Coordinated Space and Ground Monitoring of Accretion Bursts in a Protoplanetary Disk: MIRI and iSHELL observe the long-term modulation of gas within a small inner disk cavity

Jacob Hyden; Andrea Banzatti; Benjamin M. Tofflemire; Sebastiaan Krijt; Till Kaeufer; Klaus M. Pontoppidan; Carlo F. Manara; Christian Rab; John M. McCaskill; Guillaume Bourdarot; Emma T. Whelan; Joan Najita; Adrien Houge; Adwin Boogert; Catherine Dougados; Myriam Benisty; James Muzerolle Page

AI summary · arXiv: 2611.07253v1 · astro-ph.EP

Coordinated Space and Ground Monitoring of Accretion Bursts in a Protoplanetary Disk: MIRI and iSHELL observe the long-term modulation of gas within a small inner disk cavity

Jacob Hyden, Andrea Banzatti, Benjamin M. Tofflemire, Sebastiaan Krijt, Till Kaeufer, Klaus M. Pontoppidan, Carlo F. Manara, Christian Rab,

and 9 more authors

John M. McCaskill, Guillaume Bourdarot, Emma T. Whelan, Joan Najita, Adrien Houge, Adwin Boogert, Catherine Dougados, Myriam Benisty, James Muzerolle Page

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The essentials

Coordinated infrared monitoring shows that hot molecular gas in DQ Tau fades and its emitting region moves outward over successive accretion bursts, unlike hydrogen and continuum emission.

Based on the abstract only: check the details in the original paper.

Question

How does molecular gas in DQ Tau respond to repeated accretion bursts, and is its variability driven primarily by changing chemistry or disk dynamics?

Method

The study monitored DQ Tau with seven ground- and space-based instruments over 40 days, covering three sequential bursts. It analyzed nine JWST-MIRI and nine IRTF-iSHELL epochs, using H₂O and CO line luminosities and widths to estimate changes in the emitting gas and its Keplerian radii.

Findings

Result Molecular line luminosities and widths decreased over roughly 30–35 days, consistent with the hot emitting gas becoming cooler and less massive as it receded outward within the inner cavity.
See the passage in the paper
the line luminosity and width of all hot molecular gas tracers decrease over $\sim30$-35 days, consistent with an emitting region decreasing in temperature and mass as it recedes to larger radii within the $\sim 0.2$-0.4 au inner cavity perturbed by the binary.
Result Molecular emission responded differently to accretion bursts than HI and the 5-micron continuum.
See the passage in the paper
the molecular emission does not react like HI and the 5-$μ$m continuum with each accretion burst
Authors’ interpretation The authors argue that disk dynamics, rather than burst-triggered chemical changes, dominate the observed infrared molecular variability.
See the passage in the paper
The infrared molecular spectrum of DQ Tau is affected more by disk dynamics then by chemical changes triggered by variable accretion
Authors’ interpretation The observed variability is consistent with gas accumulating near the disk edge and modulating burst intensity and inner-cavity density every four to five orbits, although the cause of this modulation is unknown.
See the passage in the paper
The variability observed in all tracers in this study is consistent with a scenario where gas mass builds up near the disk edge to modulate the burst peak intensity and gas density in the inner cavity every $\sim4$-5 orbital periods. The origin of this modulation is still unclear.

Limitations

The physical origin of the proposed modulation on four-to-five-orbit timescales remains unclear.
See the passage in the paper
The origin of this modulation is still unclear.
The monitoring covers only about 40 days and three sequential bursts, limiting the scope of the reported variability to this observation interval.
See the passage in the paper
We have monitored this system with seven instruments from ground and space over 40 days.

Why it matters

The coordinated observations add line-width-based estimates of molecular emitting radii alongside luminosity measurements, revealing that hot molecular gas evolves differently from other burst tracers. The authors argue that this behavior supports disk dynamics and chemical relaxation times longer than the accretion-burst duration.

Written by AI from the paper. Passages are checked word for word against the text we analysed; the rest may contain errors.

AI-generated keywords: DQ Tau accretion bursts molecular gas inner disk dynamics infrared spectroscopy

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Comprehensive Summary
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Original abstract

The paper investigates how molecular gas in the inner disk of DQ Tau responds to recurring accretion bursts. DQ Tau is an eccentric binary system with accretion activity that pulses on an orbital period of about 16 days. The study examines whether hot molecular gas changes in response to individual bursts and whether variations in its emission reveal how the disk’s gas distribution evolves. The authors monitored DQ Tau for 40 days with seven instruments at ground-based and space-based facilities. Their molecular-gas analysis draws on nine observing epochs from JWST’s Mid-Infrared Instrument (MIRI) and nine from the IRTF’s iSHELL spectrograph. The observations cover three successive accretion bursts, with accretion-luminosity pulses that increased in strength by factors of approximately 9 to 80. A central contribution is the measurement of line broadening in carbon monoxide observed with iSHELL and water observed with MIRI. The authors use these line widths to estimate the Keplerian radii of the emitting gas, comparing changes in the emitting-region size with changes in line luminosity. Unlike hydrogen emission and the 5-micrometer continuum, the molecular tracers did not respond to each burst in the same way. Instead, the luminosities and widths of all the hot molecular-gas tracers declined over roughly 30 to 35 days. The authors interpret this combined decline as evidence that the molecular-emitting region became cooler and less massive while moving outward. They place this evolution within the small inner disk cavity, estimated to span about 0.2 to 0.4 astronomical units and to be perturbed by the binary. The molecular emission therefore appears to trace evolving disk structure rather than simply tracking burst intensity. The authors also conclude that disk dynamics affect the infrared molecular spectrum more strongly than chemical changes driven by variable accretion. This interpretation is consistent with models in which chemical relaxation takes much longer than the bursts, with relevant timescales expected to exceed 10 days. The observed variability is also consistent with a scenario in which gas accumulates near the disk edge and periodically modulates both burst peak intensity and gas density in the inner cavity every four to five orbital periods. The mechanism behind this longer-term modulation remains unknown. This assessment is based on the paper’s title and abstract; the full text was not available in the supplied material. As a result, the available information does not establish measurement uncertainties, the precise method used to derive Keplerian radii, the behavior of individual lines, or how the authors evaluated alternative explanations. The proposed link between gas buildup, disk dynamics, and burst modulation is therefore best regarded as a scenario consistent with the observations, rather than a resolved explanation for the modulation’s origin.

When Accretion Bursts Fade, What Happens to the Gas Around DQ Tau?

In a young star system, gas can move inward in a steady stream—or arrive in dramatic pulses. DQ Tau is an eccentric binary whose orbit brings its two stars close together about every 16 days. These close encounters are associated with recurring accretion bursts, when material from the surrounding disk falls onto the stars. A new study asks whether hot molecular gas in the disk’s inner region responds to each burst, and what its changing light can reveal about the disk itself.

The study, titled “Coordinated Space and Ground Monitoring of Accretion Bursts in a Protoplanetary Disk: MIRI and iSHELL observe the long-term modulation of gas within a small inner disk cavity,” was written by Jacob Hyden, Andrea Banzatti, Benjamin M. Tofflemire, Sebastiaan Krijt, Till Kaeufer, Klaus M. Pontoppidan et al.

A 40-Day Campaign

To follow the system through its changing activity, the researchers monitored DQ Tau for 40 days using seven instruments at ground-based and space-based facilities. Their analysis of molecular gas centers on nine observing epochs from JWST’s Mid-Infrared Instrument, or MIRI, and nine from the IRTF’s iSHELL spectrograph.

The observations covered three successive accretion bursts. The bursts were not equally strong: accretion-luminosity pulses increased in strength by factors of roughly 9 to 80. This sequence gave the team an opportunity to compare molecular emission with burst activity as the system changed over time.

A key part of the analysis was measuring the widths of molecular emission lines. The team examined carbon monoxide observed with iSHELL and water observed with MIRI. Line widths can provide clues to how quickly the emitting gas moves. By using them to estimate the gas’s Keplerian radii—the distances at which material would orbit at the measured speeds—the researchers could compare changes in the emitting region’s apparent size with changes in its brightness.

Molecular Gas Did Not Follow Every Burst

Some signals in DQ Tau responded to accretion activity differently from the molecular tracers. Hydrogen emission and the continuum near 5 micrometers did not show the same behavior as the hot molecular gas. Rather than rising and falling in step with each burst, the luminosities and line widths of all the hot molecular-gas tracers declined over approximately 30 to 35 days.

That shared downward trend is important because it suggests that molecular emission is not simply a direct meter of burst strength. The authors interpret the combined decline in brightness and line width as evidence that the molecular-emitting region became cooler and less massive while moving outward. In this picture, the changing spectrum reflects an evolving gas distribution, not just the immediate response of molecules to a brighter accretion episode.

Changes Inside a Small, Disturbed Cavity

The proposed evolution takes place in DQ Tau’s small inner disk cavity, estimated to span about 0.2 to 0.4 astronomical units. The binary is thought to perturb this region, making its gas distribution dynamic. Changes in where molecular emission arises, how much warm gas is present, and how hot that gas is could all alter the observed infrared spectrum.

The authors conclude that disk dynamics influence the molecular spectrum more strongly than chemical changes driven by variable accretion. This interpretation fits models in which chemistry takes longer to adjust than the bursts themselves: relevant chemical relaxation times are expected to exceed 10 days. If the chemistry responds slowly, changes in gas location and structure may be the more immediate explanation for the observed trend.

A Longer-Term Rhythm?

The observations also fit a broader scenario in which gas builds up near the disk edge. That material could periodically affect both the peak intensity of accretion bursts and the density of gas in the inner cavity, with changes recurring every four to five orbits. Because DQ Tau’s orbit lasts about 16 days, this would imply a modulation on a timescale longer than a single burst cycle.

But a scenario consistent with the data is not the same as a mechanism that has been established. The process behind this longer-term modulation remains unknown. The results point toward an evolving and dynamically influenced inner disk, while leaving open exactly how material accumulates and how that accumulation shapes the bursts.

What the Study Can—and Cannot—Establish

The reported findings make molecular line widths and luminosities useful clues to changing disk structure. They also show why following a system across multiple bursts matters: a molecular signal may evolve over weeks even when it does not mirror each individual pulse.

There are limits to what can be assessed from the available summary. It does not provide measurement uncertainties, the precise method used to derive Keplerian radii, the behavior of individual lines, or details of how alternative explanations were evaluated. The connection between gas buildup, disk dynamics, and burst modulation should therefore be treated as a plausible interpretation of the observations—not a resolved explanation for the underlying mechanism.

Created on 09 Nov. 2026

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Coordinated Space and Ground Monitoring of Accretion Bursts in a Protoplanetary Disk: MIRI and iSHELL observe the long-term modulation of gas within a small inner disk cavity

The essentials

Question

Method

Findings

Limitations

Why it matters

Read further

Definitions

When Accretion Bursts Fade, What Happens to the Gas Around DQ Tau?

A 40-Day Campaign

Molecular Gas Did Not Follow Every Burst

Changes Inside a Small, Disturbed Cavity

A Longer-Term Rhythm?

What the Study Can—and Cannot—Establish

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