One meter class telescopes could bring important contributions in the acquisition of lightcurves of near earth asteroids (NEAs), based on which rotations and other physical properties could be ...derived or constrained. Part of a collaboration between IAC, ESA and the EURONEAR during the semester 2015A, the IAC80 and OGS telescopes at Teide Observatory in Tenerife were allocated for a photometric project during 64 nights spread in a few observing runs. The main funding for this long observing mission was raised by the student observer Radu Cornea from private sponsors based in his natal city of Sibiu, Romania, mentioned in the Acknowledgements. We observed 33 lightcurves of NEAs not published before, including 10 potentially hazardous asteroids (PHAs). Based on the quality of the Fourier period fits, we sorted the results in four groups which include 7 secured periods, 9 candidate periods, 10 tentative periods and 7 objects not solved. We resolved periods or suggested constraints for 13 NEAs having no other rotation knowledge (including 3 PHAs), confirming periods for other 6 targets published by other authors (mainly by Brian Warner). We suggested tumbling or binary nature for 6 targets (probing one of them) recommended for future dedicated campaigns. We derived ellipsoid shape ratios for 21 NEAs (including 4 PHAs) not known before.
ABSTRACT
We present new results of the observing program which is a part of the NEOROCKS project aimed to improve knowledge on physical properties of near-Earth Objects (NEOs) for planetary defense. ...Photometric observations were performed using the 1.2-m telescope at the Haute-Provence observatory (France) in the BVRI filters of the Johnson–Cousins photometric systems between June 2021 and April 2022. We obtained new surface colours for 42 NEOs. Based on the measured colours, we classified 20 objects as S-complex, nine as C-complex, nine as X-complex, two as D-type, one object as V-type, and one object remained unclassified. For all the observed objects, we estimated their absolute magnitudes and diameters. Combining these new observations with the previously acquired data within the NEOROCKS project extended our data set to 93 objects. The majority of objects in the data set with diameters D < 500 m belongs to a group of silicate bodies, which could be related to observational bias. Based on MOID and ΔV values we selected 14 objects that could be accessible by a spacecraft. Notably, we find D-type asteroid (163014) 2001 UA5 and A-type asteroid 2017 SE19 to be of particular interest as possible space mission targets.
Context. Stellar occultations have become one of the best techniques to gather information about the physical properties of trans-Neptunian objects (TNOs), which are critical objects for ...understanding the origin and evolution of our Solar System. Aims: The purpose of this work is to determine, with better accuracy, the physical characteristics of the TNO (84922) 2003 VS2 through the analysis of the multichord stellar occultation on 2019 October 22 and photometric data collected afterward. Methods: We predicted, observed, and analyzed the multichord stellar occultation of the Second Gaia Data Release (Gaia DR2) source 3449076721168026624 (mυ = 14.1 mag) by the plutino object 2003 VS2 on 2019 October 22. We performed aperture photometry on the images collected and derived the times when the star disappeared and reappeared from the observing sites that reported a positive detection. We fit the extremities of such positive chords to an ellipse using a Monte Carlo method. We also carried out photometric observations to derive the rotational light curve amplitude and rotational phase of 2003 VS2 during the stellar occultation. Combining the results and assuming a triaxial shape, we derived the 3D shape of 2003 VS2. Results: Out of the 39 observatories involved in the observational campaign, 12 sites, located in Bulgaria (one), Romania (ten), and Serbia (one), reported a positive detection; this makes it one of the best observed stellar occultations by a TNO so far. Considering the rotational phase of 2003 VS2 during the stellar occultation and the rotational light curve amplitude derived (Am = 0.264 ± 0.017 mag), we obtained a mean area-equivalent diameter of DAeq = 545 ± 13 km and a geometric albedo of 0.134 ± 0.010. By combining the rotational light curve information with the stellar occultation results, we derived the best triaxial shape for 2003 VS2, which has semiaxes a = 339 ± 5 km, b = 235 ± 6 km, and c = 226 ± 8 km. The derived aspect angle of 2003 VS2 is θ = 59° ± 2° or its supplementary θ = 121° ± 2°, depending on the north-pole position of the TNO. The spherical-volume equivalent diameter is DVeq = 524 ± 7 km. If we consider large albedo patches on its surface, the semi-major axis of the ellipsoid could be ~ 10 km smaller. These results are compatible with the previous ones determined from the single-chord 2013 and four-chord 2014 stellar occultations and with the effective diameter and albedo derived from Herschel and Spitzer data. They provide evidence that 2003 VS2's 3D shape is not compatible with a homogeneous triaxial body in hydrostatic equilibrium, but it might be a differentiated body and/or might be sustaining some stress. No secondary features related to rings or material orbiting around 2003 VS2 were detected. The photometric data used to obtain the rotational light curve of (84922) 2003 VS2 are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/663/A121
This data paper presents lightcurves of 101 near Earth asteroids (NEAs) observed mostly between 2014 and 2017 as part of the EURONEAR photometric survey using 11 telescopes with diameters between 0.4 ...and 4.2 m located in Spain, Chile, Slovakia and Romania. Most targets had no published data at the time of observing, but some objects were observed in the same period mainly by B. Warner, allowing us to confirm or improve the existing results. To plan the runs and select the targets, we developed the public
Long Planning
tool in PHP. For preliminary data reduction and rapid follow-up planning we developed the
LiDAS
pipeline in Python and IRAF. For final data reduction, flux calibration, night linkage and Fourier fitting, we used mainly
MPO Canopus
. Periods of 18 targets are presented for the first time, and we could solve or constrain rotation for 16 of them. We secured periods for 45 targets (
U
∼
3
), found candidate periods for other 16 targets (
U
∼
2
), and we propose tentative periods for other 32 targets (
U
∼
1
). We observed 7 known or candidate binary NEAs, fiting 3 of them (2102 Tantalus, 5143 Heracles and 68348). We observed 8 known or candidate tumbling NEAs, deriving primary periods for 3 objects (9400, 242708 and 470510). We evidenced rapid oscillations (few minutes) and could fit fast tentative periods
TP
2 for 5 large newly suggested tumbling or binary candidates (27346, 112985, 285625, 377732, 408980), probably discovering at least one new binary NEA (2011 WO41). We resolved periods of 4 special objects which include two proposed space mission targets (163249 and 101955 Bennu), one very fast rotator NEA discovered by EURONEAR (2014 NL52) and the “Halloween asteroid” (2015 TB145). Using Mercator in simultaneous 3 band MAIA imaging, we could evidence for the first time clear variation in the color lightcurves of 10 NEAs. The periods derived from the
g
–
r
color lightcurves are found to match individual band period fits for 4 NEAs (27346, 86067, 112985 and 275976).
These are the first results of an observational program devoted to the complete physical data of asteroids that could produce or feed meteoroid streams. Our results are based on the optical ...observation at Pic du Midi observatory in April 6–7, 2016 and January 17–18, 2018. We will present the light curve of asteroid (259221) 2003 BA21, associated with Daytime Sextantids (221 DSX) and November θ Aurigids (390 THA); the light curves and colors of asteroid (363599) 2004 FG11, associated with Daytime ζ Perseids (172 ZPE) as well as g − r and g − i; and the corresponding reflectances for the (85953) 1999 FK21, associated with Daytime ξ Sagittariids (100 XSA). We will also present the colors for two additional objects, namely, (5141) Tachibana and (43032) 1999 VR26.
Context. The potentially hazardous asteroid (PHA) (357439) 2004 BL86 grazed Earth on January 26, 2015 at a distance of about 1.2 million km. This favorable geometry allowed observing it to derive its ...physical and dynamical parameters. (357439) 2004 BL86 was previously estimated to be a 500-m body. We study it also considering possible mechanisms that might mitigate the effect of asteroids that might become dangerous for Earth. Aims. Physical and dynamical investigations of this peculiar object were performed to be able to characterize this object. Methods. We used spectral observations obtained in the visible (V) using the Isaac Newton Telescope and in the near-infrared (NIR) using the InfraRed Telescope Facility. A complementary photometric survey during two nights was also provided by the Astronomical Observatory Cluj-Feleacu station in Romania. We anlyzed the data using reliable mathematical tools that were previously published under the acronym M4AST. Results. VNIR spectral observations classify (357439) 2004 BL86 as V-type asteroid. The mineralogical analysis reveals its similarities to howardite-eucrite-diogenite meteorites. The band analysis reveals that the object is more similar to a eucritic and howarditic composition, and that it originated from the crust of a large parent body. The analysis yields a mineralogical solution of Wo17Fs39 with an error bar of 4%. Based on the average value of the thermal albedo for V-type objects, its diameter was re-estimated to a value of 290 ± 30 m. The dynamical analysis shows a chaotical behavior of (357439) 2004 BL86. The statistics on meteorite falls show that (357439) 2004 BL86 does not appear to significantly contribute to the current howardite-eucrite-diogenite meteorite flux. For the two photometrical observing runs the following values of the rotational period and peak-to-peak amplitude were estimated for the light curves: 2.637 ± 0.024 h, 0.105 ± 0.007 mag, and 2.616 ± 0.061 h, 0.109 ± 0.018 mag, respectively.
As part of the EURONEAR project, almost 70,000 mosaic Suprime‐Cam images taken between 1999 and 2013 were data‐mined for about 9,800 near‐Earth asteroids (NEAs) known by 2013 May. Using our PRECOVERY ...server and the new Find Subaru CCD tool, we scrutinized 4,186 candidate CCD images possibly holding 518 NEAs. We found 113 NEAs as faint as V<25
magnitude, their positions being measured in 589 images using Astrometrica, and then reported to the Minor Planet Center. Among them, 18 objects represent encounters of previously single opposition NEAs, their orbital arcs being extended by up to 10 years. In the second part of this work, we searched for unknown NEAs in 78 sequences (780 CCD fields) of 4–5 mosaic images selected from the same Suprime‐Cam archive and totaling 16.6 deg2, with the aim to assess the faint NEA distribution observable with an 8‐m class survey. A total of 2,018 moving objects were measured, from which we identified 18 better NEA candidates. Using the Rcfilter in good weather conditions, mostly dark time and sky directions slightly biased towards the ecliptic, at least one NEA could be discovered in every 1 deg2 surveyed.
The ESO/MPG WFI and the INT WFC wide field archives comprising 330 000 images were mined to search for serendip‐itous encounters of known Near Earth Asteroids (NEAs) and Potentially Hazardous ...Asteroids (PHAs). A total of 152 as‐teroids (44 PHAs and 108 other NEAs) were identified using the PRECOVERY software, their astrometry being measured on 761 images and sent to the Minor Planet Centre. Both recoveries and precoveries were reported, including prolonged orbital arcs for 18 precovered objects and 10 recoveries. We analyze all new opposition data by comparing the orbits fitted before and after including our contributions. We conclude the paper presenting “Mega‐Precovery”, a new online service focused on data mining of many instrument archives simultaneously for one or a few given asteroids. A total of 28 instrument archives have been made available for mining using this tool, adding together about 2.5 million images forming the “Mega‐Archive”
Context.
The population of near-Earth asteroids (NEAs) shows a large variety of objects in terms of physical and dynamical properties. They are subject to planetary encounters and to strong solar ...wind and radiation effects. Their study is also motivated by practical reasons regarding space exploration and long-term probability of impact with the Earth.
Aims.
We aim to spectrally characterize a significant sample of NEAs with sizes in the range of ~0.25–5.5 km (categorized as large), and search for connections between their spectral types and the orbital parameters.
Methods.
Optical spectra of NEAs were obtained using the
Isaac Newton
Telescope (INT) equipped with the IDS spectrograph. These observations are analyzed using taxonomic classification and by comparison with laboratory spectra of meteorites.
Results.
A total number of 76 NEAs were observed. We spectrally classified 44 of them as Q/S-complex, 16 as B/C-complex, eight as V-types, and another eight belong to the remaining taxonomic classes. Our sample contains 27 asteroids categorized as potentially hazardous and 31 possible targets for space missions including (459872) 2014 EK24, (436724) 2011 UW158, and (67367) 2000 LY27. The spectral data corresponding to (276049) 2002 CE26 and (385186) 1994 AW1 shows the 0.7
μ
m feature which indicates the presence of hydrated minerals on their surface. We report that Q-types have the lowest perihelia (a median value and absolute deviation of 0.797 ± 0.244 AU) and are systematically larger than the S-type asteroids observed in our sample. We explain these observational evidences by thermal fatigue fragmentation as the main process for the rejuvenation of NEA surfaces.
Conclusions.
In general terms, the taxonomic distribution of our sample is similar to the previous studies and matches the broad groups of the inner main belt asteroids. Nevertheless, we found a wide diversity of spectra compared to the standard taxonomic types.
Context. The EUROpean Near Earth Asteroid Research (EURONEAR) is a network which envisions to bring some European contributions into the general context traced by the Spaceguard Foundation which was ...carried out during the last 15 years mainly by the US with some modest European and amateur contributions. Aims. The number of known near Earth asteroids (NEAs) and potentially hazardous asteroids (PHAs) has increased tremendously, mainly thanks to five major surveys all focused on the discovery of new bodies. But also other facilities are required to follow-up and improvement the orbital parameters and to study the physical properties of the known bodies. These goals are better achieved by a co-ordinated network such as EURONEAR. Methods. Astrometry is mandatory in order to acquire the positional information necessary to define and improve orbits of NEAs and PHAs and to study their trajectories through the solar system, especially in the vicinity of Earth. Photometry is required to derive some physical information about NEAs and PHAs. In order to achieve these objectives, the main method of research of the EURONEAR is the follow-up programme of objects selected by a few criteria, carried out mostly at 1 m-class telescopes endowed with medium and large field cameras. Results. 162 NEAs summing more than 1500 individual positions were observed for a total time of 55 nights in both visiting mode and regular runs using nine telescopes located in four countries. The observations were reduced promptly and reported to the Minor Planet Centre (MPC) which validated and included them in the MPC and NEODyS databases following the improvement of their orbital elements. For one binary NEA we acquired photometry and were able to determine its orbital and rotational periods. Complementary to the follow-up work, as many as 500 unknown moving objects consistent with new Main Belt asteroids and one possible NEA were discovered in the analyzed fields. Conclusions. Our positions present 1$\arcsec$ precision with an accuracy of 0.2–0.4$\arcsec$, sufficient for achieving our immediate main goals. The observations and data reduction were conducted by our network members, which included some students and amateurs supervised by professional astronomers. In most cases, we increased the observational arcs decreasing the uncertainties in the orbits, while in some cases the new positions allowed us to recover some bodies endangered to be lost, defining their orbits.
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