HI Intensity Mapping with the MIGHTEE Survey: First Results of the H i Power Spectrum

Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) (2025)

Authors:

Aishrila Mazumder, Laura Wolz, Zhaoting Chen, Sourabh Paul, Mario G Santos, Matt Jarvis, Junaid Townsend, Srikrishna Sekhar, Russ Taylor

Abstract:

Abstract We present the first results of the H i intensity mapping power spectrum analysis with the MeerKAT International GigaHertz Tiered Extragalactic Exploration (MIGHTEE) survey. We use data covering ∼ 4 square degrees in the COSMOS field using a frequency range 962.5 MHz to 1008.42 MHz, equivalent to H i emission in 0.4 < z < 0.48. The data consists of 15 pointings with a total of 94.2 hours on-source. We verify the suitability of the MIGHTEE data for H i intensity mapping by testing for residual systematics across frequency, baselines and pointings. We also vary the window used for H i signal measurements and find no significant improvement using stringent Fourier mode cuts. We compute the H i power spectrum at scales 0.5 Mpc−1 ≲ k ≲ 10 Mpc−1 in auto-correlation as well as cross-correlation between observational scans using power spectrum domain averaging for pointings. We report consistent upper limits of 29.8  mK2Mpc3 from the 2σ cross-correlation measurements and 25.82 mK2Mpc3 from auto-correlation at k ∼2 Mpc−1.The low signal-to-noise in this data potentially limits our ability to identify residual systematics, which will be addressed in the future by incorporating more data in the analysis.

A Persistent Disk Wind and Variable Jet Outflow in the Neutron-star Low-mass X-Ray Binary GX 13+1

The Astrophysical Journal American Astronomical Society 986:1 (2025) 41

Authors:

Daniele Rogantini, Jeroen Homan, Richard M Plotkin, Maureen van den Berg, James Miller-Jones, Joey Neilsen, Deepto Chakrabarty, Rob P Fender, Norbert Schulz

A Multi-wavelength Characterization of the 2023 Outburst of MAXI J1807+132: Manifestations of Disk Instability and Jet Emission

(2025)

Authors:

Sandeep K Rout, M Cristina Baglio, Andrew Hughes, David M Russell, DM Bramich, Payaswini Saikia, Kevin Alabarta, Montserrat Armas Padilla, Sergio Campana, Stefano Covino, Paolo D'Avanzo, Rob Fender, Paolo Goldoni, Jeroen Homan, Fraser Lewis, Nicola Masetti, Sara Motta, Teo Munoz-Darias, Alessandro Papitto, Thomas D Russell, Gregory Sivakoff, Jakob van den Eijnden

Slow and steady: long-term evolution of the 76-second pulsar J0901−4046

Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) (2025)

Authors:

MC Bezuidenhout, NDR Bhat, M Caleb, LN Driessen, F Jankowski, M Kramer, V Morello, I Pastor-Marazuela, K Rajwade, J Roy, BW Stappers, M Surnis, J Tian

Abstract:

Abstract PSR J0901−4046, a likely radio-loud neutron star with a period of 75.88 seconds, challenges conventional models of neutron star radio emission. Here, we showcase results from 46 hours of follow-up observations of PSR J0901−4046 using the MeerKAT, Murriyang, GMRT, and MWA radio telescopes. We demonstrate the intriguing stability of the source’s timing solution over more than three years, leading to an RMS arrival-time uncertainty of just ∼10−4 of the rotation period. Furthermore, non-detection below 500 MHz may indicate a low-frequency turnover in the source’s spectrum, while no secular decline in the flux density of the source over time, as was apparent from previous observations, has been observed. Using high time-resolution MeerKAT data, we demonstrate two distinct quasi-periodic oscillation modes present in single pulses, with characteristic time scales of 73 ms and 21 ms. We also observe a statistically significant change in the relative prevalence of distinct pulse morphologies compared to previous observations, possibly indicating a shift in the magnetospheric composition over time. Finally, we show that the W50 pulse width is nearly constant from 544–4032 MHz, consistent with zero radius-to-frequency mapping. The very short duty cycle (∼1.4○) is more similar to radio pulsars with periods >5 seconds than to radio-loud magnetars. This, along with the lack of magnetar-like outbursts or timing glitches, complicates the identification of the source with ultra-long period magnetar models.

Colloquium: The Cosmic Dipole Anomaly

(2025)

Authors:

Nathan Secrest, Sebastian von Hausegger, Mohamed Rameez, Roya Mohayaee, Subir Sarkar