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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"

38158 results found.

  1. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  2. Fermi GRB 260314A: Global MASTER-Net observations report
  3. Fermi GRB 260313A: Global MASTER-Net observations report
  4. GRB 260314A: Fermi GBM Final Real-time Localization
  5. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  6. GRB 260313A: A Correction to the Fermi GBM Final Localization
  7. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  8. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  9. GRB 260310B: Insight-HXMT/HE detection
  10. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  11. GRB 260310A: NOT optical polarimetry
  12. GRB 260312B: AstroSat CZTI detection
  13. Swift BAT trigger 1500295: A solar flare
  14. GRB 260313A: Fermi GBM Final Real-time Localization
  15. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  16. Swift BAT trigger 1500287: A solar flare
  17. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  18. GRB 260308A: Insight-HXMT/HE detection
  19. GRB 260307A: CALET Gamma-Ray Burst Monitor detection
  20. GRB 260310A / AT 2026fgk: Location in the Epeak - Eiso diagram
  21. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  22. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  23. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  24. GRB260310A / AT2026fgk: P200 Spectroscopy
  25. GRB 260312B: Glowbug gamma-ray detection
  26. GRB 260310A: Fermi GBM Observation
  27. GRB 260310A: potential optical counterpart
  28. Fermi GRB 260312B: Global MASTER-Net observations report
  29. Fermi GRB 260311B: Global MASTER-Net observations report
  30. Swift BAT trigger 1500148: A solar flare
  31. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  32. GRB 260312B: Fermi GBM Final Real-time Localization
  33. GRB 260310B: GECAM-B observation of a burst
  34. Retraction of GCN 43965: GRB is actually solar flare
  35. GRB 260312A: Swift detection of a burst
  36. GRB 260311B: Fermi GBM Final Real-time Localization
  37. GRB 260131A/B: radio detection with the VLA
  38. GRB260307A: GECAM-B observation of a burst
  39. GRB 260308A: SVOM/GRM observation of a short GRB
  40. EP260306a: Mondy optical upper limit
  41. GRB 260310A: AstroSat CZTI detection of a long burst
  42. GRB 260311A: Fermi GBM Final Real-time Localization
  43. Fermi GRB 260310B: Global MASTER-Net observations report
  44. GRB 260310B: Fermi GBM Final Real-time Localization
  45. Fermi GRB 260310A: Global MASTER-Net observations report
  46. GRB 260307B: SVOM/ECLAIRs refined analysis
  47. GRB 260208A: radio detection with the VLA
  48. GRB 260310A: Fermi GBM Final Real-time Localization
  49. GRB 260307A: Glowbug gamma-ray detection
  50. GRB 260308A: Fermi GBM Final Real-time Localization
  51. Fermi GBM Sub-Threshold Detection of GRB 260307B
  52. GRB 260307B: Mephisto optical upper limits
  53. GRB 260307B: possible NOT optical counterpart
  54. GRB 260307B: SVOM/VT upper limit with X band data analysis
  55. Fermi GRB 260307A: Global MASTER-Net observations report
  56. GRB 260307B: SVOM/VT optical candidate
  57. GRB 260307B: SVOM/C-GFT upper limit
  58. GRB 260307B: SVOM detection of a burst
  59. GRB 260307A: Fermi GBM Final Localization
  60. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  61. GRB 260207A: TESS Detection and Possible VLA Counterpart
  62. EP260302a: Optical afterglow rebrightening
  63. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  64. GRB 260303A: 1.3m DFOT optical upper limit (duplicate submission)
  65. GRB 260303A: 1.3m DFOT optical upper limit
  66. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  67. GRB 260303A: SVOM/ECLAIRs refined analysis
  68. Fermi GRB 260305A: Global MASTER-Net observations report
  69. GRB 260305A: Fermi GBM Final Real-time Localization
  70. GRB 260303B: AstroSat CZTI detection
  71. GRB 260304A: AstroSat CZTI detection of a long burst
  72. GRB 260303A: SVOM/VT optical observations
  73. GRB 260303A: J-band observations with WINTER
  74. GRB 260303B: NuSTAR detection of prompt emission
  75. EP260302a: Global MASTER-Net observations report
  76. Fermi GRB 260303B: Global MASTER-Net observations report
  77. IceCube-260217A: No Candidate Transients from the Zwicky Transient Facility
  78. GRB 260228A: SVOM/ECLAIRs refined analysis
  79. GRB 260225A: SVOM/ECLAIRs refined analysis
  80. GRB 260303B: BALROG localization (Fermi Trigger 794237065 / GRB 260303559)
  81. GRB 260303B: Fermi GBM Final Real-time Localization
  82. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  83. GRB 260303A: SVOM detection of a burst
  84. GRB 260228A: EP-FXT follow-up observation
  85. GRB 251130B: TERI Gamma-ray detection
  86. GRB 260208A: TERI Gamma-ray detection
  87. GRB 260302A: Fermi GBM Final Real-time Localization
  88. EP260227a: Mondy optical observations
  89. GRB 260228A: CAHA 2.2m telescope optical upper limit
  90. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  91. GRID detection of GRB 260225D
  92. GRB 260228A: SVOM/VT optical upper limits
  93. GRB 260225D: SVOM/GRM observation
  94. GRB 260225B: SVOM/GRM observation
  95. GRB 260228A: SVOM detection of a burst
  96. GRB 260226A: Asiago r-band upper limit
  97. GRB 260225A: SVOM/VT optical continued observations and upper limit
  98. GRID detection of GRB 260223A
  99. EP260227a: Global MASTER-Net observations report
  100. GRB 260226A: Insight-HXMT/HE detection of the very bright burst

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