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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"

23153 results found.

  1. GRB 250704A: SVOM/ECLAIRs refined analysis
  2. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
  3. IceCube-250708A: No Candidates from WINTER
  4. EP/WXT 01709181970: GOTO observations confirm stellar variability
  5. EP-WXT trigger 01709181970. confirmation of a stellar flare by BOOTES-6
  6. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 4-Update Localization Volume
  7. IceCube-250706A: No Candidates from WINTER
  8. GRB 250704B / EP250704a: VLA radio detection
  9. EP250704a/GRB250704B : HCT optical and NIR upper limits
  10. GRB 250706B/C: Konus-Wind analysis of the prompt emission
  11. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  12. GRB 250704B: CALET Gamma-Ray Burst Monitor detection
  13. GRB 250702F: radio detection with the VLA
  14. GRB 250706B/C: VLT/X-shooter redshift z = 0.942
  15. IceCube-250706A: EP-FXT follow-up observations
  16. GRB 250706B/C: Fermi-LAT detection
  17. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  18. EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
  19. GRB 250706B: Swift/UVOT Detection
  20. GRB 250706C: Konus-Wind detection of a very bright GRB ~1200 s before GRB 250706B
  21. GRB 250702F: GRANDMA observations
  22. GRB 250706B: refined SVOM/MXT data analysis
  23. GRB 250706A: Swift/UVOT Upper Limits
  24. GRB 250706B: REM optical observations
  25. GRB 250706A: REM optical/NIR observations
  26. IceCube-250416A: DDOTI Optical Upper Limit
  27. IceCube-250706A: COLIBRÍ optical upper limits
  28. Swift GRB 250706A: Global MASTER-Net observations report
  29. GRB 250706A: SAO RAS optical observations
  30. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  31. GRB250706B: Swift-XRT counterpart detection
  32. GRB 250706B: iTelescope optical observations
  33. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  34. GRB 250706B: SVOM/VT optical observation
  35. GRB 250706B: TRT bright optical counterpart detection
  36. GRB 250706A: Swift detection of a burst
  37. GRB 250704B: Swift-XRT refined Analysis
  38. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  39. GRB 250703A: EIRSAT-1 GMOD Detection
  40. GRB 250704B: Swift/UVOT Upper Limits
  41. GRB 250704A: Swift/UVOT Detection
  42. Konus-Wind detection of GRB 250703A
  43. IPN triangulation of GRB 250703A
  44. EP250704a/GRB 250704B: GSP observations of the optical counterpart
  45. Konus-Wind detection of short/hard GRB 250704B/ EP250704a
  46. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  47. GRB 250702F: Kilonova-Catcher optical afterglow detection
  48. GRB 250702F: Monte Agliale Observatory optical observations
  49. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  50. EP250704a / GRB 250704B: VLT/X-shooter spectroscopic redshift z = 0.661
  51. EP250704a / GRB 250704B: SAO RAS optical observations
  52. GRBs 250702B,D,E / EP250702a: fast fading, extremely red counterpart
  53. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 3-Initial Localization Volume
  54. EP250704a / GRB 250704B: Pan-STARRS iz-band imaging and photometry
  55. EP 250704a: BOOTES-5 optical detection
  56. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  57. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  58. GRBs 250702B/C/D/E / EP250702a: Swift/UVOT Upper Limits
  59. EP250704a / GRB250704B: Swift-XRT counterpart detection
  60. GRB 250704A: Swift-XRT afterglow detection
  61. Konus-Wind detection of GRB 250702F
  62. EP250704a / GRB 250704B - REM observations
  63. GRB 250702F: GROWTH-India Telescope optical observations
  64. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  65. EP250704a: COLIBRÍ optical counterpart candidate
  66. GRB 250704A: REM detection of the optical afterglow
  67. LIGO/Virgo/KAGRA S250704ab: Coverage and upper limits from MAXI/GSC observations
  68. LIGO/Virgo/KAGRA S250704ab: Identification of a GW compact binary merger candidate
  69. GRB 250702F: Swift/UVOT Detection
  70. GRB 250702A: CALET Gamma-Ray Burst Monitor detection
  71. GRBs 250702B,C,D,E / EP250702a: 2.2m CAHA optical upper limit
  72. GRBs 250702B/C/D/E / EP250702a: Swift XRT localization
  73. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  74. GRB 250702F: TRT Optical Observation
  75. GRB 250703A: DDOTI Optical Upper Limit
  76. GRBs 250702B,C,D,E / EP250702a: Konus-Wind detection of a hard X-ray transient activity
  77. GRB 250702F: REM optical afterglow detection
  78. EP250702a: Global MASTER-Net observations report
  79. GRB 250702F: DDOTI Optical Observation
  80. GRB 250702B,C,D,E / EP 250702a: MAXI/GSC detection
  81. EP250702a/GRB 250702B,C,D,E: GOTO optical upper limits
  82. GRB 250702F: COLIBRÍ Observations of the Afterglow
  83. GRB 250702F: GTC/OSIRIS+ spectroscopic redshift z = 1.520
  84. GRB 250702F: GOTO optical counterpart detection
  85. GRB 250702F: Ondrejov D50 optical afterglow detection
  86. GRB 250702F: Swift detection of a burst with an optical counterpart
  87. Konus-Wind detection of GRB 250627A
  88. LIGO/Virgo/KAGRA S250702n: Identification of a GW compact binary merger candidate
  89. GRB 250628B: Swift-XRT observations
  90. LIGO/Virgo/KAGRA S250629bs: Identification of a GW compact binary merger candidate
  91. LIGO/Virgo/KAGRA S250629ae: Identification of a GW compact binary merger candidate
  92. GRB 250628A: REM optical/NIR upper limits
  93. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate
  94. GRB 250628A: Swift/UVOT Upper Limits
  95. GRB 250628A: Swift-XRT refined Analysis
  96. Swift GRB 250628A: Global MASTER-Net observations report
  97. GRB 250628A: Swift detection of a burst
  98. GRB 250625A: Swift-BAT refined analysis
  99. Fermi Gamma-ray Burst Monitor trigger 772720540/250627525 is not a GRB
  100. GRB 250625A: GTC/OSIRIS+ spectroscopic observations of the potential host galaxy

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