Aims. Most hot Jupiters are expected to spiral in toward their host stars because the angular momentum of the orbital motion is transferred to the stellar spin. Their orbits can also precess as a ...result of planet-star interactions. Calculations show that both effects might be detected for the very-hot exoplanet WASP-12 b using the method of precise transit-timing over a time span of about 10 yr. Methods. We acquired new precise light curves for 29 transits of WASP-12 b, spannning four observing seasons from November 2012 to February 2016. New mid-transit times, together with those from the literature, were used to refine the transit ephemeris and analyze the timing residuals. Results. We find that the transit times of WASP-12 b do not follow a linear ephemeris with a 5σ confidence level. They may be approximated with a quadratic ephemeris that gives a change rate in the orbital period of (−2.56 ± 0.40) × 10-2 s yr-1. The tidal quality parameter of the host star was found to be equal to 2.5 × 105, which is similar to theoretical predictions for Sun-like stars. We also considered a model in which the observed timing residuals are interpreted as a result of the apsidal precession. We find, however, that this model is statistically less probable than the orbital decay.
We present the second installment of GOSSS, a massive spectroscopic survey of Galactic O stars, based on new homogeneous, high signal-to-noise ratio, R ~ 2500 digital observations from both ...hemispheres selected from the Galactic O-Star Catalog (GOSC). In this paper we include bright stars and other objects drawn mostly from the first version of GOSC, all of them south of delta = -20degrees, for a total number of 258 O stars. We also revise the northern sample of Paper I to provide the full list of spectroscopically classified Galactic O stars complete to B = 8, bringing the total number of published GOSSS stars to 448. Extensive sequences of exceptional objects are given, including the early Of/WN, O Iafpe, Ofc, ON/OC, Onfp, Of?p, and Oe types, as well as double/triple-lined spectroscopic binaries. The new spectral subtype O9.2 is also discussed. The magnitude and spatial distributions of the observed sample are analyzed. We also present new results from OWN, a multi-epoch high-resolution spectroscopic survey coordinated with GOSSS that is assembling the largest sample of Galactic spectroscopic massive binaries ever attained. The OWN data combined with additional information on spectroscopic and visual binaries from the literature indicate that only a very small fraction (if any) of the stars with masses above 15-20 M sub(middot in circle) are born as single systems. In the future we will publish the rest of the GOSSS survey, which is expected to include over 1000 Galactic O stars.
Abstract We report here the performance and first results of the new multiband optical polarimeter DIPOL-1, installed at the Sierra Nevada Observatory 90 cm T90 telescope (SNO, Granada, Spain). ...DIPOL-1 is equipped with a plane parallel calcite plate and λ /2 retarder for modulating the intensity of two perpendicularly polarized beams, and a high readout speed CMOS camera that allows for fast, time-dense coverage. We characterize the performance of this instrument through a series of tests on zero- and high-polarization standard stars. The instrumental polarization in the Nasmyth focus was well determined, with a very stable contribution of 4.0806% ± 0.0014% in the optical R band. For bright high-polarization standards ( m R < 8) we reach precisions <0.02% in polarization degree and 0.°1 in polarization angle for exposures of 2–4 min. The polarization properties of these stars have been constrained, providing more recent results also about possible variability for future studies of some of the most used calibrators. Moreover, we have tested the capability of observing much fainter objects, in particular through blazar observations, where we reach a precision of <0.5%−0.6% and <0.°5 for faint targets ( m R ∼ 16.5) with exposures of ∼1 hr. For brighter targets ( m R ∼ 14.5−15), we can aim for time-dense observations with errors <0.2%−0.4% and <1°−1.°5 in 5–20 min. We have successfully performed a first campaign with DIPOL-1, detecting significant polarized emission of several blazars, with special attention to the highest ever polarization degree measured from blazar 3C 345 at ∼32%.
We present the first installment of a massive spectroscopic survey of Galactic O stars, based on new, high signal-to-noise ratio, R ~ 2500 digital observations from both hemispheres selected from the ...Galactic O-Star Catalog of Maiz Apellaniz et al. and Sota et al. The spectral classification system is rediscussed and a new atlas is presented, which supersedes previous versions. Extensive sequences of exceptional objects are given, including types Ofc, ON/OC, Onfp, Of?p, Oe, and double-lined spectroscopic binaries. The remaining normal spectra bring this first sample to 184 stars, which is close to complete to B = 8 and north of Delta *d = --20? and includes all of the northern objects in Maiz Apellaniz et al. that are still classified as O stars. The systematic and random accuracies of these classifications are substantially higher than previously attainable, because of the quality, quantity, and homogeneity of the data and analysis procedures. These results will enhance subsequent investigations in Galactic astronomy and stellar astrophysics. In the future, we will publish the rest of the survey, beginning with a second paper that will include most of the southern stars in Maiz Apellaniz et al.
Abstract
The search for Earth-like planets around late-type stars using ultrastable spectrographs requires a very precise characterization of the stellar activity and the magnetic cycle of the star, ...since these phenomena induce radial velocity (RV) signals that can be misinterpreted as planetary signals. Among the nearby stars, we have selected Barnard’s Star (Gl 699) to carry out a characterization of these phenomena using a set of spectroscopic data that covers about 14.5 yr and comes from seven different spectrographs: HARPS, HARPS-N, CARMENES, HIRES, UVES, APF, and PFS; and a set of photometric data that covers about 15.1 yr and comes from four different photometric sources: ASAS, FCAPT–RCT, AAVSO, and SNO. We have measured different chromospheric activity indicators (H α, Ca ii HK, and Na i D), as well as the full width at half-maximum (FWHM), of the cross-correlation function computed for a sub-set of the spectroscopic data. The analysis of generalized Lomb–Scargle periodograms of the time series of different activity indicators reveals that the rotation period of the star is 145 ± 15 d, consistent with the expected rotation period according to the low activity level of the star and previous claims. The upper limit of the predicted activity-induced RV signal corresponding to this rotation period is about 1 m s−1. We also find evidence of a long-term cycle of 10 ± 2 yr that is consistent with previous estimates of magnetic cycles from photometric time series in other M stars of similar activity levels. The available photometric data of the star also support the detection of both the long-term and the rotation signals.
New massive members of Cygnus OB2 Berlanas, S. R.; Herrero, A.; Comerón, F. ...
Astronomy and astrophysics (Berlin),
04/2018, Volume:
612
Journal Article
Peer reviewed
Open access
Context. The Cygnus complex is one of the most powerful star forming regions at a close distance from the Sun (~1.4 kpc). Its richest OB association Cygnus OB2 is known to harbor many tens of O-type ...stars and hundreds of B-type stars, providing a large homogeneous population of OB stars that can be analyzed. Many studies of its massive population have been developed in the last decades, although the total number of OB stars is still incomplete. Aim. Our aim is to increase the sample of O and B members of Cygnus OB2 and its surroundings by spectroscopically classifying 61 candidates as possible OB-type members of Cygnus OB2, using new intermediate resolution spectroscopy. Methods. We have obtained intermediate resolution (R ~ 5000) spectra for all of the OB-type candidates between 2013 and 2017. We thus performed a spectral classification of the sample using HeI-II and metal lines rates, as well as the Marxist Ghost Buster (MGB) software for O-type stars and the IACOB standards catalog for B-type stars. Results. From the whole sample of 61 candidates, we have classified 42 stars as new massive OB-type stars, earlier than B3, in Cygnus OB2 and surroundings, including 11 O-type stars. The other candidates are discarded as they display later spectral types inconsistent with membership in the association. We have also obtained visual extinctions for all the new confirmed massive OB members, placing them in a Hertzsprung-Russell Diagram using calibrations for Teff and luminosity. Finally, we have studied the age and extinction distribution of our sample within the region. Conclusions. We have obtained new blue intermediate-resolution spectra suitable for spectral classification of 61 OB candidates in Cygnus OB2 and surroundings. The confirmation of 42 new OB massive stars (earlier than B3) in the region allows us to increase the young massive population known in the field. We have also confirmed the correlation between age and Galactic longitude previously found in the region. We conclude that many O and early B stars at B > 16 mag are still undiscovered in Cygnus.
This is the third installment of the Galactic O-Star Spectroscopic Survey (GOSSS), a massive spectroscopic survey of Galactic O stars, based on new homogeneous, high signal-to-noise ratio, R~ 2500 ...digital observations selected from the Galactic O-Star Catalog. In this paper, we present 142 additional stellar systems with O stars from both hemispheres, bringing the total of O-type systems published within the project to 590. Among the new objects, there are 20 new O stars. We also identify 11 new double-lined spectroscopic binaries, 6 of which are of O+O type and 5 of O+B type, and an additional new tripled-lined spectroscopic binary of O+O+B type. We also revise some of the previous GOSSS classifications, present some egregious examples of stars erroneously classified as O-type in the past, introduce the use of luminosity class IV at spectral types O4-O5.5, and adapt the classification scheme to the work of Arias et al.
ABSTRACT
We present the first spectroscopic orbit of the O-type double-lined star HD 168112 A,B. We analyse 101 high-resolution optical spectra identifying the absorption lines of both components. ...The orbital solution presents a relatively long period, P = 513.52 ± 0.01 d, and a high eccentricity, e = 0.743 ± 0.005. The binary system consists of two very similar stars of minimum masses of ∼25 M⊙, effective temperatures of ∼40 000 K, and surface gravities of ∼3.7 dex. The system has a minimum semimajor axis a sin i ∼ 1000 R⊙. We confirm that the A and B visual components identified via interferometry do correspond to the spectroscopic ones. We also analyse the underlying stellar groups using Gaia DR3 data and ground-based spectroscopy as part of the Villafranca project, determining that NGC 6604 is at a distance of $1942^{+38}_{-36}$ pc and giving spectral classifications for 23 massive stellar systems in Villafranca O-035 and the surrounding Ser OB2 association, for which we provide the most complete census of massive stars to date.
Synchrotrons can provide long spills of particles by employing resonant extraction where the circulating beam is slowly ejected over thousands to millions of turns by exploiting the amplitude growth ...caused by a transverse resonance. In the CERN Super Proton Synchrotron (SPS), this method is used to satisfy the experimental requests of the North Area. However, the extracted particle flux is modulated by power-converter ripple, an issue shared across all sychrotrons that perform resonant extraction. In order to suppress such modulations, empty-bucket techniques can be employed, which take advantage of chromaticity to quickly accelerate particles into resonant motion by using a longitudinal rf system. This paper explores empty-bucket techniques via theory, simulation, and measurement, providing a systematic characterization with general applicability to any machine. Additionally, the operational implementation in the SPS is detailed, where the impact on the beam profile and extracted intensity is addressed. Published by the American Physical Society 2024
ABSTRACT
The T Tauri star CVSO 30, also known as PTFO 8-8695, was studied intensively with ground-based telescopes as well as with satellites over the last decade. It showed a variable light curve ...with additional repeating planetary transit-like dips every ∼10.8 h. However, these dimming events changed in depth and duration since their discovery and from autumn 2018 on, they were not even present or near the predicted observing times. As reason for the detected dips and their changes within the complex light curve, e.g. a disintegrating planet, a circumstellar dust clump, stellar spots, possible multiplicity, and orbiting clouds at a Keplerian co-rotating radius were discussed and are still under debate. In this paper, we present additional optical monitoring of CVSO 30 with the meter class telescopes of the Young Exoplanet Transit Initiative in Asia and Europe over the last 7 yr and characterize CVSO 30 with the new Early Data Release 3 of the European Space Agency-Gaia mission. As a result, we describe the evolution of the dimming events in the optical wavelength range since 2014 and present explanatory approaches for the observed variabilities. We conclude that orbiting clouds of gas at a Keplerian co-rotating radius are the most promising scenario to explain most changes in CVSO 30’s light curve.
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