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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"

23584 results found.

  1. Swift GRB 250725A: Global MASTER-Net OT detection
  2. GRB 250721A: Fermi GBM Observation
  3. SVOM J195836+32283/sb25072103: NIR observations with WINTER
  4. Swift-BAT trigger 1334535 is not a GRB
  5. GRB 250713A : SVOM/ECLAIRs refined analysis
  6. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  7. GRB 250721A: MAXI/GSC detection
  8. GRB 250717B: COLIBRÍ optical upper limit
  9. Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
  10. Swift Trigger 1334535: a possible GRB 250718A
  11. GRB 250717B: Fermi GBM Observation
  12. Konus-Wind detection of GRB 250716A
  13. GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
  14. GRB 250716A: GOTO tentative optical counterpart candidate
  15. GRB 250702B,D,E / EP250702a: H.E.S.S. very-high-energy gamma-ray observations
  16. GRB 250713A: Mephisto optical upper limits
  17. GRB 250713A: SVOM/VT optical upper limit
  18. GRB 250713A: SVOM/C-GFT upper limit
  19. GRB 250713A: Swift-XRT observations
  20. GRB 250713A: EP-FXT counterpart detection
  21. EP250711a: COLIBRÍ continuous optical observations
  22. GRB 250706A: Swift-BAT refined analysis
  23. GRB 250702F: Swift-BAT refined analysis
  24. GRB 250628A: Swift-BAT refined analysis
  25. GRB 250713A: SVOM detection of a long burst
  26. GRB 250711A: DDOTI Optical Upper Limit
  27. LIGO/Virgo/KAGRA S250712cd: Identification of a GW compact binary merger candidate
  28. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  29. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  30. EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  31. GRB 250704A: GRANDMA observations
  32. GRB 250704A: SVOM/ECLAIRs refined analysis
  33. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
  34. IceCube-250708A: No Candidates from WINTER
  35. EP/WXT 01709181970: GOTO observations confirm stellar variability
  36. EP-WXT trigger 01709181970. confirmation of a stellar flare by BOOTES-6
  37. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 4-Update Localization Volume
  38. IceCube-250706A: No Candidates from WINTER
  39. GRB 250704B / EP250704a: VLA radio detection
  40. EP250704a/GRB250704B : HCT optical and NIR upper limits
  41. GRB 250706B/C: Konus-Wind analysis of the prompt emission
  42. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  43. GRB 250704B: CALET Gamma-Ray Burst Monitor detection
  44. GRB 250702F: radio detection with the VLA
  45. GRB 250706B/C: VLT/X-shooter redshift z = 0.942
  46. IceCube-250706A: EP-FXT follow-up observations
  47. GRB 250706B/C: Fermi-LAT detection
  48. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  49. EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
  50. GRB 250706B: Swift/UVOT Detection
  51. GRB 250706C: Konus-Wind detection of a very bright GRB ~1200 s before GRB 250706B
  52. GRB 250702F: GRANDMA observations
  53. GRB 250706B: refined SVOM/MXT data analysis
  54. GRB 250706A: Swift/UVOT Upper Limits
  55. GRB 250706B: REM optical observations
  56. GRB 250706A: REM optical/NIR observations
  57. IceCube-250416A: DDOTI Optical Upper Limit
  58. IceCube-250706A: COLIBRÍ optical upper limits
  59. Swift GRB 250706A: Global MASTER-Net observations report
  60. GRB 250706A: SAO RAS optical observations
  61. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  62. GRB250706B: Swift-XRT counterpart detection
  63. GRB 250706B: iTelescope optical observations
  64. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  65. GRB 250706B: SVOM/VT optical observation
  66. GRB 250706B: TRT bright optical counterpart detection
  67. GRB 250706A: Swift detection of a burst
  68. GRB 250704B: Swift-XRT refined Analysis
  69. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  70. GRB 250703A: EIRSAT-1 GMOD Detection
  71. GRB 250704B: Swift/UVOT Upper Limits
  72. GRB 250704A: Swift/UVOT Detection
  73. Konus-Wind detection of GRB 250703A
  74. IPN triangulation of GRB 250703A
  75. EP250704a/GRB 250704B: GSP observations of the optical counterpart
  76. Konus-Wind detection of short/hard GRB 250704B/ EP250704a
  77. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  78. GRB 250702F: Kilonova-Catcher optical afterglow detection
  79. GRB 250702F: Monte Agliale Observatory optical observations
  80. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  81. EP250704a / GRB 250704B: VLT/X-shooter spectroscopic redshift z = 0.661
  82. EP250704a / GRB 250704B: SAO RAS optical observations
  83. GRBs 250702B,D,E / EP250702a: fast fading, extremely red counterpart
  84. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 3-Initial Localization Volume
  85. EP250704a / GRB 250704B: Pan-STARRS iz-band imaging and photometry
  86. EP 250704a: BOOTES-5 optical detection
  87. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  88. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  89. GRBs 250702B/C/D/E / EP250702a: Swift/UVOT Upper Limits
  90. EP250704a / GRB250704B: Swift-XRT counterpart detection
  91. GRB 250704A: Swift-XRT afterglow detection
  92. Konus-Wind detection of GRB 250702F
  93. EP250704a / GRB 250704B - REM observations
  94. GRB 250702F: GROWTH-India Telescope optical observations
  95. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  96. EP250704a: COLIBRÍ optical counterpart candidate
  97. GRB 250704A: REM detection of the optical afterglow
  98. LIGO/Virgo/KAGRA S250704ab: Coverage and upper limits from MAXI/GSC observations
  99. LIGO/Virgo/KAGRA S250704ab: Identification of a GW compact binary merger candidate
  100. GRB 250702F: Swift/UVOT Detection

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