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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"

41622 results found.

  1. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  2. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  3. GRB 260310B: Insight-HXMT/HE detection
  4. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  5. GRB 260310A: NOT optical polarimetry
  6. GRB 260312B: AstroSat CZTI detection
  7. GRB 260313A: Fermi GBM Final Real-time Localization
  8. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  9. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  10. GRB 260308A: Insight-HXMT/HE detection
  11. GRB 260310A / AT 2026fgk: Location in the Epeak - Eiso diagram
  12. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  13. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  14. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  15. GRB260310A / AT2026fgk: P200 Spectroscopy
  16. GRB 260312B: Glowbug gamma-ray detection
  17. GRB 260310A: Fermi GBM Observation
  18. GRB 260310A: potential optical counterpart
  19. Fermi GRB 260312B: Global MASTER-Net observations report
  20. Fermi GRB 260311B: Global MASTER-Net observations report
  21. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  22. GRB 260312B: Fermi GBM Final Real-time Localization
  23. GRB 260310B: GECAM-B observation of a burst
  24. Retraction of GCN 43965: GRB is actually solar flare
  25. GRB 260312A: Swift detection of a burst
  26. GRB 260311B: Fermi GBM Final Real-time Localization
  27. GRB 260131A/B: radio detection with the VLA
  28. EP260302a: MeerKAT radio counterpart
  29. GRB260307A: GECAM-B observation of a burst
  30. GRB 260308A: SVOM/GRM observation of a short GRB
  31. GRB 260310A: AstroSat CZTI detection of a long burst
  32. GRB 260311A: Fermi GBM Final Real-time Localization
  33. Fermi GRB 260310B: Global MASTER-Net observations report
  34. GRB 260310B: Fermi GBM Final Real-time Localization
  35. Fermi GRB 260310A: Global MASTER-Net observations report
  36. GRB 260307B: SVOM/ECLAIRs refined analysis
  37. GRB 260208A: radio detection with the VLA
  38. GRB 260310A: Fermi GBM Final Real-time Localization
  39. GRB 260307A: Glowbug gamma-ray detection
  40. GRB 260308A: Fermi GBM Final Real-time Localization
  41. Fermi GBM Sub-Threshold Detection of GRB 260307B
  42. GRB 260307B: Mephisto optical upper limits
  43. GRB 260307B: possible NOT optical counterpart
  44. GRB 260307B: SVOM/VT upper limit with X band data analysis
  45. Fermi GRB 260307A: Global MASTER-Net observations report
  46. GRB260307B: GROWTH-India Telescope optical upper limit
  47. GRB 260307B: SVOM/VT optical candidate
  48. GRB 260307B: SVOM/C-GFT upper limit
  49. GRB 260307B: SVOM detection of a burst
  50. GRB 260307A: Fermi GBM Final Localization
  51. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  52. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  53. GRB 260207A: TESS Detection and Possible VLA Counterpart
  54. EP260302a: SVOM/VT optical observation
  55. EP260306a: Gemini-North redshift z = 4.773
  56. EP260306a: SVOM/VT optical observation
  57. EP260302a: Gemini-South redshift z = 1.535
  58. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  59. EP260306a: Einstein Probe detection of an X-ray transient
  60. The EP-WXT trigger 01709258759: Las Cumbres discovery of the optical counterpart
  61. EP260302a: Optical afterglow rebrightening
  62. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  63. GRB 260303A: 1.3m DFOT optical upper limit
  64. EP260214b: ATCA 6 GHz observations
  65. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  66. GRB 260303A: SVOM/ECLAIRs refined analysis
  67. Fermi GRB 260305A: Global MASTER-Net observations report
  68. GRB 260305A: Fermi GBM Final Real-time Localization
  69. GRB 260303B: AstroSat CZTI detection
  70. GRB 260304A: AstroSat CZTI detection of a long burst
  71. SVOM/sb26030408: SVOM detection of an X-ray transient likely associated with Beta Persei
  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. EP260302a: analysis of the follow-up EP-FXT observation
  83. EP260227a: Gemini-South optical observations
  84. EP260302a: LCO observations
  85. EP260302a: BOOTES-7 optical counterpart detection at early times
  86. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  87. GRB 260303A: SVOM detection of a burst
  88. GRB 260228A: EP-FXT follow-up observation
  89. EP260302a: Einstein Probe detection of an X-ray transient
  90. The EP-WXT trigger 01709258736: Las Cumbres discovery of the optical counterpart
  91. GRB 251130B: TERI Gamma-ray detection
  92. GRB 260208A: TERI Gamma-ray detection
  93. GRB 260302A: Fermi GBM Final Real-time Localization
  94. EP260227a: Mondy optical observations
  95. GRB 260228A: CAHA 2.2m telescope optical upper limit
  96. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  97. EP260227a: Mephisto optical detection
  98. GRID detection of GRB 260225D
  99. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
  100. EP260227a: further LCO observations

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