Large Surveys with Small Telescopes, Day 2
|Astrometric Surveys: from photographic plates to CCDs
A review is given about astrometric, ground-based surveys including plate measure machines and CCD techniques. The Astrographic Catalogue project of around 1900 was the first of its kind, followed by AGK2, AGK3, Palomar and other Schmidt plate surveys and modern astrographs dedicated for astrometry (Hamburg, USNO). The full potential of those surveys could only recently be realized using accurate plate measure machines (PDS, NOFS, StarScan, DAMIAN). The UCAC project was the first all-sky astrometric survey performed using a CCD detector, while the URAT program was the last such ground-based effort.
|One Million Variable Stars from the OGLE Survey
The Optical Gravitational Lensing Experiment (OGLE) began in 1992 and it has now become one of the world's largest optical surveys devoted to searching for variability in the sky. During its long history, the OGLE survey collected about one trillion individual photometric measurements for over two billion stars in the Milky Way and in nearby galaxies. These data has led to many discoveries in various fields of astronomy: gravitational lensing and microlensing, extrasolar planets, structure of galaxies, cosmic distance scale, Kuiper belt objects, etc. Variable stars occupy a special position among the most important achievements of the survey. The OGLE Collection of Variable Stars currently contains nearly one million objects of various types and this is the largest set of variable stars ever obtained by any astronomical project. I will present the most spectacular OGLE discoveries in the field of variable stars.
|Robotic astronomy with the Las Cumbres Observatory
The Las Cumbres Observatory (LCO) is an independent, non-profit foundation dedicated to time-domain astronomical observations at optical wavelengths. To this end, LCO has constructed a homogeneous world-wide network of 21 robotic telescopes, which includes the two 2m Faulkes telescopes, 9$\times$1m telescopes, and 10$\times$40cm telescopes. The telescopes are outfitted for imaging and spectroscopy at wavelengths between the atmospheric UV cutoff and the roughly 1-micron limit of silicon detectors.
|The Dragonfly Telephoto Array: Exploring the Low Surface Brightness Universe
The Dragonfly Telephoto Array, comprised of 48 individual Canon telephoto lenses operating together as a single telescope, provides an innovative approach to low surface brightness imaging. Sub-nanometer coatings on each optical element reduce scattered light from nearby bright stars and compact galaxy centers — typically a key obstacle for integrated light observations — by an order of magnitude, and Dragonfly’s large field of view (2 x 2.6 degrees for a single frame) provides a large-scale view of the low surface brightness skies. I will introduce Dragonfly, and present highlights from both past and ongoing deep optical surveys. Finally, I will provide a preview of our team’s upcoming survey and instrumentation plans.
|The Evryscope: Science from the First Full-Sky Gigapixel-Scale Telescope(1)
The Evryscope, built by astronomers at the University of North Carolina, was deployed at CTIO in May 2015 and represents the world's first full-sky gigapixel-scale telescope. With its 24 separate individual telescopes sharing a common mount, the system images an 8000 square degree field of view once every two minutes. The Evryscope has been building 1\%-precision, high-cadence light curves for all accessible objects brighter than 16th magnitude since August 2016 and will continue to do so for several more years. With the final Evryscope reduction pipeline having just been completed, multi-year light curves are now being produced for millions of Southern-hemisphere stars. Here I present an overview of the telescope's design and performance, and I discuss early science results with a focus on M dwarf flares, variable hot subdwarf systems, exoplanet discovery \& characterization, and optical transients.
|An introduction to the Zwicky Transient Facility
The Zwicky Transient Facility began its 3 year time-domain survey in March 2018, using its camera with a 47 square degree field on the Palomar 48-inch Schmidt telescope. As part of the its surveys, ZTF carries out high-cadence observation of selected Galactic fields as well as moderate cadence observations of a 3000 square degree field at higher declination. Additionally, 40\% of ZTF observing time is dedicated to two public surveys: one covering the entire Northern sky every three nights in g and r passbands and one visiting the Galactic Plane every night in g and r. Real-time transient alerts from these surveys have been public since June 2018 and the first release of archival imaging and time series data is scheduled for Summer 2019. In this talk I will describe the survey and present some early results.
|An Occultation Network as a Detector of Distant Solar System Objects
We discuss the feasibility of and present initial designs and cost estimates for a large (N~2000) network of small photometric telescopes that is purpose-built to monitor V$<$15 Gaia Mission program stars for occultations by minor solar system bodies. The implementation of this network would permit measurement of the solar system's tidal gravity field to high precision, thereby revealing the existence of distant trans-Neptunian objects such as the proposed “Planet Nine". As a detailed example of the network capabilities, we investigate how occultations by Jovian Trojans can be monitored to track the accumulation of gravitational perturbations, thereby constraining the presence of undetected massive solar system bodies. In particular, we show that the tidal influence of Planet Nine can be discerned from that of smaller, nearer Kuiper belt objects. Moreover, ephemerides for all small solar system bodies observed in occultation could be significantly improved using this network, thereby improving spacecraft navigation and refining Solar System N-body modeling. Finally, occultation monitoring would generate direct measurements of size distributions for asteroid populations, permitting a better understanding of their origins.
|Asteroids monitoring with 1.2m Baldone Schmidt (code 069) telescope
CCD observations of the asteroids are obtained with the 0.80/1.20 m, f/3 Baldone Schmidt telescope of the Baldone observatory (code 069) of the Institute of Astronomy of University of Latvia. Now the telescope is equipped with two CCD STX-16803 36 X 36 mm cameras. In the Minor Planet Circulars and the Minor Planet Electronic Circulars we published 3511 astrometric positions of 826 asteroids. Among them, 48 asteroids were newly discovered at Baldone. For 36 of these asteroids the precise orbits were calculated. The orbits and the evolution of orbital elements of two interesting asteroids, (428694) 2008 OS9 from the Apollo group and the Centaur (330836) Orius (2009 HW77), were recalculated including new observations obtained after 2011. From the earliest years of data, the archive of Baldone Schmidt telescope contain more than 22 000 direct wide field images. Digital processing of photographic plates of star field allow, in addition to the main tasks to carry out a massive search for images of small bodies of the solar system and determine their coordinates. From the observations of earlier epoch, we can extract information about the locations of these bodies well before discovering them. Modern approach to processing early photographic observations with new technologies can be an effective instrument for rediscovery of asteroids and obtain correction their orbits. We analyzed the results of observations of clusters in UBVR bands and some ultraviolet plates of other star fields made on the 1.2-m Baldone Schmidt telescope.At the moment, all images of known minor planets on 70 plates with 9.8 - 17.1 stellar magnitude were identified. The catalog of positions and magnitudes of the searching asteroids was compiled. Among them are detected positions for 10 asteroids which at the time of observation were the earliest of the world's known observations of these asteroids. All asteroids positions were compared with the ephemeris JPl DE431.
|Observatorium Wendelstein – Status, Use and Future Strategy
We will describe the capabilities of the Observatorium Wendelstein (University of Munich,LMU), mainly of its 2m telescope with its three operational imaging and spectroscopic instruments. We will describe their performances based on a few science examples, partly survey type programs. Finally, we will discuss strategies how to benefit from the Wendelstein Observatory in times of up-coming new major astronomy resources.
|Surveying exoplanets across the spectrum - following the TraCS of exoplanets
In this talk, I will describe the efforts done by the Wendelstein observatory in following up known exoplanets and planet candidates both spectroscopically and photometrically. We are currently installing a high-resolution spectrograph, calibrated with an LFC, and a simultaneous 3-channel camera that covers photometric bands between u and Ks. With the latter, we are currently performing a transit survey where we observe primary and secondary in order to determine their Transit Colour Signature (TraCS).
|Microlensing survey of M31 with the 2m Wendelstein telescope
The determination of the mass function (MF) of stars as a function of environment and metallicity is of fundamental importance, e.g., for understanding the star formation process, the mass-to-light ratios of galaxies, and the evolution of galaxies. The pixel microlensing technique applied to images of M31 with a 2m class telescope is able to constrain the mass function of stars and remnants for the bulge of M31. The bulge of M31 is metal rich and old and in this respect very different from the environments for which for e.g. the faint-end MF can be determined up to now. On the other hand, its stellar population is similar to the one of massive elliptical galaxies. High quality observations with a PSF better than 0.8 arcsec over several weeks of the M31 bulge can yield enough micro lensing events to discriminate between some of the major currently discussed faint-end MFs (e.g. Kroupa, Zoccali, Chabrier) and additionally provide the number and distribution of stellar remnants and therefore the complete M/L ratio.
|Periodic Variables in the ASAS-SN and APOGEE Surveys
I would like to present the results of a search for periodic variable stars among the targets observed by the Apache Point Observatory Galactic Evolution Experiment (APOGEE) using photometry from the All-Sky Automated Survey for Supernovae (ASAS-SN). The catalog consists of 1925 periodic variables selected from more than 258000 APOGEE targets. The sample is homogeneously classified into 430 eclipsing and ellipsoidal binaries, 140 classical pulsators (Cepheids, RR Lyrae and delta Scuti), 720 long period variables (pulsating red giants) and 635 rotational variables. The search was performed using both visual inspection and machine learning techniques. The light curves were also modeled with the damped random walk stochastic process. The median [Fe/H] of variable objects is lower by 0.3 dex than that of the whole APOGEE sample. The median of eclipsing binaries and ellipsoidal variables is shifted to the lower [Fe/H] by 0.2 dex. Eclipsing binaries and rotational variables exhibit significantly broader spectral lines than the rest of the sample.
|SPECULOOS - On the hunt for habitable planets well-suited for atmospheric characterization (I)
After the astonishing discovery of seven Earth-sized planets around TRAPPIST-1, a Jupiter-sized star only 12 pc away, the hunt for temperate, rocky exoplanets goes into its next phase. The SPECULOOS survey is a new transit survey focusing on the ~1000 brightest (K$\leq$12.5) ultra-cool dwarfs (spectral type M7 or later). Its main objective is to detect temperate terrestrial worlds well-suited for detailed atmospheric characterization with upcoming JWST and ELTs. It also aims to probe the frequency and diversity of short-period planets around the lowest-mass stars and brown dwarfs. In this talk, I will present SPECULOOS, its current status, as well as its first results.
|Newest results of the Next Generation Transit Survey (NGTS)
In 2018 the firsts transiting exoplanets discovered with NGTS have been published. NGTS consists of twelve telescopes sited at ESO premise on Paranal, Chile. The optimal photometric conditions on site combined with the optimized instrument allow us to detect signals a magnitude smaller compared to previous ground based wide field surveys. With the sensitivity reaching more into the red wavelength NGTS focus to detect Neptune sized planets around K-dwarfs. One of these planets is NGTS-4b which lies directly in the middle of the sub-jovian desert. With its high photometric precision and time resolution NGTS data allows not only for the search of transiting exoplanets but for a wide range of scientific applications related to variability of stars. Already now several studies on stellar flares are based on NGTS data. All NGTS observations will be accessible over the ESO archive. The first light curves of hundred thousands of stars are already accessible.
|E. W. Guenther
|Spectroscopy for determing the statistics of planets in transit surveys
Since the mass and life-time of the protoplanetary disk depends on the mass of the host stars, the properties of the planets are expected to depend on the mass of the host stars too. The question thus is how the properties of planets change with the mass of the host star. Determining the statistics of planets for stars of different masses using radial-velocity surveys is not easy, because the accuracy of radial-velocity measurements strongly depends on the rotation velocity, the number of spectral lines and also on the activity-level of the host star. Transit surveys are strongly biased towards short period planets and biased against large stars but it is easy to correct for these effects. It is also relatively easy to calculate the correction factors for activity-level if the activity-level of the stars are known. Transit surveys are thus ideal to detect short-period planets of hot stars like WASP-33b, KELT-9, or MASCARA-1. In order to determine the statistics as a function of stellar mass, all we have to do is to characterize the sample of stars. For The CoRoT-mission we have done this using the AAOmega multi-object spectrograph. This worked out very well given that each CoRoT-field had a size of 1.5x3.0 (1.5x1.5) degrees and AAOmega a field-of-view of 2 degrees. However, how are we going to characterize the sample of PLATO 2.0 given that each field has size of 2250 square degrees? A new approach is certainly needed. The interesting aspect is that this is an opportunity for small telescopes, given that the main targets will be between 4 to 11 mag.
|The Gaia catalogue of hot subluminous stars
Based on data from the ESA Gaia Data Release 2 (DR2) and several ground-based, multi-band photometry surveys we have compiled an all-sky catalogue of 39800 hot subluminous star candidates selected in Gaia DR2 by means of colour, absolute magnitude, and reduced proper motion cuts. We expect the majority of the candidates to be hot subdwarf stars of spectral type B and O, followed by blue horizontal branch stars of late B-type (HBB), hot post-AGB stars, and central stars of planetary nebulae. The catalogue is magnitude limited to G$<$19 mag and covers the whole sky. Cross-matching this catalogue with large surveys of all kinds, we are aiming to compile the first volume-complete 500 pc sample of sdO/B stars.