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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

45606 results found.

  1. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  2. EP260429a: Global MASTER-Net observations report
  3. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  4. GRB 260424B: AstroSat CZTI detection
  5. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  6. EP260429a: LCO optical upper limits
  7. EP260430a: LCO optical upper limits
  8. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  9. GRB 260429A: Fermi GBM Detection
  10. Fermi GRB 260429A: Global MASTER-Net observations report
  11. EP260430a: Global MASTER-Net observations report
  12. EP260430a: Einstein Probe detection of an X-ray transient
  13. EP260429a: EP-WXT detection of a fast X-ray transient
  14. GRB 260429A: Fermi GBM Final Real-time Localization
  15. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  16. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  17. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  18. GRB 260428A: AstroSat CZTI detection
  19. Fermi GRB 260428A: Global MASTER-Net observations report
  20. EP260416a: Mondy and Terskol optical upper limits
  21. GRB 260424B: Glowbug gamma-ray detection of a short burst
  22. GRB 260424B: COLIBRÍ optical upper limit
  23. Konus-Wind detection of GRB 260424B
  24. GRB 260428A: Fermi GBM Final Real-time Localization
  25. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  26. GRB 260424C: Fermi GBM Final Localization
  27. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  28. IPN triangulation of GRB 260424B (short)
  29. GRB 260424B: SVOM/GRM detection of a short burst
  30. IceCube-260425A - IceCube observation of a high-energy neutrino candidate track-like event
  31. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  32. IceCube Alert 260425A: Global MASTER-Net observations report
  33. Fermi trigger No 798737427: Global MASTER-Net observations report
  34. GRB 260401A: cubesat Avion detection
  35. GRB 260424A: AstroSat CZTI detection of a long burst
  36. EP260321a: Upper limits from ATCA radio observations
  37. GRB 260421B: Kilonova-Catcher optical afterglow detection
  38. GRB 260421B: Insight-HXMT/HE detection
  39. The EP-WXT trigger 01709258652: Mondy optical observations
  40. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  41. EP260416a: Mondy optical observations
  42. GRB 260421B: SVOM/ECLAIRs refined analysis
  43. GRB 260421B: 3.6m DOT optical observation
  44. EP260416a: ZTSh R band observations
  45. EP-WXT trigger 01709260362: FRAM-ORM optical observations confirm flaring star G 151-9
  46. IceCube-Cascade 260418A: Upper limits from a search for additional neutrino events in IceCube
  47. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  48. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  49. GRB 260419A: AstroSat CZTI detection
  50. GRB 260421B: SVOM/GRM observation
  51. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  52. GRB 260421B: EP-FXT follow-up observation
  53. The EP-WXT trigger 01709260362 is likely a flaring star
  54. GOTO26djh/AT2026jpw: ATCA radio detection
  55. GRB 260421B: J-band upper limit with WINTER
  56. GRB 260421B: LCO optical counterpart detection
  57. GRB 260421B: Fermi GBM Observation
  58. Fermi Gamma-ray Burst Monitor trigger 798482368/260421694 is not a GRB
  59. GRB 260421A: AstroSat CZTI detection
  60. GOTO26djh/AT2026jpw: radio detection at 15GHz
  61. GRB 260412A: SVOM/ECLAIRs refined analysis
  62. GRB 260421B: SVOM/VT optical observations
  63. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  64. GRB 260310A: Late-time Chandra X-ray Detection
  65. GRB 260418A: Insight-HXMT/HE detection
  66. EP260416a: 1.3m DFOT optical observation
  67. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  68. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  69. Fermi GRB 260421C: Global MASTER-Net observations report
  70. GRB 260421C: Fermi GBM Final Real-time Localization
  71. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  72. Fermi GRB 260421B: Global MASTER-Net observations report
  73. GRB 260421B: BOOTES-7 early optical afterglow detection
  74. GRB 260421B: LCO optical afterglow confirmation
  75. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  76. GRB 260421B: TRT optical counterpart detection
  77. GRB 260421B: SVOM detection of a long burst
  78. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  79. GRB 260421B: Fermi GBM Final Real-time Localization
  80. Fermi GRB 260421A: Global MASTER-Net observations report
  81. GRB 260421A: Fermi GBM Final Real-time Localization
  82. EP260321a: VLA radio follow-up
  83. GRB 260412A: LCOGT Optical Upper Limits
  84. The EP-WXT trigger 01709260314 is likely a flaring star
  85. EP260416a: Optical follow-up observations with Kinder
  86. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  87. EP-WXT trigger 01709260303: KAIT optical observations
  88. EP260416a: 1.5m OSN and 2.2m CAHA optical monitoring
  89. The EP-WXT trigger 01709260303 is likely a flaring star
  90. GRB 260417A: SVOM/GRM observation
  91. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  92. GRB 260419B: Fermi GBM Final Real-time Localization
  93. GRB 260419A: Fermi GBM Final Real-time Localization
  94. Fermi trigger No 798275385: Global MASTER-Net observations report
  95. EP260417a: GROWTH-India Telescope optical upper limit
  96. Fermi GRB 260417B: Global MASTER-Net observations report
  97. EP260417b: GROWTH-India Telescope optical upper limit
  98. EP260416a: Ondrejov D50 optical detection
  99. GRB 260418B: Fermi GBM Final Real-time Localization
  100. EP260416a: VLT/FORS2 spectroscopic redshift confirmation

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