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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"

5479 results found.

  1. MAXI GRB260827.40: Global MASTER-Net observations report
  2. The EP-WXT trigger 01709291839 is likely the known LMXB 4U 1745-203
  3. EP260822a: Global MASTER-Net observations report
  4. IceCube Alert 260825A: Global MASTER-Net observations report
  5. GRB 260822A: GROWTH-India Telescope Upper Limits
  6. Fermi-LAT Gamma-ray Observations of IceCube-260821A
  7. IceCube-260821A: Upper limits from a search for additional neutrino events in IceCube
  8. GRB 260818B: VLA radio observations
  9. IceCube-260821A - IceCube observation of a high-energy neutrino candidate track-like event
  10. GRB 260818B: NOT optical upper limits
  11. GRB 260818B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  12. GRB 260818A: SVOM possible detection of a long and faint GRB
  13. EP260812a: refined analysis of the EP-WXT and autonomous EP-FXT observation
  14. GRB 260317A: SVOM/ECLAIRs detection through offline targeted search and its possible association to magnetar 1E 1841-04.5
  15. GRB 260804A: CALET Gamma-Ray Burst Monitor detection
  16. Fermi GRB 260808A: Global MASTER-Net observations report
  17. EP260806a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  18. EP260806a: OSIRIS+/GTC redshift z=0.089
  19. GRB 260804A: Glowbug gamma-ray detection
  20. GRB 260804A: Fermi GBM Final Real-time Localization
  21. Fermi GRB 260802B: Global MASTER-Net observations report
  22. EP260731a: COLIBRÍ optical upper limit
  23. EP260731a: NOT optical upper limit
  24. EP260727a: SAO RAS optical observations
  25. EP260727a: OHP/T193 optical observations
  26. The EP-WXT trigger 01709276927 (EP260727a?): NOT likely optical counterpart
  27. GRB 260727B: Fermi GBM Final Real-time Localization
  28. GRB 260726A: SVOM detection of a burst
  29. GRB 260616A: cubesat Avion detection
  30. EP260723a: Continued Liverpool Telescope observations suggest hours long optical plateau or rebrightening
  31. Fermi GBM trigger 806384210/260722151 is not a GRB
  32. GRB 260714B: COLIBRÍ optical counterpart candidate
  33. IceCube Alert 260709A: Global MASTER-Net observations report
  34. GRB260708B: MAXI/GSC detection
  35. Fermi GBM trigger 805087514/260707142 (GRB 260707A) is not a GRB
  36. GRB 260705A: Candidate Optical Counterpart from SOAR and Gemini-South and Possible Association with GRB 260705B
  37. GRB 260707A: Fermi GBM Final Real-time Localization
  38. IceCube-260704A: Upper limits from a search for additional neutrino events in IceCube
  39. GRB 260705A: LCO optical upper limits
  40. GRB 260703B: Fermi GBM Final Localization
  41. Fermi trigger No 804738310: Global MASTER-Net observations report
  42. Fermi GRB 260703A: Global MASTER-Net observations report
  43. GRB 260703A: Fermi GBM Final Localization
  44. GRB 260610B / AT2026owq: SAO RAS, CrAO and INASAN further optical observations and light curve
  45. Fermi trigger No 804552016: Global MASTER-Net observations report
  46. Fermi GRB 260628A: Global MASTER-Net observations report
  47. EP260623a: REM optical/NIR afterglow detection
  48. GRB 260616A: AstroSat CZTI detection
  49. GRB 260616A: SVOM/GRM observation
  50. EP260618a: COLIBRÍ optical counterpart candidate
  51. GRB 260616A: Fermi GBM Observation
  52. Konus-Wind detection of GRB 260616A
  53. GRB 260616A: Fermi-LAT detection
  54. The EP-WXT trigger 01709270148 is likely a flaring star
  55. GRB 260616A: BALROG localization (Fermi Trigger 803272919 / GRB 260616140)
  56. GRB 260616A: Fermi GBM Final Real-time Localization
  57. GRB 260603C: AstroSat CZTI detection
  58. GRB 260610B / AT2026owq: further SAO RAS optical observations
  59. GRB 260610B: IAC-80 Optical observations
  60. GRB 260607A: GOTO tentative optical counterpart candidate GOTO26fqf / AT2026ong
  61. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
  62. Fermi GRB 260604C: Global MASTER-Net observations report
  63. Fermi GRB 260604C: Global MASTER-Net observations report
  64. GRB 260603A: Simeiz Zeiss-1000 optical upper limit
  65. GRB 260603B: Fermi GBM Final Localization
  66. EP260601a/GRB 260601B: EP-FXT follow-up observation
  67. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  68. Fermi trigger No 802141998: Global MASTER-Net observations report
  69. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  70. EP260602a: COLIBRÍ optical observations
  71. GRB260601B/EP260601a: NOT near-infrared observations
  72. SVOM GRB260603.23: Global MASTER-Net observations report
  73. Fermi GRB 260602B: Global MASTER-Net observations report
  74. Fermi GRB 260602B: Global MASTER-Net observations report
  75. EP260602a: SVOM/VT optical candidate
  76. Fermi trigger No 801900520: Global MASTER-Net observations report
  77. GRB 260531A: MAXI/GSC detection
  78. IPN triangulation of GRB 260527A / EP260527a
  79. GRB 260529A: GOTO tentative optical afterglow candidate
  80. Fermi GRB 260529A: Global MASTER-Net observations report
  81. Fermi trigger No 801580882: Global MASTER-Net observations report
  82. Fermi GRB 260526A: Global MASTER-Net observations report
  83. GRB 260522A: GOTO optical upper limit
  84. GRB 260307A: TERI Gamma-ray detection
  85. GRB 260519B: Fermi GBM Final Localization
  86. GRB 260516D: GOTO optical counterpart detection
  87. GRB 260516D: GTC/OSIRIS+ spectroscopic redshift z = 1.801
  88. Fermi GRB 260516C: Global MASTER-Net observations report
  89. EP260514a: SVOM/VT optical candidate
  90. Fermi GRB 260516B: Global MASTER-Net observations report
  91. EP260514a: COLIBRÍ optical upper limits
  92. SVOM GRB 260515A: Global MASTER-Net observations report
  93. SVOM GRB 260515A: MASTER OT J151044.43+243321.7 optical counterpart detection
  94. Fermi GRB 260512A: Global MASTER-Net observations report
  95. GRB 260511B: further SAO RAS optical observations
  96. GRB 260511B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  97. GRB 260511B: LCO optical counterpart detection
  98. GRB 260510C: SVOM/COLIBRÍ (FM-GFT) further optical observations
  99. GRB 260511B: SVOM/COLIBRÍ (FM-GFT) optical observations
  100. GRB 260511B: SVOM detection of a burst

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