Telescope Network Research Articles

Photometric Observations of KEPLER Mission’s Eclipsing Binary EPIC 201458798 (V0337Leo)

Abstract Two follow up observing sessions of Kepler’s Eclipsing Binary star system EPIC 201458798 (from the K2 mission) were conducted in the Spring of 2018 and 2019 utilizing the 0.4 m subnet of the Los Cumbres Observatory Global Telescope network. The total duration of observations for each session (∼77 days) was comparable with the duration of observations by the Kepler telescope ∼80 days. 900–1000 images were obtained during each session with an integrating time around 1 minute, resulting in about 800 mag measurements per session. In contrast, the Kepler telescope provided almost continuous measurements of this star with an integration time per image of about 30 minutes, resulting in about 3250 photometric points. In contrast to the Kepler telescope measurements, which were conducted with one very broad filter, the observations in this study used four filters: B, V, ip, and rp. This data was processed and the period, time of minimum, and depth of the eclipses was determined. The results were compared with the data obtained by the Kepler telescope and other historical records.

Systematic KMTNet Planetary Anomaly Search. I. OGLE-2019-BLG-1053Lb, a Buried Terrestrial Planet

Abstract In order to exhume the buried signatures of “missing planetary caustics” in Korea Microlensing Telescope Network (KMTNet) data, we conducted a systematic anomaly search of the residuals from point-source point-lens fits, based on a modified version of the KMTNet EventFinder algorithm. This search revealed the lowest-mass-ratio planetary caustic to date in the microlensing event OGLE-2019-BLG-1053, for which the planetary signal had not been noticed before. The planetary system has a planet–host mass ratio of q = (1.25 ± 0.13) × 10−5. A Bayesian analysis yielded estimates of the mass of the host star, M host = 0.61 − 0.24 + 0.29 M ⊙ , the mass of its planet, M planet = 2.48 − 0.98 + 1.19 M ⊕ , the projected planet–host separation, a ⊥ = 3.4 − 0.5 + 0.5 au, and the lens distance, D L = 6.8 − 0.9 + 0.6 kpc. The discovery of this very-low-mass-ratio planet illustrates the utility of our method and opens a new window for a large and homogeneous sample to study the microlensing planet–host mass ratio function down to q ∼ 10−5.

Observations of interplanetary scintillation of the 2005 May 13 coronal mass ejection: numerical models

ABSTRACT The 2005 May 13 eruption was an Earth-directed coronal mass ejection (CME) observed using the Multi-Element Radio-Linked Interferometer Network telescope system in the UK as it traversed the Interplanetary Medium on 2005 May 14. Observations of interplanetary scintillation (IPS) provide information on the solar wind conditions, which include velocities and density. In addition, it is also possible to calculate other parameters related to the turbulence and geometry of density irregularities in the solar wind from observations of IPS. Previous analyses have shown that IPS information can be difficult to interpret when a complex structure is crossing the line of sight since the physical properties of the plasma may change quite drastically with distance from the Sun. In order to compare and relate the internal structure of a CME and its physical changes, with the results from observations of IPS obtained previously, we carried out a numerical simulation of the 2005 May 13 eruptive event as it propagates into the IPM, adapting the geometrical properties derived by IPS analysis. In this work, we give a possible explanation of some signatures of CME sub-structure from the point of view of the IPS technique combined with what the modelling reveals.

Detecting the impact of software vulnerability on attacks: A case study of network telescope scans

Network scanning is one of the first steps in gathering information about a target before launching attacks. It is used to scan for vulnerable devices and exposed services in order to exploit them. Such exploits can result in data breaches or network disruption, which can be very costly for organizations. There are many factors, including technical and non-technical, affecting the volume of scanning activities. In this paper, we study the impact of vulnerability disclosure on the volume of scans over time and propose a machine learning-based approach to predict this impact. We conducted a comprehensive data collection of network scans from two network telescopes hosted in different countries, as well as the disclosed vulnerabilities from 2014 to 2019. We then designed a set of features to characterize the disclosed vulnerabilities and used several classifiers to predict whether a vulnerability will impact the volume of daily scans. The resulting classifier achieves over 85% accuracy in predicting the impact. In addition, we performed an analysis of the key characteristics of vulnerabilities that directly affect scanning activities. Our findings show that this approach is able to classify vulnerabilities that have an impact on network scans. The implementation of our model and validation tests proved the efficiency of the selected features, as well as the robustness of our model to classify vulnerabilities’ impact on scans.

New or Increased Cometary Activity in (2060) 95P/Chiron

Abstract Asteroid Terrestrial-impact Last Alert System (ATLAS) observations of Centaur (2060) 95P/Chiron show a brightening in the apparent magnitude not due rotational light curves or phase effects. This onset or enhancement of cometary activity started after 2021 February 8 UT and continued in later observations from 2021 June 18 UT onward. Recent ATLAS observations and deeper follow-up imaging obtained using the Las Cumbres Observatory 1.0 m robotic telescope network find no confirmed signature of coma or tail-like features.

ROLE OF THE 3.6M DOT TO INVESTIGATE CONNECTIONS BETWEEN LONG-GRBS AND CORE-COLLAPSE SNE

Newly installed 3.6m DOT at Nainital (Uttarakhand) is a novel facility for the time domain astronomy. Because of the longitudinal advantage of India, it could be used to study new transients reported by a global network of robotic telescopes. Observations with the 4K × 4K CCD Imager at the axial port of the 3.6m DOT will be very helpful in the near future towards understanding the different physical aspects of time-critical events, e.g., Gamma-ray bursts (GRBs), Supernovae, Gravitational wave candidates, etc. Using the Imager with broadband filters (Bessel UBVRI and SDSS ugriz), ~6.5' × 6.5' images could be obtained to attempt various science goals in synergy with other multi-band facilities. In this study, we present an analysis of unpublished R-band data of GRB 171205A/SN 2017iuk spanning between ~12 to 105 days since burst, that observed using the 3.6m DOT with 4K × 4K CCD Imager. In the R-band light curve, a bump appears to start from ~3 days, which shows the peak at ~15 days after the burst, clearly indicates photometric evidence of association of SN with GRB 171205A.

Constraining bright optical counterparts of fast radio bursts

Context. Fast radio bursts (FRBs) are extremely energetic pulses of millisecond duration and unknown origin. To understand the phenomenon that emits these pulses, targeted and un-targeted searches have been performed for multiwavelength counterparts, including the optical. Aims. The objective of this work is to search for optical transients at the positions of eight well-localized (< 1″) FRBs after the arrival of the burst on different timescales (typically at one day, several months, and one year after FRB detection). We then compare this with known optical light curves to constrain progenitor models. Methods. We used the Las Cumbres Observatory Global Telescope (LCOGT) network to promptly take images with its network of 23 telescopes working around the world. We used a template subtraction technique to analyze all the images collected at differing epochs. We have divided the difference images into two groups: In one group we use the image of the last epoch as a template, and in the other group we use the image of the first epoch as a template. We then searched for optical transients at the localizations of the FRBs in the template subtracted images. Results. We have found no optical transients and have therefore set limiting magnitudes to the optical counterparts. Typical limits in apparent and absolute magnitudes for our LCOGT data are ∼22 and −19 mag in the r band, respectively. We have compared our limiting magnitudes with light curves of super-luminous supernovae (SLSNe), Type Ia supernovae (SNe Ia), supernovae associated with gamma-ray bursts (GRB-SNe), a kilonova, and tidal disruption events (TDEs). Conclusions. Assuming that the FRB emission coincides with the time of explosion of these transients, we rule out associations with SLSNe (at the ∼99.9% confidence level) and the brightest subtypes of SNe Ia, GRB-SNe, and TDEs (at a similar confidence level). However, we cannot exclude scenarios where FRBs are directly associated with the faintest of these subtypes or with kilonovae.

THE BOOTES NETWORK IN THE GRAVITATIONAL WAVE ERA

The Burst Optical Observer and Transient Exploring System (BOOTES) is a world-wide automatic telescope network which aims to repaid follow-up of transient and astrophysical sources in the sky for which the first station was installed in 1998. With the advent in 2015 of the LIGO/Virgo interferometers, as part of the new generation of detectors designed for the detection of the signal of gravitational waves, a new window to explore the Universe has been opened. Here we present the status of the BOOTES network, the related strategies regarding the follow-up of gravitational wave events and the developments in the Gravitational Wave Era. Some preliminary results regarding the BOOTES follow-up observations are presented.

DECAM-GROWTH SEARCH FOR THE FAINT AND DISTANT BINARY NEUTRON STAR AND NEUTRON STAR-BLACK HOLE MERGERS IN O3A

Synoptic searches for the optical counterpart to a binary neutron star (BNS) or neutron star-black hole (NSBH) merger can pose significant challenges towards the discovery of kilonovae and performing multi-messenger science. In this work, we describe the advantage of a global multi-telescope network towards this end, with a particular focus on the key and complementary role the Dark Energy Camera (DECam) plays in multi-facility follow-up. We describe the Global Relay of Observatories Watching Transients Happen (GROWTH) Target-of-Opportunity (ToO) Marshal, a common web application we built to ingest events, plan observations, search for transient candidates, and retrieve performance summary statistics for all of the telescopes in our network. Our infrastructure enabled us to conduct observations of two events during O3a, S190426c and S190510g. Furthermore, our analysis of deep DECam observations of S190814bv conducted by the DESGW team, and access to a variety of global follow-up facilities allowed us to place meaningful constraints on the parameters of the kilonova and the merging binary. We emphasize the importance of a global telescope network in conjunction with a power telescope like DECam in performing searches for the counterparts to gravitational-wave sources.

LONG-TERM PHOTOMETRY WITH SKYNET ROBOTIC TELESCOPE NETWORK

In this paper, we describe the Skynet Robotic Telescope Network, a network of about 2 dozen small optical telescopes spanning four continents. For a prospective user of the network, we provide details on its operation and mention certain caveats potentially affecting observations taken under the control of Skynet software. The actual performance of the network is demonstrated by long-term observations of two blazars: OJ 49 and 3C 279. We show their photometric light curves acquired with a subset of Skynet telescopes in the 2018/19 observing seasons. Preliminary results of the analysis of the variability of these two targets are given, including the quantitative properties of light variations and the periods of possible Quasi Periodic Oscillations (QPOs) found in the seasonal light curves.

Original Research By Young Twinkle Students (ORBYTS): Ephemeris Refinement of Transiting Exoplanets III

We report photometric follow-up observations of thirteen exoplanets (HATS-1 b, HATS-2 b, HATS-3 b, HAT-P-18 b, HAT-P-27 b, HAT-P-30 b, HAT-P-55 b, KELT-4A b, WASP-25 b, WASP-42 b, WASP-57 b, WASP-61 b and WASP-123 b), as part of the Original Research By Young Twinkle Students (ORBYTS) programme. All these planets are potentially viable targets for atmospheric characterisation and our data, which were taken using the LCOGT network of ground-based telescopes, will be combined with observations from other users of ExoClock to ensure that the transit times of these planets continue to be well-known, far into the future.

Observations of U Leporis

U Leporis (U Lep) is a pulsating variable that demonstrates periodic variation in apparent magnitude consistent with RR Lyrae variable stars. Images were acquired by the 0.4 meter telescopes of the Las Cumbres Observatory Global Telescope network in the visible (B, V) and near infrared (i and z) over a two week period in October 2019 and analyzed using Astrosource. Light curves were constructed for each of the four bandpasses, yielding a mean period of 0.581±0.011 days. The middle apparent magnitudes determined for the B, V, i, and z filters were 10.75, 10.55, 10.30, and 10.35 respectively. Color excess E(B-V) was determined by two methods (1) minimizing variance in the calculated distances for the V, i, and z bands (0.065) and (2) galactic dust (0.029), with the second method preferred. Distances in parsecs to U Lep were determined for the V (968±38), i (932±33), and z (951±38) filters. The average distance of 950±21 compares favorably to that obtained by Klein (977±8 pc) and less so to Gaia DR2 (1076±36 pc).

Broken Power-law Energy Spectra of the Accelerated Electrons Detected in Radio and Hard X-Rays during the SOL2013-05-13 Event

Abstract Solar flares, resulting from magnetic activity of the Sun, are among the most energetic events in the solar system and in extreme cases directly affect our highly technological society. In this work, we analyze a solar flare detected at millimeter and centimeter wavelengths, as well as X-rays above 1 MeV. Observations of solar flares at these energy bands provide diagnostics of the energetic accelerated electrons and the magnetic fields where the emission is produced. During the SOL2013-05-13 solar flare, radio data were obtained by the telescope system POlarisation Emission of Millimeter Activity at the Sun, which observes the Sun at 45 and 90 GHz with polarization measurements, and at microwaves (1–15 GHz) by the Radio Solar Telescope Network. For the same event, X-ray emission was detected by the RHESSI and Fermi satellites. Spectra at both wavelengths were constructed and fit separately to yield the accelerated electron energy distribution that produced the emission. The optically thin radio spectral index was calculated by fitting the Ramaty model of gyrosynchrotron emission to the observed radio spectrum, whereas the hard X-ray spectral index was obtained from the spectral fit assuming a thermal emission model plus a nonthermal broken power-law distribution. Finally, both spectral indexes were compared and confirmed that the index obtained from the radio spectrum agrees with the index of the X-ray spectrum for energies above the break energy of ∼600 keV. Thus, the hard X-rays more energetic than 600 keV and high radio frequencies of solar flares are emitted by the same population of high-energy accelerated electrons. This result indicates that the accelerated electrons have an energy distribution best represented by a broken power law, with a breakup above energies around 1 MeV.

The Automatic Observation Management System of the GWAC Network. I. System Architecture and Workflow

The Ground Wide Angle Camera Network (GWAC-N) is a network of robotic multi-aperture, multiple field-of-view (FoV) optical telescopes. The main contingent of GWAC-N instruments are provided by the Ground Wide Angle Cameras Array (GWAC-A), and additional, narrower FoV telescopes are utilized to provide fast multi-band follow-up capabilities. The primary scientific goal of the GWAC-N is to search for optical counterparts of gamma-ray bursts that will be detected by the Space Variable Object Monitor (SVOM) satellite. The GWAC-N performs many additional observing tasks including follow-up of Target of Opportunities (ToO) targets and the detection (and monitoring) of variable objects and optical transients. To handle these use cases (and to allow for extensibility), we have designed ten observation modes and 175 observation strategies, including a joint strategy with multiple GWAC-N telescopes for the follow-up of gravitational wave (GW) events. To perform these observations, we develop an Automatic Observation Management (AOM) system capable of performing object management, dynamic scheduling, automatic broadcasting across the network, and image handling. The AOM system combines the individual telescopes which comprise the GWAC-N into a network and smoothly organizes all associated operations, completely meeting the requirements dictated by GWAC-N. With its modular design, the AOM is scientifically and technically viable for other general-purpose telescope networks. As the GWAC-N extends and evolves, the AOM will greatly enhance its discovery potential. In this first paper of a series, we present the scientific goals of the GWAC-N and detail the hardware, software, and workflow developed to achieve these goals. The structure, technical design, implementation, and performance of the AOM system are also described in detail. We conclude with a summary of the current status of the GWAC-N and our near-future development plan.

Space Debris Tracking with the Poisson Labeled Multi-Bernoulli Filter.

This paper presents a Bayesian filter based solution to the Space Object (SO) tracking problem using simulated optical telescopic observations. The presented solution utilizes the Probabilistic Admissible Region (PAR) approach, which is an orbital admissible region that adheres to the assumption of independence between newborn targets and surviving SOs. These SOs obey physical energy constraints in terms of orbital semi-major axis length and eccentricity within a range of orbits of interest. In this article, Low Earth Orbit (LEO) SOs are considered. The solution also adopts the Partially Uniform Birth (PUB) intensity, which generates uniformly distributed births in the sensor field of view. The measurement update then generates a particle SO distribution. In this work, a Poisson Labeled Multi-Bernoulli (PLMB) multi-target tracking filter is proposed, using the PUB intensity model for the multi-target birth density, and a PAR for the spatial density to determine the initial orbits of SOs. Experiments are demonstrated using simulated SO trajectories created from real Two-Line Element data, with simulated measurements from twelve telescopes located in observatories, which form part of the Falcon telescope network. Optimal Sub-Pattern Assignment (OSPA) and CLEAR MOT metrics demonstrate encouraging multi-SO tracking results even under very low numbers of observations per SO pass.

Recent developments in the implementation of European Space Surveillance & Tracking (EU SST)–Security and data policy

European Space Surveillance & Tracking (EU SST) is the European Union's operational capability for safeguarding space infrastructure and contributing to global burden-sharing in the domain of Space Situational Awareness (SSA). Implemented by a Consortium of EU member states in cooperation with the EU Satellite Centre, EU SST today serves over 100 user organizations with free services, such as Collision Avoidance for over 210 satellites. The Consortium operates a growing sensor network of radars, telescopes and lasers, which remain under the authority of the member states, reflecting the dual dimension of the SSA domain. Measurements and orbit data from the contributing sensors are shared through a dedicated platform, the EU SST Database.As the Consortium increasingly shares data through the Database on a daily basis and will be processing that data into a European catalogue precursor, the Consortium's internal Security Committee is responsible for further developing the EU SST data policy that must balance the requirements for transparency and safety of flight with security constraints linked to precise and timely information on the nature, specifications and location of certain space objects.This article reports on recent developments in the implementation of EU SST with regard to security and data policy. It highlights the unique governance and data sharing model of EU SST, the diverse architecture of existing SSA sharing agreements, and data security considerations.

Automated VLBI scheduling using AI-based parameter optimization

Within this work, a new geodetic very long baseline interferometry (VLBI) scheduling approach inspired by evolutionary processes based on selection, crossover and mutation is presented. It mimics the biological concept “surviving of the fittest” to iteratively explore the scheduling parameter space looking for the best solution. Besides providing high-quality results, one main benefit of the proposed approach is that it enables the generation of fully automated and individually optimized schedules. Moreover, it generates schedules based on transparent rules, well-defined scientific goals and by making decisions based on Monte Carlo simulations. The improvements in terms of precision of geodetic parameters are discussed for various observing programs organized by the International VLBI Service for Geodesy and Astrometry (IVS), such as the OHG, R1, and T2 programs. In the case of schedules with a difficult telescope network, an improvement in the precision of the geodetic parameters up to 15% could be identified, as well as an increase in the number of observations of up to 10% compared to classical scheduling approaches. Due to the high quality of the produced schedules and the reduced workload for the schedulers, various IVS observing programs are already making use of the evolutionary parameter selection, such as the AUA, INT2, INT3, INT9, OHG, T2 and VGOS-B program.

Method of global survey involving data of muon telescope network

In 1967, the Yu.G. Shafer Institute of Cosmophysical Research and Aeronomy developed a global survey method that allowed application of the global network of neutron monitors as a single device, simultaneously oriented to various directions and providing information on distribution of cosmic rays per each measured moment. By analogy with this approach, a method for calculation of anisotropy parameters of high-energy cosmic rays has been proposed, involving measurement data from the Global Muon Detector Network and Yakutsk stations. To implement the method, receiving vectors of the stations have been calculated, making it possible to consider associations between cosmic ray variations in the interplanetary medium and those observed at Earth. The paper also discusses some methodological issues related to correct determination of angular distribution of cosmic rays in the interplanetary space. Based on the modified method of global survey, parameters of the first two moments of the angular distribution of cosmic rays for 2012–2018 have been calculated.

Potential asteroid discoveries by the ESA Gaia mission

Context. Since July 2014, the Gaia mission of the European Space Agency has been surveying the entire sky down to magnitude 20.7 in the visible. In addition to the millions of daily observations of stars, thousands of Solar System objects (SSOs) are observed. By comparing their positions, as measured by Gaia, to those of known objects, a daily processing pipeline filters known objects from potential discoveries. However, owing to Gaia’s specific observing mode, which follows a predetermined scanning law designed for stars as “fixed” objects on the celestial sphere, potential newly discovered moving objects are characterized by very few observations, which are acquired over a limited time. Furthermore, these objects cannot be specifically targeted by Gaia itself after their first detection. This aspect was recognized early on in the design of the Gaia data processing. Aims. A daily processing pipeline dedicated to these candidate discoveries was set up to release calls for observations to a network of ground-based telescopes. Their aim is to acquire follow-up astrometry and to characterize these objects. Methods. From the astrometry measured by Gaia, preliminary orbital solutions are determined, allowing us to predict the position of these potentially newly discovered objects in the sky while accounting for the large parallax between Gaia and the Earth (separated by 0.01 au). A specific task within the Gaia Data Processing and Analysis Consortium has been responsible for the distribution of requests for follow-up observations of potential Gaia SSO discoveries. Since late 2016, these calls for observations (nicknamed “alerts”) have been published via a Web interface with a quasi-daily frequency, together with observing guides, which is freely available to anyone worldwide. Results. Between November 2016 and the end of the first year of the extended mission (July 2020), over 1700 alerts were published, leading to the successful recovery of more than 200 objects. Among them, six have a provisional designation assigned with the Gaia observations; the others were previously known objects with poorly characterized orbits, precluding identification at the time of Gaia observations. There is a clear trend for objects with a high inclination to be unidentified, revealing a clear bias in the current census of SSOs against high-inclination populations.

NEOExchange - an online portal for NEO and Solar System science

Las Cumbres Observatory (LCO) has deployed a homogeneous telescope network of ten 1-m telescopes to four locations in the northern and southern hemispheres, with a planned network size of twelve 1-m telescopes at 6 locations. This network is very versatile and is designed to respond rapidly to target of opportunity events and also to perform long term monitoring of slowly changing astronomical phenomena. The global coverage, available telescope apertures, and flexibility of the LCO network make it ideal for discovery, follow-up, and characterization of Solar System objects such as asteroids, Kuiper Belt Objects, comets, and especially Near-Earth Objects (NEOs).We describe the development of the “LCO NEO Follow-up Network” which makes use of the LCO network of robotic telescopes and an online, cloud-based web portal, NEOexchange, to perform photometric characterization and spectroscopic classification of NEOs and follow-up astrometry for both confirmed NEOs and unconfirmed NEO candidates.The follow-up astrometric, photometric, and spectroscopic characterization efforts are focused on those NEO targets that are due to be observed by the planetary radar facilities and those on the Near-Earth Object Human Space Flight Accessible Targets Study (NHATS) lists. Our astrometric observations allow us to improve target orbits, making radar observations possible for objects with a short arc or large orbital uncertainty, which could be greater than the radar beam width. Astrometric measurements also allow for the detection and measurement of the Yarkovsky effect on NEOs. The photometric and spectroscopic data allows us to determine the light curve shape and amplitude, measure rotation periods, determine the taxonomic classification, and improve the overall characterization of these targets. We are also using a small amount of the LCO NEO Follow-up Network time to confirm newly detected NEO candidates produced by the major sky surveys such as ATLAS, Catalina Sky Survey (CSS) and PanSTARRS (PS1). We will describe the construction of the NEOexchange NEO follow-up portal and the development and deployment methodology adopted which allows the software to be packaged and deployed anywhere, including in off-site cloud services. This allows professionals, amateurs, and citizen scientists to plan, schedule and analyze NEO imaging and spectroscopy data using the LCO network and acts as a coordination hub for the NEO follow-up efforts. We illustrate the capabilities of NEOexchange and the LCO NEO Follow-up Network with examples of first period determinations for radar-targeted NEOs and its use to plan and execute multi-site photometric and spectroscopic observations of (66391) 1999 KW4, the subject of the most recent planetary defense exercise campaign.