Planet Hunters IX. KIC 8462852 – where's the flux? Boyajian, T. S; LaCourse, D. M; Rappaport, S. A ...
Monthly notices of the Royal Astronomical Society,
04/2016, Letnik:
457, Številka:
4
Journal Article
Recenzirano
Odprti dostop
Over the duration of the Kepler mission, KIC 8462852 was observed to undergo irregularly shaped, aperiodic dips in flux of up to ∼20 per cent. The dipping activity can last for between 5 and 80 d. We ...characterize the object with high-resolution spectroscopy, spectral energy distribution fitting, radial velocity measurements, high-resolution imaging, and Fourier analyses of the Kepler light curve. We determine that KIC 8462852 is a typical main-sequence F3 V star that exhibits no significant IR excess, and has no very close interacting companions. In this paper, we describe various scenarios to explain the dipping events observed in the Kepler light curve. We confirm that the dipping signals in the data are not caused by any instrumental or data processing artefact, and thus are astrophysical in origin. We construct scenario-independent constraints on the size and location of a body in the system that are needed to reproduce the observations. We deliberate over several assorted stellar and circumstellar astrophysical scenarios, most of which have problems explaining the data in hand. By considering the observational constraints on dust clumps in orbit around a normal main-sequence star, we conclude that the scenario most consistent with the data in hand is the passage of a family of exocomet or planetesimal fragments, all of which are associated with a single previous break-up event, possibly caused by tidal disruption or thermal processing. The minimum total mass associated with these fragments likely exceeds 10−6 M⊕, corresponding to an original rocky body of >100 km in diameter. We discuss the necessity of future observations to help interpret the system.
The ultrafast-rotating (P sub(rot)approximate 0.44 d) fully convective single M4 dwarf V374Peg is a well-known laboratory for studying intense stellar activity in a stable magnetic topology. As an ...observable proxy for the stellar magnetic field, we study the stability of the light curve, hence the spot configuration. We also measure the occurrence rate of flares and coronal mass ejections (CMEs). We have analysed spectroscopic observations, BV(RI) sub(C) photometry covering 5 yrs, and additional R sub(C) photometry that expands the temporal base over 16 yr. The light curve suggests an almost rigid-body rotation and a spot configuration that is stable over about 16 yrs, confirming the previous indications of a very stable magnetic field. We observed small changes on a nightly timescale and frequent flaring, including a possible sympathetic flare. The strongest flares seem to be more concentrated around the phase where the light curve indicates a smaller active region. Spectral data suggest a complex CME with falling-back and re-ejected material with a maximal projected velocity of ~675kms super(-1). We observed a CME rate that is much lower than expected from extrapolations of the solar flare-CME relation to active stars.
We present a detailed analysis of the bright Cepheid-type variable star V1154 Cygni using 4 yr of continuous observations by the Kepler space telescope. We detected 28 frequencies using the standard ...Fourier transform method. We identified modulation of the main pulsation frequency and its harmonics with a period of ~159 d. This modulation is also present in the Fourier parameters of the light curve and the O - C diagram. We detected another modulation with a period of about 1160 d. The star also shows significant power in the low-frequency region that we identified as granulation noise. The effective time-scale of the granulation agrees with the extrapolated scalings of red giant stars. Non-detection of solar-like oscillations indicates that the pulsation inhibits other oscillations. We obtained new radial velocity observations that are in a perfect agreement with previous years data, suggesting that there is no high-mass star companion of V1154 Cygni. Finally, we discuss the possible origin of the detected frequency modulations.
We report the discovery of four transiting F-M binary systems with companions between 0.1 and 0.2 M in mass by the HATSouth survey. These systems have been characterized via a global analysis of the ...HATSouth discovery data, combined with high-resolution radial velocities and accurate transit photometry observations. We determined the masses and radii of the component stars using a combination of two methods: isochrone fitting of spectroscopic primary star parameters and equating spectroscopic primary star rotation velocity with spin-orbit synchronization. These new very low mass companions are HATS550-016B (
,
), HATS551-019B (
,
), HATS551-021B (
,
) and HATS553-001B (
,
). We examine our sample in the context of the radius anomaly for fully convective low-mass stars. Combining our sample with the 13 other well-studied very low mass stars, we find a tentative 5 per cent systematic deviation between the measured radii and theoretical isochrone models.
Context.
Binary Cepheids play an important role in the investigation of the calibration of the classical Cepheid period-luminosity relationship. Therefore, a thorough study of individual Cepheids ...belonging to binary systems is necessary.
Aims.
Our aim is to determine the orbit of the binary system V1344 Aql using newly observed and earlier published spectroscopic and photometric data.
Methods.
We collected new radial velocity observations using medium resolution (
R
≈ 11 000 and
R
⪅ 20 000) spectrographs, and we updated the pulsation period of the Cepheid based on available photometric observations using an
O
−
C
diagram. Separating the pulsational and orbital radial velocity variations for each observational season (year), we determined the orbital solution for the system using
χ
2
minimisation.
Results.
The updated pulsation period of the Cepheid estimated for the epoch of HJD 2458955.83 is 7.476826 days. We determined orbital elements for the first time in the literature. The orbital period of the system is about 34.6 yr, with an eccentricity of
e
= 0.22.
We report the discovery by the HATSouth survey of HATS-4b, an extrasolar planet transiting a V = 13.46 mag G star. HATS-4b has a period of P approximately 2.5167 days, mass of M sub(p) approximately ...1.32 M sub(Jup), radius of R sub(p) approximately 1.02 R sub(Jup), and density of rho sub(p) = 1.55 + or - 0.16 g cm super(-3) approximately 1.24 rho sub(Jup). The host star has a mass of 1.00 M sub(odot), a radius of 0.92 R sub(odot), and a very high metallicity Fe/H = 0.43 + or - 0.08. HATS-4b is among the densest known planets with masses between 1 and 2 M sub(J) and is thus likely to have a significant content of heavy elements of the order of 75 M sub(+ in circle). In this paper we present the data reduction, radial velocity measurements, and stellar classification techniques adopted by the HATSouth survey for the CORALIE spectrograph. We also detail a technique for simultaneously estimating v sin i and macroturbulence using high resolution spectra.
Planet Hunters IX. KIC 8462852 – where's the flux? Boyajian, T. S.; LaCourse, D. M.; Rappaport, S. A. ...
Monthly notices of the Royal Astronomical Society,
04/2016, Letnik:
457, Številka:
4
Journal Article
KIC 8560861 (HD 183648) is a marginally eccentric (e = 0.05) eclipsing binary with an orbital period of Porb = 31.973 d, exhibiting mmag amplitude pulsations on time-scales of a few days. We present ...the results of the complex analysis of high- and medium-resolution spectroscopic data and Kepler Q0 - Q16 long cadence photometry. The iterative combination of spectral disentangling, atmospheric analysis, radial velocity and eclipse timing variation studies, separation of pulsational features of the light curve, and binary light curve analysis led to the accurate determination of the fundamental stellar parameters. We found that the binary is composed of two main-sequence stars with an age of 0.9 plus or minus 0.2 Gyr, having masses, radii and temperatures of M1 = 1.93 plus or minus 0.12 M..., R1 = 3.30 plus or minus 0.07 R..., Teff1 = 7650 plus or minus 100 K for the primary, and M2 = 1.06 plus or minus 0.08 M..., R2 = 1.11 plus or minus 0.03 R..., Teff2 = 6450 plus or minus 100 K for the secondary. After substracting the binary model, we found three independent frequencies, two of which are separated by twice the orbital frequency. We also found an enigmatic half orbital period sinusoidal variation that we attribute to an anomalous ellipsoidal effect. Both of these observations indicate that tidal effects are strongly influencing the luminosity variations of HD 183648. The analysis of the eclipse timing variations revealed both a parabolic trend, and apsidal motion with a period of Pobsapse=10400 plus or minus 3000 y, which is ten times faster than what is theoretically expected. These findings might indicate the presence of a distant, unseen companion. (ProQuest: ... denotes formulae/symbols omitted.)
We report the discovery of HATS-1b, a transiting extrasolar planet orbiting the moderately bright V = 12.05 G dwarf star GSC 6652-00186, and the first planet discovered by HATSouth, a global network ...of autonomous wide-field telescopes. HATS-1b has a period of P approximately 3.4465 days, mass of M sub(p) approximately 1.86 M sub(J), and radius of R sub(p) approximately 1.30 R sub(J). The host star has a mass of 0.99 M sub(odot) and radius of 1.04 R sub(odot). The discovery light curve of HATS-1b has near-continuous coverage over several multi-day timespans, demonstrating the power of using a global network of telescopes to discover transiting planets.
PDF
