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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"

23574 results found.

  1. EP260806a: COLIBRÍ optical observations
  2. EP260806a: OSIRIS+/GTC redshift z=0.089
  3. GRB 260715A: cubesat Avion detection
  4. GRB 260708A: cubesat Avion detection
  5. SN 2026stf / GRB 260708A: ATLAS forced photometry
  6. GRB 260730B: Glowbug gamma-ray detection
  7. GRB 260805C: Glowbug gamma-ray detection
  8. GRB 260805B: Glowbug gamma-ray detection
  9. Fermi GRB 260805A: Global MASTER-Net observations report
  10. GRB 260804A: Glowbug gamma-ray detection
  11. AT 2026wki: EP/FXT follow-up observations
  12. GRB 260730B: CALET Gamma-Ray Burst Monitor detection
  13. GRB 260708A: LCO further optical observations show supernova features
  14. Fermi GRB 260802B: Global MASTER-Net observations report
  15. GRB 260802A: SVOM/VT optical upper limits from VHF data
  16. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  17. EP260731a: COLIBRÍ optical upper limit
  18. GRB 260727A: SVOM/ECLAIRs refined analysis
  19. GRB 260726A: SVOM/ECLAIRs refined analysis
  20. EP260728a: COLIBRÍ optical upper limit
  21. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  22. EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
  23. EP260727a: SAO RAS optical observations
  24. GRB 260727A: AbAO and SAO RAS optical observations
  25. GRB 260726A: Fermi GBM Observation
  26. EP260727a: 1.5m OSN optical counterpart detection
  27. Konus-Wind detection of GRB 260727A
  28. EP260727a: NUTTELA-TAO Early Optical Limits
  29. GRB 260727A: Glowbug gamma-ray detection
  30. GRB 260726A: J-band upper limit with WINTER
  31. GRB 260727A: J-band upper limit with WINTER
  32. GRB 260726A: SVOM ECLAIRs improved position and MXT possible detection of a counterpart
  33. GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
  34. EP260723a: SVOM/ECLAIRs Upper Limit
  35. GRB 260727A: GOTO early optical upper limit
  36. GRB 260727A: Kilonova-Catcher optical upper limit
  37. Fermi GRB 260726A: Global MASTER-Net observations report
  38. GRB 260616A: cubesat Avion detection
  39. GRB 260718A: SVOM/ECLAIRs refined analysis
  40. EP260723a: COLIBRÍ optical observations
  41. IceCube-260722A: One candidate from the Zwicky Transient Facility (ZTF)
  42. IceCube Alert 260722A: Global MASTER-Net observations report
  43. Konus-Wind detection of GRB 260721A
  44. GRB 260721A: NuSTAR detection of prompt emission
  45. Konus-Wind detection of GRB 260714B
  46. Fermi trigger No 806104130: Global MASTER-Net observations report
  47. Fermi GRB 260718A: Global MASTER-Net observations report
  48. GRB 260710A: SVOM/GRM observation
  49. GRB 260718A : GRANDMA and KNC upper limits
  50. GRB 260718A: SVOM/VT optical upper limits from VHF data
  51. GRB 260618B: EP-FXT follow-up observation upper limit
  52. GRB 260714B: COLIBRÍ optical counterpart candidate
  53. SVOM sb26071506: Global MASTER-Net observations report
  54. GRB 260710A: AstroSat CZTI detection
  55. GRB 260714B: AstroSat CZTI detection
  56. IceCube-260712A: LAST optical follow-up observations of the IceCube neutrino candidate
  57. EP260713a: Einstein Probe detection of an X-ray transient
  58. GRB 260708A: slowly decaying X-ray emission observed by EP/FXT
  59. EP260623a: KAIT optical observations
  60. GRB 260708A: GRANDMA Optical Observations
  61. GRB 260710A: Fermi GBM Detection
  62. IceCube-260708A: Observations with the Vera C. Rubin Observatory
  63. EP-WXT trigger 0170924151 : RAPAS optical counterpart candidate detection
  64. GRB 260708A: Glowbug gamma-ray detection
  65. GRB 260706A : GRANDMA Upper limits
  66. GRB 260708A: Kilonova-Catcher optical afterglow detection
  67. Fermi LAT GRB 260708A: MASTER OT J150237.02-435307.7 optical counterpart detection
  68. IceCube Alert 260709A: Global MASTER-Net observations report
  69. LAT GRB260708.42: Global MASTER-Net observations report
  70. GRB260708B: MAXI/GSC detection
  71. GRB 260706A: Further EP-FXT follow-up observation
  72. GRB 260706A: SVOM/VT optical upper limits
  73. EP260707a: TRT optical upper limit
  74. GRB 260705C: Glowbug gamma-ray detection of a short burst
  75. GRB 260706A: SVOM/ECLAIRs refined analysis
  76. GRB 260704A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  77. GRB 260706A: REM optical/NIR observations
  78. GRB 260706A: LCO optical upper limit
  79. GRB 260705A: SVOM/ECLAIRs refined analysis
  80. GRB 260706A: SVOM detection of a burst
  81. GRB 260706A: Fermi GBM Final Real-time Localization
  82. The EP-WXT trigger 01709274014: KAIT confirmation of a stellar flare
  83. IceCube260704A: OHP/T193 optical observations
  84. GRB 260629A: AstroSat CZTI detection
  85. Fermi trigger No 804738310: Global MASTER-Net observations report
  86. Fermi GRB 260703A: Global MASTER-Net observations report
  87. GRB 260623A: Glowbug gamma-ray detection
  88. GRB 260610B / AT2026owq: SAO RAS, CrAO and INASAN further optical observations and light curve
  89. Fermi trigger No 804552016: Global MASTER-Net observations report
  90. Fermi GRB 260628A: Global MASTER-Net observations report
  91. EP260626a: COLIBRÍ optical upper limit
  92. Konus-Wind detection of GRB 260623B / EP260623a
  93. EP260623a: TNG NIR afterglow detection
  94. Konus-Wind detection of GRB 260618B
  95. EP260623a: WINTER J-band observations
  96. GRB 260617A: Glowbug gamma-ray detection of a short burst
  97. EP260623a: Optical follow-up observations with Kinder
  98. EP260623a: TRT optical observations
  99. EP260623a: REM optical/NIR afterglow detection
  100. EP 260623a: COLIBRÍ optical observations

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