Schmidt Telescope Research Articles

The digitized First Byurakan Survey database. New carbon stars confirmed

Some amount of the new carbon ( C ) stars was confirmed among the sample of the Late-Type Stars (LTSs) candidates, selected on the Digitized First Byurakan Survey (DFBS) spectral plates. The DFBS is the digitized version of the First Byurakan Survey (FBS, or Markarian survey). The FBS was the first systematic survey of the extragalactic sky. This objective-prism survey was carried out in 1965- 1980 by B. E. Markarian and colleagues using the 1 m Schmidt telescope of the Byurakan Astrophysical Observatory. In this work we present Gaia DR3 photometric data, spectra, light curves, distances, high above/below Galactic plane, radial velocities (RV), and other important physical characteristics from modern astronomical catalogues for some amount new confirmed DFBS carbon stars. The confirmation is based on Gaia DR3 BP/RP low-resolution spectral database. In previous studies of the DFBS plates, these objects were presented as LTSs candidates. Some objects are located more than 7 kpc from the Galactic plane. Four of them are N-type C stars, from which two are Mira-type variables. The remaining objects are CH-type giants at high Galactic latitudes. Most probably they present binary systems.

The Digitized First Byurakan Survey Database. Late-type stars candidates. New confirmations

More than 3000 Late-Type Stars (LTS) candidates was confirmed among the sample, selected on the Digitized First Byurakan Survey (DFBS) spectral plates. The DFBS is the digitized version of the First Byurakan Survey (FBS, or Markarian survey). This objective-prism survey was carried out in 1965- 1980 by B. E. Markarian and colleagues using the 1 m Schmidt telescope of the Byurakan Astrophysical Observatory (BAO). FBS spectral plates have been used long period to search and study faint LTS (Ctype (carbon) and M-type) stars at high Galactic latitudes. Thousands of objects was confirmed as LTS. The confirmation is based on Gaia DR3 BP/RP low-resolution spectral database. In previous studies of the DFBS plates, these objects were presented as LTS candidates. Some objects are located more than 10 kpc. The predominant part of the new confirmed objects are M dwarfs.

Results of a long-term optical variability study of 11 quasars and VRI photometry of comparison stars

ABSTRACT We present the results of a 15-yr long-term optical monitoring of 11 quasars conducted with the 2-m Ritchey–Chretien–Coude and the 50/70 cm Schmidt telescopes at the Rozhen National Astronomical Observatory, Bulgaria. Our observations are performed with standard Johnson-Cousins $VRI$ band filters and for each quasar we present a set of comparison standard stars that can be used for monitoring of objects in these fields (including finding charts for the stars identification). The variability and periodicity of each quasar are analysed individually and discussed. The physical properties of each quasar, such as their classification, redshift, and radio structures, are also discussed based on previous literature. Damped random walk model shows the best or the second best fit to the light curves of all objects. However, in six cases periodic models provide comparably good fits and make these six objects a valuable addition to the growing sample of quasars with periodic flux variation. They will be suitable for further investigation of the hitherto unclear mechanisms that give rise to this variability pattern. Our results provide important insights into the long-term variability and physical properties of quasars, which can further deepen our understanding of the nature and evolution of active galaxy nuclei.

New Herbig–Haro objects associated with embedded sources

ABSTRACT We continue to present the results of the Byurakan Narrow Band Imaging Survey (BNBIS). The main goal of this survey is to search for Herbig–Haro (HH) objects and jets in Galactic dark clouds. In this work we present the results of the search in the vicinity of infrared sources that are bright in the WISE survey and embedded in the dark clouds. The survey is performed with the 1-m Schmidt telescope of Byurakan Observatory, lately equipped with a new CCD detector, which allows to obtain one square degree images of the sky in various filters. Narrow-band filters were used to obtain H α and [S ii] images, and a medium-width filter was used for the continuum imaging. New HH flows and knots were found near six embedded IR sources, which constitutes a significant proportion of the objects observed. At least two of the newly found HH flows (HH 1226 and HH 1227) lie in isolated dark clouds, thus pointing to active star formation in these regions. Other flows are also located in detached and dense globules or filaments. The length of the HH 1228 flow is about 1 pc; it has also a molecular hydrogen counterpart of the same extension. Coordinates, charts, detailed descriptions and distance estimates are provided. The lower limits of bolometric luminosities of the source stars are typical for low-mass young stellar objects.

ASTRONOMICAL TESTS OF A MEDIUM FORMAT DIGITAL CAMERA ON A LARGE SCHMIDT TELESCOPE

Installation, testing and astronomical capabilities of a medium format digital camera (Fujifilm GFX 50R) on the 1-meter Schmidt Telescope at the National Astronomical Observatory of Venezuela are described. Main useful features and drawbacks are also discussed.

On the nature of apparent transient sources on the National Geographic Society–Palomar Observatory Sky Survey glass copy plates

Abstract We examine critically recent claims for the presence of above-atmosphere optical transients in publicly available digitized scans of Schmidt telescope photographic plate material derived from the National Geographic Society–Palomar Observatory Sky Survey. We employ the publicly available SuperCOSMOS Sky Survey catalogues to examine statistically the morphology of the sources. We develop a simple, objective, and automated image classification scheme based on a random forest decision tree classifier. We find that the putative transients are likely to be spurious artefacts of the photographic emulsion. We suggest a possible cause of the appearance of these images as resulting from the copying procedure employed to disseminate glass copy survey atlas sets in the era before large-scale digitization programmes.

Elastic Data Binning: Time-Series Sketching for Time-Domain Astrophysics Analysis

Time-domain astrophysics analysis (TDAA) involves observational surveys of celestial phenomena that may contain irrelevant information because of several factors, one of which is the sensitivity of the optical telescopes. Data binning is a typical technique for removing inconsistencies and clarifying the main characteristics of the original data in astrophysics analysis. It splits the data sequence into smaller bins with a fixed size and subsequently sketches them into a new representation form. In this study, we introduce a novel approach, called elastic data binning (EBinning), to automatically adjust each bin size using two statistical metrics based on the Student's t-test for linear regression and Hoeffding inequality. EBinning outperforms well-known algorithms in TDAA for extracting relevant characteristics of time-series data, called lightcurve. We demonstrate the successful representation of various characteristics in the lightcurve gathered from the Kiso Schmidt telescope using EBinning and its applicability for transient detection in TDAA.

Elastic Data Binning: Time-Series Sketching for Time-Domain Astrophysics Analysis

Time-domain astrophysics analysis (TDAA) involves observational surveys of celestial phenomena that may contain irrelevant information because of several factors, one of which is the sensitivity of the optical telescopes. Data binning is a typical technique for removing inconsistencies and clarifying the main characteristics of the original data in astrophysics analysis. It splits the data sequence into smaller bins with a fixed size and subsequently sketches them into a new representation form. In this study, we introduce a novel approach, called elastic data binning (EBinning), to automatically adjust each bin size using two statistical metrics based on the Student's t-test for linear regression and Hoeffding inequality. EBinning outperforms well-known algorithms in TDAA for extracting relevant characteristics of time-series data, called lightcurve. We demonstrate the successful representation of various characteristics in the lightcurve gathered from the Kiso Schmidt telescope using EBinning and its applicability for transient detection in TDAA.

A detailed infrared detectors systems overview of MOONS VLT instrument

MOONS is a multi‐object spectrograph that will be installed at the Nasmyth focus of the VLT ESO Telescopes in Chile. The instrument has the capacity to deploy approximately 1000 fibers over a field of view of 500 square arcminutes, with a total wavelength coverage of from 0.6 to 1.8 m, offering both low‐ and medium‐resolution modes. The high demand for fast and large optics in all spectral channels prompted the use of similar Schmidt cameras. As a result, the Detector Unit (DU) must be located within the optical beam and its footprint must be minimized to reduce vignetting. The instrument consists of four H4RG‐15um pixel detectors and two fully depleted LBNL CCDs. This article provides a comprehensive description of the detector systems, focusing particularly on the H4RG‐15, including a brief overview of the newly developed cryogenic pre‐amplifier for 64‐output operation, and a detailed discussion of the woven cable technology used for signal routing. Some results of the characterization of three H4RG detectors are presented, with a focus on crosstalk and buffer output performance. The use of the buffer output for the H4RG results in a glow‐per‐read observed at the bottom of the detectors. This article also describes the trade‐offs and alternatives used to optimize detector performance in this situation.

PHOTOMETRIC OBSERVATIONS OF MINOR PLANETS WITH THE TONANTZINTLA SCHMIDT CAMERA I. LIGHT CURVE ANALYSIS OF MAIN-BELT AND NEAR-EARTH ASTEROIDS

We report photometric observations of nine main-belt asteroids (MBAs), four near-Earth asteroids (NEAs), and one Mars-crossing asteroid (MCA) carried out with the historical Tonantzintla Schmidt Camera between 2015 and 2018, as part of a process of reactivation of this telescope for astrometric and photometric follow-up observations of MBAs and NEAs. This observational program is part of the commitment made by INAOE when requesting its inclusion in the International Asteroid Warning Network (IAWN). We present the light curves of these 14 asteroids and their corresponding Fourier analyses to determine the rotation period of the asteroids and the brightness amplitude of their light curves.

Reflective multi-immersion microscope objectives inspired by the Schmidt telescope

Imaging large, cleared samples requires microscope objectives that combine a large field of view (FOV) with a long working distance (WD) and a high numerical aperture (NA). Ideally, such objectives should be compatible with a wide range of immersion media, which is challenging to achieve with conventional lens-based objective designs. Here we introduce the multi-immersion ‘Schmidt objective’ consisting of a spherical mirror and an aspherical correction plate as a solution to this problem. We demonstrate that a multi-photon variant of the Schmidt objective is compatible with all homogeneous immersion media and achieves an NA of 1.08 at a refractive index of 1.56, 1.1-mm FOV and 11-mm WD. We highlight its versatility by imaging cleared samples in various media ranging from air and water to benzyl alcohol/benzyl benzoate, dibenzyl ether and ethyl cinnamate and by imaging of neuronal activity in larval zebrafish in vivo. In principle, the concept can be extended to any imaging modality, including wide-field, confocal and light-sheet microscopy.

A search for transient, monochromatic light from the Galactic plane

ABSTRACT The Galactic plane was searched for transient, monochromatic light at optical and near-IR wavelengths to detect pulses shorter than 1 s. An objective-prism Schmidt telescope of 0.28-m aperture and a CMOS camera were used to observe 973 square deg, with 8864 exposures of 1-s each, within a strip 2.1 deg wide along the Galactic plane, from Galactic longitude −4 deg to +248 deg. All exposures were analysed for transient, monochromatic sources using a ‘difference image’ algorithm that yielded 11 candidate sources. All 11 sources were found to be associated with either astrophysical emission-line objects or aircraft with subsecond blinking lights. Our survey ‘rediscovered’ many Wolf–Rayet stars, M dwarf flare stars, and planetary nebulae. It also identified an aircraft, of unknown type, that apparently had a nearly monochromatic lamp and a xenon lamp. This survey would have revealed optical and near-IR pulses having a power of ∼180 GW (wavelength dependent) if emitted by a 10-m aperture laser located 1 kiloparsec away. These non-detections of laser pulses from the Galactic plane, including a 10-deg region towards the Galactic centre, add to the non-detections from more than 5000 nearby stars. Indeed, all-sky surveys for emission-line objects (e.g. ionized gas, supernovae remnants, and active galactic nuclei) would have revealed lasers of a wide range of average brightness, wavelength, and cadence. The absence of beacons reveals more of a SETI desert, notably at the intensely surveyed optical and radio wavelengths.

Armenian Virtual Observatory: Status and activities

Among all astronomical data, a large spectroscopic database is especially useful for understanding the nature of all observed objects. The Astrophysical Virtual Observatories (AVOs) have been created in a number of countries using their available databases and current observing material as a collection of interoperating data archives and software tools to form a research environment for processing complex data-intensive and compute-intensive research workflows. The Armenian Virtual Observatory (ArVO) is a project of the Byurakan Astrophysical Observatory (BAO) aimed at construction of a modern system for data archiving, extraction, acquisition, reduction, use and publication. ArVO is based on the Digitized First Byurakan Survey (DFBS) and is the Armenian contribution to the International Virtual Observatories Alliance (IVOA). One of the ArVO’s main tasks is to create and utilize a global Spectroscopic Virtual Observatory, which will combine data from DFBS and other low-dispersion spectroscopic databases, as well as provide the first understanding on the nature of any object up to B=18m. Hence, ArVO will utilize the DFBS as an appropriate large spectroscopic database. In the frame of ArVO, BAO collaborates with the Institute of Informatics and Automation Problems (IIAP) of the National Academy of Sciences of Armenia to develop software ecosystem for ArVO satisfying the IVOA standards. Besides the DFBS, ArVO provides access to the Digitized Second Byurakan Survey (SBS) database, the Byurakan photographic archive, and BAO 2.6 m and 1 m Schmidt telescopes modern observations.

Research on key technologies of inverted 3-FOV Schmidt telescope

Research on key technologies of inverted 3-FOV Schmidt telescope

OBSERVATION OF AN OCCULTATION OF THE UCAC4 488-082551 STAR BY ASTEROID (76228) 2000 EH 75 ON 31 MAY 2022

Observations of an occultation of the UCAC4 488-082551 star by asteroid (76228) 2000 EH 75 were carried out on 31 May 2022 at Kryzhanivka observation station of Odesa I. I. Mechnykov National University (the observatory code A85). A set of instruments, which included a Schmidt telescope (the primary mirror diameter D = 271.25 mm; the corrector plate diameter D k = 223.9 mm; the focal length F = 440 mm), a GPS receiver and Videoscan-415-2001 CCD camera, was used to perform observations. The observing conditions were as follows: clear sky, the star’s altitude 49 0 south, the Moon was below the local horizon. The target star from the UCAC4 catalogue (Zacharias et al. 2013) has the following photometric parameters: m B = 14.008; m V = 12.720; m r = 12.284; m i = 11.813. The diameter of the star has not been determined. Asteroid (76228) is a Main Belt asteroid with an orbital period of 4.17178 years. It has an absolute magnitude of 14.93, the visible geometric albedo of 0.123±0.013 and diameter of 5.00±0.23 km (Masiero et al. 2011). The time of occultation predicted using ephemerides was 23:52:44±4 sec. The maximum duration of the occultation was 0.4 sec, provided that the observing site was located at the centre of the occultation track (strip). A drop in the star’s brightness observed during occultation was about 8 m . The occultation event was recorded as a sequence of GIF images with the exposure time of 0.5 sec per frame. The system clock of the computer used for the occultation recording was controlled with a GPS receiver in a fashion similar to that described in the paper by Karbovsky et al. (2017). The data processing yielded an estimate of the occultation duration of 0.46±0.04 sec. The uncertainty of the occultation start time within exposure results in the total estimate of accuracy in timing the maximum phase of occultation 23:52:44.06±0.10 sec. The chord length across the asteroid estimated by timing the occultation is L = 9.2±0.8. This chord length is close to the estimates of the asteroid diameter reported in the paper by Masiero et al. (2011).

Some studies on First Byurakan Survey late-type stars

Markarian survey (or the First Byurakan Survey, FBS), was the first systematic survey of the extragalactic sky. This objective-prism survey was carried out in 1965-1980 by B. E. Markarian and his colleagues using the 1 m Schmidt telescope of the Byurakan Astrophysical Observatory and resulted in discovery of 1517 UV-excess (Markarian) galaxies. FBS low-resolution spectral plates have been used long period to search and study faint late-type stars (LTSs, M-type and C(carbon) stars) at high galactic latitudes. I will review in this paper the results obtained for late-LTSs using FBS spectral plates. At present the survey is digitized and DFBS database is available. This paper reports also recent new discovered C and M-type stars, and a huge amount of the LTSs candidates selected in the DFBS data base. This paper informed also detecting some amount of the new dwarf carbon (dC) star candidates.

Fast optical flares from M dwarfs detected by a one-second-cadence survey with Tomo-e Gozen

Abstract We report on a one-second-cadence wide-field survey for M-dwarf flares using the Tomo-e Gozen camera mounted on the Kiso Schmidt telescope. We detect 22 flares from M3–M5 dwarfs with a rise time of 5 s ≲ trise ≲ 100 s and an amplitude of 0.5 ≲ ΔF/F⋆ ≲ 20. The flare light-curves mostly show steeper rises and shallower decays than those obtained from the Kepler one-minute cadence data and tend to have flat peak structures. Assuming a blackbody spectrum with a temperature of 9000–15000 K, the peak luminosities and energies are estimated to be 1029 erg s−1 ≲ Lpeak ≲ 1031 erg s−1 and 1031 erg ≲ Eflare ≲ 1034 erg, which constitutes the bright end of fast optical flares for M dwarfs. We confirm that more than $90\%$ of the host stars of the detected flares are magnetically active based on their Hα-emission-line intensities obtained by LAMOST. An estimated occurrence rate of detected flares is ∼0.7 per day per active star, indicating they are common in magnetically active M dwarfs. We argue that the flare light-curves can be explained by the chromospheric compression model: the rise time is broadly consistent with the Alfvén transit time of a magnetic loop with a length scale of lloop ∼ 104 km and a field strength of 1000 gauss, while the decay time is likely determined by the radiative cooling of the compressed chromosphere down near to the photosphere with a temperature of ≳ 10000 K. These flares from M dwarfs could be a major contamination source for a future search of fast optical transients of unknown types.

Catalog of Quasars Produced from the Results of a Medium-Band Photometric Survey at a 1-m Schmidt Telescope

Catalog of Quasars Produced from the Results of a Medium-Band Photometric Survey at a 1-m Schmidt Telescope

A search for monochromatic light towards the Galactic Centre

ABSTRACT A region 140 square degrees towards the Galactic Centre was searched for monochromatic optical light, both pulses shorter than 1 s and continuous emission. A novel instrument was constructed that obtains optical spectra of every point within 6 square deg every second, able to distinguish lasers from astrophysical sources. The system consists of a modified Schmidt telescope, a wedge prism over the 0.28-m aperture, and a fast CMOS camera with 9500 × 6300 pixels. During 2021, a total of 34 800 exposures were obtained and analysed for monochromatic sources, both subsecond pulses and continuous in time. No monochromatic light was found. A benchmark laser with a 10-m aperture and located 100 light years (ly) away would be detected if it had a power more than ∼60 megawatt (MW) during 1 s, and from 1000 ly away, 6000 MW is required. This non-detection of optical lasers adds to previous optical SETI non-detections from more than 5000 nearby stars of all masses, from the Solar gravitational lens focal points of Alpha Centauri, and from all-sky searches for broadband optical pulses. These non-detections, along with those of broadband pulses, constitute a growing SETI desert in the optical domain.

Video observations of tiny near-Earth objects with Tomo-e Gozen

Abstract We report the results of video observations of tiny (diameter less than 100 m) near-Earth objects (NEOs) with Tomo-e Gozen on the Kiso 105 cm Schmidt telescope. The rotational period of a tiny asteroid reflects its dynamical history and physical properties since smaller objects are sensitive to the Yarkovsky–O’Keefe–Radzievskii–Paddack (YORP) effect. We carried out video observations of 60 tiny NEOs at 2 fps from 2018 to 2021 and successfully derived the rotational periods and axial ratios of 32 NEOs including 13 fast rotators with rotational periods less than 60 s. The fastest rotator found during our survey is 2020 HS$_\mathsf {7}$ with a rotational period of 2.99 s. We statistically confirmed that there is a certain number of tiny fast rotators in the NEO population, which have been missed with all previous surveys. We have discovered that the distribution of the tiny NEOs in a diameter and rotational period (D–P) diagram is truncated around a period of 10 s. The truncation with a flat-top shape is not explained well by either a realistic tensile strength of NEOs or the suppression of YORP by meteoroid impacts. We propose that the dependence of the tangential YORP effect on the rotational period potentially explains the observed pattern in the D–P diagram.