74 research outputs found
Transit Timing Analysis in the HAT-P-32 System
We present the results of 45 transit observations obtained for the transiting exoplanet HATP- 32b. The transits have been observed using several telescopes mainly throughout the YETI (Young Exoplanet Transit Initiative) network. In 25 cases, complete transit light curves with a timing precision better than 1.4 min have been obtained. These light curves have been used to refine the system properties, namely inclination i, planet-to-star radius ratio Rp/Rs, and the ratio between the semimajor axis and the stellar radius a/Rs. First analyses by Hartman et al. suggests the existence of a second planet in the system, thus we tried to find an additional body using the transit timing variation (TTV) technique. Taking also the literature data points into account, we can explain all mid-transit times by refining the linear ephemeris by 21 ms. Thus, we can exclude TTV amplitudes of more than ∼1.5min
Multi-site campaign for transit timing variations of WASP-12 b: possible detection of a long-period signal of planetary origin
The transiting planet WASP-12 b was identified as a potential target for
transit timing studies because a departure from a linear ephemeris was reported
in the literature. Such deviations could be caused by an additional planet in
the system. We attempt to confirm the existence of claimed variations in
transit timing and interpret its origin. We organised a multi-site campaign to
observe transits by WASP-12 b in three observing seasons, using 0.5-2.6-metre
telescopes. We obtained 61 transit light curves, many of them with
sub-millimagnitude precision. The simultaneous analysis of the best-quality
datasets allowed us to obtain refined system parameters, which agree with
values reported in previous studies. The residuals versus a linear ephemeris
reveal a possible periodic signal that may be approximated by a sinusoid with
an amplitude of 0.00068+/-0.00013 d and period of 500+/-20 orbital periods of
WASP-12 b. The joint analysis of timing data and published radial velocity
measurements results in a two-planet model which better explains observations
than single-planet scenarios. We hypothesize that WASP-12 b might be not the
only planet in the system and there might be the additional 0.1 M_Jup body on a
3.6-d eccentric orbit. A dynamical analysis indicates that the proposed
two-planet system is stable over long timescales.Comment: Accepted for publication in A&
YETI observations of the young transiting planet candidate CVSO 30 b
CVSO 30 is a unique young low-mass system, because, for the first time, a
close-in transiting and a wide directly imaged planet candidates are found
around a common host star. The inner companion, CVSO 30 b, is the first
possible young transiting planet orbiting a previously known weak-lined T-Tauri
star. With five telescopes of the 'Young Exoplanet Transit Initiative' (YETI)
located in Asia, Europe and South America we monitored CVSO 30 over three years
in a total of 144 nights and detected 33 fading events. In two more seasons we
carried out follow-up observations with three telescopes. We can confirm that
there is a change in the shape of the fading event between different
observations and that the fading event even disappears and reappears. A total
of 38 fading event light curves were simultaneously modelled. We derived the
planetary, stellar, and geometrical properties of the system and found them
slightly smaller but in agreement with the values from the discovery paper. The
period of the fading event was found to be 1.36 s shorter and 100 times more
precise than the previous published value. If CVSO 30 b would be a giant planet
on a precessing orbit, which we cannot confirm, yet, the precession period may
be shorter than previously thought. But if confirmed as a planet it would be
the youngest transiting planet ever detected and will provide important
constraints on planet formation and migration time-scales.Comment: 14 pages (20 with appendix), 7 figures (16 with appendix), 6 tables
(7 with appendix
Mass Ejection by Strange Star Mergers and Observational Implications
We determine the Galactic production rate of strangelets as a canonical input
to calculations of the measurable cosmic ray flux of strangelets by performing
simulations of strange star mergers and combining the results with recent
estimates of stellar binary populations. We find that the flux depends
sensitively on the bag constant of the MIT bag model of QCD and disappears for
high values of the bag constant and thus more compact strange stars. In the
latter case strange stars could coexist with ordinary neutron stars as they are
not converted by the capture of cosmic ray strangelets. An unambiguous
detection of an ordinary neutron star would then not rule out the strange
matter hypothesis.Comment: 5 pages, 2 eps figures; referee comments included, accepted by Phys.
Rev. Let
A Possible Detection of Occultation by a Proto-planetary Clump in GM Cephei
GM Cep in the young (~4 Myr) open cluster Trumpler 37 has been known to be an
abrupt variable and to have a circumstellar disk with very active accretion.
Our monitoring observations in 2009-2011 revealed the star to show sporadic
flare events, each with brightening of < 0.5 mag lasting for days. These
brightening events, associated with a color change toward the blue, should
originate from an increased accretion activity. Moreover, the star also
underwent a brightness drop of ~1 mag lasting for about a month, during which
the star became bluer when fainter. Such brightness drops seem to have a
recurrence time scale of a year, as evidenced in our data and the photometric
behavior of GM Cep over a century. Between consecutive drops, the star
brightened gradually by about 1 mag and became blue at peak luminosity. We
propose that the drop is caused by obscuration of the central star by an
orbiting dust concentration. The UX Orionis type of activity in GM Cep
therefore exemplifies the disk inhomogeneity process in transition between
grain coagulation and planetesimal formation in a young circumstellar disk.Comment: In submission to the Astrophysical Journal, 4 figure
A Novel Manganese Efflux System, YebN, Is Required for Virulence by Xanthomonas oryzae pv. oryzae
Manganese ions (Mn2+) play a crucial role in virulence and protection against oxidative stress in bacterial pathogens. Such pathogens appear to have evolved complex mechanisms for regulating Mn2+ uptake and efflux. Despite numerous studies on Mn2+ uptake, however, only one efflux system has been identified to date. Here, we report on a novel Mn2+ export system, YebN, in Xanthomonas oryzae pv. oryzae (Xoo), the causative agent of bacterial leaf blight. Compared with wild-type PXO99, the yebN mutant was highly sensitive to Mn2+ and accumulated high concentrations of intracellular manganese. In addition, we found that expression of yebN was positively regulated by Mn2+ and the Mn2+-dependent transcription regulator, MntR. Interestingly, the yebN mutant was more tolerant to methyl viologen and H2O2 in low Mn2+ medium than PXO99, but more sensitive in high Mn2+ medium, implying that YebN plays an important role in Mn2+ homoeostasis and detoxification of reactive oxygen species (ROS). Notably, deletion of yebN rendered Xoo sensitive to hypo-osmotic shock, suggesting that YebN may protect against such stress. That mutation of yebN substantially reduced the Xoo growth rate and lesion formation in rice implies that YebN could be involved in Xoo fitness in host. Although YebN has two DUF204 domains, it lacks homology to any known metal transporter. Hence, this is the first report of a novel metal export system that plays essential roles in hypo-osmotic and oxidative stress, and virulence. Our results lay the foundations for elucidating the complex and fascinating relationship between metal homeostasis and host-pathogen interactions
Quantifying Sources of Variability in Infancy Research Using the Infant-Directed-Speech Preference
Psychological scientists have become increasingly concerned with issues related to methodology and replicability, and infancy researchers in particular face specific challenges related to replicability: For example, high-powered studies are difficult to conduct, testing conditions vary across labs, and different labs have access to different infant populations. Addressing these concerns, we report on a large-scale, multisite study aimed at (a) assessing the overall replicability of a single theoretically important phenomenon and (b) examining methodological, cultural, and developmental moderators. We focus on infants’ preference for infant-directed speech (IDS) over adult-directed speech (ADS). Stimuli of mothers speaking to their infants and to an adult in North American English were created using seminaturalistic laboratory-based audio recordings. Infants’ relative preference for IDS and ADS was assessed across 67 laboratories in North America, Europe, Australia, and Asia using the three common methods for measuring infants’ discrimination (head-turn preference, central fixation, and eye tracking). The overall meta-analytic effect size (Cohen’s d) was 0.35, 95% confidence interval = [0.29, 0.42], which was reliably above zero but smaller than the meta-analytic mean computed from previous literature (0.67). The IDS preference was significantly stronger in older children, in those children for whom the stimuli matched their native language and dialect, and in data from labs using the head-turn preference procedure. Together, these findings replicate the IDS preference but suggest that its magnitude is modulated by development, native-language experience, and testing procedure
Advanced module for model parameter extraction using global optimization and sensitivity analysis for electron beam proximity effect correction
International audienc
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