- ID:
- ivo://CDS.VizieR/J/A+A/395/129
- Title:
- Cyclotron lines in Vela X-1
- Short Name:
- J/A+A/395/129
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Fitting parameters for the phase resolved spectra of the 2000 and 1998 observation are given. The model in use is the Negative Positive EXponential (NPEX) model (with Gamma_2_ always fixed to -2, Mihara, 1995, Ph.D. Thesis, Riken, Tokyo) modified by photoelectric absorption, an additive iron line at ~6.4keV, and none, one, or two cyclotron resonant scattering features (CRSF)s at ~25 and ~50keV. The phase bins for the 2000 observation are: - rise, center, and fall of the main pulse - rise part 1, rise part 2, center, and fall of the secondary pulse - the two inter pulse phases The phase bins for the 1998 observation are: - rise and fall of the main pulse - rise and fall of the secondary pulse - the two inter pulse phases
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/478/1763
- Title:
- Detectability of radio emission from exoplanets
- Short Name:
- J/MNRAS/478/1763
- Date:
- 19 Jan 2022 00:23:37
- Publisher:
- CDS
- Description:
- Like the magnetized planets in our Solar system, magnetized exoplanets should emit strongly at radio wavelengths. Radio emission directly traces the planetary magnetic fields and radio detections can place constraints on the physical parameters of these features. Large comparative studies of predicted radio emission characteristics for the known population of exoplanets help to identify what physical parameters could be the key for producing bright, observable radio emission. Since the last comparative study, many thousands of exoplanets have been discovered. We report new estimates for the radio flux densities and maximum emission frequencies for the current population of known exoplanets orbiting pre-main-sequence and main-sequence stars with spectral types F-M. The set of exoplanets predicted to produce observable radio emission are Hot Jupiters orbiting young stars. The youth of these systems predicts strong stellar magnetic fields and/or dense winds, which are the key for producing bright, observable radio emission. We use a new all-sky circular polarization Murchison Widefield Array survey to place sensitive limits on 200MHz emission from exoplanets, with 3{sigma} values ranging from 4.0 to 45.0mJy. Using a targeted Giant Metrewave Radio Telescope observing campaign, we also report a 3{sigma} upper limit of 4.5mJy on the radio emission from V830 Tau b, the first Hot Jupiter to be discovered orbiting a pre-main-sequence star. Our limit is the first to be reported for the low-frequency radio emission from this source.
- ID:
- ivo://CDS.VizieR/J/ApJ/897/L10
- Title:
- Disturbance storm time index; 1903 Sun outburst
- Short Name:
- J/ApJ/897/L10
- Date:
- 15 Nov 2021 09:20:23
- Publisher:
- CDS
- Description:
- While the Sun is generally more eruptive during its maximum and declining phases, observational evidence shows certain cases of powerful solar eruptions during the quiet phase of solar activity. Occurring in the weak Solar Cycle 14 just after its minimum, the extreme space weather event in 1903 October-November is one of these cases. Here, we reconstruct the time series of geomagnetic activity based on contemporary observational records. With the mid-latitude magnetograms, the 1903 magnetic storm is thought to be caused by a fast coronal mass ejection (~1500km/s) and is regarded as a superstorm with an estimated minimum of the equivalent disturbance storm time index (Dst') of ~-531nT. The reconstructed time series has been compared with the equatorward extension of auroral oval (~44.1 in invariant latitude) and the time series of telegraphic disturbances. This case study shows that potential threats posed by extreme space weather events exist even during weak solar cycles or near their minima.
- ID:
- ivo://CDS.VizieR/J/A+A/440/373
- Title:
- Earthbound interplanetary shocks
- Short Name:
- J/A+A/440/373
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This table contains space weather data based on 360 interplanetary shocks (forward and reverse) observed by ACE during the 80 month time period from January 1998 to August 2004. Data from ACE, WIND, LASCO and GOES are included, as well as Dst, Ap, SC information and SEC prediction times.
- ID:
- ivo://CDS.VizieR/J/ApJS/229/34
- Title:
- Effects of preionization in radiative shocks
- Short Name:
- J/ApJS/229/34
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we treat the preionization problem in shocks over the velocity range 10<v_s_<1500km/s in a self-consistent manner. We identify four distinct classes of solutions controlled by the value of the shock-precursor parameter, {Psi}=Q/v_s_, where Q is the ionization parameter of the UV photons escaping upstream. This parameter determines both the temperature and the degree of ionization of the gas entering the shock. In increasing velocity, the shock solution regimes are cold neutral precursors (v_s_<~40km/s), warm neutral precursors (40<~v_s_<~75km/s), warm partly ionized precursors (75<~v_s_<~120km/s), and fast shocks in which the preshock gas is in photoionization equilibrium and is fully ionized. The main effect of a magnetic field is to push these velocity ranges to higher values and to limit the postshock compression. In order to facilitate comparison with observations of shocks, we provide a number of convenient scaling relationships for parameters, such as postshock temperature, compression factors, cooling lengths, and H{beta} and X-ray luminosity.
- ID:
- ivo://CDS.VizieR/J/ApJ/774/6
- Title:
- Empirical scaling laws for shell dynamos
- Short Name:
- J/ApJ/774/6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Numerical dynamo models always employ parameter values that differ by orders of magnitude from the values expected in natural objects. However, such models have been successful in qualitatively reproducing properties of planetary and stellar dynamos. This qualitative agreement fuels the idea that both numerical models and astrophysical objects may operate in the same asymptotic regime of dynamics. This can be tested by exploring the scaling behavior of the models. For convection-driven incompressible spherical shell dynamos with constant material properties, scaling laws had been established previously that relate flow velocity and magnetic field strength to the available power. Here we analyze 273 direct numerical simulations using the anelastic approximation, involving also cases with radius-dependent magnetic, thermal, and viscous diffusivities. These better represent conditions in gas giant planets and low-mass stars compared to Boussinesq models. Our study provides strong support for the hypothesis that both mean velocity and mean magnetic field strength scale as a function of the power generated by buoyancy forces in the same way for a wide range of conditions.
- ID:
- ivo://CDS.VizieR/J/A+A/550/A43
- Title:
- Equation of state for magnetized plasmas
- Short Name:
- J/A+A/550/A43
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have developed an analytical equation of state (EOS) for magnetized fully-ionized plasmas that cover a wide range of temperatures and densities, from low-density classical plasmas to relativistic, quantum plasma conditions. This EOS directly applies to calculations of structure and evolution of strongly magnetized white dwarfs and neutron stars. We review available analytical and numerical results for thermodynamic functions of the nonmagnetized and magnetized Coulomb gases, liquids, and solids. We propose a new analytical expression for the free energy of solid Coulomb mixtures. Based on recent numerical results, we have constructed analytical approximations for the thermodynamic functions of harmonic Coulomb crystals in quantizing magnetic fields. The analytical description ensures a consistent evaluation of all astrophysically important thermodynamic functions based on the first, second, and mixed derivatives of the free energy. Our numerical code for calculation of thermodynamic functions based on these approximations has been made publicly available. Using this code, we calculate and discuss the effects of electron screening and magnetic quantization on the position of the melting point in a range of densities and magnetic fields relevant to white dwarfs and outer envelopes of neutron stars. We consider also the thermal and mechanical structure of a magnetar envelope and argue that it can have a frozen surface which covers the liquid ocean above the solid crust.
- ID:
- ivo://CDS.VizieR/J/A+A/450/763
- Title:
- Evolutionary state of magnetic CP stars
- Short Name:
- J/A+A/450/763
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The photospheres of about 5-10% of the upper main sequence stars exhibit remarkable chemical anomalies. Many of these chemically peculiar (CP) stars have a global magnetic field, the origin of which is still a matter of debate. We present a comprehensive statistical investigation of the evolution of magnetic CP stars, aimed at providing constraints to the theories that deal with the origin of the magnetic field in these stars.
- ID:
- ivo://CDS.VizieR/J/MNRAS/451/74
- Title:
- Excited-state hydroxyl maser polarimetry
- Short Name:
- J/MNRAS/451/74
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present polarimetric maser observations with the Australia Telescope Compact Array of excited-state hydroxyl (OH) masers. We observed 30 fields of OH masers in full Stokes polarization with the Compact Array Broadband Backend at both the 6030 and 6035 MHz excited-state OH transitions, and the 6668 MHz methanol maser transition, detecting 70 sites of maser emission. Amongst the OH we found 112 Zeeman pairs, of which 18 exhibited candidate {pi} components. This is the largest single full polarimetric study of multiple sites of star formation for these frequencies, and the rate of 16 percent {pi} components clearly indicates that the {pi} component exists, and is comparable to the percentage recently found for ground-state transitions. This significant percentage of {pi} components, with consistent proportions at both ground- and excited-state transitions, argues against Faraday rotation suppressing the {pi} component emission. Our simultaneous observations of methanol found the expected low level of polarization, with no circular detected, and linear only found at the =<10 percent level for the brightest sources.
- ID:
- ivo://CDS.VizieR/J/MNRAS/411/L46
- Title:
- Exoplanet magnetic fields
- Short Name:
- J/MNRAS/411/L46
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- An asymmetry between the ingress and egress times was observed in the near-UV light curve of the transit planet WASP-12b. Such asymmetry led us to suggest that the early ingress in the UV light curve of WASP-12b, compared to the optical observations, is caused by a shock around the planet, and that shocks should be a common feature in transiting systems. Here, we classify all the transiting systems known to date according to their potential for producing shocks that could cause observable light curve asymmetries.
