameters θ much less than or equivalent to 1, producing big errors in the Yarkovsky effect estimation for most of the studied asteroids. Fitting asteroids with 3-axial ellipsoids gives a good approximation to the Yarkovsky effect. These two corrections (on the thermal model and on the asteroid shape) dramatically increase the accuracy of the Yarkovsky effect prediction, but further refinements are needed to precisely account for the asteroid obliquity, orbit eccentricity, and the seasonal Yarkovsky effect.
Acknowledgements. This work was partially funded by the National Research Foundation of Ukraine, project N2020.02/0371 “Metallic asteroids: search for parent bodies of iron meteorites, sources of extraterrestrial resources”. OG is grateful to the European Federation of Academies of Sciences and Humanities (ALLEA EFDS-FL-16). VL acknowledges financial support from the German Excellence Strategy via the Heidelberg Cluster of Excellence (EXC 2181 - 390900948) “STRUCTURES”'. She also thanks for computing resources provided by the Ministry of Science, Research and the Arts (MWK) of the State of Baden-Württemberg through bwHPC and the German Science Foundation (DFG) through grants INST 35/1134-1 FUGG and 35/1597-1 FUGG, and also for data storage at SDS@hd funded through grants INST 35/1314-1 FUGG and INST 35/1503-1 FUGG.
References
[1] Vokrouhlický D. et al. (2015), in Asteroids IV (Tucson, AZ: Univ. Arizona Press), p.509-531; [2] Lagerros J. S. V. (1996), Astron. Astrophys., 310, p.1011-1020; [3] Golubov O. et al. (2016), Mon. Not. R. Astron. Soc., 458 (4), p.3977-3989.
How to cite: Mikhalchenko, O., Golubov, O., and Lipatova, V.: Revised analytic theory of the Yarkovsky force, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-645, https://doi.org/10.5194/epsc2024-645, 2024.
Using multi-directional measurements from the TESS, we aim to determine the approximate shape and rotation axis of asteroids in the main belt. As a benchmark study, we selected 43 minor planets based on three criteria: each must have observations in at least three separate TESS sectors, an apparent magnitude of <= 17, and a corresponding solution in the DAMIT (Database of Asteroid Models from Inversion Techniques) database. Due to the limited number of observations per target, we apply a low degree-of-freedom, simple shape model of a triaxial ellipsoid, but consider different scattering laws, taking into account the actual illumination geometry obtained from relative positions of the observer and a possible pole solution. The resulting best-fit spin axis orientations show good agreement with the DAMIT solutions. We will use this technique to obtain shape and spin axis solutions for ten thousands of asteroids observed with TESS.
Figure 1.: Pole orientation χ2 map of (22) Kalliope. Possible rotation axes as a function of size from the TESS light curves. The contours represent 5, 10 and 15% of the value of the data line. White circles represent the DAMIT solutions. The white dots show the 100 smallest values of the data set while the red dots show their median.
How to cite: Takács, N., Kiss, C., Pál, A., and Szakáts, R.: Shape and rotation modelling of asteroids based on multi-directional TESS measurements, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-101, https://doi.org/10.5194/epsc2024-101, 2024.
Introduction
The knowledge of the current dynamic of Near Earth Asteroids (NEAs) is essential. Accurate astrometric measurements acquired over a large time span are important to provide reliable orbits and impact probability. With growing number of observations and a large number of already existing data, a rapid and accurate algorithm for follow-up and precovery of NEAs is required.
In this work we focus on precovery of asteroids. The New Astrometric Reduction of Old Observations (NAROO) program is dedicated to the measurement of astrophotographic plates and the analysis of old observations [1]. It has access to a collection of more than ten thousand plates from 1949 to 2000. Photographic plates consist of a substantial source of old observations of NEAs but they can be difficult to retrieve, as positions predicted back in time from orbit propagation can be highly imprecise and the objects are generally faint.
Basic principles
The orbits of most of the NEAs, and in particular newly discovered ones, are not precise, therefore the accurate positions of these asteroids are unknown. In the majority of cases the trajectory itself is quite well defined, but there is an uncertainty in the position along the orbit. Over time, this uncertainty grows and can reach even the whole orbit (the mean anomaly is undefined). Because of that, our nominal prediction of the spherical coordinates of an asteroid on a photographic plate can be far from the real one. It is also possible that the nominal orbital solution tells us that the object is not on the plate, however, a significant part of the uncertainty region is, and, hence, there is still a probability that the object can be found on the plate.
Partial banana mapping method
In order to find if a Near-Earth Object can be on the photographic plate, we use a modification of a Partial Banana Mapping method [2]. In Fig. 1 one can see a schematic illustration of the method. The idea is that we take a covariance matrix of the asteroid in equinoctial orbital elements and consider the largest eigen vector of the matrix (which corresponds to the main axis of the curvilinear uncertainty region). Then we take several samples on this line (virtual asteroids) and project them onto celestial sphere with their uncertainties. This approach will give us the uncertainty region of the asteroid on the celestial sphere. If the region intersects with the plate, it means there is a chance of the object being on the plate and we can even provide the probability. We also estimate the length of the uncertainty region as well as visual magnitudes of the virtual asteroids.
Fig. 1. The scheme of the banana shaped uncertainty region of the asteroid. Point A is the nominal position of the asteroid. The bold line is the nominal asteroid’s orbit.
Computations
We tested the method with asteroid 2015 UM67 (506074) Svarog. In the test we simulated the scenario that it is the end of 2015 year, so we only have 3 months arc observations of the object. The result can be found in Fig. 2.
Fig. 2. Possible position (blue dots) of asteroid (506074) Svarog on 1990/03/01 06:00:00. The purple square represents the photographic plate. The orange dot is the nominal position of the object. The red dot in the plate is the position where the object was actually found. The green line is the uncertainty region of the nominal position constructed only from the covariance matrix in right ascension and declination.
As one can see the method could successfully predict the possible positions of the object and the actual observation is exactly in the 5 uncertainty region. This region is indeed curved, as one can compare it to the straight green line, directly obtained from the local covariance matrix. On the other hand, we can not get accurate predictions of the asteroid position using only the nominal position with its covariance matrix.
It took approximately 0.359 seconds to compute these results for asteroid Svarog on a PC with 12th Gen Intel(R) Core(TM) i7-12700H 2.30 GHz processor. On the contrary the Monte Carlo approach is required to integrate at least 1000 orbits of virtual asteroids and it takes 109.51 seconds (305 times longer!). This proves that our method is an efficient technique for asteroid follow-up and precovery.
To crossmatch all the NEAs with about 9000 photographic plates, available at Paris observatory, it takes only 1 day of computation.
Acknowledgments
This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 101068341 “NEOForCE”. This study shows outcomes from the NAROO program which was supported by the DIM-ACAV of Ile-de-France region, PSL Research University, the Programme National GRAM and the Programme National de Planétologie (PNP) of CNRS/INSU with INP and IN2P3, co-funded by CNES.
References:
[1] Robert, V., Desmars, J., Lainey, V., et al. 2021, A&A, 652, A3.
[2] Vavilov D. E. (2020) MNRAS, 492, 4546–4552.
How to cite: Vavilov, D., Hestroffer, D., Liu, Z., Robert, V., and Desmars, J.: Rapid technique for follow-up and precovery of asteroids, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-548, https://doi.org/10.5194/epsc2024-548, 2024.
C-complex asteroids are dark, low-albedo objects, mainly containing carbon components. Their spectra are usually featureless, especially in the visible-near-infrared (VNIR) wavelengths. However, for some taxonomic types, absorption has been found in the near-UV (NUV) range. Laboratory studies have shown similarities to spectra of chondrite meteorites, demonstrating that this absorption is a result of charge transfer involving iron ions (Fe2+ and Fe3+)[9,10,14], particularly in hydrated silicates and clay minerals [6]. These minerals exhibit strong NUV absorption, even in low-albedo asteroids. This option can be used to detect the presence of hydrated minerals (and hence water) and organic minerals on C-complex asteroids. Detecting hydrated minerals on asteroids is crucial for understanding their history and the processes that have shaped them. Moreover, spectroscopy of the UV spectrum can show a link to space weathering [7] - the process by which the surfaces of asteroids are altered by exposure to solar radiation and micrometeoroid impacts. Observations can help characterize the effects of space weathering on asteroid surfaces, providing insights into their age and history.
Our spectroscopic studies of C-complex asteroids are performed with the 10-m Southern African Large Telescope (SALT), located in Sutherland, South Africa. It is equipped, among all, with the RSS spectrograph, which we used to get asteroid spectra with the resolution of R=800. One of the unique characteristics of SALT is its high throughput in the NUV region, caused by the NaCl correction lens. In November 2023 we started observations of primitive asteroids with SALT, and during the conference, we will present spectra of several of them, obtained in the 0.32-0.9 μm range. Additionally, we will discuss the observational strategy, including searching for solar analogue stars in the NUV range in the southern hemisphere.
Figure 1. Reflectance spectrum of asteroid (1101) Clematis obtained with SALT on 20th Dec 2023. The original asteroid spectrum was divided by the spectrum of a solar analogue star BD+002717 (confirmed by [11] to be almost identical to the Sun in NUV range). The result has been normalized to 1 at the 0.55 μm wavelength.
Acknowledgments: All observations reported in this abstract were obtained with the Southern African Large Telescope (SALT). This work has been done under the SALT programs 2023-2-SCI-025 and 2024-1-SCI-012 (PI: T. Kwiatkowski). Polish participation in SALT is funded by grant No. MEiN nr 2021/WK/01
References:
[1] Cloutis et al. (2011a), Icarus, 212, 180
[2] Cloutis et al. (2011b), Icarus, 216, 309
[3] Cloutis et al. (2012), Icarus, 220, 586
[4] Feierberg et al. (1981), Geochim. Cosmochim. Acta, 45, 971
[5] Feierberg et al. (1985), Icarus, 63, 183
[6] Gaffey, McCord (1979), Asteroids I, 688
[7] Hendrix, Vilas (2019) Geophysical Research Letters, 46(24), 24
[8] Hiroi et al. (2021), Polar Science, 29, 100723
[9] Howell et al. (2011), EPSC-DPS Joint Meeting 2011, Vol. 2011, 637
[10] Rivkin et al. (2015), AJ, 150, 198
[11] Tatsumi et al. (2022) A&A, 664, A107
[12] Tatsumi et al. (2023) A&A, 672, A189
[13] Tinaut-Ruano et al. (2023) A&A, 669, L14
[14] Vilas (1994), Icarus, 111, 456
How to cite: Mykhailova, S. S., Kwiatkowski, T., De Leon, J., Tatsumi, E., and Dimitrov, W.: Determination of the near-UV absorption in the spectra of primitive asteroids, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-639, https://doi.org/10.5194/epsc2024-639, 2024.
Introduction
Barbarian asteroids are unique because of their wide negative branch of the polarisation phase curves. Their name comes from (234) Barbara for which such behaviour was first observed [1]. They reside in the inner part of the Main Belt and are mainly of the L taxonomic class. Since magnitude-phase curves are sensitive to the asteroid surface properties, the question arises as to whether Barbarian asteroids' magnitude-phase curves are also anomalous. To answer this, we are carrying out photometric observations of Barbarian asteroids, fitting their phase curves with the [H,G], [H, G12], and [H, G1, G2] phase functions. These parameters are then compared with those of other asteroids in search of deviations. The results for (599) Luisa and (729) Watsonia have been presented in [2]. At the conference, we will show mag-phase curves for another three Barbarians: (234) Barbara, (236) Honoria, and (980) Anacostia.
Observations and Reduction
Photometric observations were carried out using several telescopes in different observatories in the Johnson R band. For Honoria, we collected data during its 2012 opposition and for Barbara and Anacostia during the 2022 and 2023 oppositions, respectively. CCD images were reduced in a standard way, including bias, dark subtraction, and flat-field correction. The magnitudes of asteroids and standard stars were obtained with aperture photometry using the Photometry Pipeline package [3].
Results
For each asteroid, composite lightcurves from data collected during the opposition were obtained. Synodic periods were derived by a standard Fourier series fit procedure (Fig. 1). The composite lightcurves were used to correct the partial lightcurves (which did not cover all rotation phases) to the same level of maximum brightness. The magnitudes of the maxima of brightness from different nights were then plotted against the phase angle, producing mag-phase curves, which were fitted with three different phase functions (Fig. 2). This allowed us to compare the obtained G1, G2 parameters with similar parameters obtained by [4] for 127 Main Belt asteroids. The final results will be presented at the conference.
Fig. 1. Composite lightcurve of (980) Anacostia
Fig. 2. Magnitude-phase curve of (980) Anacostia, based on maxima of brightness obtained from the composite lightcurve
References
[1] Cellino, A., et al. (2006) The strange polarimetric behavior of asteroid (234) Barbara, Icarus, 180, 565
[2] Mykhailova, S., et al. (2023) What do the phase curves tell us about the Barbarian asteroids. Asteroids, Comets, Meteors Conference, Flagstaff, Arizona. LPI Contribution No. 2851, 2023, id. 2202
[3] Mommert, M. (2017) PHOTOMETRYPIPELINE: An automated pipeline for calibrated photometry, Astronomy and Computing, 18, 47
[4] Shevchenko, V. G., et al. (2016). Planetary and Space Science, 123, 101
How to cite: Kwiatkowski, T., Mykhailova, S., Podlewska-Gaca, E., Kamiński, K., Ryzhov, O., and Bosh, J. M.: Magnitude-phase curves of the Barbarian asteroids (234) Barbara, (236) Honoria, and (980) Anacostia, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-858, https://doi.org/10.5194/epsc2024-858, 2024.
Introduction
The determination of asteroid spin periods is crucial for understanding the physical properties and evolutionary history of these celestial bodies. The Kepler Space Telescope, initially designed for exoplanet detection, provided valuable data on asteroid rotation periods during its K2 extension in the ecliptic see Fig. 1. This research summarizes the methods and findings from the Kepler/K2 observations of main-belt asteroids. It highlights the extraction and analysis of light
curves, discusses the challenges encountered, and presents the results obtained. Additionally, the analysis includes the correlation between rotation periods and asteroid taxonomy, as well as a comparison with previously estimated rotation periods.
 |
| Fig. 1: Location and coverage of the Kepler/K2 observing fields in the sky. The ecliptic plane is shown as a solid line. |
Asteroid spin periods offer significant insights into their internal structures, shapes, densities, and surface properties. This information is vital for understanding the formation and evolution of the solar system since asteroids are considered remnants of early planetary building blocks. Determining the rotation periods of asteroids also allows for the identification and study of binary systems, enhancing our knowledge of asteroid interactions and dynamics (Margot et al. 2015).
Most asteroids exhibit rotation periods exceeding two hours, primarily due to the "spin barrier" phenomenon, which refers to the upper limit of the rotation speed at which asteroids can remain intact without disintegrating due to centrifugal forces (Holsapple 2007). Consequently, long-term observations are required to accurately determine these periods.
Kepler’s Data
Kepler’s data are available in two cadences: long cadence (30-minute intervals) and short cadence (one-minute intervals). The data are stored in Target Pixel Files (TPF), which include two-dimensional arrays for pixel values and one-dimensional arrays for time stamps and cadence numbers. The time stamps are recorded in Barycentric Julian Date (BJD) format. Each TPF also contains metadata about the target star and specifics of the observation.
Observation Limits
The magnitude limit of Kepler’s observations restricts the accuracy of faint asteroid light curves. The Kepler dataset includes over one million asteroid events brighter than the observational depth magnitude limit of 20 mags. However, the presence of bright stars in the TPF’s field of view necessitates focusing on asteroids brighter than 18 magnitudes for reliable light curve extraction (Berthier et al. 2016).
The limited field of view of approximately one square arcminute and the typical proper motion of main-belt asteroids (about 30 arcseconds per hour) constrain the ability to determine long spin periods. Therefore, asteroids appearing in the Kepler TPFs at least ten times were prioritized, covering half of the spin period range for most known asteroids.
The integration time of the obtained frames limits the detection of rotation periods shorter than 30 minutes. This constraint is significant since most monolithic or rubble-pile asteroids have spin barriers for around 2-2.5 hours (Pravec & Harris 2000).
Light Curve Extraction
To extract light curves from the TPF files, the total flux values across all frames were first calculated. Cotrending Basis Vectors (CBV) were then applied to correct the flux, followed by the selection of points with precomputed time crossings of the asteroids within the field of view. The Lomb-Scargle periodogram technique was used to identify periodic signals within noisy or unevenly sampled data, focusing on periods between one and ten hours (Scargle 1982). The example light curve of the asteroid 204557 Danmark is shown in Fig. 2.
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Fig. 2: An example of a light curve extracted from Kepler K2 data for the asteroid 204557 Danmark. The plot shows the normalized flux as a function of time (in BKJD days), illustrating the periodic variations in brightness due to the asteroid's rotation.
|
Results
The rotation periods of several hundred asteroids were calculated, showing a strong correlation with data from ground-based observations, validating the approach. Comparisons with sparse light curves from the Palomar Transient Factory also demonstrated high accuracy. Future surveys like ZTF, Pan-STARRS, and LSST, combined with Kepler data, will further refine asteroid rotation period determinations.
The analysis of rotation periods in relation to asteroid taxonomy revealed distinct patterns among different classes of asteroids. By comparing the rotation periods with known taxonomic categories, it was observed that certain types of asteroids, such as C-type (carbonaceous) and S-type (silicaceous), exhibit characteristic rotation periods that align with their physical properties and formation histories. This correlation helps in understanding the compositional diversity and evolutionary processes of asteroid populations (de León et al. 2020).
The rotation periods obtained from the Kepler K2 data were compared with those estimated from ground-based observations and other sky surveys. The strong agreement between these datasets confirms the reliability of Kepler’s observations for asteroid spin period analysis. This comparison also highlights the potential for combining different observational techniques to achieve a more comprehensive understanding of asteroid rotational dynamics (Pravec et al.
2002).
References
Margot, J. L., Pravec, P., Taylor, P., Carry, B., & Jacobson, S. A. (2015). Binary asteroid population. Icarus, 248, 89-121.
Holsapple, K. A. (2007). Spin limits of Solar System bodies: From the small fast-rotators to 2003 EL61. Icarus, 187(2), 500-509.
Borucki, W. J., et al. (2010). Kepler planet-detection mission: Introduction and first results. Science, 327(5968), 977-980.
Howell, S. B., et al. (2014). The K2 Mission: Characterization and Early Results. PASP, 126, 398.
Berthier, J., et al. (2016). Prediction of transits of Solar system objects in Kepler/K2 images: an extension of the Virtual Observatory service SkyBoT. MNRAS, 458, 3394-3398.
Pravec, P., & Harris, A. W. (2000). Fast and slow rotation of asteroids. Icarus, 148(1), 12-20.
Scargle, J. D. (1982). Studies in astronomical time series analysis. II. Statistical aspects of spectral analysis of unevenly spaced data. ApJ, 263, 835-853.
de León, J., et al. (2020). Reflectance spectra and taxonomy of near-Earth and Mars-crossing asteroids. Icarus, 341, 113636.
Pravec, P., Harris, A. W., & Michalowski, T. (2002). Asteroid Rotations. Asteroids III, 113-122.
How to cite: Sergeyev, A., Carry, B., Eggl, S., Santerne, A., and Berthier, J.: Rotation periods of asteroids from Kepler/K2's unintended observations, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-942, https://doi.org/10.5194/epsc2024-942, 2024.
TTT (Two-meter Twin Telescope) installation is a network of four telescopes located at the Teide Observatory, in the island of Tenerife (Canary Islands, Spain). TTT1 and TTT2 telescopes are two 0.80 m AltAz telescopes with two Nasmyth ports of both telescopes (f/4.4 and f/6.8). The f/4.4 is equipped with QHY411M cameras, composed of 151 Mpixel 3.76 μm sCMOS sensors, resulting in an effective FoV of 51.4x 38.3 arcmin2 and a pixel scale of 0.22" pixel−1. The f/6.8 has a Ikon-L 936 (FOV: 17.34’ × 17.34’, 0.51 ’’/px) and a SWIR QHY990Pro II InGaAs camera (FOV: 4.64’ x 3.5’, Plate scale: 0.2 ’’/px).
They operate fully robotically and feature a QPIS (Queue Planning Intelligent System) managed by a machine learning algorithm, supervised by senior astronomers with proven observational experience.
Scientific proposals are evaluated within 48 hours. Once approved, observations can be conducted and, if they are successful, images could be obtained in 24 hours -astrometric & photometric calibrated in real time-.
TTT1 and TTT2 have been operated on routinely since december 2022 and demonstrated to provide excellent photometric measurements. We have been running different scientific programs on exoplanetary transits (see Figure 1), asteroids follow-up astrometry and photometry (see Figure 2), and comets. Some of the most interesting results, including exoplanets and Near Earth Asteroids lightcurves will be presented.
Figure 1. Phased-folded transit taken on 22 December 2022 in T, g′, r′, and zcut filters. The coloured lines show the best transit model in each filter. Reproduced from Mallorquín et al. (2024) (10.48550/arXiv.2402.17448)
Figure 2. Phased light curve of 2023 DZ2 (fast rotator) computed from photometric measurements obtained by TTT1 and TTT2. The rotation period and amplitude of the curve are shown in the lower left corner of the top panel. The total coverage is 9.8 h, distributed over three consecutive nights. Reproduced from Popescu et al. (2023) ( https://doi.org/10.1051/0004-6361/202346751).
How to cite: Serra-Ricart, M., R. Alarcón, M., Licandro, J., and Abárzuza, F.: Two-meter Twin Telescope (TTT). A new way of doing science, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-631, https://doi.org/10.5194/epsc2024-631, 2024.
The growing volume of astronomical data produced by telescopic facilities presents significant challenges and extraordinary opportunities for the scientific community. Specifically, the Canary Islands Observatories generate approximately 1 petabyte of raw images annually from nearly thirty telescope installations, both public and private. These images are released into the public domain after a standard proprietary period of one year, enabling a variety of targeted research initiatives. In this communication, we introduce AsteroiDB, a dynamic and comprehensive catalog of asteroid photometry in the visible spectral range, compiled from archival images taken by various telescopes and instruments at the Canary Islands Observatories. To facilitate this, we have developed a series of innovative, open-source algorithms optimized for CUDA-based graphics processing units (GPUs). These kernel-based algorithms are designed to enhance the efficiency and speed of processing, calibration, and detection of point objects, and to accurately determine their astrometry and photometry. A brief introduction to the key aspects of these algorithms will be provided, followed by a demonstration of their performance across various GPU models.
The archive from the TTT1 and TTT2 telescopes, located at the Teide Observatory, has been processed to date. These are privately funded 80-cm telescopes that employ two distinct instruments: a CCD camera iKon936-L BEX2-DD (g+r, ugriz filters) with a field of view (FOV) of 17.3 x 17.3 arcmin, and a CMOS camera QHY411 (g+r, gri filters) with an FOV of 39 x 52 arcmin. Since March 2023, a total of 7,500 hours of observation have been conducted, resulting in the processing of 320,000 images (400 TB of data). This has yielded 950,000 photometric data points from 12,000 unique solar system objects, with 1,500 of these objects observed more than 100 times.
This communication presents preliminary results of the photometry, including data from additional telescopes such as the forthcoming Transient Survey Telescope (TST), a 1-meter wide-field telescope scheduled to begin operation in May 2024, and the prototype of ATLAS-Teide, the fifth node of the asteroid impact early warning system ATLAS, which will be installed at the Teide Observatory by the end of 2024. Furthermore, we will present research that has already made use of this data–e.g. Popescu et al. (2023) or de la Fuente Marcos et al. (2024), see Fig. 1. Additionally, we will discuss new investigations that are currently underway. Furthermore, the AsteroiDB User Interface will be introduced, which allows for dynamic access to the database, the addition of new datasets from other photometric catalogs, and the retrieval of detailed information on rotation periods or phase curves, among other features. Future prospects include integrating all other telescopes at the Canary Islands Observatories equipped with imaging instruments into the catalog and conducting specific studies on solar system science, with a particular focus on the Near Earth Asteroid population.
Figure 1. Phased light curve of 2023 FY3 derived from photometric measurements obtained by the TTT1 and TTT2 telescopes. The object was at mV = 18.4 at the moment of the observation, continuous exposures of 6.5-sec were taken using the sCMOS camera QHY411. The rotation period and amplitude of the curve are shown at the upper left. Reproduced from de la Fuente Marcos et al. (2024).
References
Marcel M. Popescu, O. Văduvescu, J. de León, C. de la Fuente Marcos, R. de la Fuente Marcos, M. O. Stănescu, M. R. Alarcon, M. Serra Ricart, J. Licandro, D. Berteşteanu, M. Predatu, L. Curelaru, F. Barwell, K. Jhass, C. Boldea, A. Aznar Macías, L. Hudin and B. A. Dumitru. Discovery and physical characterization as the first response to a potential asteroid collision: The case of 2023 DZ2. A&A, 676 (2023) A126. https://doi.org/10.1051/0004-6361/202346751.
de la Fuente Marcos, C. de la Fuente Marcos, J. de León, M. R. Alarcon, J. Licandro, M. Serra-Ricart, D. García-Álvarez, A. Cabrera-Lavers. When the horseshoe fits: Characterizing 2023 FY3 with the 10.4 m Gran Telescopio Canarias and the Two-meter Twin Telescope. A&A 681 A4 (2024). https://doi.org/10.1051/0004-6361/202347663.
How to cite: R. Alarcon, M., Licandro, J., and Serra-Ricart, M.: AsteroiDB: The Asteroid Legacy Archive of the Canary Islands Observatories, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-640, https://doi.org/10.5194/epsc2024-640, 2024.
Asteroid observability from the ground depends on the object distance to the Sun and to the observer, on the object’s Sun-Earth phase angle, on the object shape and on its surface reflectivity properties. Additionally, several magnitude systems have been proposed in the last decades to model the visual magnitude of the object based on the mentioned parameters, as for example the H, G system, the H, G1, G2 system or the H, G12system. Independently of the magnitude system used, there is a three-dimensional representation of the geometrical locus of equal visual magnitude when this value is constrained, which we have called the detection polar. We analyse the shape of this geometrical locus for the H, G magnitude system and its applicability to the representation of the detectability of an asteroid in its trajectory. We also present ESA's Synodic Orbit Visualisation Tool and provide examples of its use to analyse the graphical representation of a NEO trajectory and the observability region for a given limiting visual magnitude defined by the detection polar.
Given the H, G magnitude system and a limiting visual magnitude Vlim the detection polar computation results from the intersection of two families of curves. The first set of curves is given by the phase angles, having the Sun and the observer as focal points and resulting in arcs of circumference passing by both focuses. The second family of curves is derived from constant values of the distance product from the asteroid to the two focuses as derived from the H, G system equation. These are represented by the so-called Cassini ovals. Defining the relative magnitude B as Vlim-H, the results of the intersections of both families are a new set of curves for varying values of the parameter B (see Figure 1, which assumes G = 0.15). Starting with B = -2 mag we observe two heart-like solutions located at each of the focal points with the shape tip pointing in the direction of the opposition effect. As the value of the relative magnitude grows the shapes size increases accordingly. When B reaches a value of 1.6685 mag (not represented in the figure) the two shapes make contact and they transform into two other shapes; an external one that keeps growing and an internal one that joins the two focal points and that decreases in size as the relative magnitude grows. The detectability region is described by the area between both shapes. At this point, no visibility constraints other than the mentioned magnitude system have been considered in the plots. However, it is expected that the derived solution close to the Sun will be affected by a low solar elongation as seen from the Earth, thus limiting the possibilities of observing that part of the detection polar.
All those constraints and shapes can be easily simulated in ESA’s Synodic Orbit Visualisation Tool (SOVT), a software tool which allows the graphical representation of the mentioned detection polars extended to 3D shapes, in conjunction with the representation of the co-rotational motion of the object in space. An example of such representation is provided in Figure 2 for asteroid (367943) Duende between 01/01/2007 and 01/01/2018. The object was discovered in its close approach with Earth in February 2012 at an approximate visual magnitude of 19 and had an even closer approach on 15 February 2013. It can be observed how the trajectory transformed on that date from a long-synodic period Apollo orbit into a relatively short synodic period Aten orbit. The estimated absolute magnitude of this asteroid is 24.05 mag. The detection polar represented in the figure is the one corresponding to a limiting magnitude of 19, similar to the one at its discovery. This translates into a relative magnitude parameter of B = -5.05 mag, thus implying a very small detection polar, noticeable in the figure.
The SOVT thus allows analysing in a very direct and intuitive way when and how a NEO would become observable from Earth by a given telescope.
Figure 1: Evolution of the detection polar for relative magnitude values of B = -2 mag (upper left), B = 0 mag (upper-right), B = +2 mag (lower-left) and B = +4 mag (lower-right) in a Sun-Earth co-rotating reference frame, with the Sun in the origin and the Earth at location (1,0). The values of the plots are measured in astronomical units.
Figure 2: Screenshot of the SOVT for asteroid (367943) Duende between 01/01/2007 and 01/01/2018. It can be observed how the trajectory (in red) crosses the detection polar around Earth (in yellow) twice and transforms from a long-synodic period Apollo orbit into a relatively short synodic period Aten orbit. Additional plots are available at the right side of the plotting panel providing the evolution of the distance to the Earth, the phase angle and the visual magnitude.
How to cite: Cano, J. L., Micheli, M., Ramírez Moreta, P., Hoffmann, T., and Moissl, R.: The Asteroid Detection Polar and ESA’s Synodic Orbit Visualisation Tool, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-389, https://doi.org/10.5194/epsc2024-389, 2024.