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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"
  1. Swift-BAT trigger 1334535 is not a GRB
  2. GRB 250721A: Swift-XRT observations
  3. GRB 250722A: Fermi GBM Final Real-time Localization
  4. GRB 250713A : SVOM/ECLAIRs refined analysis
  5. GRB 250717B: SVOM/GRM observation
  6. LIGO/Virgo/KAGRA S250711q: Updated Sky localization
  7. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  8. GRB 250721A: Tiled Swift observations
  9. GRB 250721A: MAXI/GSC detection
  10. GRB 250721A: Fermi GBM Final Localization
  11. GRB 250720B: Fermi GBM Final Localization Correction
  12. GRB 250720A: Fermi GBM Final Localization
  13. Fermi trigger No 774730635: Global MASTER-Net observations report
  14. LIGO/Virgo/KAGRA S250720j: Retraction of GW compact binary merger candidate
  15. Fermi Gamma-ray Burst Monitor trigger 774670514/250720094 is not a GRB
  16. EP250702a/GRB250702B,D,E: SVOM/VT optical upper limit
  17. GRB 250717B: COLIBRÍ optical upper limit
  18. LIGO/Virgo/KAGRA S250711q: Upper limits from Swift/BAT-GUANO
  19. GRB 250717B: Swift-XRT observations
  20. GRB 250718B: Fermi GBM Final Localization Correction
  21. GRB 250718B: Fermi GBM Final Real-time Localization
  22. Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
  23. Swift Trigger 1334535: a possible GRB 250718A
  24. Swift GRB250718.01: Global MASTER-Net observations report
  25. GRB 250717B: Swift ToO observations
  26. GRB 270713A: Kitab and AbAO Optical Observations
  27. GRB 250717B: Fermi GBM Observation
  28. GRB 250717B: Swift/BAT-GUANO arcminute localization of a burst
  29. Konus-Wind detection of GRB 250716A
  30. GRB 250716A: Swift-XRT afterglow detection
  31. GRB 250717B: Fermi GBM Final Real-time Localization
  32. GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
  33. GRB 250717A: Fermi GBM Final Real-time Localization
  34. GRB 250716A: Swift ToO observations
  35. GRB 250716A: GOTO tentative optical counterpart candidate
  36. GRB 250716A: Fermi GBM Observation
  37. GRB 250714A: SVOM/GRM observation
  38. Fermi GRB 250716A: Global MASTER-Net observations report
  39. GRB 250716A: Fermi GBM Final Real-time Localization
  40. Fermi GRB 250715A: Global MASTER-Net observations report
  41. GRB 250715A: Fermi GBM Final Real-time Localization
  42. EP250702a / GRB 250702B,D,E: Hubble Space Telescope Observations
  43. GRB 250702B,D,E / EP250702a: H.E.S.S. very-high-energy gamma-ray observations
  44. GRB 250713A: Mephisto optical upper limits
  45. Fermi GRB 250714A: Global MASTER-Net observations report
  46. GRB 250713A: SVOM/VT optical upper limit
  47. GRB 250713A: NOT optical upper limits
  48. GRB 250713A: OHP/T193 upper limit
  49. GRB 250713A: SVOM/C-GFT upper limit
  50. GRB 250714A: Fermi GBM Final Real-time Localization
  51. GRB 250706B/C: 7DT Follow-up Observations
  52. GRB 250713A: Swift-XRT observations
  53. GRB 250713A: EP-FXT counterpart detection
  54. EP250711a: COLIBRÍ continuous optical observations
  55. GRB 250706A: Swift-BAT refined analysis
  56. GRB 250702F: Swift-BAT refined analysis
  57. GRB 250628A: Swift-BAT refined analysis
  58. LIGO/Virgo/KAGRA S250712cd: Updated Sky localization
  59. GRB 250713A: JinShan optical upper limits
  60. GRB 250713A: SVOM detection of a long burst
  61. EP250711a: Global MASTER-Net observations report
  62. GRB 250711A: DDOTI Optical Upper Limit
  63. LIGO/Virgo/KAGRA S250712cd: Identification of a GW compact binary merger candidate
  64. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate (duplicate submission)
  65. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  66. GRB 250711A: SVOM/GRM observation
  67. EP250711a: NOT optical counterpart candidate
  68. EP250711a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  69. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  70. Fermi GRB 250711A: Global MASTER-Net observations report
  71. EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  72. GRB 250704A: GRANDMA observations
  73. GRB 250711A: BALROG localization (Fermi Trigger 773937617 / GRB 250711611)
  74. GRB 250711A: Fermi GBM Final Real-time Localization
  75. GRB 250704A: SVOM/ECLAIRs refined analysis
  76. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
  77. GRB 250702B,D,E/EP250702A: JCMT sub-mm observations at 350 GHz
  78. GRB 250704B / EP250704a: 1.3 GHz MeerKAT Detection
  79. GRB 250702B,D,E / EP250702a: ALMA detection
  80. LIGO/Virgo/KAGRA S250629bs: Upper limits from Swift/BAT-GUANO
  81. LIGO/Virgo/KAGRA S250629ae: Upper limits from Swift/BAT-GUANO
  82. IceCube-250708A: No Candidates from WINTER
  83. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  84. GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz
  85. GRB 250702B,D,E / EP250702a: 10 GHz detection with the VLA
  86. IceCube-250708A: Upper limits from a search for additional neutrino events in IceCube
  87. GRB 250709A: Fermi GBM Final Localization
  88. IPN triangulation of GRB 250704B (short/hard, consistent with EP 250704a)
  89. GRB 250706B/C: Insight-HXMT detection
  90. EP/WXT 01709181970: GOTO observations confirm stellar variability
  91. EP-WXT trigger 01709181970. confirmation of a stellar flare by BOOTES-6
  92. EP250704a/GRB 250704B: 10 GHz VLA detection
  93. The EP-WXT trigger 01709181970 is likely a flaring star
  94. GRB250702 B,D,E / EP250702a: MOSFIRE imaging of the afterglow
  95. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 4-Update Localization Volume
  96. IceCube-250706A: No Candidates from WINTER
  97. IPN triangulation of GRB 250706C (consistent with the GRB 250706B)
  98. IceCube-250706A: No Candidates from the Zwicky Transient Facility
  99. IceCube-250708A - IceCube observation of a high-energy neutrino candidate track-like event
  100. GRB 250704B / EP250704a: VLA radio detection

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