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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"

5497 results found.

  1. GRB 260917B: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  2. MAXI GRB260916.37: Global MASTER-Net observations report
  3. GRB 260914A: VLT/X-shooter observations and redshift confirmation
  4. GRB 260915A: SVOM/VT optical upper limits from VHF data
  5. Fermi GBM Sub-Threshold Detection of GRB 260915A
  6. EP Alert 260914.53: Global MASTER-Net observations report
  7. GRB 260915A: SVOM detection of a burst
  8. GRB 260914A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  9. GRB 260909A: OSN 1.5m, CAHA 2.2m and GTC 10.4m optical upper limits
  10. EP Alert 260909.53: Global MASTER-Net observations report
  11. The EP-WXT trigger 01709306297 is likely the known LMXB 4U 1745-203
  12. Fermi trigger No 810554827: Global MASTER-Net observations report
  13. Fermi GRB 260907A: Global MASTER-Net observations report
  14. GRB 260903A: SAO RAS optical observations
  15. EP Alert 260903.62: Global MASTER-Net observations report
  16. GRB 260903A: EP-FXT follow-up observation
  17. SVOM GRB260903A: Global MASTER-Net observations report
  18. Fermi GBM trigger 809666623/260829141 is not a GRB
  19. MAXI GRB260827.40: Global MASTER-Net observations report
  20. The EP-WXT trigger 01709291839 is likely the known LMXB 4U 1745-203
  21. EP260822a: Global MASTER-Net observations report
  22. IceCube Alert 260825A: Global MASTER-Net observations report
  23. GRB 260822A: GROWTH-India Telescope Upper Limits
  24. Fermi-LAT Gamma-ray Observations of IceCube-260821A
  25. IceCube-260821A: Upper limits from a search for additional neutrino events in IceCube
  26. GRB 260818B: VLA radio observations
  27. IceCube-260821A - IceCube observation of a high-energy neutrino candidate track-like event
  28. GRB 260818B: NOT optical upper limits
  29. GRB 260818B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  30. GRB 260818A: SVOM possible detection of a long and faint GRB
  31. EP260812a: refined analysis of the EP-WXT and autonomous EP-FXT observation
  32. GRB 260317A: SVOM/ECLAIRs detection through offline targeted search and its possible association to magnetar 1E 1841-04.5
  33. GRB 260804A: CALET Gamma-Ray Burst Monitor detection
  34. Fermi GRB 260808A: Global MASTER-Net observations report
  35. EP260806a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  36. EP260806a: OSIRIS+/GTC redshift z=0.089
  37. GRB 260804A: Glowbug gamma-ray detection
  38. GRB 260804A: Fermi GBM Final Real-time Localization
  39. Fermi GRB 260802B: Global MASTER-Net observations report
  40. EP260731a: COLIBRÍ optical upper limit
  41. EP260731a: NOT optical upper limit
  42. EP260727a: SAO RAS optical observations
  43. EP260727a: OHP/T193 optical observations
  44. The EP-WXT trigger 01709276927 (EP260727a?): NOT likely optical counterpart
  45. GRB 260727B: Fermi GBM Final Real-time Localization
  46. GRB 260726A: SVOM detection of a burst
  47. GRB 260616A: cubesat Avion detection
  48. EP260723a: Continued Liverpool Telescope observations suggest hours long optical plateau or rebrightening
  49. Fermi GBM trigger 806384210/260722151 is not a GRB
  50. GRB 260714B: COLIBRÍ optical counterpart candidate
  51. IceCube Alert 260709A: Global MASTER-Net observations report
  52. GRB260708B: MAXI/GSC detection
  53. Fermi GBM trigger 805087514/260707142 (GRB 260707A) is not a GRB
  54. GRB 260705A: Candidate Optical Counterpart from SOAR and Gemini-South and Possible Association with GRB 260705B
  55. GRB 260707A: Fermi GBM Final Real-time Localization
  56. IceCube-260704A: Upper limits from a search for additional neutrino events in IceCube
  57. GRB 260705A: LCO optical upper limits
  58. GRB 260703B: Fermi GBM Final Localization
  59. Fermi trigger No 804738310: Global MASTER-Net observations report
  60. Fermi GRB 260703A: Global MASTER-Net observations report
  61. GRB 260703A: Fermi GBM Final Localization
  62. GRB 260610B / AT2026owq: SAO RAS, CrAO and INASAN further optical observations and light curve
  63. Fermi trigger No 804552016: Global MASTER-Net observations report
  64. Fermi GRB 260628A: Global MASTER-Net observations report
  65. EP260623a: REM optical/NIR afterglow detection
  66. GRB 260616A: AstroSat CZTI detection
  67. GRB 260616A: SVOM/GRM observation
  68. EP260618a: COLIBRÍ optical counterpart candidate
  69. GRB 260616A: Fermi GBM Observation
  70. Konus-Wind detection of GRB 260616A
  71. GRB 260616A: Fermi-LAT detection
  72. The EP-WXT trigger 01709270148 is likely a flaring star
  73. GRB 260616A: BALROG localization (Fermi Trigger 803272919 / GRB 260616140)
  74. GRB 260616A: Fermi GBM Final Real-time Localization
  75. GRB 260603C: AstroSat CZTI detection
  76. GRB 260610B / AT2026owq: further SAO RAS optical observations
  77. GRB 260610B: IAC-80 Optical observations
  78. GRB 260607A: GOTO tentative optical counterpart candidate GOTO26fqf / AT2026ong
  79. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
  80. Fermi GRB 260604C: Global MASTER-Net observations report
  81. Fermi GRB 260604C: Global MASTER-Net observations report
  82. GRB 260603A: Simeiz Zeiss-1000 optical upper limit
  83. GRB 260603B: Fermi GBM Final Localization
  84. EP260601a/GRB 260601B: EP-FXT follow-up observation
  85. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  86. Fermi trigger No 802141998: Global MASTER-Net observations report
  87. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  88. EP260602a: COLIBRÍ optical observations
  89. GRB260601B/EP260601a: NOT near-infrared observations
  90. SVOM GRB260603.23: Global MASTER-Net observations report
  91. Fermi GRB 260602B: Global MASTER-Net observations report
  92. Fermi GRB 260602B: Global MASTER-Net observations report
  93. EP260602a: SVOM/VT optical candidate
  94. Fermi trigger No 801900520: Global MASTER-Net observations report
  95. GRB 260531A: MAXI/GSC detection
  96. IPN triangulation of GRB 260527A / EP260527a
  97. GRB 260529A: GOTO tentative optical afterglow candidate
  98. Fermi GRB 260529A: Global MASTER-Net observations report
  99. Fermi trigger No 801580882: Global MASTER-Net observations report
  100. Fermi GRB 260526A: Global MASTER-Net observations report

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