Category Archives: Uncategorised

UTMOST publishes timing results for over 200 pulsars

 

A major part of UTMOST’s time on sky is spent observing pulsars — the extremely dense remnants of supernova explosions. Discovered just over 50 years ago, pulsars allow us to make tests of fundamental physical theory (such as relativity), examine the properties of dense matter, and map the properties of the ionised gas in the Milky Way and other galaxies, just to name a few.

UTMOST has now published our first results for timing the pulses of over 200 pulsars in the Southern Sky. Led by PhD student Fabian Jankowski — who now has a postdoctoral position at Manchester University — the project timed over 400 pulsars. For 205 of these (8 of which are in binaries, and 4 of which are millisecond pulsars) we publish updated timing models, together with their flux densities, flux density variability, and pulse widths at 843 MHz, derived from observations spanning between 1.4 and 3 years.

Screenshot_2018-12-13_12-12-02
Over 200 individual pulses from the pulsar J0820-1350, seen in this stacked image, showing the special property of drifting “sub-pulses”. UTMOST is has detected single pulses from more than 100 different pulsars, although most do not show such exotic behaviour.

The paper, which has been accepted for publication in the Monthly Notices of the Royal Astronomical Society, is available on the astrophysics archive.

Magnetar XTE J1810-197 seen in radio outburst

A magnetar is a highly magnetic neutron star — formed when a star ends its life in a supernova explosion.  They are the most magnetic objects known in the Universe.

“XTE J1810-197” is one such magnetar – it was discovered in 2006 by an X-ray satellite, and was picked up at a wide range of radio wavelengths as well. It was the first magnetar found to also exhibited pulsar-like behaviour. Over the following year it faded gradually away and become more and more difficult to pick up.

On December 8th 2018, observers in the UK using the Lovell telescope picked it up strongly as part of regular monitoring looking for just such an event. The reported the sudden intense change in its radio emission as an Astronomer’s Telegram.

PhD student Marcus Lower used UTMOST to observe the magnetar on December 12th 2018, and picked it up very strongly — sufficiently so to see many individual pulses as the magnetar rotates every 5 or so seconds.

J1809-1943_121218

The pulse from the magnetar is seen clearly running vertically through the plot, which shows intriguing fine structure which is typical of magnetars.

An Astronomer’s Telegram reporting our detection of XTE J1810-197 at low radio frequencies can be found here.

 

 

 

 

Two new FRBs discovered by UTMOST

At UTC 2018-10-16-04:16:56.3, we found a bright fast radio burst (FRB181016) as part of the ongoing search program (UTMOST), at the Molonglo telescope.

A second, unrelated FRB (FRB181017) was found the following day at UTC 2018-10-17-10:24:37.4 (2018-10-17.4337662).

Molonglo is a 1.6 km long East-West array (Bailes et al 2017) 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).

FRB181016 and FRB181017 were 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. 

FRB180116 : The dispersion measure (DM) that maximizes the signal-to-noise ratio is: 1984 pc cm^-3. The DM estimate of NE2001 model is ~90 pc cm^-3, and YMW16 model is ~69 pc cm^-3 at the position of the FRB, resulting in an intergalactic excess of ~1900 pc cm^-3. The upper limit on the DM-inferred redshift is thus z ~ 1.8.

An early estimate (lower limit) of the event’s apparent fluence is ~ 70 Jy ms (corrected for attenuation of the primary beam in the RA direction, but not in the Dec direction), width ~ 6.88 ms, with a detected signal-to-noise ratio = 20.

The most likely position is RA = 15:46:20.5, DEC = -25:24:32, J2000, Galactic: Gl = 345.51 deg, Gb = 22.67 deg. The 95% confidence localisation arc is as follows: (RA, DEC) in (hours, deg)

15.769447 -28.263972
15.769986 -27.763111
15.770511 -27.262250
15.771028 -26.761389
15.771531 -26.260500
15.772025 -25.759639
15.772508 -25.258778
15.772983 -24.757917
15.773447 -24.257028
15.773900 -23.756167
15.774344 -23.255306
15.774781 -22.754417
15.775206 -22.253556

A formula describing the localisation arc is:

RA = 15.768768 – 1.106528e-3*(DEC – 25.409019) – 2.038129e-05*(DEC – 25.409019)**2

Where RA is in hours, Dec is in deg, and is valid in the Dec [-29.8,-21.1]

Screenshot_2018-10-17_15-44-23

Dedispersed dynamic spectrum of FRB181016. A small amount of residual RFI is seen in the left half of the plot at a frequency of ~840-842 MHz, and is not part of the FRB.

localisation

Localisation plot for FRB181016, with the center of the localisation arc marked by the green cross. The telescope boresight position is marked by the blue cross.

 

FRB180117 : The dispersion measure (DM) that maximizes the signal-to-noise ratio is: 240 pc cm^-3. The DM estimate of NE2001 model is ~38 pc cm^-3, and YMW16 model is ~27 pc cm^-3 at the position of the FRB, resulting in an intergalactic excess of ~205 pc cm^-3. The upper limit on the DM-inferred redshift is thus z ~ 0.2.

An early estimate (lower limit) of the event’s apparent fluence is ~ 95 Jy ms (corrected for attenuation of the primary beam in the RA direction, but not in the Dec direction), width ~ 2.6 ms, with a signal-to-noise ratio = 66.

The most likely position is RA =22:05:55 , DEC = -08:50:30, J2000, Galactic: Gl =  50.5 deg, Gb = -47.0 deg. The 95% confidence localisation arc is as follows: (RA, DEC) in (hours, deg)

22.098256 -11.698444
22.098303 -11.197472
22.098350 -10.696472
22.098403 -10.195500
22.098456 -9.694500
22.098511 -9.193528
22.098569 -8.692528
22.098631 -8.191556
22.098692 -7.690556
22.098756 -7.189583
22.098822 -6.688583
22.098892 -6.187611

A formula describing the localisation arc is:

RA = 22.101947 +2.654839e-4*(DEC -8.943028) + 4.195246e-06*(DEC -8.9430278)**2

Where RA is in hours, Dec is in deg, and is valid in the Dec [-13.20,-4.68]

frb181017

Dedispersed dynamic spectrum of FRB181017

FRB20181017_localisation_2610649 (1)

Localisation plot for FRB181017, with the center of the localisation arc marked by the green cross. The telescope boresight position is marked by the blue cross.

Follow-up observations of the FRBs are encouraged.

FRB180528 – UTMOST’s 6th FRB

 

On 2018-05-28-04:24:00.9 UTC (2018-05-28.18334375), UTMOST found a new FRB (FRB180528) as part of the ongoing search program at the Molonglo Radio Telescope (see Bailes et al. 2017, arxiv.org/abs/1708.09619). This is the sixth Molonglo FRB overall (See Atel #10867, ATel #10697 and Caleb et al. 2017, MNRAS, 468, 3746). The FRB was discovered in real time, and voltage capture was successfully triggered (see Farah et al 2018, https://arxiv.org/abs/1803.05697).

The dispersion measure (DM) of the FRB is: 899 pc cm^-3, which is substantially in excess of the Galactic DM as estimated by the NE2001 (www.nrl.navy.mil/rsd/RORF/ne2001/) model (~69 pc cm^-3). The upper limit on the DM-inferred redshift z is thus z~0.7. The S/N in the detection beam is 14, and a preliminary estimate of the event’s fluence is ~ 18 +/- 4 Jyms. This is a lower limit as the event’s position is poorly constrained in the North-South direction within the primary beam. The FRB’s estimated width (full width half power) is 1.3 ms.

Source localisation is excellent in the Right Ascension (~ 5 arcsec at 1-sigma) but poor in Declination (~1.2 deg at 1-sigma). The most likely position is RA = 06:38:48.7, DEC = -49:53:59, J2000, Galactic: Gl = 258.87 deg, Gb = -22.35 deg. The 95% confidence localisation arc is as follows: (RA, DEC) in (hours,deg)

6.642039 -53.065500
6.642700 -52.664778
6.643347 -52.264056
6.643978 -51.863306
6.644594 -51.462583
6.645197 -51.061833
6.645786 -50.661083
6.646361 -50.260361
6.646925 -49.859611
6.647475 -49.458861
6.648014 -49.058139
6.648542 -48.657389
6.649056 -48.256639
6.649561 -47.855889
6.650056 -47.455139
6.650539 -47.054389
6.651011 -46.653667

A formula describing the localisation arc is:

RA = 6.39652461344 – 0.00642068726059*(DEC – 49.8996671717) – 3.9200674396e-05*(DEC -49.8996671717)**2

Where RA is in hours, DEC is in deg, and is valid in the DEC range [-54,-46].

2018-05-30

Waterfall plot for FRB180528.

FRB20180528_localisation_860559

Localisation plot for FRB180528, with the center of the localisation arc marked by the green square. The telescope boresight position is marked by the blue square. The positions of 3 pulsars are also marked.

 

 

 

 

Remarkable time and frequency structure in FRB170827

UTMOST has made the first ever discovery of an FRB with an automated system, enabling remarkable time and frequency structures to be seen in the event.

Screenshot_2018-03-21_12-49-33

The FRB occurred on 27th Aug 2017. It was the first one discovered by Swinburne University of Technology PhD student Wael Farah — who had trained the computers on-site at Molonglo observatory to recognise FRB candidates from the many sources of interference radio telescopes see. His software works so quickly that he is able to save the full time and frequency resolution data on the event for later analysis. This feat has never been acheived before for an initial detection of an FRB.

The data reveal remarkable time and frequency structure in the FRB (as seen above). The event has a complex profile in time — with at least three peaks in the emission clearly visible. It also has striking striations and patchiness in the emission as a function of the observing frequency.

Where does this patchiness in the FRB’s spectrum arise? It can be partly explained by the effect the Milky Way gas has on a pulse coming from the distant universe — as we think is the case for FRBs. But this can’t be the whole story, as the striations in the spectrum are so narrow that something else must be affecting the pulse. One possibility is that the striations are intrinsic to the source itself and are telling us about the still unknown mechanism that makes FRBs. They might also arise in the Intergalactic Medium — the tenuous ionised gas that lies between galaxies — and telling us about the properties of this gas as the pulse traverses space over hundreds of millions of years before reaching Earth.

A paper describing this remarkable FRB has been submitted to Monthly Notices of the Royal Astronomical Society.

Congratulations to Wael Farah for this very fine achievement!

UTMOST welcomes Cherie Day and Vivek Gupta

UTMOST is delighted to welcome two new PhD students, Cherie Day  and Vivek Gupta.

Cherie Day joins us from the University of California Berkeley, where she did a B.A. in Astrophysics. She has been closely involved with testing the prototype HERA dish/feed combination and antenna design work for HYPERION, and worked on exoplanet transits with SOFIA .

Vivek has an M.Tech. degree in Engineering Physics from the Indian Institute of Technology (Banaras Hindu University) Varanasi, and has worked as an intern with Dr. Joseph Lazio at CalTech (June- August 2016), characterizing variations in the dispersion measures of several pulsars observed by NANOGrav in its 9 year data release.

Cherie and Vivek are both going to work on the UTMOST-2D project with Adam Deller, Chris Flynn and Matthew Bailes, to bring accurate localisation on the sky of Fast Radio Bursts to the UTMOST project.

A very warm welcome to both our new PhD students!

 

FRB170922 – UTMOST finds the widest FRB yet

On 2017-09-22-11:23:33.4 UTC (2017-09-22.4746921296), UTMOST found a new FRB as part of the ongoing search program at the Molonglo Radio Telescope (see Bailes et al. 2017, arxiv.org/abs/1708.09619). This is the fifth Molonglo FRB overall (See ATel #10697 and Caleb et al. 2017, MNRAS, 468, 3746).

The optimal dispersion measure (DM) that maximizes the signal-to-noise ratio is: 1111 pc cm^-3, which is substantially in excess of the Galactic DM as estimated by the NE2001 (www.nrl.navy.mil/rsd/RORF/ne2001/) model (~ 45 pc cm^-3) and the YMW16 (www.xao.ac.cn/ymw16/) model (~ 33 pc cm^-3). The upper limit on the DM-inferred redshift is thus ~0.8. The S/N in the detection beam is 22, and an early estimate of the event’s fluence is ~ 60 +/- 15 Jy ms. The FRB’s estimated width (full width half power) is 26 ms.

Source localisation is excellent in the Right Ascension (~ 5 arcsec at 1-sigma) but poor in Declination (~1.2 deg at 1-sigma). The most likely position is RA = 21:29:50.61, DEC = -07:59:40.49, J2000, Galactic: Gl = 45.1°, Gb = -38.7°. The 95% confidence localisation arc is as follows:

21:29:50.50 -10:21:32.1
21:29:50.48 -09:52:40.9
21:29:50.49 -09:23:49.8
21:29:50.52 -08:54:58.6
21:29:50.56 -08:26:07.4
21:29:50.62 -07:57:16.2
21:29:50.63 -07:52:27.7
21:29:50.71 -07:23:36.5
21:29:50.81 -06:54:45.3
21:29:50.92 -06:25:54.1
21:29:51.06 -05:57:03.0
21:29:51.21 -05:28:11.8

A formula describing the localisation arc is:

RA = 21.500702 + 3.753954e-4*(DEC – 7.994579) + 1.053305e-5*(DEC – 7.994579)^2

Where RA is in hours, DEC is in deg, and is valid in the DEC range [-12.36,-3.63]

Follow-up observations of the FRB are encouraged.

 

Screen Shot 2017-10-20 at 10.13.50 AM

 

atelfrb5.localisationThe blue cross is the telescope pointing center; the green cross is the highest probability position of the FRB, and the line indicates the localisation arc.  Several low DM pulsars in the field of view are also seen in grey.

 

 

 

 

 

 

CAASTRO / Swinburne to host FRB workshop

On February 14-16, 2018, Swinburne University of Technology will host an international workshop entitled “FRB2018: Finding and Understanding Fast Radio Bursts“. The workshop will cover a broad range of FRB instrumentation and science, but with a particular focus on directions over the coming ~5 years, as the number of detected FRBs expands rapidly and their localisation becomes commonplace.

The key themes of the workshop will be:

Understanding FRB progenitors and their host environments.

This requires:
Real-time detection and localisation with interferometers.

Can we achieve these goals more effectively via:

Synergies between current facilities and/or identifying opportunities for existing facility upgrades?

Leading FRB researchers from FRB collaborations world-wide have been invited to present recent results and future directions, offering an opportunity to build and extend collaborations.

Registration is now open.

FRB170827 — first FRB detection with an automated system

On 2017-08-27-16:20:18 UTC (2017-08-27.68076389), we found a bright burst as part of the ongoing FRB search program (UTMOST), at the Molonglo telescope.

Molonglo is a 1.6 km long East-West array (see Bailes et al 2017) 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).

FRB170827 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. Using 300 ms of voltage data, we improved localisation of the FRB by repointing the array to different directions and maximising S/N.

The most likely position is RA = 00:49:18.66, DEC = -65:33:02.3, J2000. The optimal dispersion measure (DM) that maximizes the signal-to-noise ratio is: 176.4 pc cm^-3. The DM estimate of NE2001 model is ~37 pc cm^-3, and YMW16 model is ~27 pc cm^-3 at this position, resulting in an intergalactic excess of ~145 pc cm^-3, the lowest known. The upper limit on the DM-inferred redshift is thus ~0.15. An early estimate of the event’s fluence is ~ 20 Jy ms, width ~ 395 us, with a signal-to-noise ratio > 90.

The 95% confidence localisation arc is as follows:

00:50:09.05 -67:54:48.9
00:50:01.57 -67:35:35.5
00:49:54.31 -67:16:22.2
00:49:47.25 -66:57:08.7
00:49:40.40 -66:37:55.3
00:49:33.74 -66:18:41.9
00:49:27.27 -65:59:28.4
00:49:20.98 -65:40:14.9
00:49:14.85 -65:21:01.4
00:49:08.90 -65:01:47.8
00:49:03.09 -64:42:34.3
00:48:57.45 -64:23:20.7
00:48:51.95 -64:04:07.1
00:48:46.59 -63:44:53.5
00:48:41.36 -63:25:39.9
00:48:37.53 -63:11:14.7

A formula describing the localization arc is: DEC = -60.71088 -253.7786*(RA – 0.8) + 1480.220*(RA – 0.8)^2.
Where RA is in hours, Dec is in deg, and is valid in the RA range [0.84, 0.81].

Note that this localisation arc crosses through the SMC (Small Magellanic Cloud) if extended a further ~6 degrees, where we expect a beam attenuation of ~15 dB. We note that the measured DM of the FRB is similar to SMC pulsars.

frb170827

Screen Shot 2017-08-31 at 7.51.30 pm

UTMOST on the Science Show

Screenshot_2017-05-02_14-14-15

UTMOST PhD student –  and now a postdoc – Manisha Caleb, has appeared on the Science Show on the Australian national broadcaster (ABC) talking about the 3 Fast Radio Bursts (FRBs) she discovered with the Molonglo telescope.

UTMOST is an interferometer and places the point of origin of the FRBs well beyond the Earth — at least 10,000 km away.

http://www.abc.net.au/radionational/programs/scienceshow/

Link to the audio

For our news item on this story, see here