- ID:
- ivo://CDS.VizieR/J/ApJ/793/L4
- Title:
- Polar network index for the solar cycle studies
- Short Name:
- J/ApJ/793/L4
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Sun has a polar magnetic field which oscillates with the 11 yr sunspot cycle. This polar magnetic field is an important component of the dynamo process which operates in the solar convection zone and produces the sunspot cycle. We have direct systematic measurements of the Sun's polar magnetic field only from about the mid-1970s. There are, however, indirect proxies which give us information about this field at earlier times. The Ca-K spectroheliograms taken at the Kodaikanal Solar Observatory during 1904-2007 have now been digitized with 4kx4k CCD and have higher resolution (~0.86 arcsec) than the other available historical data sets. From these Ca-K spectroheliograms, we have developed a completely new proxy (polar network index, hereafter PNI) for the Sun's polar magnetic field. We calculate PNI from the digitized images using an automated algorithm and calibrate our measured PNI against the polar field as measured by the Wilcox Solar Observatory for the period 1976-1990. This calibration allows us to estimate the polar fields for the earlier period up to 1904. The dynamo calculations performed with this proxy as input data reproduce reasonably well the Sun's magnetic behavior for the past century.
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- ID:
- ivo://CDS.VizieR/J/A+A/475/359
- Title:
- Predicting radio fluxes of extrasolar planets
- Short Name:
- J/A+A/475/359
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Close-in giant extrasolar planets ("Hot Jupiters") are believed to be strong emitters in the decametric radio range. We present the expected characteristics of the low-frequency magnetospheric radio emission of all currently known extrasolar planets, including the maximum emission frequency and the expected radio flux. We also discuss the escape of exoplanetary radio emission from the vicinity of its source, which imposes additional constraints on detectability. We compare the different predictions obtained with all four existing analytical models for all currently known exoplanets. We also take care to use realistic values for all input parameters.
- ID:
- ivo://CDS.VizieR/J/A+A/647/A60
- Title:
- Prominence average magnetic fields in cycle XXI
- Short Name:
- J/A+A/647/A60
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The aim of the present paper is to publish 24 synoptic maps of solar filaments, in which 296 prominence average unambiguous magnetic field vectors were determined by Pic-du-Midi observations between 1974 and 1982, which is the ascending phase of cycle XXI. The magnetic field was determined by interpretation of the Hanle effect observed in the HeI D3 line. Previou the prominence field polarity and prominence chirality were applied to solve the fundamental ambiguity. The meas averaged in each prominence for accuracy reasons. The result is twofold. First, alternating field directions can be observed from one neutral line to the next general field alignment is found along a solar North-South field distorted under the differential rotation effect. The about prominence and their magnetic field coordinates are provided as on-line material associated to this paper.
- ID:
- ivo://CDS.VizieR/J/AJ/156/149
- Title:
- Properties of massive giant planets & brown dwarfs
- Short Name:
- J/AJ/156/149
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present thermodynamic material and transport properties for the extreme conditions prevalent in the interiors of massive giant planets and brown dwarfs. They are obtained from extensive ab initio simulations of hydrogen-helium mixtures along the isentropes of three representative objects. In particular, we determine the heat capacities, the thermal expansion coefficient, the isothermal compressibility, and the sound velocity. Important transport properties such as the electrical and thermal conductivity, opacity, and shear viscosity are also calculated. Further results for associated quantities, including magnetic and thermal diffusivity, kinematic shear viscosity, as well as the static Love number k_2_ and the equidistance, are presented. In comparison to Jupiter-mass planets, the behavior inside massive giant planets and brown dwarfs is stronger dominated by degenerate matter. We discuss the implications on possible dynamics and magnetic fields of those massive objects. The consistent data set compiled here may serve as a starting point to obtain material and transport properties for other substellar H-He objects with masses above one Jovian mass and finally may be used as input for dynamo simulations.
- ID:
- ivo://CDS.VizieR/J/ApJ/893/L20
- Title:
- Proton synchrotron gamma-rays in blazars
- Short Name:
- J/ApJ/893/L20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The origin of high-energy emission in blazars jets (i.e., leptonic versus hadronic) has been a longstanding matter of debate. Here, we focus on one variant of hadronic models where proton synchrotron radiation accounts for the observed steady {gamma}-ray blazar emission. Using analytical methods, we derive the minimum jet power (P_j,min_) for the largest blazar sample analyzed to date (145 sources), taking into account uncertainties of observables and jet's physical parameters. We compare P_j,min_ against three characteristic energy estimators for accreting systems, i.e., the Eddington luminosity, the accretion disk luminosity, and the power of the Blandford-Znajek process, and find that P_j,min_ is about 2 orders of magnitude higher than all energetic estimators for the majority of our sample. The derived magnetic field strengths in the emission region require either large amplification of the jet's magnetic field (factor of 30) or place the {gamma}-ray production site at sub-pc scales. The expected neutrino emission peaks at ~0.1-10EeV, with typical peak neutrino fluxes ~10^-4^ times lower than the peak {gamma}-ray fluxes. We conclude that if relativistic hadrons are present in blazar jets, they can only produce a radiatively subdominant component of the overall spectral energy distribution of the blazar's steady emission.
- ID:
- ivo://CDS.VizieR/J/ApJ/737/L35
- Title:
- Pulsed Alfven waves in the solar wind
- Short Name:
- J/ApJ/737/L35
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using 3s plasma and magnetic field data from the Wind spacecraft located in the solar wind well upstream from Earth, we report observations of isolated, pulse-like Alfvenic disturbances in the solar wind. These isolated events are characterized by roughly plane-polarized rotations in the solar wind magnetic field and velocity vectors away from the directions of the underlying field and velocity and then back again. They pass over Wind on timescales ranging from seconds to several minutes. These isolated, pulsed Alfven waves are pervasive; we have identified 175 such events over the full range of solar wind speeds (320-550km/s) observed in a randomly chosen 10 day interval.
- ID:
- ivo://CDS.VizieR/J/A+A/628/A106
- Title:
- Radial velocity time series of EK Eridani
- Short Name:
- J/A+A/628/A106
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present further evidence of acoustic oscillations in the slowly rotating overactive G8 sub-giant EK Eri. This star was observed with the 1m Hertzsprung SONG telescope at the Observatorio del Teide for two different runs of 8 and 13 nights, respectively, that were separated by about a year. We determined a significant excess of power around {nu}_max_=253+/-3uHz in the first observing run and were able to determine a large separation, {Delta}_{nu}_=16.430+/-22uHz. No significant excess of power was instead detected in a subsequent SONG observing season, as also supported by our analysis of the simultaneous TESS photometric observations. We propose a new amplitude-luminosity relation in order to account for the missing power in the power spectrum. Based on the evolutionary stage of this object, we argue that a standard {alpha}^2^{OMEGA} dynamo cannot be excluded as the possible origin for the observed magnetic field.
- ID:
- ivo://CDS.VizieR/J/A+A/552/A19
- Title:
- Radio-farIR correlation in NGC 6946
- Short Name:
- J/A+A/552/A19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We derive the distribution of the synchrotron spectral index across NGC 6946 and investigate the correlation between the radio continuum (synchrotron) and far-infrared (FIR) emission using the KINGFISH Herschel PACS and SPIRE data.
- ID:
- ivo://CDS.VizieR/J/ApJ/648/629
- Title:
- Radio observations of late M, L, and T dwarfs
- Short Name:
- J/ApJ/648/629
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- I present radio observations of 90 dwarf stars and brown dwarfs of spectral type M5-T8. Three sources exhibit radio activity, in addition to the six objects previously detected in quiescence and outburst, leading to an overall detection rate of ~10% for objects later than M7.
- ID:
- ivo://CDS.VizieR/J/MNRAS/469/2313
- Title:
- Radio pulsars post-glitchs
- Short Name:
- J/MNRAS/469/2313
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Timing observations of rapidly rotating neutron stars revealed a great number of glitches, observed from both canonical radio pulsars and magnetars. Among them, 76 glitches have shown exponential relaxation(s) with characteristic decay times ranging from several days to a few months, followed by a more gradual recovery. Glitches displaying exponential relaxation with single or multiple decay time constants are analysed in terms of a model based on the interaction of the vortex lines with the toroidal arrangement of flux tubes in the outer core of the neutron star. Model results agree with the observed time-scales in general. Thus, the glitch phenomenon can be used to deduce valuable information about neutron star structure, in particular on the interior magnetic field configuration which is unaccessible from surface observations. One immediate conclusion is that the magnetar glitch data are best explained with a much cooler core and therefore require that direct Urca-type fast-cooling mechanisms should be effective for magnetars.
