Vogt, Majbritt

[["dc.bibliographiccitation.firstpage","L89"],["dc.bibliographiccitation.issue","1"],["dc.bibliographiccitation.journal","Monthly Notices of the Royal Astronomical Society"],["dc.bibliographiccitation.lastpage","L93"],["dc.bibliographiccitation.volume","443"],["dc.contributor.author","Anglada-Escude, Guillem"],["dc.contributor.author","Arriagada, Pamela"],["dc.contributor.author","Tuomi, Mikko"],["dc.contributor.author","Zechmeister, Mathias"],["dc.contributor.author","Jenkins, S."],["dc.contributor.author","Ofir, Aviv"],["dc.contributor.author","Dreizler, Stefan"],["dc.contributor.author","Gerlach, Enrico"],["dc.contributor.author","Marvin, Christopher J."],["dc.contributor.author","Reiners, Ansgar"],["dc.contributor.author","Jeffers, Sandra V."],["dc.contributor.author","Butler, R. Paul"],["dc.contributor.author","Vogt, S. S."],["dc.contributor.author","Amado, Pedro J."],["dc.contributor.author","Rodriguez-Lopez, Cristina"],["dc.contributor.author","Berdinas, Zaira M."],["dc.contributor.author","Morin, Julien"],["dc.contributor.author","Crane, Jeffrey D."],["dc.contributor.author","Shectman, Stephen A."],["dc.contributor.author","Thompson, Ian B."],["dc.contributor.author","Diaz, M."],["dc.contributor.author","Rivera, Eugenio J."],["dc.contributor.author","Sarmiento, Luis F."],["dc.contributor.author","Jones, Hugh R. A."],["dc.date.accessioned","2018-11-07T09:35:24Z"],["dc.date.available","2018-11-07T09:35:24Z"],["dc.date.issued","2014"],["dc.description.abstract","Exoplanets of a few Earth masses can be now detected around nearby low-mass stars using Doppler spectroscopy. In this Letter, we investigate the radial velocity variations of Kapteyn's star, which is both a sub-dwarf M-star and the nearest halo object to the Sun. The observations comprise archival and new HARPS (High Accuracy Radial velocity Planet Searcher), High Resolution Echelle Spectrometer (HIRES) and Planet Finder Spectrograph (PFS) Doppler measurements. Two Doppler signals are detected at periods of 48 and 120 d using likelihood periodograms and a Bayesian analysis of the data. Using the same techniques, the activity indices and archival All Sky Automated Survey (ASAS-3) photometry show evidence for low-level activity periodicities of the order of several hundred days. However, there are no significant correlations with the radial velocity variations on the same time-scales. The inclusion of planetary Keplerian signals in the model results in levels of correlated and excess white noise that are remarkably low compared to younger G, K and M dwarfs. We conclude that Kapteyn's star is most probably orbited by two super-Earth mass planets, one of which is orbiting in its circumstellar habitable zone, becoming the oldest potentially habitable planet known to date. The presence and long-term survival of a planetary system seem a remarkable feat given the peculiar origin and kinematic history of Kapteyn's star. The detection of super-Earth mass planets around halo stars provides important insights into planet-formation processes in the early days of the Milky Way."],["dc.identifier.doi","10.1093/mnrasl/slu076"],["dc.identifier.isi","000357291900019"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/32376"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Oxford Univ Press"],["dc.relation.issn","1365-2966"],["dc.relation.issn","0035-8711"],["dc.title","Two planets around Kapteyn's star: a cold and a temperate super-Earth orbiting the nearest halo red dwarf"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","74"],["dc.bibliographiccitation.firstpage","74"],["dc.bibliographiccitation.issue","2"],["dc.bibliographiccitation.journal","The Astrophysical Journal"],["dc.bibliographiccitation.volume","830"],["dc.contributor.author","Anglada-Escude, Guillem"],["dc.contributor.author","Tuomi, Mikko"],["dc.contributor.author","Arriagada, Pamela"],["dc.contributor.author","Zechmeister, Mathias"],["dc.contributor.author","Jenkins, J. S."],["dc.contributor.author","Ofir, Aviv"],["dc.contributor.author","Dreizler, Stefan"],["dc.contributor.author","Gerlach, Enrico"],["dc.contributor.author","Marvin, Christopher J."],["dc.contributor.author","Reiners, Ansgar"],["dc.contributor.author","Jeffers, Sandra V."],["dc.contributor.author","Butler, R. Paul"],["dc.contributor.author","Vogt, S. S."],["dc.contributor.author","Amado, Pedro J."],["dc.contributor.author","Rodriguez-Lopez, Cristina"],["dc.contributor.author","Berdinas, Zaira M."],["dc.contributor.author","Morin, Julien"],["dc.contributor.author","Crane, Jeffrey D."],["dc.contributor.author","Shectman, Stephen A."],["dc.contributor.author","Diaz, M. R."],["dc.contributor.author","Sarmiento, Luis F."],["dc.contributor.author","Jones, Hugh R. A."],["dc.date.accessioned","2018-11-07T10:06:54Z"],["dc.date.available","2018-11-07T10:06:54Z"],["dc.date.issued","2016"],["dc.description.abstract","Stellar activity may induce Doppler variability at the level of a few m s(-1) which can then be confused by the Doppler signal of an exoplanet orbiting the star. To first order, linear correlations between radial velocity measurements and activity indices have been proposed to account for any such correlation. The likely presence of two super-Earths orbiting Kapteyn's star was reported in Anglada-Escude et al., but this claim was recently challenged by Robertson et al., who argued for evidence of a rotation period (143 days) at three times the orbital period of one of the proposed planets (Kapteyn's b, P = 48.6 days) and the existence of strong linear correlations between its Doppler signal and activity data. By re-analyzing the data using global statistics and model comparison, we show that such a claim is incorrect given that (1) the choice of a rotation period at 143 days is unjustified, and (2) the presence of linear correlations is not supported by the data. We conclude that the radial velocity signals of Kapteyn's star remain more simply explained by the presence of two super-Earth candidates orbiting it. We note that analysis of time series of activity indices must be executed with the same care as Doppler time series. We also advocate for the use of global optimization procedures and objective arguments, instead of claims based on residual analyses which are prone to biases and incorrect interpretations."],["dc.identifier.doi","10.3847/0004-637X/830/2/74"],["dc.identifier.eissn","1538-4357"],["dc.identifier.isi","000396001400001"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/39187"],["dc.notes.intern","DOI Import GROB-354"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Iop Publishing Ltd"],["dc.relation.issn","1538-4357"],["dc.relation.issn","0004-637X"],["dc.title","No Evidence for Activity Correlations in the Radial Velocities of Kapteyn's Star"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","184"],["dc.bibliographiccitation.issue","1-2"],["dc.bibliographiccitation.journal","Astronomische Nachrichten"],["dc.bibliographiccitation.lastpage","187"],["dc.bibliographiccitation.volume","334"],["dc.contributor.author","Anglada-Escude, Guillem"],["dc.contributor.author","Butler, R. Paul"],["dc.contributor.author","Reiners, Ansgar"],["dc.contributor.author","Jones, Hugh R. A."],["dc.contributor.author","Tuomi, Mikko"],["dc.contributor.author","Jenkins, J. S."],["dc.contributor.author","Barnes, J. R."],["dc.contributor.author","Vogt, S. S."],["dc.contributor.author","Zechmeister, Mathias"],["dc.date.accessioned","2018-11-07T09:28:18Z"],["dc.date.available","2018-11-07T09:28:18Z"],["dc.date.issued","2013"],["dc.description.abstract","The current precision radial velocities techniques to detect low mass planets in M dwarf are quickly reviewed. This includes high resolution spectroscopic observations made both in the optical and in the near infrared. We discuss that, given the current instrumental performance, optical RVs are still far ahead over other approaches. However, this situation might change soon with the advent of new spectrographs with red/nIR capabilities. We review a newly developed method to obtain precision RV measurements on stabilized spectrographs and how it is implemented to archival HARPS observations. In addition to get much closer to the photon noise, this approach allows us to identify and filter out wavelength dependent noise sources achieving unprecedented accuracy on G, K and specially M dwarfs. We show how including red/infrared observations is of paramount importance to efficiently and unambiguously detect very low mass planets around cool spectral types. As examples, we show new measurements on Barnard's star indicating that the star is stable down to 0.9 cm s(-1) over a time-span of 4 years and how RV signals correlated with activity indices disappear when using the reddest half of the HARPS wavelength range. To conclude, we present new results, detections and describe the implications in terms of planet/multi-planet abundances around cool stars. (C) 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim"],["dc.identifier.doi","10.1002/asna.201211775"],["dc.identifier.isi","000325859900043"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/30739"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Wiley-v C H Verlag Gmbh"],["dc.relation.issn","1521-3994"],["dc.relation.issn","0004-6337"],["dc.title","Surfing the photon noise: New techniques to find low-mass planets around M dwarfs"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","A48"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.volume","549"],["dc.contributor.author","Tuomi, Mikko"],["dc.contributor.author","Anglada-Escude, Guillem"],["dc.contributor.author","Gerlach, Enrico"],["dc.contributor.author","Jones, Hugh R. A."],["dc.contributor.author","Reiners, Ansgar"],["dc.contributor.author","Rivera, Eugenio J."],["dc.contributor.author","Vogt, S. S."],["dc.contributor.author","Butler, R. Paul"],["dc.date.accessioned","2018-11-07T09:30:35Z"],["dc.date.available","2018-11-07T09:30:35Z"],["dc.date.issued","2013"],["dc.description.abstract","Context. The K2.5 dwarf HD 40307 has been reported to host three super-Earths. The system lacks massive planets and is therefore a potential candidate for having additional low-mass planetary companions. Aims. We re-derive Doppler measurements from public HARPS spectra of HD 40307 to confirm the significance of the reported signals using independent data analysis methods. We also investigate these measurements for additional low-amplitude signals. Methods. We used Bayesian analysis of our radial velocities to estimate the probability densities of different model parameters. We also estimated the relative probabilities of models with differing numbers of Keplerian signals and verified their significance using periodogram analyses. We investigated the relation of the detected signals with the chromospheric emission of the star. As previously reported for other objects, we found that radial velocity signals correlated with the S-index are strongly wavelength dependent. Results. We identify two additional clear signals with periods of 34 and 51 days, both corresponding to planet candidates with minimum masses a few times that of the Earth. An additional sixth candidate is initially found at a period of 320 days. However, this signal correlates strongly with the chromospheric emission from the star and is also strongly wavelength dependent. When analysing the red half of the spectra only, the five putative planetary signals are recovered together with a very significant periodicity at about 200 days. This signal has a similar amplitude as the other new signals reported in the current work and corresponds to a planet candidate with M sin i similar to 7 M-circle plus (HD 40307 g). Conclusions. We show that Doppler measurements can be filtered for activity-induced signals if enough photons and a sufficient wavelength interval are available. If the signal corresponding to HD 40307 g is a genuine Doppler signal of planetary origin, this candidate planet might be capable of supporting liquid water on its surface according to the current definition of the liquid water habitable zone around a star and is not likely to suffer from tidal locking. Also, at an angular separation of similar to 46 mas, HD 40307 g would be a primary target for a future space-based direct-imaging mission."],["dc.identifier.doi","10.1051/0004-6361/201220268"],["dc.identifier.fs","602594"],["dc.identifier.isi","000313745000048"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/9961"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/31339"],["dc.notes.intern","Merged from goescholar"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Edp Sciences S A"],["dc.relation","info:eu-repo/grantAgreement/EC/FP7/213646"],["dc.relation.issn","1432-0746"],["dc.relation.issn","0004-6361"],["dc.relation.orgunit","Fakultät für Physik"],["dc.title","Habitable-zone super-Earth candidate in a six-planet system around the K2.5V star HD 40307"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dc.type.version","published_version"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]