Radio pulsar studies in Poland and prospects for the POLFAR - - PowerPoint PPT Presentation

Radio pulsar studies in Poland and prospects for the POLFAR telescopes.

Wojciech Lewandowski Janusz Gil Institute for Astronomy, University of Zielona Góra

Pulsar Group at the Janusz Gil Institute of Astronomy

• Prof. Giorgi Melikidze

Dr hab. Jarosław Kijak Dr hab. Wojciech Lewandowski Dr Andrzej Szary Dr Krzysztof Maciesiak PhD students Karolina Rożko Olga Koralewska Collaborators: Dipanjan Mitra (NCRA Pune, India) Rahul Basu (IUCAA Pune, India) Yashvant Gupta (NCRA Pune, India) Axel Jessner (MPIfR, Bonn) Duncan Lorimer (West Virginia U.) Kaustubh Rajwade (WVU/Manchester Univ.)

Main Topics of study:

• Pulsar radio emission mechanism – observations and theory
• Pulsar spectra
• Iinterstellar medium (ISM) studies using pulsar observations

Studies of the pulsar emission mechanism using single pulse analysis

PSR B1857-26, Mitra & Rankin (2004) Edwards & Stappers (2002)

Characteristics of single pulses:

• Drifting subpulses
• Large/giant pulses
• Nulling

van Leeuwen et al. (2002)

Characteristic periodicities:

• P2 – distance

between subpulses

• P3 – subpulse re-

appearance at the same phase

• P4 – carousel

rotation time (?)

P2 P3 P4

Fourier Based methods used to analyse pulse stacks: Longitude Resolved Fluctuation Spectrum (LRFS)

From: Meterwavelength Single-pulse Polarimetric Emission Survey. II. The Phenomenon of drifting Subpulses; Basu, Mitra, Melikidze, Maciesiak, Skrzypczak, Szary, ApJ, (2016)

Important results: the P3 – luminosity dependence

Result from MSPES: pulsars with luminosities above a certain limit (right side of the picture) would have P3 lower than 1 pulse period – which is undetectable due to the aliasing effect (Basu et al., 2016)

Observations of PSR B1133+16 (8 GHz Effelsberg Data)

~30 P1 periodicity visible in both fluctuation spectrum as well as in the periodic nulls.

From: Single-pulse analysis of PSR B1133+16 at 8.35 GHz and carousel circulation time, Honnappa, Lewandowski, Kijak et a. MNRAS (2012)

LRFS Periodic null folding

Pulsar magnetosphere studies – Partially Screened Gap in a non-dipole polar cap

More details of the model in the next talk by Andrzej Szary From: Two modes of Partially Screened Gap, Szary, Melikidze and Gil, ApJ, 2015

Most pulsars radio spectra can be described by a single power-law with a an average spectra index of a = -1.8 (Maron et al. 2000) or a = -1.60 (Jankowski et al., 2018)

• 2. Pulsars spectra study

Distribution of puslar spectra indices from Jankowski et al. (2018) – Spectral properties of 441 radio pulsars

What are the Gigahertz-Peaked Spectra pulsars?

Timeline: 1995 – Lorimer et al., spectra of 280 pulsars, some of them nearly flat 2000 – Maron et al. - an extension of the above with new observations. Pulsars with broken spectra, a hint of a high frequency beaks 2007 – Kijak et al. – two pulsars with a high frequency turn-overs 2011 – Kijak et al. - another three objects with a turn-over above 1 GHz. The name Gigahertz-Peaked Spectra pulsars (GPS) was introduced. A few percent of sources were classified as "broken spectra" – two power-laws, steeper spectra at higher frequencies

Kijak, Lewandowski, Maron, Gupta, Jessner, 2011, A&A, 521 A16 Kijak, Dembska, Lewandowski, Melikidze, Sendyk, 2011, MNRAS, 418, L114

These objects:

• tend to adjoin various peculiar

surroundings, i.e. PWNe and dense HII regions

• preffer large DMs
• are usually relatively young

2013 – Kijak et al. – based on literature data: two radio magnetars with GPS! 2013 – Allen et al. – PSR J2007+2722 (Einstein@Home X-ray discovery) – spectrum peaks at 1.5 GHz

• 2014. 2015 – Dembska et al. – PSR J1740+1000

2015 – Lewandowski et al. – SgrA* radio-magnetar is a GPS source 2017 – Kijak et al. – 17 known GPS pulsars; 2018 – Jankowski et al. (2018) – another four GPS pulsars in the study of the spectra of 441 sources

Kijak, Tarczewski, Lewandowski, Melikidze, 2013, ApJ, 722, 4

What causes the GPS phenomenon? PSR B1259-63 may hold a key to the puzzle. A pulsar-Be star binary with a long-period (1237 day), eccentric orbit (e=0.87). Be stars are known to have strong stellar wind, both equatorial and polar. The disk formed from the equatorial wind causes the pulsar eclipses. Thermal absorption in the polar wind may be enough to cause B1259-63 spectra to bend.

Kijak, Dembska, Lewandowski, Melikidze, Sendyk, 2011, MNRAS, 418, L114

The radio spectrum evolves with the orbital phase.

PWN simulation (Bucciantini, 2002, A&A, 387, 1066)

How does B1259-63 relate to isolated GPS pulsars? Pulsars in or behind HII regions: same case as B1259-63, only the matter is lower density, but the several-parsec sizes make up for it. (this is true in the case of GPS pulsar B1054-62) Pulsar Wind Nebulae – may they cause similar effects? Seems that some PWNs may have large enough densities (up to ne=2000 cm-3) and sizes (up to 1 parsec) for the thermal free-free absorption to kick in. SNR filaments which may by another candidate (densities up to 8000 cm-3) and sizes up to a fraction of a parsec.

No GPS Weak GPS/broken spectrum (?)

GPS?

Lewandowski, Rożko, Kijak, Melikidze (2015).

Comet-shaped Pulsar Wind Nebulae

PWN structure from Buccantini et al. (2002)

The current state of GPS pulsar studies:

Around 30 sources known including 3 of 5 known radio-magnetars: 17 + 5 published (Kijak et al. 2017 + Allen et al., 2013, Jankowski et al. 2017), 8 in press, 5- 8 good candidates that require some additional observations

A sample of 4 GPS pulsars from Kijak et al., ApJ, 2017

Two radio-magnetars with GPS.

Spectral modeling: Optical depth: Free fit parameters: A – pulsar intrinsic flux scale a – intrinsic pulsar spectra index B – frequency-independent optical depth parameter Modeling of the spectra provides constrains on the physical parameters of potential absorbers.

Interesting GPS neutron stars: SgrA* magnetar (SGR J1745-2900)

Outburst on April 26, 2013, visible as radio pulsar until 2017(?) Picture: NASA, Chandra X-ray Observatory Radio pulse profiles from Thorne, Eatough et al. (2015)

Modeled spectra of SGR J1745-2900 using:

• Absorption in the expanding shell of an outburst
• External absorption: Ne = 290 cm-3, S = 1.5 pc, T= 100 K

Expanding shell:

• Density decreasing like 1/r2

(1/t2 assuming constant expansion velocity)

• Temperature decreasing

like t-1

• Required initial density:

2∙104 of Goldreich-Julian co-rotation density

• Initial temperature: 109 K

Absorption parameters on May 1st:

• T = 900 K,
• Ne = 7∙105 cm-3,
• d = 0.7 light-day (6∙10-4 pc)

Lewandowski et al. 2015

Spectral data from ATCA (8- 20 GHz (Shannon & Johnston 2013)

Lewandowski et al. (2013), MNRAS

Scattering is frequency dependant, and is clearly more noticeable at lower frequencies. This frequency dependance gives us a way to estimate the energy spectrum of the turbulence in the ISM. For Kolmogorov's turbulence spectrum (b=11/3) the expected a=4.4.

• 3. The study of Interstellar Medium: Interstellar Scattering

Until 2013: multi-frequency scattering and scintillation observations available

• nly for 27 objects (out of 2400 pulsars

known). Scatter time frequency scaling index vesrus the dispersion measure.

Theory predicts the values of α between 4.0 (the critical spectrum) and 4.4 (Kolmogorov's spectrum). Most of the pulsars lie beyond this range, and lower values of α dominate! Strangely, the average values for the whole population are relatively close to 4.0.

Only for sources with the largest DM (the most distant objects) a significant deviation can be seen.

Until 2013: multi-frequency scattering and scintillation observations available

• nly for 27 objects (out of 2400 pulsars

known). Scatter time frequency scaling index vesrus the dispersion measure.

Theory predicts the values of α between 4.0 (the critical spectrum) and 4.4 (Kolmogorov's spectrum). Most of the pulsars lie beyond this range, and lower values of α dominate! Strangely, the average values for the whole population are relatively close to 4.0.

Only for sources with the largest DM (the most distant objects) a significant deviation can be seen.

Normalized amount of scattering versus disperssion measure (DM). Why are the scintillation based measurements lower than the trend indicated by the scattering estimates? Is the theoretical scatter time versus decorrelation bandwidth relation true? For two pulsars (the Vela pulsar and PSR B1933+16) we have both the scattering based and the scintillation based measurements.

They indicate C1≈5 !

?

The amount of scattering (cont.)

Lewandowski, Dembska, Kijak, Kowalinska (2013) Lewandowski, Kowalińska, Kijak (2015a) Lewandowski, Rożko, Kijak, Bhattacharya, Roy (2015b)

LOFAR in Poland is already working and observing pulsars!

Members of the POLFAR consortium imvolved in pulsar

• bservations using polish LOFAR Statiions:

UZ, Zielona Góra: Jarosław Kijak, Wojciech Lewandowski, Marek Sendyk UWM, Olsztyn: Andrzej Krankowski, Leszek Błaszkiewicz, Tomasz Sidorowicz UJ, Kraków: Krzysztof Chyży, Marian Soida, Bartosz Śmierciak, Małgorzata Curyło CBK Warszawa: Hanna Rothkaehl, Mariusz Pożoga, Barbara Matyjasik

LOFAR in Poland: POLFAR consortium

Study of individual pulses with LOFAR sungle stations: PSR B1133+16 from FR606-Nancay compared to GMRT

Pulse phase

• 0.05 0 0.05

Pulse phase

• 0.05 0 0.05

Pulse number Pulse number

GMRT LOFAR Single pulse observations possible with LOFAR single stations for about two-three dozen pulsars

PSR B0329+54: mode changes at 150 MHz, using PL612

Białkowski, Lewandowski, Kijak, Błaszkiewicz, Krankowski, Osłowski, 2018 (in press)

GPS Pulsar J1740+1000

• Early LOFAR observations suggest a simple power –law spectrum (Bilous et al. 2016)
• Our new observations (GMRT, GBT) suggest a GPS nature.
• Solution: Interferometric flux measureent using International LOFAR Telescope

?

Obsservations already done (Dec 2017/Jan 2018) waiting for data analysis

From: Multi-frequency

• bservations and spectral

analysis of two gigahertz- peaked spectra pulsars , Rożko,Rajwade, Lewandowski, Kijak, Basu and Lorimer, (2018) in press

Scattered pulse profiles from the PL-612 station in Bałdy near Olsztyn, (120 minutes) In collaboration with L. Błaszkiewicz, A. Krankowski, T. Sidorowicz (UWM) Interstellar scattering: wide fractional bandwidth allows to see the strongly dependant scattering change within the band!

3Gb/s (1.2 TB per hour)

UJ PIONIER UZ

Since June, 2017, regular pulsar

• bservatins using the PL611

station (Łazy, near Kraków) that are stored and analysed in Zielona Góra. (with the help of K. Chyży, M. Soida and B. Śmierciak, UJ)

PSR J1509+5531: individual pulses from PL611, HBA band (150 MHz) First data from the LBA receivers (45-81 MHz)

November 2017: First pulsar data from PL610 (Borówiec near Poznan, governed by CBK Warsaw) – in collaboration with H. Rothkaehl and M. Pożoga. Observing setup (per station):

• 4 Xeon-3 processors (40 cores),
• 256 GB RAM
• 20-90 TB data storage (depending on station)
• 10 Gb/s network connection (3.2 Gb/s used per station)

3 days a week (Friday-Sunday) are local time. That is 72 TB of data to analyse per station!

The Polish LOFAR stations have a significant scientific potential!

Thank you for your attention!