Possible Corotation of the Milliarcsecond Radio Structure of the Close Binary HR 1099

Ransom, R. R.; Bartel, N.; Bietenholz, M. F.; Lebach, D. E.; Ratner, M. I.; Shapiro, I. I.; Lestrade, J. F.

doi:10.1086/340300

Cited by 17 publications

(21 citation statements)

References 34 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…VLBA observations of HR 1099 by Ransom et al (2002) provide reasonable evidence that during times of high Figure 6 The spectral structure in the highly polarised 2.368 GHz data of 08 April across the 104-MHz bandwidth of the compact array. The panels are arranged in increasing values of mid-UT of the 25-min integrations making up the data.…”

Section: Orbital-phase Dependencementioning

confidence: 89%

“…The VLBA maps of Ransom et al (2002) show that a relatively weaker 8.4-GHz gyro-synchrotron source was detected near the position of the G5 star only when the system was in a state of high activity. A mapping of four equal subdivisions of the data resulted in this source moving its position in a manner consistent with the orbital motion of the G5 dwarf about the K2 subgiant.…”

Section: The Two-star Coherent Sourcementioning

confidence: 98%

See 1 more Smart Citation

The Coherent Radio Emission from the RS CVn Binary HR 1099

Slee

Wilson

Ramsay

2008

Publ. – Astron. Soc. Aust

View full text Add to dashboard Cite

Abstract:The Australia Telescope was used in March-April 2005 to observe the 1.384 and 2.368-GHz emissions from the RS CVn binary HR 1099 in two sessions, each of 9-h duration and 11 days apart. Two intervals of highly polarised emission, each lasting 2-3 h, were recorded. During this coherent emission we employed a recently installed facility to sample the data at 78-ms intervals to measure the fine temporal structure and, in addition, all the data were used to search for fine spectral structure. We present the following observational results: (1) ∼100% left-hand circularly polarised emission was seen at both 1.384 and 2.368 GHz during separate epochs; (2) the intervals of highly polarised emission lasted for 2-3 h on each occasion; (3) three 22-min integrations made at 78-ms time resolution showed that the modulation index of the Stokes V parameter increased monotonically as the integration time was decreased and was still increasing at our resolution limit; (4) the extremely fine temporal structure strongly indicates that the highly polarised emission is due to an electron-cyclotron maser operating in the corona of one of the binary components; (5) the first episode of what we believe is ECME (electron-cyclotron maser emission) at 1.384 GHz contained a regular frequency structure of bursts with FWHM ∼48 MHz, which drifted across the spectrum at ∼0.7 MHz min −1 . Our second episode of ECME at 2.368 GHz contained wider-band frequency structure, which did not permit us to estimate an accurate bandwidth or direction of drift; (6) the two ECME events reported in this paper agree with six others reported in the literature in occurring in the binary orbital phase range 0.5-0.7; (7) in one event of 8-h duration, two independent maser sources were operating simultaneously at 1.384 and 2.368 GHz.We discuss two kinds of maser sources that may be responsible for driving the observed events that we believe are powered by ECME. One is based on the widely reported 'loss-cone anisotropy', the second on an auroral analogue, which is driven by an unstable 'horseshoe' distribution of fast-electron velocities with respect to the magnetic field direction. Generally, we favour the latter, because of its higher growth rate and the possibility of the escape of radiation which has been emitted at the fundamental electron cyclotron frequency. If the auroral analogue is operating, the magnetic field in the source cavity is ∼500 G at 1.384 GHz and ∼850 G at 2.368 GHz; the source brightness temperatures are of the order T B ∼ 10 15 K.We suggest that the ECME source may be an aurora-like phenomenon due to the transfer of plasma from the K2 subgiant to the G5 dwarf in a strong stellar wind, an idea that is based on VLBA maps showing the establishment of an 8.4 GHz source near the G5 dwarf at times of enhanced radio activity in HR 1099.

show abstract

Section: Orbital-phase Dependencementioning

confidence: 89%

Section: The Two-star Coherent Sourcementioning

confidence: 98%

The Coherent Radio Emission from the RS CVn Binary HR 1099

Slee

Wilson

Ramsay

2008

Publ. – Astron. Soc. Aust

View full text Add to dashboard Cite

show abstract

“…For other VLBI images of RS CVn stars, we refer the interested reader to Ransom et al (2002Ransom et al ( , 2003, Lestrade et al (1995), Massi et al (1988), and Mutel et al (1985).…”

Section: Introductionmentioning

confidence: 99%

VLBI FOR GRAVITY PROBE B . VII. THE EVOLUTION OF THE RADIO STRUCTURE OF IM PEGASI

Bietenholz

Bartel

Lebach

et al. 2012

ApJS

Self Cite

View full text Add to dashboard Cite

We present measurements of the total radio flux density as well as very long baseline interferometry images of the star, IM Pegasi, which was used as the guide star for the NASA/Stanford relativity mission Gravity Probe B. We obtained flux densities and images from 35 sessions of observations at 8.4 GHz (λ = 3.6 cm) between 1997 January and 2005 July. The observations were accurately phase-referenced to several extragalactic reference sources, and we present the images in a star-centered frame, aligned by the position of the star as derived from our fits to its orbital motion, parallax, and proper motion. Both the flux density and the morphology of IM Peg are variable. For most sessions, the emission region has a single-peaked structure, but 25% of the time, we observed a two-peaked (and on one occasion perhaps a three-peaked) structure. On average, the emission region is elongated by 1.4 ± 0.4 mas (FWHM), with the average direction of elongation being close to that of the sky projection of the orbit normal. The average length of the emission region is approximately equal to the diameter of the primary star. No significant correlation with the orbital phase is found for either the flux density or the direction of elongation, and no preference for any particular longitude on the star is shown by the emission region.

show abstract

“…Quiescent radio emission from the Sun is largely due to bremsstrahlung and gyroresonance emission above sunspots, but the process in active stars appears to be different. The detection of circular polarization (e.g, Mutel et al, 1998;Beasley and Güdel, 2000;Ransom et al, 2002) rules out bremsstrahlung emission or highly relativistic synchrotron emission. Systematic studies of the spectral indices of active stars (e.g., Mutel et al, 1998) point to gyrosynchrotron emission.…”

Section: List Of Tablesmentioning

confidence: 99%

“…For these observations, the HSA consisted of the ten 25-meter very long baseline array (VLBA) antennas, the 100-meter Green Bank Telescope, the 100-meter Effelsberg radiotelescope, and the Very Large Array in phased array mode. We observed at a frequency of 15 GHz, a crucial choice since it provided a resolving beam size (0.4 mas x 0.6 mas) which was half the size of most previous VLBI observations (Beasley and Güdel, 2000;Lestrade et al, 1988;Massi et al, 1999;Mutel et al, 1985;Ransom et al, 2002;Mutel et al, 1998) and much smaller than the projected orbital separation (2.3 mas). This made it possible to to discern the detailed radio morphology of the system and its association with the individual components.…”

Section: Observationsmentioning

confidence: 99%

Very long baseline interferometry of evolved binary systems

Peterson¹

View full text Add to dashboard Cite

Our understanding of the magnetic fields of stars is nearly monopolized by knowledge of our own sun. Very-long baseline radio interferometry (VLBI) provides a means of directly imaging the radio coronae of other stars at a high enough resolution to discern discrete features, something not possible with other observational methods. It also allows the highest positional accuracy of any observational method available. This thesis details the VLBI study of two nearby radio-loud stars in close binary systems. Both systems were observed at numerous epochs spaced over a range of several months with the global-scale radio interferometer array the VLBA-HSA. These observations were combined with archival data from the National Radioastronomy Observatory (NRAO) Archive. The resulting positions, as well as previously published positions, were used to calculate a least-squares solution for all the orbital and astrometric parameters of both systems. This made it possible to determine the position of the physical star with respect to the radio emission in each image. The images of both stars were found to conform to theoretical emission produced by a model dipolar magnetosphere with a filled or partially-filled coronal loop.

show abstract

Possible Corotation of the Milliarcsecond Radio Structure of the Close Binary HR 1099

Cited by 17 publications

References 34 publications

The Coherent Radio Emission from the RS CVn Binary HR 1099

The Coherent Radio Emission from the RS CVn Binary HR 1099

VLBI FOR GRAVITY PROBE B . VII. THE EVOLUTION OF THE RADIO STRUCTURE OF IM PEGASI

Very long baseline interferometry of evolved binary systems

Contact Info

Product

Resources

About