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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. GRB 250725A: Fermi GBM Final Real-time Localization
  2. Fermi GRB 250725A: Global MASTER-Net observations report
  3. Swift GRB 250725A: Global MASTER-Net observations report
  4. EP250702a/GRB250702 B,E,D: MeerKAT radio observations at 3.06 GHz
  5. SVOM J195836+32283 is not a real source
  6. EP250702a/GRB250702 B,D,E: uGMRT Radio detection in 1.26 GHz
  7. SVOM J195836+32283/sb25072103: Second VT observation
  8. SVOM J195836+32283/sb25072103: Liverpool Telescope detection of an extended source
  9. GRB 250723B: Fermi GBM Final Real-time Localization
  10. GRB 250721A: Fermi GBM Observation
  11. GRB 250723A: Fermi GBM Final Real-time Localization
  12. SVOM J195836+32283/sb25072103: Swift XRT/UVOT upper limits
  13. SVOM J195836+32283/sb25072103: NIR observations with WINTER
  14. Swift-BAT trigger 1334535 is not a GRB
  15. GRB 250721A: Swift-XRT observations
  16. GRB 250722A: Fermi GBM Final Real-time Localization
  17. GRB 250713A : SVOM/ECLAIRs refined analysis
  18. GRB 250717B: SVOM/GRM observation
  19. LIGO/Virgo/KAGRA S250711q: Updated Sky localization
  20. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  21. GRB 250721A: Tiled Swift observations
  22. GRB 250721A: MAXI/GSC detection
  23. GRB 250721A: Fermi GBM Final Localization
  24. GRB 250720B: Fermi GBM Final Localization Correction
  25. GRB 250720A: Fermi GBM Final Localization
  26. Fermi trigger No 774730635: Global MASTER-Net observations report
  27. LIGO/Virgo/KAGRA S250720j: Retraction of GW compact binary merger candidate
  28. Fermi Gamma-ray Burst Monitor trigger 774670514/250720094 is not a GRB
  29. EP250702a/GRB250702B,D,E: SVOM/VT optical upper limit
  30. GRB 250717B: COLIBRÍ optical upper limit
  31. LIGO/Virgo/KAGRA S250711q: Upper limits from Swift/BAT-GUANO
  32. GRB 250717B: Swift-XRT observations
  33. GRB 250718B: Fermi GBM Final Localization Correction
  34. GRB 250718B: Fermi GBM Final Real-time Localization
  35. Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
  36. Swift Trigger 1334535: a possible GRB 250718A
  37. Swift GRB250718.01: Global MASTER-Net observations report
  38. GRB 250717B: Swift ToO observations
  39. GRB 270713A: Kitab and AbAO Optical Observations
  40. GRB 250717B: Fermi GBM Observation
  41. GRB 250717B: Swift/BAT-GUANO arcminute localization of a burst
  42. Konus-Wind detection of GRB 250716A
  43. GRB 250716A: Swift-XRT afterglow detection
  44. GRB 250717B: Fermi GBM Final Real-time Localization
  45. GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
  46. GRB 250717A: Fermi GBM Final Real-time Localization
  47. GRB 250716A: Swift ToO observations
  48. GRB 250716A: GOTO tentative optical counterpart candidate
  49. GRB 250716A: Fermi GBM Observation
  50. GRB 250714A: SVOM/GRM observation
  51. Fermi GRB 250716A: Global MASTER-Net observations report
  52. GRB 250716A: Fermi GBM Final Real-time Localization
  53. Fermi GRB 250715A: Global MASTER-Net observations report
  54. GRB 250715A: Fermi GBM Final Real-time Localization
  55. EP250702a / GRB 250702B,D,E: Hubble Space Telescope Observations
  56. GRB 250702B,D,E / EP250702a: H.E.S.S. very-high-energy gamma-ray observations
  57. GRB 250713A: Mephisto optical upper limits
  58. Fermi GRB 250714A: Global MASTER-Net observations report
  59. GRB 250713A: SVOM/VT optical upper limit
  60. GRB 250713A: NOT optical upper limits
  61. GRB 250713A: OHP/T193 upper limit
  62. GRB 250713A: SVOM/C-GFT upper limit
  63. GRB 250714A: Fermi GBM Final Real-time Localization
  64. GRB 250706B/C: 7DT Follow-up Observations
  65. GRB 250713A: Swift-XRT observations
  66. GRB 250713A: EP-FXT counterpart detection
  67. EP250711a: COLIBRÍ continuous optical observations
  68. GRB 250706A: Swift-BAT refined analysis
  69. GRB 250702F: Swift-BAT refined analysis
  70. GRB 250628A: Swift-BAT refined analysis
  71. LIGO/Virgo/KAGRA S250712cd: Updated Sky localization
  72. GRB 250713A: JinShan optical upper limits
  73. GRB 250713A: SVOM detection of a long burst
  74. EP250711a: Global MASTER-Net observations report
  75. GRB 250711A: DDOTI Optical Upper Limit
  76. LIGO/Virgo/KAGRA S250712cd: Identification of a GW compact binary merger candidate
  77. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate (duplicate submission)
  78. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  79. GRB 250711A: SVOM/GRM observation
  80. EP250711a: NOT optical counterpart candidate
  81. EP250711a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  82. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  83. Fermi GRB 250711A: Global MASTER-Net observations report
  84. EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  85. GRB 250704A: GRANDMA observations
  86. GRB 250711A: BALROG localization (Fermi Trigger 773937617 / GRB 250711611)
  87. GRB 250711A: Fermi GBM Final Real-time Localization
  88. GRB 250704A: SVOM/ECLAIRs refined analysis
  89. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
  90. GRB 250702B,D,E/EP250702A: JCMT sub-mm observations at 350 GHz
  91. GRB 250704B / EP250704a: 1.3 GHz MeerKAT Detection
  92. GRB 250702B,D,E / EP250702a: ALMA detection
  93. LIGO/Virgo/KAGRA S250629bs: Upper limits from Swift/BAT-GUANO
  94. LIGO/Virgo/KAGRA S250629ae: Upper limits from Swift/BAT-GUANO
  95. IceCube-250708A: No Candidates from WINTER
  96. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  97. GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz
  98. GRB 250702B,D,E / EP250702a: 10 GHz detection with the VLA
  99. IceCube-250708A: Upper limits from a search for additional neutrino events in IceCube
  100. GRB 250709A: Fermi GBM Final Localization

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