Probing Compact Binary Coalescences in the Decihertz GW Band with IndIGO-D

Introduction to the show: ident: Astrophysics Radio. Generated commentary on the latest astrophysics papers.

Vera: Hi, I'm Vera.

Jocelyn: And I'm Jocelyn, here with Subrahmanyan.

Vera: We're looking at the paper: "Probing Compact Binary Coalescences in the Decihertz GW Band with IndIGO-D".

Jocelyn: Here's the gist of the paper. The gist The study analyzes IndIGO-D, a decihertz gravitational-wave mission concept, focusing on an L-shaped interferometer in a heliocentric orbit to probe compact binary coalescences across the 0.1 – 10 Hz band, bridging the gap between LISA and terrestrial detectors.

Vera: Detector Geometry and Orbital Configuration The IndIGO-D detector consists of three spacecraft forming an L-shaped interferometer with 1000 km arms, operating in a heliocentric orbit to achieve ppm-level arm-length stability.

Jocelyn: The vertex spacecraft follows a circular trajectory in the ecliptic plane, and the orbits of the other two spacecraft must be eccentric and inclined by 60◦ with respect to the ecliptic plane to result in a fixed arm-length configuration up to first order in α=l/2R.

Vera: The orbital inclination is given by tanϵ = √3α / (1 + α).

Paper summary: Vera: We're diving into the summary of this paper now, "Probing Compact Binary Coalescences in the Decihertz GW Band with IndIGO-D." The main point is that they are analyzing a specific mission concept called IndIGO-D, which uses an L-shaped interferometer in a heliocentric orbit to probe compact binary coalescences across the zero point one to ten Hz band <ref:2601.06956#pg1,an L-shaped interferometer in a heliocentric orbit>.

Jocelyn: They claim this setup bridges the gap between LISA and next-generation ground-based detectors by focusing on sources that last longer during their inspiral, which is what makes this frequency range so important for them.

Subrahmanyan: The paper points out that they are specifically interested in intermediate-mass black-hole binaries with masses in the one hundred two to one hundred three solar mass range because IndIGO-D can see them detectable to redshifts z ∼ one hundred three which is a very far reach <ref:2601.06956#pg1,intermediate-mass black-hole binaries with masses>.

Vera: And for binary neutron star systems, they find that they are observable out to a horizon redshift of z less than zero point three, allowing for continuous multi-band coverage with Voyager-class interferometers from the decihertz regime up to the merger.

Jocelyn: So what this means is that we can monitor these BNS systems continuously from their early inspiral phase in this lower frequency band and keep tracking them until they merge, which is a major improvement over just catching them at a single point in time.

Subrahmanyan: And they also used simulated binary neutron star systems with component source-frame masses of one point four solar masses to figure out the fraction of sources that are detectable by both IndIGO-D and Voyager.

Vera: The finding is that about eighteen percent of the sources are detectable by IndIGO-D and about twenty-six percent by Voyager, demonstrating a significant fraction of BNS systems within z less than or equal to zero point three three remain jointly detectable in dHz and ground-based detector bands.

Jocelyn: That overlap is important because it means we have a population of these systems that can be followed up with multi-band observations from both space and ground detectors simultaneously.

Subrahmanyan: This directly supports the idea of filling the spectral gap between mHz and terrestrial observations by demonstrating that there are overlapping detection windows for many compact binaries.

Vera: So, this paper is essentially mapping out what IndIGO-D can actually do in terms of detection rates and source reach across different mass ranges and redshift ranges.

Jocelyn: It's showing the practical application of this concept by giving us concrete numbers on how many events we might expect to see in terms of detection rates, which is what you need to know.

Subrahmanyan: And from a cosmological standpoint, they are extending the reach for intermediate-mass black hole systems far beyond what we can currently achieve with other tools.

Conclusion: Vera: So, looking at the title, "Probing Compact Binary Coalescences in the Decihertz GW Band with IndIGO-D," it really captures the essence of what they are trying to do: using this new mission concept to look at a very specific frequency window for these compact binary events.

Jocelyn: The authors, Sharma, Tahelyani, Sengupta, and Mitra are all focused on designing this specific L-shaped geometry in a heliocentric orbit for stability.

Subrahmanyan: What this means is that they are showing how a mission concept can actually be designed to fill a gap in the current observational landscape for gravitational waves by connecting different frequency regimes together.

Vera: They're demonstrating that these kinds of missions aren't just theoretical exercises but they are feasible designs, and they provide a practical pathway toward multi-band observations.

Jocelyn: The implications are that when we combine the precision with the extension of reach, you get something much more powerful for studying the population statistics of compact binaries.

Subrahmanyan: It suggests that if we can keep pushing this concept forward, we might uncover entirely new populations of black holes or even understand how they formed in these distant environments.