Observation of a 2016 Ganymede stellar occultation event with the SOAO 0.6m telescope

Tobias Cornelius Hinse,Emiliano D’Aversa,Fabrizio Oliva,Giuseppe Sindoni 한국천문학회 2017 天文學會報 Vol.42 No.2

5-body dynamics in the Kepler-47 exoplanetary system: Predicting stable orbits of a third circumbinary planet

Tobias Cornelius Hinse 한국천문학회 2014 天文學會報 Vol.39 No.2

Photometric Defocus Observations of Transiting Extrasolar Planets

HINSE TOBIAS CORNELIUS,한원용,윤요나,이정욱,김용기,김천휘 한국우주과학회 2015 Journal of Astronomy and Space Sciences Vol.32 No.1

We have carried out photometric follow-up observations of bright transiting extrasolar planets using the CbNUOJ 0.6m telescope. We have tested the possibility of obtaining high photometric precision by applying the telescope defocustechnique, allowing the use of several hundred seconds in exposure time for a single measurement. We demonstrate thatthis technique is capable of obtaining a root-mean-square scatter of sub-millimagnitude order over several hours for a V~10 host star, typical for transiting planets detected from ground-based survey facilities. We compared our results withtransit observations from a telescope operated in in-focus mode. High photometric precision was obtained due to thecollection of a larger amount of photons, resulting in a higher signal compared to other random and systematic noisesources. Accurate telescope tracking is likely to further contribute to lowering systematic noise by exposing the same pixelson the CCD. Furthermore, a longer exposure time helps reduce the effect of scintillation noise which otherwise has asignificant effect for small-aperture telescopes operated in in-focus mode. Finally we present the results of modelling fourlight-curves in which a root-mean-square scatter of 0.70 to 2.3 milli-magnitudes was achieved.

THE PROPOSED QUADRUPLE SYSTEM SZ HERCULIS: REVISED LITE MODEL AND ORBITAL STABILITY STUDY

Hinse, Tobias Cornelius,Goź,dziewski, Krzysztof,Lee, Jae Woo,Haghighipour, Nader,Lee, Chung-Uk American Institute of Physics 2012 The Astronomical journal Vol.144 No.2

<P>In a recent study, Lee et al. presented new photometric follow-up timing observations of the semidetached binary system SZ Herculis and proposed the existence of two hierarchical cirumbinary companions. Based on the light-travel time effect, the two low-mass M-dwarf companions are found to orbit the binary pair on moderate to high eccentric orbits. The derived periods of these two companions are close to a 2:1 mean-motion orbital resonance. We have studied the stability of the system using the osculating orbital elements as presented by Lee et al. Results indicate an orbit-crossing architecture exhibiting short-term dynamical instabilities leading to the escape of one of the proposed companions. We have examined the system's underlying model parameter space by following a Monte Carlo approach and found an improved fit to the timing data. A study of the stability of our best-fitting orbits also indicates that the proposed system is generally unstable. If the observed anomalous timing variations of the binary period is due to additional circumbinary companions, then the resulting system should exhibit a long-term stable orbital configuration much different from the orbits suggested by Lee et al. We, therefore, suggest that based on Newtonian-dynamical considerations, the proposed quadruple system cannot exist. To uncover the true nature of the observed period variations of this system, we recommend future photometric follow-up observations that could further constrain eclipse-timing variations and/or refine light-travel time models.</P>

[발표취소] Stable 5-body orbits in the Kepler-47 exoplanetary system: Predicting stable orbits of a possible third circumbinary planet

Tobias Cornelius Hinse 한국천문학회 2014 天文學會報 Vol.39 No.1

Using Light Travel Time Effect to Detect Circumbinary Planets with Ground-Based Telescopes

Hinse, Tobias Cornelius 한국천문학회 2012 天文學會報 Vol.37 No.2

In the past few years, two-planet circumbinary systems (e.g., HW Vir, NN Ser, DP Leo and HU Aqr) have been detected around short-period eclipsing binaries using ground-based telescopes. The existence of these planets has been inferred by interpreting the O-C variations of the mid-eclipse times. We have tested the orbital stability of these systems and propose to use Light Travel Time Effect (LITE) to detect such circumbinary planets from the ground. We generated synthetically the LITE signal of a two-planet circumbinary system with the aim to apply an analytic LITE model to recover the underlying synthetic system. To mimic a degree of realism inherent to ground-based observations, we added to the synthetic LITE data white noise with a Gaussian distribution and sampled the synthetic LITE signal randomly. We successfully recovered the original system demonstrating that two-planet circumbinary systems can be detected using ground-based telescopes, provided the timing measurements of the mid-eclipses are sufficiently accurate and the observing baseline is long enough to ensure a sufficient coverage of all involved periods. We used HU Aqr as a test system and applied our model to its proposed planetary bodies considering near-circular orbits. We present the results of our calculations and discuss the LITE-detectability of a HU Aqr-like system.

THE ECLIPSING SYSTEM EP ANDROMEDAE AND ITS CIRCUMBINARY COMPANIONS

Lee, Jae Woo,Hinse, Tobias Cornelius,Park, Jang-Ho American Institute of Physics 2013 The Astronomical journal Vol.145 No.4

<P>We present new long-term CCD photometry for EP And acquired during the period 2007-2012. The light curves display total eclipses at primary minima and season-to-season light variability. Our synthesis for all available light curves indicates that the eclipsing pair is a W-type overcontact binary with parameters of q = 2.578, i = 83.°3, ΔT = 27 K, f = 28%, and l<SUB>3</SUB> = 2%-3%. The asymmetric light curves in 2007 were satisfactorily modeled by a cool spot on either of the eclipsing components from a magnetic dynamo. Including our 95 timing measurements, a total of 414 times of minimum light spanning about 82 yr was used for a period study. A detailed analysis of the eclipse timing diagram revealed that the orbital period of EP And has varied as a combination of an upward-opening parabola and two periodic variations, with cycle lengths of P<SUB>3</SUB> = 44.6 yr and P<SUB>4</SUB> = 1.834 yr and semi-amplitudes of K<SUB>3</SUB> = 0.0100 days and K<SUB>4</SUB> = 0.0039 days, respectively. The observed period increase at a fractional rate of +1.39 × 10<SUP>–10</SUP> is in excellent agreement with that calculated from the W-D code and can be plausibly explained by some combination of mass transfer from the primary to the secondary star and angular momentum loss due to magnetic braking. The most reasonable explanation for both cycles is a pair of light-travel-time effects driven by the possible existence of a third and fourth component with projected masses of M<SUB>3</SUB> = 0.25 M<SUB>☉</SUB> and M<SUB>4</SUB> = 0.90 M<SUB>☉</SUB>. The more massive companion could be revealed using high-resolution spectroscopic data extending over the course of a few years and could also be a binary itself. It is possible that the circumbinary objects may have played an important role in the formation and evolution of the eclipsing pair, which would cause it to have a short initial orbital period and thus evolve into an overcontact configuration by angular momentum loss.</P>

THE<i>KEPLER</i>ECLIPSING SYSTEM KIC 5621294 AND ITS SUBSTELLAR COMPANION

Lee, Jae Woo,Hong, Kyeongsoo,Hinse, Tobias Cornelius IOP Publishing 2015 The Astronomical journal Vol.149 No.3

THE SUB-SATURN MASS TRANSITING PLANET HAT-P-12b

Lee, Jae Woo,Youn, Jae-Hyuck,Kim, Seung-Lee,Lee, Chung-Uk,Hinse, Tobias Cornelius American Institute of Physics 2012 The Astronomical journal Vol.143 No.4

<P>We present new photometric data of the transiting planet HAT-P-12b observed in 2011. Our three transit curves are modeled using the JKTEBOP code and adopting the quadratic limb-darkening law. Including our measurements, 18 transit times spanning about 4.2 yr were used to determine the improved ephemeris with a transit epoch of 2,454,187.85560 ± 0.00011 BJD and an orbital period of 3.21305961 ± 0.00000035 days. The physical properties of the star-planet system are computed using empirical calibrations from eclipsing binary stars and stellar evolutionary models, combined with both our transit parameters and previously known spectroscopic results. We found that the absolute dimensions of the host star are M<SUB>A</SUB> = 0.73 ± 0.02 M<SUB>☉</SUB>, R<SUB>A</SUB> = 0.70 ± 0.01 R<SUB>☉</SUB>, log g<SUB>A</SUB> = 4.61 ± 0.02, ρ<SUB>A</SUB> = 2.10 ± 0.09 ρ<SUB>☉</SUB>, and L<SUB>A</SUB> = 0.21 ± 0.01 L<SUB>☉</SUB>. The planetary companion has M<SUB>b</SUB> = 0.21 ± 0.01 M<SUB>Jup</SUB>, R<SUB>b</SUB> = 0.94 ± 0.01 R<SUB>Jup</SUB>, log g<SUB>b</SUB> = 2.77 ± 0.02, ρ<SUB>b</SUB> = 0.24 ± 0.01 ρ<SUB>Jup</SUB>, and T<SUB>eq</SUB> = 960 ± 14 K. Our results agree well with standard models of irradiated gas giants with a core mass of 11.3 M<SUB>⊕</SUB>.</P>

THE TRIPLY ECLIPSING HIERARCHICAL TRIPLE STAR KIC002856960

Lee, Jae Woo,Kim, Seung-Lee,Lee, Chung-Uk,Lee, Byeong-Cheol,Park, Byeong-Gon,Hinse, Tobias Cornelius IOP Publishing 2013 The Astrophysical journal Vol.763 No.2

<P>In a recent study, Armstrong et al. presented an eclipsing binary star of about 6.2 hr period with transit-like tertiary signals occurring every 204.2 days in the Kepler public data of KIC002856960 and proposed three possible hierarchical structures: (AB) b, (AB) C, and A(BC). We analyzed the Kepler light curve by including a third light source and one starspot on each binary component. The results represent that the close eclipsing pair is in a low-mass eccentric-orbit, detached configuration. Based on 123 eclipse timings calculated from the Wilson-Devinney binary model, a period study of the close binary reveals that the orbital period has experienced a sinusoidal variation with a period and a semi-amplitude of 205 +/- 2 days and 0.0021 +/- 0.0002 days, respectively. The period variation would be produced by the light-travel-time effect due to a gravitationally bound third body with a minimum mass of M-3 sin i(3) = 0.76 M-circle dot in an eccentric orbit of e(3) = 0.61. This is consistent with the presence of third light found in our light curve solution and the tertiary signal of 204.2 day period most likely arises from the K-type star crossed by the close eclipsing binary. Then, KIC002856960 is a triply eclipsing hierarchical system, A(BC), consisting of a close binary with two M-type dwarfs and a more massive K-type component. The presence of the third star may have played an important role in the formation and evolution of the close pair, which may ultimately evolve into a contact system by angular momentum loss.</P>