Kepler-411 Star Activity: Connection between Starspots and Superflares

Stellar magnetic activity, just like that of the Sun, manifests itself in the form of flares and spots on the surface of the star. In the solar case, the largest flares originate from large active regions. In this work, we present a study of the activity of the star Kepler-411, including spot modeling from planetary transits. Our goal was to search for a connection between the area of starspots with the energy of superflares produced by this star. Kepler-411 is a K2V-type star with an average rotation period of 10.52 days, radius of 0.79 R ⊙, and a mass of 0.83 M ⊙, which was observed by the Kepler satellite for about 600 days. Transit mapping allowed for the characterization of 198 starspots with estimates of their radius and temperature. Kepler-411 starspots had an average radius of (17 ± 7) × 103 km and a mean temperature of 3800 ± 700 K. Visual inspection of the light curves of Kepler-411 yields the identification of 65 superflares. The detected superflares lasted from 8 to 260 minutes and their energy varied from 1033–1035 ergs. The power-law index of the flare frequency distribution as a function of energy is (−2.04 ± 0.13) for the flare on Kepler-411. A positive correlation between the area of starspots and the energy of superflares was found when considering the averages taken every 16–35 days, with the highest correlation occurring for averages every 21 days. This timing is probably related to the lifetime of the Kepler-411 spots.

The Random Transiter – EPIC 249706694/HD 139139

ABSTRACT We have identified a star, EPIC 249706694 (HD 139139), that was observed during K2 Campaign 15 with the Kepler extended mission that appears to exhibit 28 transit-like events over the course of the 87-d observation. The unusual aspect of these dips, all but two of which have depths of 200 ± 80 ppm, is that they exhibit no periodicity, and their arrival times could just as well have been produced by a random number generator. We show that no more than four of the events can be part of a periodic sequence. We have done a number of data quality tests to ascertain that these dips are of astrophysical origin, and while we cannot be absolutely certain that this is so, they have all the hallmarks of astrophysical variability on one of two possible host stars (a likely bound pair) in the photometric aperture. We explore a number of ideas for the origin of these dips, including actual planet transits due to multiple or dust emitting planets, anomalously large TTVs, S- and P-type transits in binary systems, a collection of dust-emitting asteroids, ‘dipper-star’ activity, and short-lived starspots. All transit scenarios that we have been able to conjure up appear to fail, while the intrinsic stellar variability hypothesis would be novel and untested.

LraI fromLactococcus raffinolactisBGTRK10-1, an Isoschizomer ofEcoRI, Exhibits Ion Concentration-Dependent Specific Star Activity

Restriction enzymes are the main defence system against foreign DNA, in charge of preserving genome integrity.Lactococcus raffinolactisBGTRK10-1 expressesLraI Type II restriction-modification enzyme, whose activity is similar to that shown forEcoRI;LraI methyltransferase protects DNA fromEcoRI cleavage. The gene encodingLraI endonuclease was cloned and overexpressed inE. coli. Purified enzyme showed the highest specific activity at lower temperatures (between 13°C and 37°C) and was stable after storage at −20°C in 50% glycerol. The concentration of monovalent ions in the reaction buffer required for optimal activity ofLraI restriction enzyme was 100 mM or higher. The recognition and cleavage sequence forLraI restriction enzyme was determined as 5′-G/AATTC-3′, indicating thatLraI restriction enzyme is an isoschizomer ofEcoRI. In the reaction buffer with a lower salt concentration,LraI exhibits star activity and specifically recognizes and cuts another alternative sequence 5′-A/AATTC-3′, leaving the same sticky ends on fragments asEcoRI, which makes them clonable into a linearized vector. Phylogenetic analysis based on sequence alignment pointed out the common origin ofLraI restriction-modification system with previously describedEcoRI-like restriction-modification systems.

KIC 7385478: An Eclipsing Binary with a γ Doradus Component

We present spectroscopic and photometric analysis of the eclipsing binary KIC 7385478. We find that the system is formed by F1V + K4III–IV components. Combining results from analysis of spectroscopic data and Kepler photometry, we calculate masses and radii of the primary and the secondary components as M1 = 1.71 ± 0.08 M⊙, M2 = 0.37 ± 0.04 M⊙ and R1 = 1.59 ± 0.03 R⊙, R2 = 1.90 ± 0.03 R⊙, respectively. Position of the primary component in HR diagram is in the region of γ Doradus type pulsators and residuals from light curve modelling exhibit additional light variation with a dominant period of ~ 0.5 d. These are clear evidences of the γ Doradus type pulsations on the primary component. We also observe occasional increase in amplitude of the residuals, where the orbital period becomes the most dominant period. These may be attributed to the cool star activity originating from the secondary component.

ERK1/2 MAPKs and Wnt Signaling Pathways are Independently Involved in Adipocytokine-Mediated Aldosterone Secretion

Obesity is one major risk factor for the development of arterial hypertension, and the development of obesity-related hypertension has been associated with increased plasma aldosterone levels. Our previous work shows a direct stimulatory effect of adipokines on aldosterone secretion from human adrenocortical cells, mediated via ERK1/2-dependent upregulation of steroid acute regulatory protein (StAR) activity. Recent evidence also indicates the involvement of the Wnt-signaling pathway in fat cell-mediated aldosterone secretion. Wnt-signaling molecules are secreted by adipocytes and regulate the activity of SF-1, a key transcription factor in adrenal steroidogenesis. The goal of this study was to investigate the cellular mechanisms of adipocyte-induced aldosterone secretion in detail, and to evaluate effects and possible interactions of the ERK1/2 MAPK- and the Wnt-signaling pathways on adipocyte-induced adreno­cortical aldosterone secretion. Our results show that, similar to adipocyte-conditioned medium (ACM), β-catenin, which is an intracellular mediator of canonical Wnt-signaling, induced StAR promotor activity in human NCI-H295R adrenocortical cells, and ACM-induced StAR promotor activity depended on intact SF-1 binding sites. Wnt antagonist sFRP-1 inhibited adipokine-mediated StAR activity, but did not affect ERK1/2 MAPK activation. Accordingly, Wnt did not stimulate ERK1/2 phosphorylation in adrenocortical cells, indicating that ERK1/2 MAPK and Wnt signaling pathways are independently involved in adipocyte-mediated aldosterone secretion.

Lessons from detections of the near-infrared thermal emission of hot Jupiters

There have recently been a flood of ground-based detections of the near-infrared thermal emission of a number of hot Jupiters. Although these near-infrared detections have revealed a great deal about the atmospheric characteristics of individual hot Jupiters, the question is: what information does this ensemble of near-infrared detections reveal about the atmospheric dynamics and reradiation of all hot Jupiters? I explore whether there is any correlation between how brightly these planets shine in the near-infrared compared to their incident stellar flux, as was theoretically predicted to be the case. Secondly, I look for whether there is any correlation between the host star's activity and the planet's near-infrared emission, like there is in the mid-infrared, where Spitzer observations have revealed a correlation between the host star activity with the presence, or lack thereof, of a temperature inversion and a hot stratosphere.