Pulse Morphology and Spectral Study of LPT J1634+44 Using GMRT

Abstract: Long-period radio transients (LPTs) are a recently discovered class of Galactic coherent radio emitters characterized by rotation periods of minutes to hours and highly polarized radio pulses. Their nature remains uncertain, with proposed scenarios invoking isolated or binary systems containing neutron stars (NSs) or white dwarfs (WDs). We investigate the nature of CHIME/ILT J1634+44 through multi-band observations with the Giant Metrewave Radio Telescope (GMRT), examining its pulse morphology, spectral evolution, and timing behavior. The pulses show substantial profile variability, and the subpulse features evolve significantly across observing frequencies. Using our measurements of quasi-periodic microstructures in J1634+44 pulses as well as those of other LPTs available from literature, we show that the scaling relationship between the rotation and microstructure periods is not limited to only neutron stars but extend to white dwarfs as well. The radio spectrum of J1634+44 is highly variable and exhibits a spectral turnover that shifts toward lower frequencies across observing epochs. Interpreting this turnover as free-free absorption, we constrain the physical properties of the intervening absorbing medium. Complementing these emission diagnostics, we also present analysis of pulse arrival times spanning approximately a decade to probe the previously proposed spin-orbit resonance models for this LPT.