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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"

36188 results found.

  1. GRB 250704B: CALET Gamma-Ray Burst Monitor detection
  2. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  3. GRB 250702F: radio detection with the VLA
  4. GRB 250706B/C: VLT/X-shooter redshift z = 0.942
  5. GRB 250706B/C: Fermi-LAT detection
  6. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  7. GRB 250706B: Swift/UVOT Detection
  8. EP250702a/ GRB 250702B: NuSTAR X-ray Observations
  9. GRB 250706C: Konus-Wind detection of a very bright GRB ~1200 s before GRB 250706B
  10. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  11. GRB 250702F: GRANDMA observations
  12. GRB 250706A: Swift-XRT refined Analysis
  13. GRB 250706B: refined SVOM/MXT data analysis
  14. GRB 250706A: Swift/UVOT Upper Limits
  15. GRB 250706B: REM optical observations
  16. GRB 250706A: REM optical/NIR observations
  17. EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
  18. Swift GRB 250706A: Global MASTER-Net observations report
  19. GRB 250706A: JinShan optical upper limits
  20. GRB 250706A: SAO RAS optical observations
  21. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  22. GRB250706B: Swift-XRT counterpart detection
  23. GRB 250706B: iTelescope optical observations
  24. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  25. GRB 250706B: SVOM/VT optical observation
  26. GRB 250706B: TRT bright optical counterpart detection
  27. GRB 250706A: GROWTH-India Telescope optical upper limit
  28. GRB 250706B: SVOM detection of a long burst
  29. GRB 250706A: Swift detection of a burst
  30. GRB 250704B: Swift-XRT refined Analysis
  31. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  32. GRB 250703A: EIRSAT-1 GMOD Detection
  33. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  34. GRB 250704B: Swift/UVOT Upper Limits
  35. GRB 250704A: Swift/UVOT Detection
  36. Radio observation of GRBs 250702B,C,E / EP250702a with the Allen Telescope Array
  37. GRB 250704B: Insight-HXMT detection
  38. Konus-Wind detection of GRB 250703A
  39. IPN triangulation of GRB 250703A
  40. EP250704a/GRB 250704B: GSP observations of the optical counterpart
  41. EP250704a/GRB 250704B: FTW optical and NIR observations of the counterpart
  42. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  43. Konus-Wind detection of short/hard GRB 250704B/ EP250704a
  44. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  45. EP250704a/GRB 250704B VLT/HAWK-I NIR afterglow detection
  46. GRB 250702F: Kilonova-Catcher optical afterglow detection
  47. GRB 250702F: Monte Agliale Observatory optical observations
  48. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  49. EP250704a / GRB 250704B: VLT/X-shooter spectroscopic redshift z = 0.661
  50. EP250704a / GRB 250704B: JinShan optical observations
  51. GRB 250704A: SVOM/VT optical observation
  52. EP250704a / GRB 250704B: SAO RAS optical observations
  53. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  54. GRBs 250702B,D,E / EP250702a: fast fading, extremely red counterpart
  55. EP250704a / GRB 250704B: SVOM/VT optical blue counterpart
  56. EP250704a / GRB 250704B: Pan-STARRS iz-band imaging and photometry
  57. LIGO/Virgo/KAGRA S250704ab: Upper limits from Fermi-GBM Observations
  58. GRB 250702A: Insight-HXMT detection
  59. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  60. EP250704a / GRB250704B: Swift-XRT counterpart detection
  61. GRB 250704A: Swift-XRT afterglow detection
  62. GRB 250702B / EP2050702a: FTW optical and NIR observations
  63. Konus-Wind detection of GRB 250702F
  64. EP250704a / GRB 250704B - REM observations
  65. GRB 250702F: GROWTH-India Telescope optical observations
  66. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  67. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  68. EP250704a: Einstein Probe detection of an X-ray transient
  69. GRB 250704B: SVOM/GRM observation of a short burst
  70. GRB 250702F: optical photometry from Konkoly
  71. GRB 250704A: REM detection of the optical afterglow
  72. GRB 250702F: SVOM/VT optical observation
  73. GRB 250704A: SVOM detection of a burst
  74. GRB 250702F: Swift/UVOT Detection
  75. GRB 250702A: CALET Gamma-Ray Burst Monitor detection
  76. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  77. Fermi GRB 250703A: Global MASTER-Net observations report
  78. GRBs 250702B,C,D,E / EP250702a: 2.2m CAHA optical upper limit
  79. GRB 250702F: Swift-XRT refined Analysis
  80. GRB 250702F: Fermi GBM Observation
  81. GRB 250702F: Leavitt Observatory optical observations
  82. GRB 250702F: AKO Optical Afterglow Detection
  83. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  84. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  85. GRB 250702A: GECAM-B detection
  86. GRB 250702F: Skynet Optical Observations
  87. GRB 250424A: VIRT Optical Upper Limit
  88. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  89. EP250702a/GRB 250702B, C, D, E: EP-FXT follow-up observation
  90. GRB 250702F: TRT Optical Observation
  91. GRB 250703A: DDOTI Optical Upper Limit
  92. GRB 250702F: REM optical afterglow detection
  93. GRB 250702F: DDOTI Optical Observation
  94. GRB 250702B,C,D,E / EP 250702a: MAXI/GSC detection
  95. GRB 250703A: Fermi GBM Final Real-time Localization
  96. EP250702a/GRB 250702B,C,D,E: GOTO optical upper limits
  97. GRB 250702F: COLIBRÍ Observations of the Afterglow
  98. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  99. Fermi GRB 250702E: Global MASTER-Net observations report
  100. Fermi GRB 250702B: Global MASTER-Net observations report

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