{"id":"5200a235-d806-4bd0-9baf-a7949415f29e","arxiv_id":"2607.27688","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":3,"one_line_summary":"VLBI observations during 2025 radio flares find no detectable jet motion in GRS 1915+105, implying its obscured-state jets are slower (βΓ≲0.40) than the pre-2019 relativistic jets.","lead":"VLBI images of the black hole X-ray binary GRS 1915+105 during 2025 radio flares show bright two-sided jet structures that do not move over 5-hour observations. If real, this means jets launched in the source's current X-ray-obscured state are slower than the relativistic jets it emitted before 2019, supporting a new picture in which obscured X-ray binaries produce slower, precessing jets.","discovery_kind":"extension","skeptic_critique":{"model":"deepseek-v4-flash","headline":"βΓ≲0.40 rests on the unchecked assumption that the two epoch-B blobs are intrinsically symmetric simultaneous ejections; if this fails, a fast on-axis jet would evade the proper-motion limit.","rationale":"The paper's strongest claim is that the 2025 obscured-state jets are slower than the pre-2019 relativistic jets (βΓ≳1), quantified as βΓ≲0.40. The most direct evidence is the absence of the fast proper motions that would be expected if the historical apparent speed (~22 mas/d) persisted; this part is robust and should be credited. However, excluding all relativistic (βΓ≥1) jets requires more than ruling out one historical pattern—a fast jet viewed within a few degrees of the line of sight can have apparent transverse motion below the detection threshold. The paper closes this loophole with the βcosθ≈0.11 constraint, but that constraint is built on the assumption that the two epoch-B blobs are intrinsically symmetric and simultaneous ejections. The reader's weakest-assumption statement correctly flags both this and the adopted core position. I agree with the reader's assessment, with one refinement: the core-position issue is partially self-checked by the flux-ratio method (Eq. 2), but Eq. 2 shares the symmetry assumption. Therefore the load-bearing, least-secure condition is intrinsic symmetry/simultaneity. If that assumption is violated, the quantitative βΓ≲0.40 collapses, although the qualitative statement that the 2025 jets do not show the pre-2019 superluminal pattern survives. The paper should either present a direct test of symmetry (e.g., time-dependent midpoint and flux-ratio stability within epoch B, or multi-epoch proper-motion measurements of both blobs) or soften the abstract's 'robust support' to 'consistent with.' Since the reader already assigned CONDITIONAL, no change to the verdict is needed; this stress test sharpens the specific condition that must be met.","tokens_in":13422,"tokens_out":12594,"duration_ms":123425,"concrete_test":"Using the published time-binned epoch-B data (five 1-h bins), measure the midpoint of SE2 and NW2 and their flux-density ratio as functions of time. If the midpoint remains at the adopted core position (within fitting errors) and the flux ratio is constant, the symmetric-simultaneous-ejection assumption is supported; if the midpoint drifts or the ratio varies significantly, the assumption fails and the βΓ≲0.40 limit should be re-derived without Eq. (1)/(2). An independent, decisive test is a multi-epoch VLBI campaign with ≥2 epochs separated by days, measuring the two blobs' proper motions separately to check whether they recede from a common origin at equal rates.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central quantitative claim—βΓ≲0.40 for the 2025 jets—is derived in §3.3 from two ostensibly independent estimators: Eq. (1) (separation asymmetry, giving βcosθ=0.11±0.04) and Eq. (2) (flux-density ratio, giving βcosθ≈0.07–0.10). The paper presents these as cross-checks, but both share the same underlying postulate: the two epoch-B blobs are intrinsically symmetric and were ejected simultaneously from a common core. In epoch B no core is detected, so Eq. (1) also inherits a core position extrapolated from epoch A; a core-position error is partially mitigated by Eq. (2), but Eq. (2) fails equally if the 'counterjet' is not intrinsically identical. If the blobs are not a symmetric simultaneous pair—e.g., one component is the unrecognized core, or the counterjet has a very different intrinsic luminosity—the derived βcosθ is not a kinematic quantity. A fast jet with β≳0.9 viewed within θ≈2°–3° would have βapp≲0.39 mas/h, evading the proper-motion limit, and could still be βΓ≳1. The non-detection of historical superluminal proper motions is robust evidence against the pre-2019 jet pattern, but it does not by itself bound βΓ near unity unless the symmetry assumption holds. The abstract's 'robust support' is stronger than this.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper reports 6.7-GHz EAVN observations of the black hole X-ray binary GRS 1915+105 obtained during two radio flares in January 2025, while the source is in its post-2019 X-ray-obscured state. In epoch A the source shows a bright core with two-sided jet emission; in epoch B the core is not detected and the image is dominated by two bright, roughly symmetric blobs (SE2 and NW2). Time-binned imaging over the ~5-hour tracks yields no significant proper motion for any component, giving an apparent-speed upper limit of β_app ≲ 0.39. Using the separation asymmetry between the two blobs (βcosθ = 0.11 ± 0.04) and the flux-density ratio (βcosθ ≈ 0.07–0.10), the authors derive an intrinsic speed βΓ ≲ 0.40 for the epoch B jets. They compare this with pre-2019 measurements of βΓ ~ 1–3 and with the 2023 obscured-state value βΓ = 0.37, and interpret the result as evidence that jets in the obscured state are slower, and possibly precessing, in line with the Fender–Motta paradigm. The paper also discusses possible physical origins, including a warped, precessing disk and enhanced mass loading.","tokens_in":13792,"tokens_out":2828,"duration_ms":27981,"significance":"If the derived speed is correct, this is a valuable data point: it would show that the archetypal Galactic superluminal source, GRS 1915+105, has switched from relativistic (βΓ ≳ 1) to sub-relativistic (βΓ ≲ 0.40) jet propagation after entering its obscured state, directly supporting the emerging state-dependent jet paradigm. The proper-motion non-detection itself is robust and well presented: the authors correctly note that pre-2019 apparent speeds (~22 mas/d) would produce a ~5 mas shift over 5 hours, well above their ~1.5 mas detection threshold, while the observed residuals are consistent with zero. The paper is also commendable for its rapid-response ToO observations, the use of calibrator light curves to verify that the flux variability is intrinsic, and the transparency of the equations used. The quantitative speed limit, however, depends critically on the assumption that the two epoch-B blobs are intrinsically symmetric, simultaneous ejections from a stationary core at the position extrapolated from epoch A. That assumption is stated but its violation is not discussed or propagated, and the abstract's phrase 'robust support' overstates the strength of the kinematic inferenc","major_comments":[{"comment":"Both estimators of βcosθ assume the two epoch-B blobs are intrinsically symmetric and were ejected simultaneously from a common core. If the counterjet is intrinsically fainter or if one blob is actually the core (or a separate ejection), then Eq. (1) does not measure a kinematic asymmetry and Eq. (2) is biased by the unknown intrinsic flux ratio. The paper states the assumption but provides no test or systematic-uncertainty estimate. Because this assumption is the link between the proper-motion null result and the quantitative claim βΓ ≲ 0.40, the conclusion is not as robust as the abstract implies. A concrete test would be to compare the epoch-B morphology with the epoch-A core position and the 2023 symmetric-ejection events, or to fit a model that relaxes the symmetry and show how βcosθ changes.","section":"§3.3, Eqs. (1) and (2)"},{"comment":"The epoch-B core position is inferred from epoch A, taken seven days earlier. Any opacity-driven core shift or physical displacement of the launch site between epochs, or a position error in the epoch-A core, directly biases the measured separations Δr_app and Δr_rec used in Eq. (1). A shift of the adopted core along the jet axis changes the two separations in opposite directions and therefore produces a spurious βcosθ. The resulting systematic error is not propagated into the quoted βΓ ≲ 0.40. The authors should estimate the plausible core-shift magnitude (e.g., from the beam size and the epoch-A fit uncertainty) and show the range of βcosθ that results.","section":"§3.2, 'For epoch B, where the core is not directly detected...'"},{"comment":"The comparison with pre-2019 jets and the statement that post-2019 jets are 'slower' rests on the quantitative βΓ ≲ 0.40, which is conditional on the symmetry assumption. The proper-motion non-detection alone robustly excludes apparent speeds of ~22 mas/d, but a fast on-axis jet (β ≳ 0.9 within θ ≈ 2–3°) would also produce β_app ≲ 0.39 mas/h and would evade the proper-motion limit while still having βΓ ≳ 1. The discussion should acknowledge this degenerate possibility explicitly and separate the robust null result from the model-dependent speed inference.","section":"§4.1, 'Evidence for Slower Jets'"}],"minor_comments":[{"comment":"The phrase 'robust support' in the abstract is too strong given the symmetry assumption. Suggest 'consistent with' or 'provide further support'.","section":"Abstract and §5"},{"comment":"The choice of one quarter of the beam major axis (q = 0.25) as the detectability threshold is reasonable but arbitrary. A brief justification or a test with different q values (e.g., 0.2–0.5) would strengthen the upper limit.","section":"§3.2"},{"comment":"The table lists βΓ ≲ 0.40 for both epoch A and epoch B, but the text notes that the epoch A value is tentative (βcosθ = 0.09 ± 0.12). The table could mark this clearly or include the uncertainty.","section":"Table 1"},{"comment":"The k = 2 vs k = 3 choice is discussed with literature values, but the final βcosθ range (0.07–0.10) does not show how the uncertainty in k propagates. A one-line sensitivity statement would be helpful.","section":"§3.3, Eq. (2)"},{"comment":"The axes are clear, but the shaded 'allowed parameter space' is only bounded by the two curves; a small label indicating that the right boundary is set by β_app < 0.39 would improve readability.","section":"Figure 5"},{"comment":"The paper repeatedly refers to Y26 for details of the data reduction and component fitting. While acceptable, the reader would benefit from a summary of the fit uncertainties and the epoch-A core position error, since those are central to the epoch-B analysis.","section":"General"}],"recommendation":"major_revision","confidential_remarks":"The paper is a well-observed, timely study, but the central quantitative claim (βΓ ≲ 0.40) hinges on an unverified symmetry assumption and an extrapolated core position. The proper-motion non-detection is solid and should be emphasized as the primary result; the speed inference needs a systematic-uncertainty analysis before the paper can support the strong conclusion in the abstract. The authors should either add a test of the symmetry assumption (e.g., by relaxing it in the fitting or using archival multi-epoch data) or clearly reframe the paper as a proper-motion limit with a model-dependent speed estimate. The dependence on Y26 is heavy but not inappropriate for a companion paper."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Dear [Colleague],\n\nThe headline here is that the paper delivers a clean null result: the 2025 EAVN observations of GRS 1915+105 in its obscured state show no detectable jet motion on hour timescales, and had the jets moved at the pre-2019 superluminal rates (~22 mas/d) they would have shifted ~5 mas over the 5-hour runs. That is a solid observational statement, and it is the most useful thing in the paper. The authors also present two independent estimators for βcosθ (separation asymmetry and flux ratio) that both give small values, leading to βΓ ≲ 0.40. This is a new constraint for this source and fits the Fender–Motta picture of slower jets in obscured states.\n\nThe treatment is honest: the text explicitly notes the core-position assumption for epoch B and the intrinsic-symmetry assumption. The time-binned imaging and Gaussian fitting are standard, and the comparison with historical speeds is straightforward. The paper is a useful addition to the small but growing sample of post-2019 GRS 1915+105 jet studies.\n\nThe soft spots are in the translation from the null proper motion to a firm βΓ upper limit. The proper-motion limit alone only says the jet is not blazing across the sky at 0.9 mas/h. To turn this into βΓ ≲ 0.40, the authors need the βcosθ ≈ 0.11 measurement, and that rests on the assumption that the two epoch-B blobs are a simultaneous, intrinsically symmetric pair seen from a common launch point. The adopted core position comes from epoch A, seven days earlier; if the true launch point is offset, or if one blob is actually the core, the asymmetry argument systematically biases βcosθ. The authors acknowledge the assumption but do not propagate a systematic error bar around it. The stress-test concern about a fast on-axis jet is, however, not very damaging: for β ≈ 0.9 and θ ≈ 2–3°, the Doppler ratio would make the counterjet orders of magnitude fainter than observed, so the two-sided morphology itself rules out that escape route. The more realistic uncertainty is a moderate shift in the core position or a mild intrinsic asymmetry, which would move βΓ but not change the qualitative conclusion.\n\nThe abstract's claim of \"robust support\" for the obscured/unobscured dichotomy is a little strong for an upper limit with unquantified systematics. But the data are new, the analysis is careful, and the conclusion is directionally sound.\n\nFor a reader working on X-ray binary jets, this is worth a look. I'd send it to peer review; it deserves a referee. The main request would be to vary the core position and detection threshold, and to present the βΓ limit with a systematic band.\n\nRecommendation: accept with revisions.","headline":"New EAVN proper-motion limits indicate the 2025 obscured-state jets of GRS 1915+105 are not moving at historical superluminal speeds; the quantitative βΓ<0.40 is model-dependent but plausible.","tokens_in":14365,"tokens_out":5603,"would_cite":true,"duration_ms":52552,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"GRS 1915+105's jets in its current obscured state are slower than its pre-2019 relativistic jets, with an inferred speed βΓ ≲ 0.40 rather than the earlier βΓ ≳ 1.","keywords":["X-ray binaries","radio jets","GRS 1915+105","very long baseline interferometry","jet proper motion","superluminal motion","obscured state","black hole accretion"],"falsifier":"A direct measurement of proper motion of the 2025 jet components at a level above ~0.3 mas/h would rule out the claimed stationary, slow jets; conversely, detecting the core in a similar obscured-state flare and remeasuring βcosθ with a directly measured core position would test whether the asymmetry used here is real or an artifact of the adopted core.","tokens_in":13277,"feed_emoji":"🔭","tokens_out":2599,"duration_ms":27059,"temperature":0.7,"pith_summary":"The paper claims that the black hole X-ray binary GRS 1915+105, now in an X-ray-obscured state since 2019, is launching jets that are markedly slower than the relativistic jets it produced before 2019. Using 6.7-GHz very long baseline interferometry during two radio flares in 2025, the authors resolved two contrasting morphologies: a bright core with extended jet emission in one epoch, and two symmetric, well-separated blobs with no detectable core in the other. They detect no significant jet motion over five-hour observations, which would have been clearly visible if the jets moved at the pre-2019 superluminal apparent speeds. From the slight asymmetry in the two-sided blob separations and the lack of motion, they derive an intrinsic jet speed βΓ ≲ 0.40. If correct, this supports the emerging paradigm that jets from obscured X-ray binaries propagate more slowly and with more variable orientation than those from unobscured systems.","feed_headline":"Obscured jets of GRS 1915+105 are slow, not relativistic","feed_subtitle":"2025 VLBI observations capture sub-light jets, supporting a new picture of how black hole jets behave when hidden by gas.","key_machinery":"The central constraint comes from the ratio of the angular separations of the approaching and receding jet components from the core, βcosθ = (Δr_app − Δr_rec)/(Δr_app + Δr_rec), under the assumption that the two-sided jets are ejected simultaneously and are intrinsically symmetric. This is combined with the upper limit on apparent proper motion (≲0.3 mas/h, or β_app ≲ 0.39) to bound the intrinsic speed and viewing angle in the β–θ plane, yielding βΓ ≲ 0.40. A second, independent check uses the jet-to-counterjet brightness ratio and spectral index, giving consistent values of βcosθ.","core_discovery":"The paper reports that the jets of GRS 1915+105 observed in January 2025, during its X-ray-obscured state, do not show the apparent superluminal motion characteristic of its pre-2019 unobscured-state jets. For the epoch with two well-separated jet blobs, the measured separations from the inferred core give βcosθ = 0.11 ± 0.04, and the absence of proper motion limits the apparent speed to ≲0.39c; together these yield an intrinsic speed β ≲ 0.37, or βΓ ≲ 0.40. This is consistent with a previous measurement of βΓ = 0.37 for obscured-state ejecta in 2023, and it contrasts with the pre-2019 values of βΓ ~ 1–3. The paper argues that this change in jet speed, combined with the previously reported l","pith_inferences":["The slow speeds and orientation variations together suggest the jets may be precessing and decelerating due to interaction with a dense, obscuring outflow; multi-epoch VLBI spanning months could directly track the precession period.","If the core position in epoch B is systematically offset (e.g., due to opacity shifts), the βcosθ = 0.11 estimate could shift; a future observation that resolves the core during an obscured-state flare would provide a direct check of the intrinsic symmetry assumption.","The derived speed ~0.3–0.4c is similar to the slower jets inferred in other obscured X-ray binaries, hinting at a common mass-loading or environmental deceleration mechanism that could be tested by comparing jet power and column density across sources."],"forward_implications":["If confirmed, the 2025 jets are sub-relativistic, with speeds near 0.37c, distinct from the earlier relativistic jets with βΓ ≳ 1.","The absence of measurable proper motion over 5 hours rules out the pre-2019 apparent speeds (~22 mas/day) for these events, placing the jets in a slower kinematic class.","The two contrasting morphologies—core-plus-extended-jet versus two blobs with no core—may trace different phases of flare evolution, connecting radio spectral changes to jet structure.","These results add a second measured epoch (after 2023) to the obscured-state jet speed of GRS 1915+105, strengthening the claim that its post-2019 jets are systematically slower."],"fun_headline_variants":["GRS 1915+105 jets slow in obscured state","Sub-relativistic jets seen in GRS 1915+105's hidden phase","Obscured GRS 1915+105 launches slower jets","GRS 1915+105's obscured jets: no superluminal motion","Hidden jets of GRS 1915+105 are slow, new VLBI shows"],"cache_read_input_tokens":2304,"weakest_assumption_plain":"The speed estimate for epoch B assumes the two-sided jets were launched simultaneously and symmetrically from a fixed core, and that the core position adopted from epoch A (seven days earlier) is the true launch point; if the core is actually offset or the ejecta asymmetric, the derived βΓ upper limit is biased.","fun_headline_variants_meta":{"raw":{"variants":["GRS 1915+105 jets slow in obscured state","Sub-relativistic jets seen in GRS 1915+105's hidden phase","Obscured GRS 1915+105 launches slower jets","GRS 1915+105's obscured jets: no superluminal motion","Hidden jets of GRS 1915+105 are slow, new VLBI shows"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000301,"raw_usage":{"total_tokens":1638,"prompt_tokens":878,"completion_tokens":760,"prompt_tokens_details":{"cached_tokens":256},"prompt_cache_hit_tokens":256,"prompt_cache_miss_tokens":622,"completion_tokens_details":{"reasoning_tokens":673}},"tokens_in":622,"tokens_out":760,"duration_ms":6846,"temperature":1.0,"reasoning_tokens":673,"cache_read_input_tokens":256,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-01T03:14:33.147740+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"A direct measurement of proper motion of the 2025 jet components at a level above ~0.3 mas/h would rule out the claimed stationary, slow jets; conversely, detecting the core in a similar obscured-state flare and remeasuring βcosθ with a directly measured core position would test whether the asymmetry used here is real or an artifact of the adopted core.","supporting_citations":[],"review_version":1}