A few studies have reported a significant dearth of exoplanets with Neptune mass and radius with orbital periods below 2-4 d. This cannot be explained by observational biases because many Neptunian planets with longer orbital periods have been detected. The existence of this desert is similar to the appearance of the so-called brown-dwarf desert that suggests different formation mechanisms of planets and stellar companions with short orbital periods. Similarly, the Neptunian desert might indicate different mechanisms of formation and evolution for hot Jupiters and short-period super-Earths. We here follow a previous study and examine the location and shape of the desert in both the period-mass and period-radius planes, using the currently available large samples of planets. The desert in the period-mass plane has a relatively sharp upper edge, with a planetary mass that is inversely proportional to the planetary orbital period, while the lower, somewhat blurred, boundary is located along masses that are apparently linearly proportional to the period. The desert in the period-radius plane of the transiting planets is less clear. It seems as if the radius along the upper boundary is inversely proportional to the period to the power of one-third, while the lower boundary shows a radius that is proportional to the period to the power of two-thirds. The combination of the two upper bounds of the desert, in the period-mass and period-radius planes, yields a planetary mass-radius relation of R p /R Jup (1.2 ± 0.3)(M p /M Jup ) 0.27 ± 0.11 for 0.1 M p /M Jup 1. The derived shape of the desert, which might extend up to periods of 5-10 d, could shed some light on the formation and evolution of close-in planets.

We present a new transit timing catalog of 2599 Kepler Objects of Interest (=KOIs), using the PDC-MAP long-cadence light curves that include the full seventeen quarters of the mission (ftp://wise-ftp.tau.ac.il/pub/tauttv/TTV/ver 112).The goal is to produce an easy-to-use catalog that can stimulate further analyses of interesting systems. For 779 KOIs with high enough SNRs, we derived the timing, duration and depth of 69,914 transits. For 1820 KOIs with lower SNR, we derived only the timing of 225,273 transits. After removal of outlier timings, we derived various statistics for each KOI that were used to indicate significant variations. Including systems found by previous works, we have detected 260 KOIs which showed significant TTVs with long-term variations (>100 day), and another fourteen KOIs with periodic modulations shorter than 100 day and small amplitudes. For five of those, the periodicity is probably due to the crossing of rotating stellar spots by the transiting planets. Subject headings: planetary systems-planets and satellites: detection-techniques: miscellaneous-technique: photometricwhere the p-value of the transit model exceeded 10 −4 , using an F -test relative to the no-transit assumption.• The transit depth was larger than 10%; those KOIs were ignored in order to disregard eclipsing binaries in our analysis, with the price of leaving out some "legitimate" transits such as large planets around M-stars.• The orbital period > 300 day; those KOIs were ignored due to too few transits for a significant TTV analysis.• KOIs identified as EBs, either listed in the Villanova eclipsing binary catalog, 2 as of 2014 July, or by McQuillan, Aigrain & Mazeh (2013).• KOIs identified by this study as false alarm, listed in Table 1, with some evidence for stellar binarity or pulsation.Following these cuts we were left with 2599 KOIs. We started by folding the PDC-MAP Kepler long-cadence 3 data, with the BJD T DB timings, using the ephemeris of NASA Exoplanet Archive, in order to obtain a good template for the transit light curve (see below for details). We used the best-fit transit model to measure the timing of each individual transit (=TT) and derived its O-C-the difference between the TT and the expected time, based on a linear ephemeris. As in Mazeh et al. (2013), for KOIs with high enough SNR (see below), the TT derivation was performed while allowing the duration and depth of each transit to vary.2The first step of our analysis was finding the continuum around each transit, ignoring the points in or near the transit itself, up to 0.7 transit durations around the expected timing of the transit center. Looking at a more extended region, up to two durations around the expected transit center, we fitted six different polynomials of degrees one to six to that region. The best fit was chosen as the one with the highest degree for which the p-value of all the F -tests with regard to polynomial fits of lower degrees was lower than 10 −3 . Finally, we added this polynomial back to the data during transit and divided ...

Following Ford et al. (2011, 2012b) and Steffen et al. (2012b) we derived the transit timing of 1960 Kepler KOIs using the pre-search data conditioning (PDC) light curves of the first twelve quarters of the Kepler data. For 721 KOIs with large enough SNRs, we obtained also the duration and depth of each transit.The results are presented as a catalog for the community to use. We derived a few statistics of our results that could be used to indicate significant variations.Including systems found by previous works, we have found 130 KOIs that showed highly significant TTVs, and 13 that had short-period TTV modulations with small amplitudes. We consider two effects that could cause apparent periodic TTV -the finite sampling of the observations and the interference with the stellar activity, stellar spots in particular. We briefly discuss some statistical aspects of our detected TTVs. We show that the TTV period is correlated with the orbital period of the planet and with the TTV amplitude.

We present the results of our 600 ks RGS observation as part of the multiwavelength campaign on Mrk 509. The very high quality of the spectrum allows us to investigate the ionized outflow with an unprecedented accuracy due to the long exposure and the use of the RGS multipointing mode. We detect multiple absorption lines from the interstellar medium and from the ionized absorber in Mrk 509. A number of emission components are also detected, including broad emission lines consistent with an origin in the broad line region, the narrow O vii forbidden emission line and also (narrow) radiative recombination continua. The ionized absorber consists of two velocity components (v = −13 ± 11 km s −1 and v = −319 ± 14 km s −1 ), which both are consistent with earlier results, including UV data. There is another tentative component outflowing at high velocity, −770 ± 109 km s −1 , which is only seen in a few highly ionized absorption lines. The outflow shows discrete ionization components, spanning four orders of magnitude in ionization parameter. Due to the excellent statistics of our spectrum, we demonstrate for the first time that the outflow in Mrk 509 in the important range of log ξ between 1−3 cannot be described by a smooth, continuous absorption measure distribution, but instead shows two strong, discrete peaks. At the highest and lowest ionization parameters we cannot differentiate smooth and discrete components.

We analyze the Chandra X-ray spectrum, obtained with the HETGS grating spectrometer, of IRAS 13349+2438, which has one of the richest absorption spectra of a quasar outflow. Absorption from almost all charge states of Fe is detected. This allows for a detailed reconstruction of the absorption measure distribution (AMD), which we define as the continuous distribution of column density as a function of ionization parameter. We find a double-peaked AMD for IRAS 13349+2438, with a total (ionized) column density of N H ¼ (1:2 AE 0:3) ; 10 22 cm À2, assuming solar iron abundance. For comparison, we perform a similar analysis on the well-studied HETGS spectrum of NGC 3783. Both sources feature a deep minimum in column density that is consistent with no absorption from gas at temperatures of 4:5 < log T < 5 (K). We interpret the minima as observational evidence for thermal instability in this temperature regime.