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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"

44478 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. The EP-WXT trigger 01709258843 is not a real source
  34. GRB 260310B: GECAM-B observation of a burst
  35. Retraction of GCN 43965: GRB is actually solar flare
  36. GRB 260312A: Swift detection of a burst
  37. GRB 260311B: Fermi GBM Final Real-time Localization
  38. GRB 260131A/B: radio detection with the VLA
  39. EP260302a: MeerKAT radio counterpart
  40. GRB260307A: GECAM-B observation of a burst
  41. GRB 260308A: SVOM/GRM observation of a short GRB
  42. EP260306a: Mondy optical upper limit
  43. GRB 260310A: AstroSat CZTI detection of a long burst
  44. GRB 260311A: Fermi GBM Final Real-time Localization
  45. Fermi GRB 260310B: Global MASTER-Net observations report
  46. GRB 260310B: Fermi GBM Final Real-time Localization
  47. Fermi GRB 260310A: Global MASTER-Net observations report
  48. GRB 260307B: SVOM/ECLAIRs refined analysis
  49. GRB 260208A: radio detection with the VLA
  50. GRB 260310A: Fermi GBM Final Real-time Localization
  51. GRB 260307A: Glowbug gamma-ray detection
  52. GRB 260308A: Fermi GBM Final Real-time Localization
  53. Fermi GBM Sub-Threshold Detection of GRB 260307B
  54. GRB 260307B: Mephisto optical upper limits
  55. GRB 260307B: possible NOT optical counterpart
  56. GRB 260307B: SVOM/VT upper limit with X band data analysis
  57. Fermi GRB 260307A: Global MASTER-Net observations report
  58. GRB260307B: GROWTH-India Telescope optical upper limit
  59. GRB 260307B: SVOM/VT optical candidate
  60. GRB 260307B: SVOM/C-GFT upper limit
  61. GRB 260307B: SVOM detection of a burst
  62. GRB 260307A: Fermi GBM Final Localization
  63. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  64. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  65. GRB 260207A: TESS Detection and Possible VLA Counterpart
  66. EP260302a: SVOM/VT optical observation
  67. EP260306a: Gemini-North redshift z = 4.773
  68. EP260306a: SVOM/VT optical observation
  69. EP260302a: Gemini-South redshift z = 1.535
  70. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  71. EP260306a: Einstein Probe detection of an X-ray transient
  72. The EP-WXT trigger 01709258759: Las Cumbres discovery of the optical counterpart
  73. EP260302a: Optical afterglow rebrightening
  74. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  75. GRB 260303A: 1.3m DFOT optical upper limit (duplicate submission)
  76. GRB 260303A: 1.3m DFOT optical upper limit
  77. EP260214b: ATCA 6 GHz observations
  78. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  79. GRB 260303A: SVOM/ECLAIRs refined analysis
  80. Fermi GRB 260305A: Global MASTER-Net observations report
  81. GRB 260305A: Fermi GBM Final Real-time Localization
  82. GRB 260303B: AstroSat CZTI detection
  83. GRB 260304A: AstroSat CZTI detection of a long burst
  84. SVOM/sb26030408: SVOM detection of an X-ray transient likely associated with Beta Persei
  85. GRB 260303A: SVOM/VT optical observations
  86. GRB 260303A: J-band observations with WINTER
  87. GRB 260303B: NuSTAR detection of prompt emission
  88. EP260302a: Global MASTER-Net observations report
  89. Fermi GRB 260303B: Global MASTER-Net observations report
  90. IceCube-260217A: No Candidate Transients from the Zwicky Transient Facility
  91. GRB 260228A: SVOM/ECLAIRs refined analysis
  92. GRB 260225A: SVOM/ECLAIRs refined analysis
  93. GRB 260303B: BALROG localization (Fermi Trigger 794237065 / GRB 260303559)
  94. GRB 260303B: Fermi GBM Final Real-time Localization
  95. EP260302a: analysis of the follow-up EP-FXT observation
  96. EP260227a: Gemini-South optical observations
  97. EP260302a: LCO observations
  98. EP260302a: BOOTES-7 optical counterpart detection at early times
  99. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  100. GRB 260303A: SVOM detection of a burst

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