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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"

41632 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. Swift BAT trigger 1500295: A solar flare
  8. GRB 260313A: Fermi GBM Final Real-time Localization
  9. Swift BAT trigger 1500287: A solar flare
  10. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  11. GRB 260308A: Insight-HXMT/HE detection
  12. GRB 260307A: CALET Gamma-Ray Burst Monitor detection
  13. GRB 260310A / AT 2026fgk: Location in the Epeak - Eiso diagram
  14. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  15. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  16. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  17. GRB260310A / AT2026fgk: P200 Spectroscopy
  18. GRB 260312B: Glowbug gamma-ray detection
  19. GRB 260310A: Fermi GBM Observation
  20. GRB 260310A: potential optical counterpart
  21. Fermi GRB 260312B: Global MASTER-Net observations report
  22. Fermi GRB 260311B: Global MASTER-Net observations report
  23. Swift BAT trigger 1500148: A solar flare
  24. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  25. GRB 260312B: Fermi GBM Final Real-time Localization
  26. GRB 260310B: GECAM-B observation of a burst
  27. Retraction of GCN 43965: GRB is actually solar flare
  28. GRB 260312A: Swift detection of a burst
  29. GRB 260311B: Fermi GBM Final Real-time Localization
  30. GRB 260131A/B: radio detection with the VLA
  31. EP260302a: MeerKAT radio counterpart
  32. GRB260307A: GECAM-B observation of a burst
  33. GRB 260308A: SVOM/GRM observation of a short GRB
  34. EP260306a: Mondy optical upper limit
  35. GRB 260310A: AstroSat CZTI detection of a long burst
  36. GRB 260311A: Fermi GBM Final Real-time Localization
  37. Fermi GRB 260310B: Global MASTER-Net observations report
  38. GRB 260310B: Fermi GBM Final Real-time Localization
  39. Fermi GRB 260310A: Global MASTER-Net observations report
  40. GRB 260307B: SVOM/ECLAIRs refined analysis
  41. GRB 260208A: radio detection with the VLA
  42. GRB 260310A: Fermi GBM Final Real-time Localization
  43. GRB 260307A: Glowbug gamma-ray detection
  44. GRB 260308A: Fermi GBM Final Real-time Localization
  45. Fermi GBM Sub-Threshold Detection of GRB 260307B
  46. GRB 260307B: Mephisto optical upper limits
  47. GRB 260307B: possible NOT optical counterpart
  48. GRB 260307B: SVOM/VT upper limit with X band data analysis
  49. Fermi GRB 260307A: Global MASTER-Net observations report
  50. GRB260307B: GROWTH-India Telescope optical upper limit
  51. GRB 260307B: SVOM/VT optical candidate
  52. GRB 260307B: SVOM/C-GFT upper limit
  53. GRB 260307B: SVOM detection of a burst
  54. GRB 260307A: Fermi GBM Final Localization
  55. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  56. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  57. GRB 260207A: TESS Detection and Possible VLA Counterpart
  58. EP260302a: SVOM/VT optical observation
  59. EP260306a: Gemini-North redshift z = 4.773
  60. EP260306a: SVOM/VT optical observation
  61. EP260302a: Gemini-South redshift z = 1.535
  62. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  63. EP260306a: Einstein Probe detection of an X-ray transient
  64. The EP-WXT trigger 01709258759: Las Cumbres discovery of the optical counterpart
  65. EP260302a: Optical afterglow rebrightening
  66. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  67. GRB 260303A: 1.3m DFOT optical upper limit
  68. EP260214b: ATCA 6 GHz observations
  69. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  70. GRB 260303A: SVOM/ECLAIRs refined analysis
  71. Fermi GRB 260305A: Global MASTER-Net observations report
  72. GRB 260305A: Fermi GBM Final Real-time Localization
  73. GRB 260303B: AstroSat CZTI detection
  74. GRB 260304A: AstroSat CZTI detection of a long burst
  75. SVOM/sb26030408: SVOM detection of an X-ray transient likely associated with Beta Persei
  76. GRB 260303A: SVOM/VT optical observations
  77. GRB 260303A: J-band observations with WINTER
  78. GRB 260303B: NuSTAR detection of prompt emission
  79. EP260302a: Global MASTER-Net observations report
  80. Fermi GRB 260303B: Global MASTER-Net observations report
  81. IceCube-260217A: No Candidate Transients from the Zwicky Transient Facility
  82. GRB 260228A: SVOM/ECLAIRs refined analysis
  83. GRB 260225A: SVOM/ECLAIRs refined analysis
  84. GRB 260303B: BALROG localization (Fermi Trigger 794237065 / GRB 260303559)
  85. GRB 260303B: Fermi GBM Final Real-time Localization
  86. EP260302a: analysis of the follow-up EP-FXT observation
  87. EP260227a: Gemini-South optical observations
  88. EP260302a: LCO observations
  89. EP260302a: BOOTES-7 optical counterpart detection at early times
  90. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  91. GRB 260303A: SVOM detection of a burst
  92. GRB 260228A: EP-FXT follow-up observation
  93. EP260302a: Einstein Probe detection of an X-ray transient
  94. The EP-WXT trigger 01709258736: Las Cumbres discovery of the optical counterpart
  95. GRB 251130B: TERI Gamma-ray detection
  96. GRB 260208A: TERI Gamma-ray detection
  97. GRB 260302A: Fermi GBM Final Real-time Localization
  98. EP260227a: Mondy optical observations
  99. GRB 260228A: CAHA 2.2m telescope optical upper limit
  100. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit

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