All posts by cflynn

Frame dragging seen in a pulsar-white dwarf binary

A prediction of Einstein’s general theory of relativity is that a body that is spinning  has the capacity to “drag” space-time around with it.

A pair of stars known as PSR J1141-6545, consisting of a pulsar and a white dwarf, have been observed for several decades at the Parkes Radio telescope by a team lead by Prof Matthew Bailes. Molonglo has been observing the system for the last three years as well.

Artist’s view of a white dwarf (central blue object) and a pulsar (purple, with beams of radiation being emitted). The pulsar has a 4.8 hour orbit. Very accurate timing of the pulsar’s pulses with the Parkes Radio Telescope, and for the last three years with Molonglo, have shown that the white dwarf is dragging space time around with it, as predicted by General Relativity. Credit Mark Myers / Swinburne University of Technology

PhD student at Swinburne University of Technology, Vivek Venkatraman Krishnan has processed these data for his PhD thesis. Now a postdoctoral fellow at the Max Planck Institute for Radio Astronomy in Bonn, Vivek published his ground-breaking results in Science magazine this week.

Vivek has been able to show that frame-dragging by the white dwarf is affecting the orbit of the two stars around each other, by using the amazingly accurate clock in the system provided by the pulsar.

Timing residuals — or the accuracy of the match between a physical model for the binary system and the observational data — shown for Parkes (red, orange, purple and blue symbols, for different instruments used on the telescope) and Molonglo (green symbols) over the last few decades.

“Vivek achieved extraordinary things during his PhD at Swinburne University of Technology. He was part of the team that refurbished the Molonglo telescope back to full operations, and wrote a highly configurable software application that converted Molonglo to a fully-automated robotic system, so that we could observe this pulsar, and hundreds more besides, on a near daily basis. And what a remarkable use he has put all this hard work to, by detecting a very rare phenomenon via observations of this binary system” says Dr. Chris Flynn, who was one of Vivek’s supervisors.

Another of Vivek’s supervisors, Dr Evan Keane of the SKA organisation says : “Pulsars are super clocks in space. Super clocks in strong gravitational fields are Einstein’s dream laboratories. We have been studying one of the most unusual of these in this binary star system. Treating the periodic pulses of light from the pulsar like the ticks of a clock we can see and disentangle many gravitational effects as they change the orbital configuration, and the arrival time of the clock-tick pulses. In this case we have seen Lens-Thirring precession, a prediction of General Relativity, for the first time in any stellar system.”


Artist’s depiction of a neutron star orbiting a rapidly-spinning white dwarf. The white dwarf’s spin drags the very fabric of space-time around with it, causing the orbit to tumble in space. Credit: Mark Myers, OzGrav ARC Centre of Excellence/Swinburne University of Technology

Read more about this remarkable source at the Conversation in an article by Matthew Bailes and Vivek Venkatraman Krishnan.

Read the Science article “Lense–Thirring frame dragging induced by a fast-rotating white dwarf in a binary pulsar system“, by Venkatraman Krishnan et alia 2020

School of Cosmic Explosions visits UTMOST

As part of the ANITA school on cosmic explosions, we were delighted to host about 25 students, postdocs and staff on 5th Feb 2020 as part of the the 14th annual ANITA meeting (held at ADFA in Canberra Australia).



Swinburne researcher Dr. Chris Flynn demonstrated the telescope making live of observations of pulsars and spoke on our discoveries of fast radio bursts.

Tim Bateman spoke on the real world radio engineering and high speed data processing requirements of an active research site, and our extensive upgrade UTMOST-2D, which is bringing an order of magnitude improvement in performance.

ANITA is the Australian National Institute for Theoretical Astrophysics, and is part of the Astronomical Society of Australia.

Work begins on the UTMOST-2D outriggers and dense core upgrade at Molonglo

UTMOST is currently being upgraded to UTMOST-2D — by bringing the long retired North-South arm of the array back into operations.

View of the North-South arm, looking Southward

A completely new design for the antennas, amplifiers, signal transport and digitization has been built and tested over the last 12 months.

Dave Temby and Glenn Urquhart positioning an “outrigger” module at the far end of the South arm.

In the third week of Janauary 2020 we had a crane on site all day, positioning two completed “outrigger” modules on the far ends of the North-South arm, and removing 6 modules near the center of the array for stripping and fitting with the new detectors.

The weather was kind to us — clear skies, not too hot and (very importantly) not windy!

One of the new “cassettes”, a 1.4 meter length of 8 dual pole 4-leaf clover antennas is shown below: 6 of these cassettes make a module, one of which is being put into position in the photo above.

An eight element dual-pole cassette — antenna side.
Back of a cassette, showing the 8 LNAs (low noise amplifiers) for each of the 8 antennas, and 2 beamformers (one for each polarisation).
Two of 6 modules have been taken down for stripping and installation of the new electronics and feed elements. Six adjacent modules will form a “dense core” near the center of the array, to be used initially with two outrigger modules at either end of the North-South arm.

FRB191223 found by UTMOST

At UTC 2019-12-23-04:55:31.2 (2019-12-23.205222222), we found a fast radio burst as part of the ongoing search program (UTMOST), at the Molonglo telescope.

Molonglo is a 1.6 km long East-West array (Bailes et al 2017, PASA, 34, 45) and was operating in drift-scan mode, pointing at the meridian at the time of detection. Source localisation is excellent in Right Ascension (5 arcsec at 1-sigma) but poor in Declination (~1.2 deg at 1-sigma) (see Caleb et al 2017 MNRAS 468, 3746).

FRB191223 was found during a blind FRB search programme in real-time using an automated GPU-accelerated/machine learning-based pipeline and the raw voltages were recorded for offline processing.

The optimal dispersion measure (DM) that maximizes the signal-to-noise ratio is: 665 pc cm^-3. The DM estimate of NE2001 model is ~60.0 pc cm^-3, and YMW16 model is ~45 pc cm^-3 at this position, resulting in an intergalactic excess of ~605 pc cm^-3. The upper limit on the DM-inferred redshift is thus z ~ 0.55.

An early estimate (lower limit) of the event’s apparent fluence is ~108.1 Jyms (corrected for attenuation of the primary beam in the RA direction, but not in the Dec direction), with a detection signal-to-noise ratio = 29.4.

The most likely position is RA = 20:34:14.14, DEC = -75:08:54.19, J2000, Galactic: Gl = 318.854777 deg, Gb = -32.6614779 deg. The 95% confidence localisation arc is as follows: (RA, DEC) in (hours, deg)

20.498042       -77.518750
20.505189       -77.319778
20.512114       -77.120750
20.518828       -76.921667
20.525339       -76.722556
20.531658       -76.523417
20.537792       -76.324222
20.543747       -76.125028
20.549533       -75.925778
20.555156       -75.726472
20.560625       -75.527167
20.565942       -75.327833
20.571117       -75.128444
20.576153       -74.929056
20.581058       -74.729639
20.585833       -74.530194
20.590489       -74.330722
20.595025       -74.131222
20.599447       -73.931694
20.603761       -73.732167
20.607969       -73.532611
20.612075       -73.333028
20.616083       -73.133444
20.619994       -72.933806
20.623817       -72.734194

A formula describing the localisation arc is:

RA = 20.571174 + 2.61223e-2*(DEC + 75.127624) -1.79263e-3*(DEC + 75.127624)**2

where RA is in hours, DEC is in deg, and is valid in the range DEC = [-73, -77].

UTMOST finds first known glitch in the pulsar J0908-4913

PhD student  Marcus Lower has found the first detected glitch in the pulsar PSR J0908-4913 using UTMOST.

Pulse profile for J0908-4913.

Glitches can be caused by either “star quakes” in the neutron star that cause the surface to crack, or by the (normally frictionless) superfluid core interacting with the crust. They result in a sudden change in the spin period of the pulsar, which causes the pulsar’s radio pulses to arrive slightly earlier than normal. Their discovery is one of the major science drivers at UTMOST, as they are one of the only ways we can “see” the insides of neutron stars.

Timing residuals of the pulsar PSR J0908-4913 before (top) and after (bottom) fitting for the glitch. Credit: Marcus E. Lower.

For more information:

http://spaceaustralia.com/feature/pulsar-glitches-after-30-years

Research Notes of the AAS :

Detection of a Glitch in PSR J0908-4913 by UTMOST by Lower et al 2020.

 

FRB191107 found by UTMOST

At UTC 2019-11-07-18:55:36.7 (2019-11-07.788619213), we found a fast radio burst as part of the ongoing search program (UTMOST), at the Molonglo telescope.

Molonglo is a 1.6 km long East-West array (Bailes et al 2017, PASA, 34, 45) and was operating in drift-scan mode with pointing centred on the meridian at the time of detection. Source localisation is excellent in Right Ascension (5 arcsec at 1-sigma) but poor in Declination (~1.2 deg at 1-sigma) (see Caleb et al 2017 MNRAS 468, 3746).

FRB191107 was found during a blind FRB search programme in real-time using an automated GPU-accelerated/machine learning-based pipeline and the raw voltages were recorded for offline processing.

The optimal dispersion measure (DM) that maximizes the signal-to-noise ratio is: 714.25 pc cm^-3. The DM estimate of NE2001 model is ~127.2 pc cm^-3, and YMW16 model is ~145.9 pc cm^-3 at this position, resulting in an intergalactic excess of ~587 pc cm^-3. The upper limit on the DM-inferred redshift is thus z ~ 0.53.

An early estimate (lower limit) of the event’s apparent fluence is ~6.7 Jy ms (corrected for attenuation of the primary beam in the RA direction, but not in the Dec direction), with a detection signal-to-noise ratio = 23.3.

The most likely position is RA = 08:01:57.077, DEC = -13:44:15.52, J2000, Galactic: Gl = 233.396 deg, Gb = 8.829 deg. The 95% confidence localisation arc is as follows: (RA, DEC) in (hours, deg)

8.032725 -16.092056
8.032589 -15.591111
8.032458 -15.090167
8.032333 -14.589250
8.032211 -14.088306
8.032094 -13.587361
8.031986 -13.086417
8.031881 -12.585472
8.031778 -12.084528
8.031683 -11.583583
8.031592 -11.082639

A formula describing the localisation arc is:

RA = 8.032153 – 2.313314e-4*(DEC + 13.837823) + 1.009132e-05*(DEC + 13.837823)**2

where RA is in hours, Dec is in deg, and is valid in the range Dec = [-17.1, -10.6].

FRB190806 found by UTMOST

At UTC 2019-08-06-17:07:58.0 (2019-08-06.7138657407), we found a fast radio burst as part of the ongoing search program (UTMOST), at the Molonglo telescope.

Molonglo is a 1.6 km long East-West array (Bailes et al 2017, PASA, 34, 45) and was operating in drift-scan mode with pointing centred on the meridian at the time of detection. Source localisation is excellent in Right Ascension (5 arcsec at 1-sigma) but poor in Declination (~1.2 deg at 1-sigma) (see Caleb et al 2017 MNRAS 468, 3746).

FRB190806 was found during a blind FRB search programme in real-time using an automated GPU-accelerated/machine learning-based pipeline and the raw voltages were recorded for offline processing.

FRB190806

The optimal dispersion measure (DM) that maximizes the signal-to-noise ratio is: 388.5 pc cm^-3. The DM estimate of NE2001 model is ~30.8 pc cm^-3, and YMW16 model is ~21.57 pc cm^-3 at this position, resulting in an intergalactic excess of ~357.7 pc cm^-3. The upper limit on the DM-inferred redshift is thus z ~ 0.32.

An early estimate (lower limit) of the event’s apparent fluence is ~46.8 Jy ms (corrected for attenuation of the primary beam in the RA direction, but not in the Dec direction), width ~ 11.96 ms, with a detection signal-to-noise ratio = 14.4.

The most likely position is RA = 00:02:21.38, DEC = -07:34:54.6, J2000, Galactic: Gl = 89.92 deg, Gb = –67.25 deg. The 95% confidence localisation arc is as follows: (RA, DEC) in (hours, deg)

0.038811 -9.936472
0.038914 -9.435500
0.039014 -8.934500
0.039114 -8.433500
0.039211 -7.932528
0.039306 -7.431528
0.039397 -6.930528
0.039489 -6.429556
0.039578 -5.928556
0.039664 -5.427556
0.039750 -4.926583

A formula describing the localisation arc is:

RA = 0.03926 + 0.000189*(DEC +7.68202) – 4.01486e-06*(DEC +7.68202)**2

where RA is in hours, Dec is in deg, and is valid in the range Dec = [-11.94,-3.42].

FRB_localisation

Real-time detections of 5 Fast Radio Bursts

 

BREAKING NEWS

03/08/19 Five FRBs now published in Monthly Notices of the Royal Astronomical Society

Fast-radio-burst

An artist’s impression of the fast radio burst detected on October 17 2018 at the Molonglo Radio Telescope near Canberra, Australia. Credit: James Josephides/Swinburne

Swinburne Press Release:

https://www.swinburne.edu.au/news/latest-news/2019/08/swinburne-uses-ai-to-detect-fast-radio-bursts-in-real-time.php

Link to the Journal article:

https://academic.oup.com/mnras/article-abstract/488/3/2989/5528327?redirectedFrom=fulltext

 

 

 

SMIRF — the “Survey for Magnetars, Intermittent pulsars, RRATs and FRBs” at UTMOST

SMIRF is the “Survey for Magnetars, Intermittent pulsars, RRATs and FRBs” running at the Molonglo Radio Telescope.

Led by Swinburne PhD student (now a postdoctoral fellow at the MPIfR in Bonn), Vivek Venkatraman Krishnan, the survey has set new records in real-time searches for transient phenomena in the radio region of spectrum.

Screenshot_2019-05-07_11-29-10The regions of the southern sky surveyed by SMIRF, showing pulsar timing, search regions for new pulsars and intermittant pulsars, for new Fast Radio Bursts (FRBs) — and following up known FRBs.

SMIRF makes use of the huge field of view of the Molonglo telescope to search large swathes of sky, while also using the high spatial resolution of the 1.6 km long telescope array to detect transient sources within the surveyed regions. Seaches for transient phenomena at radio wavelengths have rarely used arrayed telescopes in this manner before, but rather made use of very sensitive single dish telescopes with relatively tiny fields-of-view.

SMIRF has the capacity to survey the entire Southern arc of the Milky Way for variable and transient radio sources every 10 days. Typically, surveys making such a large area sweep across the sky are only undertaken once in a decade. SMIRF has the capacity to undertake such surveys many times per year. As part of his PhD thesis, Vivek also implemented into SMIRF fully autonomous operation of the telescope, so that it decides which regions of sky to survey under robotic control.

Regularly and frequently surveying the sky is the key to discovering and understanding intermittancy in pulsars. Over the 5 decades since the discovery of pulsars, several thousand have been isolated and characterised in search programs at radio telescopes around the world. In the last decade or so, about 50 of these have been identified as highly variable — disappearing for months at a time and only occasionally being “on” — or giving off occasional and quite sporadic single pulses of radio energy as they only indicator of their presence.

The small numbers of such pulsar related sources is most likely a consequence of the difficulty in finding them, rather than small numbers per se. Regular and frequent scanning of the Milky Way galaxy is the key to finding many more of them, characterising their properties, and working out their relationship to the much better studied pulsars.

This is where the SMIRF program excels. PhD student Vivek Venkatraman Krishnan implemented the processing engine that runs on the telescope’s high-performance computing cluster on 56 Graphics Processing Units (GPUs). Processing 22 gigabytes of data per second, it can use the stream of digitized radio data to make timing measurements of the known pulsars in the field of view, search for new pulsars using Fast Fourier Transform techniques, while also operating commensally with the faccility’s Fast Radio Burst discovery program. It represents the state-of-the-art in such techniques, and presages the capacity required to make such searches with coming large scale facilities such as the SKA (Aquare Kilometer Array), which will use similar techniques.

The survey has found a new intermittant pulsar, seen in the plots below (showing the phase of the pulsar versus time, and the phase versus frequency):

Screenshot_2019-05-08_20-00-52

Two examples of single pulses produced by the newly found intermittant pulsar found are shown below:

Screenshot_2019-05-07_11-45-58

Around a dozen pulses from the new source were detected over the  course of 20 minutes, leading to good characterization of the source properties as an intermittant pulsar.

The first SMIRF paper, which gives a full system description overview and initial results, has been submitted to the Monthly Notices of the Royal Astronomical Society, and is available as a preprint.

FRB190322 found by UTMOST

At UTC 2019-03-22-07:00:12.3 (2019-03-22.29180903), we found a fast radio burst as part of the ongoing search program (UTMOST), at the Molonglo telescope.

FRB20190322_BEAM_245_193259

Molonglo is a 1.6 km long East-West array (Bailes et al 2017, PASA, 34, 45) and was operating in drift-scan mode with pointing centred on the meridian at the time of detection. Source localisation is excellent in Right Ascension (5 arcsec at 1-sigma) but poor in Declination (~1.2 deg at 1-sigma) (see Caleb et al 2017 MNRAS 468, 3746).

FRB190322 was found during a blind FRB search programme in real-time using an automated GPU-accelerated/machine learning based pipeline and the raw voltages were recorded for offline processing.

The optimal dispersion measure (DM) that maximizes the signal-to-noise ratio is: 724.2 pc cm^-3. The DM estimate of NE2001 model is ~47.1 pc cm^-3, and YMW16 model is ~46.78 pc cm^-3 at this position, resulting in an intergalactic excess of ~677 pc cm^-3. The upper limit on the DM-inferred redshift is thus z ~ 0.6.

An early estimate (lower limit) of the event’s apparent fluence is ~16 Jy ms (corrected for attenuation of the primary beam in the RA direction, but not in the Dec direction), width ~ 1.35 ms, with a detection signal-to-noise ratio = 12.

The most likely position is RA = 04:46:14.45, DEC = -66:55:27.8, J2000, Galactic: Gl = 278.166 deg, Gb = -36.921 deg. The 95% confidence localisation arc is as follows: (RA, DEC) in (hours, deg)

4.745128 -70.779222
4.749025 -70.278667
4.752725 -69.778056
4.756242 -69.277444
4.759589 -68.776806
4.762778 -68.276167
4.765822 -67.775500
4.768725 -67.274806
4.771503 -66.774111
4.774158 -66.273417
4.776700 -65.772694
4.779136 -65.271972
4.781472 -64.771222
4.783714 -64.270500
4.785867 -63.769722
4.787936 -63.268972
4.789925 -62.768194

A formula describing the localisation arc is:

RA = 4.7701477 + 5.677894e-3*(DEC + 67.024292) – 2.568521e-4*(DEC + 67.024292)**2

where RA is in hours, Dec is in deg, and is valid in the Dec [-71.3,-62.8]

For the dynamic spectra, and the localisation plots, follow this link.

Follow-up observations of the FRB are encouraged.