The discovery of a twinkling radio source with Apertif: Extreme scintillation from turbulent plasma in the direct solar neighbourhood

University of Groningen

The discovery of a twinkling radio source with Apertif

Oosterloo, Tom; Vedantham, Harish; Kutkin, Alexander

DOI:

10.5281/zenodo.3756570

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Publication date:

2020

Link to publication in University of Groningen/UMCG research database

Citation for published version (APA):

Oosterloo, T., Vedantham, H., & Kutkin, A. (2020). The discovery of a twinkling radio source with Apertif:

Extreme scintillation from turbulent plasma in the direct solar neighbourhood.

https://doi.org/10.5281/zenodo.3756570

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The discovery of a twinkling radio source with Apertif:

extreme scintillation from turbulent plasma

in the direct solar neighbourhood

Tom Oosterloo, Harish Vedantham, Alexander Kutkin

Astron Dwingeloo & Groningen University

New/upgraded radio telescopes with very large field of view will perform large-area

imaging surveys in the coming years (LOFAR, MWA, ASKAP, Apertif).

Study:

• Structure & kinematics of galaxies

• AGN & star formation

• FRB’s

• …

Source with strong variations on timescale of minutes!

Only a handful of such sources known!

-1

0

1

2

3

4

5

6

7

8

9

10

11

12

13

Time (h)

0

5

10

15

20

25

S

(mJy)

Apertif IHV 1 09-Apr-2019

Interstellar scintillation of point-like background

source by dense (n

e

~ 100 cm

-3

), very nearby 


(< tens of pc) linear plasma filaments moving

across the line of sight.


Origin is not clear.

Photoionised flow driven from the surface of

small, dense, neutral clumps ?

Apertif observation in the HETDEX field,

9 apr 2019.

J1402+5347 is about half a degree from

M101, so region has been observed

many times in the past decades

Not variable up to at least

January - April 2013.

Change from 2013 corresponds to an

’edge’ of the plasma of < 25 AU

No counterpart of background source in optical images,

but is detected by WISE.

Colours suggest the radio source is a dust-obscured

AGN at ‘high’ redshift

VLBI imaging (5 GHz; 2 mas) shows core with small

extension. Same flux as in low-resolution images

Monitoring shows that the variability changes dramatically!!

Very characteristic for intra-hour variables.

Two periods with no variability


13-Sep

10-Oct

Pattern of scintels moves

over the solar system

Earth rotates around the Sun

Modelling the variability

V

_rel

/

R

For circular scintels, the frequency

of the variability is

One minimum in variability

Circular scintels

V

_?

/R

Pattern of scintels moves

over the solar system

Earth rotates around the Sun

For linear scintels, the frequency

of the variability is

Modelling the variability

Linear scintels

Two minima in variability

Linear scintels

0

2

4

6

Orbital phase [rad]

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

Scintillation

rate

[min

1

]

d = 0.4 pc, v

_?

= 21.8 km/s, ✓

_R

= 6.1 rad

Simple model of purely linear filaments fits the data very well.

circular scintels are ruled out

Distance ~1 lightyear, so just outside the Oort Cloud!!

n

e

~ 100 cm

-3

Very similar as found for the other IHVs out to tens of pc

Has been suggested that these filaments are the photo-ionised

skin blown from tiny cold clumps associated with hot stars

(Walker+ 2018)

J1402+5347 appears to be a counterexample.


There is no candidate star…..

Discovered a new intra-hour variable radio source, 


thanks to the high survey speed of Apertif(?)

Variations due to interstellar scintillation caused by 


linear plasma filaments, just outside the Solar System

Similar to what seen for other IHV’s out to tens of pc

Origin of these filaments not clear.

J1402+5347 not consistent with cometary knots


associated with hot stars

Will continue to monitor…