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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"

5476 results found.

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

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