WTS-1 b

The end of the twentieth century saw a revolution in our knowledge of planetary systems. The detection of the first extrasolar planet in 1992 marked the beginning of a modern era and changed our idea of planets and planetary systems. The discoveries continue rapidly and reveal an extraordinary diversity of planetary systems and physical properties of the exoplanets, raising new questions in the field of planetary science. So far, more than 800 extrasolar planets have been detected, spanning a wide range of masses from a few Earth masses to a few tens of Jupiter masses. This Ph.D. Thesis is devoted to the confirmation via radial velocity follow-up of the candidate planets detected by the WFCAM Transit Survey (WTS), which is an on-going photometric monitoring campaign using the Wide Field Camera on the United Kingdom Infrared Telescope at Mauna Kea (Hawaii, USA). The WTS and the present work were supported by the RoPACS (Rocky Planets Around Cool Stars) group, a Marie Curie Initial Training Network funded by the Seventh Framework Programme of the European Commission. Since the WTS was primarily designed to find planets transiting M-dwarf stars, the observations are obtained in the J-band (1.25 micron). This wavelength is near to the peak of the spectral energy distribution of a typical M-dwarf. Simulations show that operating in the J-band reduces the effects of stellar variability, which became important at optical wavelengths in cool stars. The J-band light curves that show a periodic drop and pass all the selection criteria, progress to the candidate confirmation phase. After a transit depth consistency check performed with i'-band observations, intermediate resolution spectra enable to rule out false-positive eclipsing binaries scenarios. Finally, high-resolution spectroscopic follow-up is performed to confirm, by the radial velocity method, the planetary nature of the stellar companion detected by the WTS. The spectra employed in this phase were observed with the High Resolution Spectrograph (HRS) housed in the basement of the 9.2-m Hobby-Eberly Telescope (HET) in Texas, USA. The pipeline for the reduction and analysis of the HET spectra has been created. Debug, optimization and test of the whole procedure were performed observing several target stars with different apparent magnitude and spectral type. These observations allowed to estimate the precision on the velocity measures for different targets. Errorbars of 10 m/s are expected for solar type stars of magnitude up to mV=10 and SNR of the observed spectra >150. Spectra with a SNR of 30 can be measured for faint (mV=14) M stars, leading to a final radial velocity uncertainty of about 60 m/s. Furthermore, a technical problem occurring under given instrumental configurations could be identified and fixed, removing a possible source of systematic from any later observation. Finally, the zero-point offset with respect to the HARPS data was computed allowing the comparison of the HET measures with those related to any other instruments involved in radial velocity follow-up. The radial velocities computed from the HET high-resolution spectra allowed to confirm the detection of the first two extrasolar planet performed by the WTS. WTS1 b is a 4 MJ planet orbiting in 3.35 days a late F-star with possibly slightly sub-solar metallicity. With a radius of 1.49 RJ, it is the third largest planet of the known extrasolar planets in the mass range 3-5 MJ. Its unusual large radius can not be explained within the standard evolution models, even considering the strong radiation that the planet receives from the parent star. Ohmic heating could be a possible mechanism able to bring energy in the deeper layers of WTS1 b and hence explaining its radius anomaly. WTS2 b is instead a 1 MJ planet orbiting an early K-star in about 1 day only. The measure of its secondary eclipses in the Ks-band will allow to study a highly irradiated planet around a cool star, cooler than many of the currently known very hot-Jupiters host star. This will provide an insight to the effect of the stellar spectrum on the composition and structure of hot-Jupiter atmospheres. Beyond the RoPACS program, the pipeline has been employed in the radial velocity follow-up of the white dwarf NLTT 5306, confirming the presence of a brown dwarf companion of 56 MJ orbiting its host star in 102 minutes, the shortest period ever observed in such systems. The discoveries of WTS1 b and WTS2 b demonstrate the capability of WTS to find planets, even if it operates in a back-up mode during dead time on a queue-schedule telescope and despite of the somewhat randomised observing strategy. Moreover, the two new discovered planets are hot-Jupiters orbiting an F-star and a K-star. Both are hotter than an M-dwarf, the main target sample of the WTS. As described in Kovacs et al. (2012, MNRAS submitted), no planets around M-dwarf stars monitored by the WTS (mV<17) with period shorter than 10 days have been found. According to these results, the upper limit of the very hot-Jupiter planetary occurrence around M-stars can be estimated. The resulting value of 0.017 is a stricter constraint than the one derived for the Kepler M-dwarfs sample (0.04).Ende des zwanzigsten Jahrhunderts erlebte unser Verständnis von Planetensystemen eine Revolution. Die Entdeckung des ersten extrasolaren Planeten im Jahr 1992 markierte den Beginn einer ära und veränderte unser Bild von Planeten und Planetensystemen grundlegend. In den darauf folgende Jahren wurde viele weitere Detektionen erzielt, die eine ausserordentliche Vielfalt an Planetensystemen mit unterschiedlichen physikalischen Eigenschaften aufdeckten welche fortan neue Fragen auf dem Gebiet der lanetologie aufwerfen. Bis heute wurden mehr als 800 extrasolare Planeten nachgewiesen die einen weiten Bereich an Massen abdecken, der von wenigen Erdmassen bis zu ein paar Dutzend Jupitermassen reicht. Die vorliegende Ph.D. Thesis behandelt die Bestätigung von Planetenkandidaten mit Hilfe von Radialgeschwindigkeitsmessungen. Gefunden wurden die Kandidaten im Rahmen des WFCAM Transit Surveys (WTS) - einer photometrische Suchkampagne mit der Wide Field Camera am United Kingdom Infrared Telescope auf dem Mauna Kea (Hawaii, USA). Der WTS und diese Arbeit wurden im Rahmen des siebten Programms der Europäischen Kommission von der RoPACS (Rocky Planets Around Cool Stars) Gruppe, einem Marie Curie Initial Training Network, unterstützt. Da der WTS in erster Linie konzipiert wurde, um Planeten um M-Zwerge zu finden, wurden die Beobachtungen im J- Band bei ca. 1.25 micron aufgenommen. Diese Wellenlänger ist in der Nähe des Maximum der spektralen Energiverteilung eines M-Zwerges. Simulationen zeigen, dass Beobachtungen im J-Band die Effekte von stellarer Variabilität verringern, welche stärker im optischen Spektrum von kühlen Sternen auftreten. Die J-Band Lichtkurven, die einen periodischen Helligkeitsabfall zeigen und die Selektionskriterien erfüllen, wurden in der folgenden Bestätigungs-Phase weiter untersucht. Nach einem Konsistenz-Check der Transittiefe mit Hilfe von photometrischen Nachbeobachtungen im i'-Band wurden Fehldetektionen in Form von Bedeckungsveränderlichen mit Spektren mittlerer Auflösung ausgeschlossen. Danach wurden hochauflösende Spektren aufgenommen, um die WTS-Kandidaten mit der Radialgeschwindigkeits-Methode als Planeten zu bestätigen. Diese hochauflösenden Spektren wurden mit dem High Resolution Spectrograph am 9.2-m Hobby-Eberly Telescope (HET) in Texas, USA, aufgenommen. Die Daten-Analyse Pipeline für die Auswertung der HET Spektren wurde im Rahmen dieser Arbeit entwickelt. Fehlersuche, Optimierungen und Tests der gesamten Prozedur wurden mit Hilfe von Beobachtungen von mehreren Sternen mit unterschiedlicher scheinbaren Helligkeit und unterschiedlichem Spektraltypen durchgeführt. Dies erlaubte es, die Präzision der Radialgeschwindigkeitsmessungen für unterschiedliche Sterne zu bestimmen. Demnach sind Fehlerbalken von 10 m/s für sonnenähnliche Sterne mit Helligkeiten bis mV=10 und SNR der beobachteten Spektren von >150 zu erwarten. Spektren mit einem SNR von 30 können für schwache M-Sterne (mV=14) gemessen werden, für welche eine Radialgeschwindigkeitsgenauigkeit von 60 m/s erreicht wird. Des weiteren wurde ein technisches Problem identifiziert und behoben, welches für bestimmte Konfigurationen des Spektrographen auftritt. Damit wurde eine systematische Fehlerquelle für alle folgenden Beobachtungen eliminiert. Schlussendlich wurde ein Nullpukts-Offset für Daten des HARPS-Spektrographen bestimmt, welcher es erlaubt, die HET Daten mit Messungen von anderen Spektrographen, die im Prozess der Nachbeobachtungen beteiligt waren, zu kombinieren. Die Radialgeschwindigkeiten, welche aus den hochau flösenden HET Spektren bestimmt wurden, haben zur Bestätigung der ersten beiden Detektionen von extrasolaren Planeten im WTS geführt. WTS1 b ist ein 4 MJ Planet welcher in 3.35 Tagen einen späten F-Stern mit möglicherweise geringfügig subsolarer Metallizität umkreist. Mit einem Radius von 1.49 RJ ist er der drittgrösste von allen bisher gefundenen extrasolaren Planet im Massenbereich von 3-5 MJ. Der ungewöhlich grosse Radius kann nicht durch die etablierten Standardentwicklungstheorien erklärt werden, selbst wenn man die starke Einstrahlung berücksichtigt, die der Planet von seinem Mutterstern empfängt. Der Mechanismus des Ohm'schen Heizens könnte Energie in die tieferen Schichten von WTS1 b bringen und damit den anomalen Radius erklären. WTS2 b ist ein 1 MJ Planet, welcher einen frühen K-Sterne in etwa 1 Tag umrundet. Messungen der sekundären Bedeckung im Ks-Band werden es erlauben, die thermische Strahlung dieses besonderen Planeten zu messen, der Einfluss der starken Einstrahlung seines nahen Muttersterns steht, welcher aber deutlich kühler ist, als die Muttersterne anderer bekannter Hot Jupiter. Dies wird darüber Aufschluss geben, welchen Einfluss das stellare Spektrum auf die Zusammensetzung und den Aufbau von Hot Jupiter Atmosphären hat. Zusäzlich zum RoPACS Programm wurde die in dieser Arbeit entwickelte Daten-Analyse Pipeline für die Auswertung von Radialgeschwindigkeits Beobachtungen des Weissen Zwerg Sterns NLTT 5306 verwendet, welche die Existenz eines Braunen Zwerges mit 56 MJ bestätigte, der den Weissen Zwerg in nur 102 Minuten umkreist. Dies ist die kürzeste Periode, die bislang in solchen Systemen beobachtet wurde. Die Entdeckungen von WTS1 b und WTS2 b zeigen, dass der WTS Planeten finden kann, und das obwohl er als back-up Programm für schlechte Beobachtungsbedingen betrieben wird was zu einer mehr oder minder zufälligen Abfolge der Beobachtungen führt. Die beiden detektierten Planeten sind sogenannte Hot-Jupiter die einen F- bzw. einen K-Stern umrunden. Diese Sterne sind heisser als M-Zwerge, welche das Hauptziel des WTS sind. Wie in Kovacs et al. (2012, MNRAS submitted) beschrieben, wurden bislang im WTS keine Planeten um M-Zwerge mit Helligkeiten von mV <17 und Perioden kürzer als 10 Tagen gefunden. Aufgrund dieser Ergebnisse, konnte eine Obergrenze für die Planetenhäugkeit von Jupiterähnlichen Planeten um M-Zwerge bestimmt werden. Diese Obergrenze liegt bei 0.017 und ist damit präziser als die zuvor auf dem Kepler M-Zwerg Datensatz bestimmte Grenze von 0.04

Zebrafish and medaka offer insights into the neurobehavioral correlates of vertebrate magnetoreception

An impediment to a mechanistic understanding of how some species sense the geomagnetic field ("magnetoreception") is the lack of vertebrate genetic models that exhibit well-characterized magnetoreceptive behavior and are amenable to whole-brain analysis. We investigated the genetic model organisms zebrafish and medaka, whose young stages are transparent and optically accessible. In an unfamiliar environment, adult fish orient according to the directional change of a magnetic field even in darkness. To enable experiments also in juveniles, we applied slowly oscillating magnetic fields, aimed at generating conflicting sensory inputs during exploratory behavior. Medaka (but not zebrafish) increase their locomotor activity in this assay. Complementary brain activity mapping reveals neuronal activation in the lateral hindbrain during magnetic stimulation. These comparative data support magnetoreception in teleosts, provide evidence for a light-independent mechanism, and demonstrate the usefulness of zebrafish and medaka as genetic vertebrate models for studying the biophysical and neuronal mechanisms underlying magnetoreception

Discovery and characterisation of detached M-dwarf eclipsing binaries in the WFCAM Transit Survey

We report the discovery of 16 detached M-dwarf eclipsing binaries with J<16 mag and provide a detailed characterisation of three of them, using high-precision infrared light curves from the WFCAM Transit Survey (WTS). Such systems provide the most accurate and model-independent method for measuring the fundamental parameters of these poorly understood yet numerous stars, which currently lack sufficient observations to precisely calibrate stellar evolution models. We fully solve for the masses and radii of three of the systems, finding orbital periods in the range 1.5<P<4.9 days, with masses spanning 0.35-0.50 Msun and radii between 0.38-0.50 Rsun, with uncertainties of ~3.5-6.4% in mass and ~2.7-5.5% in radius. Close-companions in short-period binaries are expected to be tidally-locked into fast rotational velocities, resulting in high levels of magnetic activity. This is predicted to inflate their radii by inhibiting convective flow and increasing star spot coverage. The radii of the WTS systems are inflated above model predictions by ~3-12%, in agreement with the observed trend, despite an expected lower systematic contribution from star spots signals at infrared wavelengths. We searched for correlation between the orbital period and radius inflation by combining our results with all existing M-dwarf radius measurements of comparable precision, but we found no statistically significant evidence for a decrease in radius inflation for longer period, less active systems. Radius inflation continues to exists in non-synchronised systems indicating that the problem remains even for very low activity M-dwarfs. Resolving this issue is vital not only for understanding the most populous stars in the Universe, but also for characterising their planetary companions, which hold the best prospects for finding Earth-like planets in the traditional habitable zone.Comment: 30 pages, 14 figures, 16 tables, Accepted for publication in MNRA

C-reactive protein and carotid intima-media thickness in children with sleep disordered breathing.

Study Objectives: Obesity is a risk factor for sleep disordered breathing (SDB) in children. Plasma levels of high-sensitivity C-reactive protein (Hs-CRP) are predictive of cardiovascular morbidity in adults, and CRP levels are associated with over-weight. Increased carotid intima-media thickness (IMT) is associated with several cardiovascular risk factors. We evaluated the effect of SDB on CRP levels and IMT in lean and obese children not selected for snoring. Methods: 101 children (age 5-15 years) attending a weight clinic or scheduled for routine visit. IMT was measured with quantitative B-mode ultrasound scans. The apnea-hypopnea index (AHI) was measured overnight: AHI < 1 defined controls, AHI ≥ 1 to < 5 = mild SDB, and AHI ≥ 5 = obstructive sleep apnea (OSA). Results: AHI was significantly associated with Hs-CRP concentration (r = 0.32, p = 0.002) in all 101 children irrespective of age and sex. Body mass index (BMI) was higher in OSA children than controls (25.5 ± 7.0 vs 22.1 ± 6.9, p = 0.05). Obese children had 3.3 times more probability of having OSA (HR 3.3, 95% CI 1.2-9.3, p = 0.02) than lean children. Hs-CRP values were significantly higher in children with OSA than in children without (p = 0.011), but not when BMI z-score was added as covariate. IMT was not associated with AHI or SDB. Conclusions: The results of this study suggest an association between OSA and Hs-CRP concentrations (mainly mediated by overweight and obesity), but not between OSA and subclinical atherosclerosis. There is scope for prevention in childhood before OSA syndrome causes the irreversible damage to arteries observed in adult patients

Statins Stimulate New Myocyte Formation After Myocardial Infarction by Activating Growth and Differentiation of the Endogenous Cardiac Stem Cells

The 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) exert pleiotropic effects on cardiac cell biology which are not yet fully understood. Here we tested whether statin treatment affects resident endogenous cardiac stem/progenitor cell (CSC) activation in vitro and in vivo after myocardial infarction (MI). Statins (Rosuvastatin, Simvastatin and Pravastatin) significantly increased CSC expansion in vitro as measured by both BrdU incorporation and cell growth curve. Additionally, statins increased CSC clonal expansion and cardiosphere formation. The effects of statins on CSC growth and differentiation depended on Akt phosphorylation. Twenty-eight days after myocardial infarction by permanent coronary ligation in rats, the number of endogenous CSCs in the infarct border zone was significantly increased by Rosuvastatin-treatment as compared to untreated controls. Additionally, commitment of the activated CSCs into the myogenic lineage (c-kitpos/Gata4pos CSCs) was increased by Rosuvastatin administration. Accordingly, Rosuvastatin fostered new cardiomyocyte formation after MI. Finally, Rosuvastatin treatment reversed the cardiomyogenic defects of CSCs in c-kit haploinsufficient mice, increasing new cardiomyocyte formation by endogenous CSCs in these mice after myocardial infarction. In summary, statins, by sustaining Akt activation, foster CSC growth and differentiation in vitro and in vivo. The activation and differentiation of the endogenous CSC pool and consequent new myocyte formation by statins improve myocardial remodeling after coronary occlusion in rodents. Similar effects might contribute to the beneficial effects of statins on human cardiovascular diseases

Diabetes-Induced Cellular Senescence and Senescence-Associated Secretory Phenotype Impair Cardiac Regeneration and Function Independently of Age

Diabetes mellitus (DM) affects the biology of multipotent cardiac stem/progenitor cells (CSCs) and adult myocardial regeneration. We assessed the hypothesis that senescence and senescence-associated secretory phenotype (SASP) are main mechanisms of cardiac degenerative defect in DM. Accordingly, we tested whether ablation of senescent CSCs would rescue the cardiac regenerative/reparative defect imposed by DM. We obtained cardiac tissue from nonaged (50- to 64-year-old) patients with type 2 diabetes mellitus (T2DM) and without DM (NDM) and postinfarct cardiomyopathy undergoing cardiac surgery. A higher reactive oxygen species production in T2DM was associated with an increased number of senescent/dysfunctional T2DM-human CSCs (hCSCs) with reduced proliferation, clonogenesis/spherogenesis, and myogenic differentiation versus NDM-hCSCs in vitro. T2DM-hCSCs showed a defined pathologic SASP. A combination of two senolytics, dasatinib (D) and quercetin (Q), cleared senescent T2DM-hCSCs in vitro, restoring their expansion and myogenic differentiation capacities. In a T2DM model in young mice, diabetic status per se (independently of ischemia and age) caused CSC senescence coupled with myocardial pathologic remodeling and cardiac dysfunction. D + Q treatment efficiently eliminated senescent cells, rescuing CSC function, which resulted in functional myocardial repair/regeneration, improving cardiac function in murine DM. In conclusion, DM hampers CSC biology, inhibiting CSCs' regenerative potential through the induction of cellular senescence and SASP independently from aging. Senolytics clear senescence, abrogating the SASP and restoring a fully proliferative/differentiation-competent hCSC pool in T2DM with normalization of cardiac function

Pattern of recurrence and overall survival in esophagogastric cancer after perioperative FLOT and clinical outcomes in MSI-H population: the PROSECCO Study

Background: FLOT regimen is the standard perioperative treatment in Western countries for patients with locally advanced gastric (GC) or gastroesophageal junction cancer (GEJC). High microsatellite instability (MSI-H) and Mismatch Repair deficient (dMMR) demonstrated a favorable prognostic role and a concomitant negative predictive impact on the benefit of perioperative 5-fluorouracil-based doublets; however, its role in pts receiving FLOT chemotherapy is still unclear. Methods: This is a retrospective, multicenter observational study of 265 pts with GC/GEJC treated with perioperative FLOT regimen in 11 Italian oncology centers between January 2017 to December 2021 and analyzed for microsatellite status. Results: The MSI-H phenotype was found in 27 (10.2%) of 265 analyzed tumors. Compared to microsatellite stable (MSS) and Mismatch Repair proficient (pMMR) cases, MSI-H/dMMR were more frequently female (48.1% vs. 27.3%, p = 0.0424), elderly pts (age &gt; 70&nbsp;years, 44.4% vs. 13.4%, p = 0.0003), Laurens's intestinal type (62.5% vs. 36.1%, p = 0.02) and pts with a primary location tumor in the antrum (37 vs. 14.3%, p = 0.0004). A statistically significant difference in the rate of pathologically negative lymph node emerged (63% vs 30.7%, p = 0.0018). Compared to the MSS/pMMR tumor population, the MSI-H/dMMR subgroup had a better DFS (median not reached [NR] vs. 19.5 [15.59-23.59] mos, p = 0.031) and OS (median NR vs. 34.84 [26.68-47.60] mos, p = 0.0316). Conclusions: These real-world data confirm that FLOT treatment is effective in daily clinical practice for locally advanced GC/GEJC, also in the MSI-H/dMMR subgroup. It also showed a higher rate of nodal status downstaging and a better outcome of MSI-H/dMMR pts in comparison to MSS/pMMR