{"id":483,"date":"2024-12-30T09:01:10","date_gmt":"2024-12-30T08:01:10","guid":{"rendered":"https:\/\/home.phys.ntnu.no\/LOVE-NEST\/?p=483"},"modified":"2025-09-05T13:43:56","modified_gmt":"2025-09-05T11:43:56","slug":"the-power-of-the-dark-side-spectroscopic-studies-of-spider-pulsars","status":"publish","type":"post","link":"https:\/\/home.phys.ntnu.no\/LOVE-NEST\/the-power-of-the-dark-side-spectroscopic-studies-of-spider-pulsars\/","title":{"rendered":"The power of the dark side: spectroscopic studies of spider pulsars"},"content":{"rendered":"

[vc_row][vc_column width=”2\/3″][vc_column_text css=””]Spectroscopic studies of compact binary millisecond pulsars (‘spiders’) are crucial for finding the most massive neutron stars. Using the largest ground-based optical telescopes to take spectra of spider binaries over their orbits, we can measure the radial velocity of their companion stars, which are bright in optical wavelengths, to weigh their neutron stars, which are usually optically faint.<\/p>\n

Many spider pulsars, true to their names, slowly eat away at their companions, due to their extreme pulsar wind which tears material off their companion’s surface. This wind can have the added effect of heating one face of the companion, resulting in drastic temperature contrasts between inner ‘day’ side and outer ‘night’ side. Unfortunately, this proves problematic for accurate mass measurements, as the radial velocities measured become heavily biased towards the irradiated face.<\/p>\n

To counteract this effect, we used ‘the power of the dark side’ – we looked for radial velocity signals associated with different atomic elements, which have different temperature sensitivities and thus can appear more strongly on the companion’s night side face. This in turn results in higher radial velocities being measured from the dark side of the companion than from its irradiated face. In our research, we found strong evidence of this occurring in one spider system (PSR J1048+2339), and tentative evidence in another (PSR J1810+1744), which allowed us to place constraints on the masses of both components in both systems. We also searched for such effects in a third system, PSR J1908+2105, and were surprised to find no strong radial velocity signals from it whatsoever. Instead, we were able to place upper limits on this system, which revealed the previously misunderstood spider to be in a near face-on orbit with one of the most massive companions discovered to date.[\/vc_column_text][\/vc_column][vc_column width=”1\/3″][vc_empty_space]