All posts by cflynn

North-South arm upgrade

The upgrade of the North-South arm of the Molonglo telescope — being carried out so that we can localise Fast Radio Bursts to their host galaxies — is well under way.

Five of the 11 “modules” (9 meter long receiver elements) are now in place on the arm, and data taking on two of them in full operation.

All five are expected to be taking data by the end of October 2020.

 
Dave Temby and Angus Sutherland doing final adjustments on a newly installed module.

 

 
Two solar powered battery units are in full operation powering the newly installed modules.

Five pulsars have been observed with the system to date — Vela, J0837-4135, J1644-4559, J1752-2806 and J1243-6423.

Profile of the bright Southern pulsar J1644-4559, as seen with a small section of the NS-arm at Molonglo.

Resurgence in the radio flux of the magnetar XTE J1810-197

Following its radio revival in late-2018 (Levin et al. 2019) we have performed regular timing observations of the magnetar XTE J1810-197 with the Molonglo Observatory Synthesis Telescope as part of the UTMOST project (Bailes et al. 2017).

A single bright pulse from XTE J1810-197 which reached S/N ~100.

During a recent observation on UTC 2020-06-22-14:02:29, we measured a period averaged flux density of 35 +/- 7 mJy at 835 MHz via the radiometer equation. This is approximately a factor of 2.7 times higher than the flux density of 13 +/- 5 mJy measured 5 days earlier on UTC 2020-06-17-14:22:07, and a factor of ~5 times higher than observations in February 2020. The radio intensity appears to have decayed to flux densities between 15-20 mJy in the days following the resurgence. All observations were calibrated to the flux density of the high dispersion measure pulsar PSR J1644-4559.

Flux density measurements for XTE J1810-197, showing a bright outburst in the radio flux.

Bright single pulses with peak flux densities up to 50 +/- 15 Jy were detected in most post-resurgence observations.

Further details are available in an Astronomer’s Telegram.

Molonglo telescope’s two arms working in unison again

June 2020 : both arms of the Molonglo telescope have been brought into simultaneous operation for the first time in decades, as part of the hunt for host galaxies of Fast Radio Bursts.

Molonglo consists of two “arms” — each 1.6 km long and 11 meters wide, and aligned in the North-South and East -West directions, in a flat valley near the town of Bungendore in southern New South Wales.

The East-West arm of the telescope has been in full operation after a major upgrade 5 years ago, in a collaboration between the Swinburne University of Technology and the University of Sydney.

In 2019-2020, the long dormant North-South arm is being brought back into full operation in the UTMOST-2D project.

Observations of a bright quasar — a black hole in the center of a distant galaxy — showed a strong signal on both arms in first tests of the newly mounted North-South arm receivers in June 2020.

The quasar shows up in the signal collected on both arms as a strong peak as the source transited overhead, in observations coordinated by PhD student Vivek Gupta.

The observation shows that the project is well on the way to being able to make images of a few square degree region of the sky (about 10 times the size of the full Moon) — something that has not been done at Molonglo since the SUMSS survey in the 1990s — and eventually to localise FRBs to their host galaxies.

Congrats to the whole UTMOST-2D team for this milestone achievement!

A 9 meter long element of the North-South arm upgrade being positioned on the telescope.

FRB200607 found by UTMOST

At UTC 2020-06-07-10:37:21.7 (2020-06-07.442612269), we found a bright 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).

FRB200607 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: 466.9 pc cm^-3. The DM estimate of NE2001 model is ~30 pc cm^-3, and YMW16 model is ~25 pc cm^-3 at this position, resulting in an intergalactic excess of ~439 pc cm^-3. The upper limit on the DM-inferred redshift is thus z ~ 0.40.

An early estimate (lower limit) of the event’s apparent fluence is ~ 51 Jy ms (corrected for attenuation of the primary beam in the RA direction, but not in the Dec direction), width ~ 1.3 ms, with a detection signal-to-noise ratio = 41.

The most likely position is RA = 13:41:30.65, DEC = -05:08:24.1, J2000, Galactic: 325.4 deg, Gb = 55.5 deg. The 95% confidence localisation arc is as follows: (RA, DEC) in (hours, deg)

A formula describing the localisation arc is:

RA = 13.691826 + 1.106710e-04*(DEC + 5.204167) + 7.531360e-06*(DEC + 5.204167)**2

13.691603 -7.608750
13.691628 -7.288139
13.691653 -6.967528
13.691681 -6.646917
13.691711 -6.326306
13.691742 -6.005694
13.691775 -5.685083
13.691808 -5.364472
13.691844 -5.043861
13.691881 -4.723250
13.691919 -4.402639
13.691958 -4.082028
13.692000 -3.761417
13.692044 -3.440806
13.692089 -3.120194
13.692136 -2.799583

where RA is in hours, Dec is in deg, and is valid in the Dec range [-7.6,-2.8]

Follow-up observations of the FRB are encouraged. 

FRB200514 found by UTMOST

At UTC 2020-05-14-05:40:45.7 (2020-05-14.23664005), 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).

FRB200514 was found during a blind FRB search programme in real-time using an automated GPU-accelerated/machine learning-based pipeline. Unfortunately, raw voltages were not recorded and so we were unable to analyse the FRB at native time resolution.

The optimal dispersion measure (DM) that maximizes the signal-to-noise ratio is: 349.4 pc cm^-3. The DM estimate of NE2001 model is ~85.3 pc cm^-3, and YMW16 model is ~228.2 pc cm^-3 at this position, resulting in an intergalactic excess of ~193 pc cm^-3. The upper limit on the DM-inferred redshift is thus z ~ 0.18.

An early estimate (lower limit) of the event’s apparent fluence is ~11 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 = 9.8.

The most likely position is RA = 07:01:00.55, DEC =-45:54:25.0, J2000, Galactic: Gl = 256.1140 deg, Gb = -17.5560 deg. The 95% confidence localisation arc is as follows: (RA, DEC) in (hours, deg).

7.008703 -50.264306
7.009736 -49.763472
7.010744 -49.262639
7.011722 -48.761806
7.012675 -48.260944
7.013600 -47.760111
7.014503 -47.259250
7.015381 -46.758417
7.016236 -46.257556
7.017067 -45.756694
7.017878 -45.255833
7.018669 -44.754972
7.019439 -44.254111
7.020186 -43.753222
7.020919 -43.252361
7.021631 -42.751500
7.022325 -42.250611
7.023000 -41.749750

A formula describing the localisation arc is:

RA = 7.016655 + 1.673513e-3*(DEC + 46.007086) – 4.428062e-05*(DEC + 46.007086)**2

where RA is in hours, Dec is in deg, and is valid in the range Dec= [-50.3,-41.7]

Follow-up observations of the FRB are encouraged.

FRB200508 found by UTMOST

At UTC 2020-05-08-07:42:09.5 (2020-05-08.320943), 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).

FRB200508 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: 629 pc cm^-3. The DM estimate of NE2001 model is ~144.9 pc cm^-3, and YMW16 model is ~248.2 pc cm^-3 at this position, resulting in an intergalactic excess of ~433 pc cm^-3. The upper limit on the DM-inferred redshift is thus z ~ 0.39.

An early estimate (lower limit) of the event’s apparent fluence is ~29.7 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 = 14.33.

The most likely position is RA = 09:01:32.39, DEC =-65:35:42.7, J2000, Galactic: Gl = 282.02095755 deg, Gb = -12.5633715542 deg. The 95% confidence localisation arc is as follows: (RA, DEC) in (hours, deg).

9.083156 -69.939722
9.075233 -69.440667
9.067694 -68.941528
9.060517 -68.442306
9.053669 -67.943000
9.047136 -67.443611
9.040892 -66.944167
9.034922 -66.444667
9.029211 -65.945083
9.023739 -65.445472
9.018492 -64.945806
9.013458 -64.446083
9.008628 -63.946306
9.003986 -63.446500
8.999522 -62.946667
8.995228 -62.446778
8.991094 -61.946833
8.987114 -61.446889

A formula describing the localisation arc is:

RA = 9.026409 – 1.1189104e-2*(DEC + 65.69456) + 4.823077e-4*(DEC + 65.69456)**2

where RA is in hours, Dec is in deg, and is valid in the range Dec= [-61.5, -70]

Follow-up observations of the FRB are encouraged.


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.