We present the discovery of a new highly compact quadruple star system, TIC 219006972, consisting of two eclipsing binary stars with orbital periods of 8.3 days and 13.7 days, and an outer orbital ...period of only 168 days. This period is a full factor of 2 shorter than the quadruple with the shortest outer period reported previously, VW LMi, where the two binary components orbit each other every 355 days. The target was observed by TESS in Full-Frame Images in sectors 14-16, 21-23, 41, 48 and 49, and produced two sets of primary and secondary eclipses. These show strongly non-linear eclipse timing variations (ETVs) with an amplitude of \(\sim\)0.1 days, where the ETVs of the primary and secondary eclipses, and of the two binaries are all largely positively correlated. This highlights the strong dynamical interactions between the two binaries and confirms the compact quadruple configuration of TIC 219006972. The two eclipsing binaries are nearly circular whereas the quadruple system has an outer eccentricity of about 0.25. The entire system is nearly edge-on, with a mutual orbital inclination between the two eclipsing binary star systems of about 1 degree.
We present our second catalog of quadruple star candidates, containing 101
systems discovered in TESS Full-Frame Image data. The targets were initially
detected as eclipsing binary stars with the ...help of supervised machine learning
methods applied to sectors Sectors 1 through 54. A dedicated team of citizen
scientists subsequently identified through visual inspection two sets of
eclipses following two different periods. All 101 systems presented here pass
comprehensive photocenter motion tests confirming that both sets of eclipses
originate from the target star. Some of the systems exhibit prominent eclipse
time variations suggesting dynamical interactions between the two component
binary stars. One target is an eclipsing quintuple candidate with a (2+1)+2
hierarchical configuration, such that the (2+1) subsystem produces eclipses on
the triple orbit as well. Another has recently been confirmed as the second
shortest period quadruple reported to date. This catalog provides ephemerides,
eclipse depths and durations, sample statistics, and highlights potentially
interesting targets for future studies.
Flares, energetic eruptions on the surfaces of stars, are an unmistakable manifestation of magnetically driven emission. Their occurrence rates and energy distributions trace stellar characteristics ...such as mass and age. But before flares can be used to constrain stellar properties, the flaring-age-mass relation requires proper calibration. This work sets out to quantify flaring activity of independently age-dated main sequence stars for a broad range of spectral types using optical light curves obtained by the Kepler satellite. Drawing from the complete K2 archive, we searched 3435 \(\sim 80\) day long light curves of 2111 open cluster members for flares using the open-source software packages K2SC to remove instrumental and astrophysical variability from K2 light curves, and AltaiPony to search and characterize the flare candidates. We confirmed a total of 3844 flares on high probability open cluster members with ages from zero age main sequence (Pleiades) to 3.6 Gyr (M67). We extended the mass range probed in the first study of this series to span from Sun-like stars to mid-M dwarfs. We added the Hyades (690 Myr) to the sample as a comparison cluster to Praesepe (750 Myr), the 2.6 Gyr old Ruprecht 147, and several hundred light curves from the late K2 Campaigns in the remaining clusters. The flare energy distribution was similar in the entire parameter space, following a power law relation with exponent \(\alpha\approx 1.84-2.39\). The flaring rates declined with age, and declined faster for higher mass stars. We found evidence that a rapid decline in flaring activity occurred in M1-M2 dwarfs around Hyades/Praesepe age, when these stars spun down to rotation periods of about 10 days, while higher mass stars had already transitioned to lower flaring rates, and lower mass stars still resided in the saturated activity regime. (abridged)
We have found that the 2+2 quadruple star system BU CMi is currently the most compact quadruple system known, with an extremely short outer period of only 121 days. The previous record holder was TIC ...219006972 (Kostov et al. 2023), with a period of 168 days. The quadruple nature of BU CMi was established by Volkov et al. (2021), but they misidentified the outer period as 6.6 years. BU CMi contains two eclipsing binaries (EBs), each with a period near 3 days, and a substantial eccentricity of about 0.22. All four stars are within about 0.1 solar mass of 2.4 solar masses. Both binaries exhibit dynamically driven apsidal motion with fairly short apsidal periods of about 30 years, thanks to the short outer orbital period. The outer period of 121 days is found both from the dynamical perturbations, with this period imprinted on the eclipse timing variations (ETV) curve of each EB by the other binary, and by modeling the complex line profiles in a collection of spectra. We find that the three orbital planes are all mutually aligned to within 1 degree, but the overall system has an inclination angle near 83.5 degrees. We utilize a complex spectro-photodynamical analysis to compute and tabulate all the interesting stellar and orbital parameters of the system. Finally, we also find an unexpected dynamical perturbation on a timescale of several years whose origin we explore. This latter effect was misinterpreted by Volkov et al. (2021) and led them to conclude that the outer period was 6.6 years rather than the 121 days that we establish here.
Dipper stars are a classification of young stellar objects that exhibit dimming variability in their light curves, dropping in brightness by 10-50%, likely induced by occultations due to ...circumstellar disk material. This variability can be periodic, quasi-periodic, or aperiodic. Dipper stars have been discovered in young stellar associations via ground-based and space-based photometric surveys. We present the detection and characterization of the largest collection of dipper stars to date: 293 dipper stars, including 234 new dipper candidates. We have produced a catalog of these targets, which also includes young stellar variables that exhibit predominately bursting-like variability and symmetric variability (equal parts bursting and dipping). The total number of catalog sources is 414. These variable sources were found in a visual survey of TESS light curves, where dipping-like variability was observed. We found a typical age among our dipper sources of <5 Myr, with the age distribution peaking at ~2 Myr, and a tail of the distribution extending to ages older than 20 Myr. Regardless of the age, our dipper candidates tend to exhibit infrared excess, which is indicative of the presence of disks. TESS is now observing the ecliptic plane, which is rich in young stellar associations, so we anticipate many more discoveries in the TESS dataset. A larger sample of dipper stars would enhance the census statistics of light curve morphologies and dipper ages.
We report the discovery with TESS of a remarkable quadruple star system with a 2+1+1 configuration. The two unique characteristics of this system are that (i) the inner eclipsing binary (stars Aa and ...Ab) eclipses the star in the outermost orbit (star C), and (ii) these outer 4th body eclipses last for \(\sim\)12 days, the longest of any such system known. The three orbital periods are \(\sim\)3.3 days, \(\sim\)51 days, and \(\sim\)2100 days. The extremely long duration of the outer eclipses is due to the fact that star B slows binary A down on the sky relative to star C. We combine TESS photometric data, ground-based photometric observations, eclipse timing points, radial velocity measurements, the composite spectral energy distribution, and stellar isochones in a spectro-photodynamical analysis to deduce all of the basic properties of the four stars (mass, radius, \(T_{\rm eff}\), and age), as well as the orbital parameters for all three orbits. The four masses are \(M_{\rm Aa} =0.382\)M\(_\odot\), \(M_{\rm Ab} =0.300\)M\(_\odot\), \(M_{\rm B} =0.540\)M\(_\odot\) and \(M_{\rm C} =0.615\)M\(_\odot\), with a typical uncertainty of 0.015 M\(_\odot\).
This article presents the history of the Visual Survey Group (VSG) - a Professional-Amateur (Pro-Am) collaboration within the field of astronomy working on data from several space missions (Kepler, ...K2 and TESS). This paper covers the formation of the VSG, its survey-methods including the most common tools used and its discoveries made over the past decade. So far, the group has visually surveyed nearly 10 million light curves and authored 69 peer-reviewed papers which mainly focus on exoplanets and discoveries involving multistellar systems found using the transit method. The preferred manual search-method carried out by the VSG has revealed its strength by detecting numerous sub-stellar objects which were overlooked or discarded by automated search programs, uncovering some of the most rare stars in our galaxy, and leading to several serendipitous discoveries of unprecedented astrophysical phenomena. The main purpose of the VSG is to assist in the exploration of our local Universe, and we therefore advocate continued crowd-sourced examination of time-domain data sets, and invite other research teams to reach out in order to establish collaborating projects.
We present a catalog of 97 uniformly-vetted candidates for quadruple star systems. The candidates were identified in TESS Full Frame Image data from Sectors 1 through 42 through a combination of ...machine learning techniques and visual examination, with major contributions from a dedicated group of citizen scientists. All targets exhibit two sets of eclipses with two different periods, both of which pass photocenter tests confirming that the eclipses are on-target. This catalog outlines the statistical properties of the sample, nearly doubles the number of known multiply-eclipsing quadruple systems, and provides the basis for detailed future studies of individual systems. Several important discoveries have already resulted from this effort, including the first sextuply-eclipsing sextuple stellar system and the first transiting circumbinary planet detected from one sector of TESS data.
We report the discovery of a unique object of uncertain nature -- but quite possibly a disintegrating asteroid or minor planet -- orbiting one star of the widely separated binary TIC 400799224. We ...initially identified the system in data from TESS Sector 10 via an abnormally-shaped fading event in the light curve (hereafter 'dips'). Follow-up speckle imaging determined that TIC 400799224 is actually two stars of similar brightness at 0.62" separation, forming a likely bound binary with projected separation of ~300 au. We cannot yet determine which star in the binary is host to the dips in flux. ASAS-SN and Evryscope archival data show that there is a strong periodicity of the dips at ~19.77 days, leading us to believe that an occulting object is orbiting the host star, though the duration, depth, and shape of the dips vary substantially. Statistical analysis of the ASAS-SN data shows that the dips only occur sporadically at a detectable threshold in approximately one out of every three to five transits, lending credence to the possibility that the occulter is a sporadically-emitted dust cloud. The cloud is also fairly optically thick, blocking up to 37% or 75% of the light from the host star, depending on the true host. Further observations may allow for greater detail to be gleaned as to the origin and composition of the occulter, as well as to a determination of which of the two stars comprising TIC 400799224 is the true host star of the dips.
In this paper we present a catalog of 4584 eclipsing binaries observed during the first two years (26 sectors) of the TESS survey. We discuss selection criteria for eclipsing binary candidates, ...detection of hither-to unknown eclipsing systems, determination of the ephemerides, the validation and triage process, and the derivation of heuristic estimates for the ephemerides. Instead of keeping to the widely used discrete classes, we propose a binary star morphology classification based on a dimensionality reduction algorithm. Finally, we present statistical properties of the sample, we qualitatively estimate completeness, and discuss the results. The work presented here is organized and performed within the TESS Eclipsing Binary Working Group, an open group of professional and citizen scientists; we conclude by describing ongoing work and future goals for the group. The catalog is available from http://tessEBs.villanova.edu and from MAST.
