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Yogesh Maan

Yogesh Maan
Yogesh Maan
Visiting Fellow
National Centre for Radio Astrophysics,
Tata Institute of Fundamental Research,
Pune University Campus, Post Bag 3,
Ganeshkhind, Pune - 411007, INDIA
E-mail ymaan [at]
Office Phone +91 - 20 - 25719251
Office Extn. 9251
Office F212








Main Research Areas: Radio Pulsars and Compact Objects, Pulsar emission mechanisms, Radio astronomy instrumentation, Searches for pulsars and transients.




Yogesh Maan obtained his B.Sc. from Kurukshetra University in 2003, and his M.Sc. from Panjab University in 2005. He then joined the Joint Astronomy Programme (JAP) coordinated by the Indian Institute of Science, for his Ph.D.. Under this programme, he joined the Raman Research Institute to study several aspects of radio pulsars, and completed work for his doctoral research in 2013. Yogesh joined NCRA-TIFR as a Post-doctoral Fellow in 2014.



Research description:

Understanding the mechanism of radio emission from pulsars:

(a) The average profile (with full polarization information) of a pulsar provides valuable information about the viewing geometry as well as the underlying emission mechanism. However, clues to actual details of underlying plasma processes come from several interesting phenomena, viz. sub-pulse drifting, pulse-nulling, mode-changing, etc., observed in single pulse sequences of a significant fraction of the pulsar population. Although physical models have been proposed to explain some of these phenomena, they have been, at best, only partially successful. Inconsistencies with the proposed models have been observed in several cases. One of my primary current interests lies in studying these phenomena using an appropriately chosen sample of pulsars, so as to sample the underlying variety, and try to discern the broader physical picture which could explain the various phenomena consistently.

(b) While the characteristic timescales of the above phenomena varies from a few milliseconds to a few hundreds of seconds or more, some pulsars exhibit emission features at much shorter timescales of just a few or a few tens of nanoseconds. Such extremely short-timescale emission features represent burst-like emission, and are called giant pulses. The peak flux density and energy of a giant pulse can exceed the respective average values by factors of hundreds or even thousands. Out of nearly 2300 known pulsars, only about a dozen are known to be giant pulse emitters. Finding out clues to the physical mechanism of giant pulses, and testing the validity of proposed mechanisms for the same, are in severe need of a statistically significant number of giant pulse-emitting pulsars. Currently we are searching for giant pulse emission from a carefully chosen sample of millisecond and young pulsars, using the Giant Metrewave Radio Telescope and the Ooty Radio Telescope. While any new giant pulse emitters found in this survey will be useful, upper limits on giant pulse emission rate from the rest will be equally crucial in constraining the theoretical models.

Searching for radio pulsars and fast transients:

Although the first pulsar was discovered at 81 MHz, the majority of subsequent pulsar surveys have been carried out at higher radio frequencies (350--1400 MHz). Appropriately high frequencies have been used to avoid the effects of interstellar scattering and bright sky background, which are far more prominent at lower frequencies. However, given that the dispersive effect of the interstellar medium (which is used as a primary identifier of astronomical signals) becomes less prominent at higher frequencies, these surveys may have poorly sampled the local population of pulsars (i.e. nearby pulsars). Furthermore, radio emission from some pulsars might be detectable only at low frequencies (for some pulsars, only their wider, low frequency emission beam might cross our line of sight). Hence, pulsar searches at low frequency are necessary for completeness, although they may be suited for detecting only the local pulsar population. I am currently carrying out a search for pulsars at a very low frequency, 34 MHz, using the Gauribidanur radio telescope. Very recently, targeted searches using this telescope have resulted in the detection of the radio counterpart of the gamma-ray pulsar J1732-3131. A blind search for pulsars along several selected directions is in progress. A search for fast radio transients (i.e., single bright dispersed pulses) along these directions is also being carried out.

Astronomical instrumentation:

My other research interest lies in astronomical instrumentation. Recently, we (teams from the Raman Research Institute and the National Radio Astronomy Observatory, Green Bank) designed and developed a self-contained multi-band receiver system, intended for use with a single large aperture to facilitate sensitive and high time-resolution observations simultaneously in 10 discrete frequency bands sampling a wide spectral span (100-1500 MHz). The multi-band receiver system was used with the Robert C. Byrd Green Bank Telescope to carry out simultaneous multi-frequency observations of several bright pulsars.



Selected publications:

1. Inter-relationship between the Two Emission Cones of B1237+25 (Y. Maan & A. A. Deshpande 2014, ApJ, 792, 130)

2. RRI-GBT Multi-Band Receiver: Motivation, Design, and Development (Y. Maan et al., 2013, ApJS, 204, 12)

3. Pulsed radio emission from the Fermi-LAT pulsar J1732-3131: search and a possible detection at 34.5 MHz (Y. Maan, H. A. Aswathappa and A. A. Deshpande, 2012, MNRAS, 425, 2)


All publications:

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