Search for Radio Recombination Lines towards the Gravitational Lens PKS1830-211

A search for radio recombination lines near 20 cm at z=0.193 and z=0.886 towards the gravitational lens system PKS1830-211 has yielded upper limits of |τL| ≤ 5 × 10−5 and ≤ 5 × 10−4 at the two redshifts respectively. Based on the non-detections, we derive upper limits to the emission measure of the ionized gas in the absorbing systems. We also present continuum flux density measurements over the frequency range 0.3—45 GHz made at a single epoch.

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Radio Recombination Lines from Starburst Galaxies: High and Low Density Ionized Gas

Symposium - International Astronomical Union ◽

10.1017/s0074180900169025 ◽

2002 ◽

Vol 199 ◽

pp. 243-244

Author(s):

N.R. Mohan ◽

K.R. Anantharamaiah ◽

W.M. Goss

Keyword(s):

Flux Density ◽

Hii Regions ◽

Starburst Galaxies ◽

High Density ◽

The Other ◽

Low Density ◽

Ionized Gas ◽

Density Measurements ◽

Radio Recombination Lines ◽

Upper Limits

Radio recombination lines (RRL) at 8 GHz and 15 GHz detected from four starburst galaxies are shown to arise in compact high density HII regions, which are undetectable below ∼4 GHz. Detection of an RRL at 1.4 GHz towards one galaxy and upper limits in the other three are consistent with the presence of an equal amount of low density diffuse gas. Continuum flux density measurements using the GMRT will be important in constraining the properties of the diffuse gas.

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VLBI Observations of the 0957+561 Gravitational Lens System

Symposium - International Astronomical Union ◽

10.1017/s0074180900134473 ◽

1988 ◽

Vol 129 ◽

pp. 201-206

Author(s):

M. V. Gorenstein ◽

R. J. Bonometti ◽

N. L. Cohen ◽

E. E. Falco ◽

I. I. Shapiro ◽

...

Keyword(s):

Time Delay ◽

Flux Density ◽

Gravitational Lens ◽

Time Variability ◽

Lens System ◽

Relative Time ◽

Vlbi Observations ◽

New Information ◽

Superluminal Motion ◽

Upper Limits

A series of VLBI observations of the gravitational lens system 0957+561 at λ13 cm has yielded the positions of the A and B images, the relative magnification of their largest discernible radio structures, and the time variability of their smallest discernible radio structures. These observations have also allowed upper limits to be placed on the flux density of an expected third image. The positions and relative magnification of the A and B images provide new information with which to constrain models of the lens that forms the images. The detection of variations in the flux densities of the cores of A and B suggests that observations at shorter wavelengths may reveal superluminal motion, which may in turn provide a means to measure the relative time delay.

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Multi-frequency pulsar studies at high radio frequencies

International Astronomical Union Colloquium ◽

10.1017/s0252921100041701 ◽

1996 ◽

Vol 160 ◽

pp. 279-282

Author(s):

Michael Kramer ◽

Kiriaki M. Xilouris

Keyword(s):

Magnetic Field ◽

Flux Density ◽

Stellar Surface ◽

Active Part ◽

Frequency Range ◽

Density Spectrum ◽

Density Measurements ◽

Radio Frequencies ◽

Dipolar Structure ◽

The Magnetic Field

AbstractWe report flux density measurements, polarimetric and timing observations of pulsars made at the highest radio frequencies to date, covering the widest frequency range from 1.4 GHz to 86 GHz. We find that the magnetic field maintains its dipolar structure throughout the active part of the magnetosphere, a region located close to the stellar surface and confined to a small slab of a few stellar radii. The change in width and shape of pulse profiles saturates at mm-wavelengths while the depolarization accelerates, leading to almost completely depolarized emission. Two pulsars seem to exhibit a turn-up in their flux density spectrum at mm-wavelengths.

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The Radio Spectrum of SGR A∗

Symposium - International Astronomical Union ◽

10.1017/s0074180900232610 ◽

1996 ◽

Vol 171 ◽

pp. 342-342 ◽

Cited By ~ 1

Author(s):

T. Beckert ◽

W.J. Duschl ◽

P.G. Mezger ◽

R. Zylka

Keyword(s):

Radio Source ◽

Flux Density ◽

Radio Spectrum ◽

Frequency Range ◽

Upper Limits ◽

The Galaxy ◽

Sgr A

Sgr A∗, the enigmatic radio source located at the dynamical center of the Galaxy, is firmly detected in the frequency range of ∼ 1 – few 102 GHz. For ∼ 0.5 – 1 GHz and in the MIR range only significant upper limits of the flux density are known. Between ∼ 1.5 and 600 GHz the time averaged flux density Sv is proportional to v1/3 (v: frequency). For frequencies higher than ∼ 600 GHz as well as for those lower than ∼ 1.5 GHz, Sv drops sharply.

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VLA and MERLIN Monitoring Observations of the Gravitational Lens System B1030+074

Symposium - International Astronomical Union ◽

10.1017/s0074180900217002 ◽

2005 ◽

Vol 201 ◽

pp. 532-533

Author(s):

E. Xanthopoulos ◽

I. W. A. Browne ◽

A. R. Patnaik ◽

P. N. Wilkinson

Keyword(s):

Light Curve ◽

Flux Density ◽

Light Curves ◽

Gravitational Lens ◽

Monitoring Data ◽

Lens System ◽

Average Spacing ◽

Steady Decrease ◽

L Band

We present VLA and MERLIN monitoring data of the JVAS gravitational lens system B1030+074. The system was monitored with the VLA from February 1998 to October 1998 at 8.4-GHz during which the VLA was at its A, BnA and B configuration. The 47 epochs of observations have an average spacing of approximately 5 days. Ten MERLIN snapshots were obtained in the L-band (1.7 GHz) during the months of April, May and June 1998. Preliminary light curves of the two components of the lens system obtained from the VLA data indicate that during the period of the monitoring the A flux density showed a steady decrease. No changes are observed in the B light curve.

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VLBI Observations of the Gravitational Lens System 2016+112

Symposium - International Astronomical Union ◽

10.1017/s0074180900134497 ◽

1988 ◽

Vol 129 ◽

pp. 209-210

Author(s):

M. B. Heflin ◽

M. V. Gorenstein ◽

E. E. Falco ◽

I. I. Shapiro ◽

B. F. Burke ◽

...

Keyword(s):

Flux Density ◽

Model Fitting ◽

Gravitational Lens ◽

Vlbi Observation ◽

Lens System ◽

Vlbi Observations

On June 1, 1984 we conducted a seven station 18-cm VLBI observation of the 2016+112 gravitational lens system. Preliminary brightness distributions for A and B have been obtained via model fitting. Weak correlated flux density was detected in the C component region.

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The Gravitational Lens System B1030+074. Discovery and Follow-up

Symposium - International Astronomical Union ◽

10.1017/s007418090016231x ◽

1999 ◽

Vol 194 ◽

pp. 373-378

Author(s):

E. Xanthopoulos ◽

I. W. A. Browne ◽

L. J. King ◽

N. J. Jackson ◽

D. R. Marlow ◽

...

Keyword(s):

Time Delay ◽

Flux Density ◽

Density Ratio ◽

Hubble Constant ◽

Time Variable ◽

Gravitational Lens ◽

Lens System ◽

Double Image ◽

The Galaxy

We report the discovery of a new double image gravitational lens system B1030+074 which was found during the Jodrell Bank - VLA Astrometric Survey (JVAS). We have collected extensive radio data on the system using the VLA, MERLIN, the EVN and the VLBA as well as HST WFPC2 and NICMOS observations. The lensed images are separated by 1.56 arcseconds and their flux density ratio at centimetric wavelengths is approximately 14:1 although the ratio is slightly frequency dependent and the images appear to be time variable. The HST pictures show both the lensed images and the lensing galaxy close to the weaker image. The lensing galaxy has substructure which could be either part of the galaxy or a companion object. We have modeled B1030+074 using a Singular Isothermal Ellipsoid that yielded a time delay of 156/h50 days. This lens is likely to be suitable for the measurement of the Hubble constant.

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