High Precision Photometry for K2 Campaign 1

The two reaction wheel K2 mission promises and has delivered new discoveries in the stellar and exoplanet fields. However, due to the loss of accurate pointing, it also brings new challenges for the data reduction processes. In this paper, we describe a new reduction pipeline for extracting high precision photometry from the K2 dataset, and present public light curves for the K2 Campaign 1 target pixel dataset. Key to our reduction is the derivation of global astrometric solutions from the target stamps, from which accurate centroids are passed on for high precision photometry extraction. We extract target light curves for sources from a combined UCAC4 and EPIC catalogue -- this includes not only primary targets of the K2 campaign 1, but also any other stars that happen to fall on the pixel stamps. We provide the raw light curves, and the products of various detrending processes aimed at removing different types of systematics. Our astrometric solutions achieve a median residual of ~ 0.13". For bright stars, our best 6.5 hour precision for raw light curves is ~20 parts per million (ppm). For our detrended light curves, the best 6.5 hour precisions achieved is ~15 ppm. We show that our detrended light curves have fewer systematic effects (or trends, or red-noise) than light curves produced by other groups from the same observations. Example light curves of transiting planets and a Cepheid variable candidate, are also presented. We make all light curves public, including the raw and de-trended photometry, at http://k2.hatsurveys.org.Comment: submitted to MNRA

High-precision photometry for K2 Campaign 1

The two reaction wheel K2 mission promises and has delivered new discoveries in the stellar and exoplanet fields. However, due to the loss of accurate pointing, it also brings new challenges for the data reduction processes. In this paper, we describe a new reduction pipeline for extracting high-precision photometry from the K2 data set, and present public light curves for the K2 Campaign 1 target pixel data set. Key to our reduction is the derivation of global astrometric solutions from the target stamps, from which accurate centroids are passed on for high-precision photometry extraction. We extract target light curves for sources from a combined UCAC4 and EPIC catalogue - this includes not only primary targets of the K2 campaign 1, but also any other stars that happen to fall on the pixel stamps. We provide the raw light curves, and the products of various detrending processes aimed at removing different types of systematics. Our astrometric solutions achieve a median residual of ∼0.127 arcsec. For bright stars, our best 6.5 h precision for raw light curves is ∼20 parts per million (ppm). For our detrended light curves, the best 6.5 h precision achieved is ∼15 ppm. We show that our detrended light curves have fewer systematic effects (or trends, or red-noise) than light curves produced by other groups from the same observations. Example light curves of transiting planets and a Cepheid variable candidate, are also presented. We make all light curves public, including the raw and detrended photometry, at http://k2.hatsurveys.org

Incidental Papillary Thyroid Microcarcinoma: is Completion Surgery Required?

Rezumat Microcarcinomul papilar tiroidian descoperit incidental: este necesarã reintervenåia pentru completarea tirodectomiei? Introducere: Indicaåiile chirurgiei de completare la pacienåii cu microcarcinom papilar tiroidian (PMC) descoperit incidental pe piesa de tiroidectomie, dupã rezecåii pentru afecåiuni benigne, ramâne un subiect controversat. Metoda: Într-un studiu retrospectiv, transversal, de cohortã a 187 PMC, descoperite incidental în cursul examenului histopatologic al glandei tiroide, la 2168 pacienåi operaåi pentru afecåiuni tiroidiene benigne, am analizat influenåa tratamentului chirurgical iniåial aei al celui de completare asupra caracteristicilor anatomo-patologice asociate cu recidiva localã aei mortalitatea prin cancer tiroidian. Rezultate: La pacienåii cu tiroidectomie totalã sau aproape totalã la prima operatie, limfadenectomia ganglionilor suspecåi de malignitate la ultrasonografia postoperatorie a fost urmatã de o creaetere statistic semnificativã (p<0.01) a cazurilor cu metastaze ganglionare la examenul anatomopatologic. Chirurgia de completare efectuatã la 38 din cei 42 pacienåi cu lobectomie sau tiroidectomie subtotalã la prima intervenåie chirurgicalã nu a fost urmatã de o creaetere semnificativã a numãrului sau mãrimii tumorilor, multifocalitãåii, bilateralitãåii, invaziei extratiroidiene sau metastazelor ganglionare. În privinåa complicaåiilor postoperatorii, nu au fost diferenåe statistic semnificative între cele douã grupuri de pacienåi. Concluzii: La pacienåii cu lobectomie sau tiroidectomie subtotalã aei PMC descoperite incidental pe piesa de rezecåie, având dimensiuni 1-5 mm aei fãrã invazie extratiroidianã, chirurgia de completare nu a fost urmatã de o creaetere semnificativã a caracteristicilor patologice asociate cu morbiditatea aei mortalitatea prin cancer tiroidian. Cuvinte cheie: microcarcinom papilar tiroidian, tiroidectomie de completare, limfadenectomie Abstract Background: The indications for completion surgery in patients with thyroid papillary microcarcinoma (PMC), incidentally found in thyroids removed for benign conditions, remains a subject of debate. Methods: In a retrospective, transversal, cohort study of 187 incidental PMCs, found during histological examination of the thyroid gland in 2168 patients operated for benign thyroid conditions, we evaluated the influence of initial and completion surgery on pathological features associated to local recurrence and cancer-related mortality. Results: In the patients with almost total or total thyroidectomy at the first operation, lymphadenectomy of lymph nodes with features suggestive of malignancy on postoperative ultrasound resulted in a statistically significant (p<0.01) increase of node positive patients in pathological examination. thyroidectomy doesn't result in a significant increase of tumor size, number, multifocality, bilaterality, invasion or nodal metastases. There were no significant differences in postoperative complications between the two groups. Conclusions: In patients with less than total thyroidectomy and incidentally found PMC in resection specimens, 1-5 mm in greatest dimension and without extrathyroidal extension, completion surgery was not followed by a significant increase of pathological features associated to cancer related morbidity and mortality