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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"

34210 results found.

  1. GRB 251202B: Fermi GBM Final Real-time Localization
  2. IPN triangulation of GRB 251129B (short/hard)
  3. GRB251129A/EP251129a: Swift UVOT detection
  4. GRB 251129B: AstroSat CZTI detection
  5. GRB 251202A: Fermi GBM Observation
  6. GRB 251202A: Swift/UVOT Detection
  7. GRB 251201B: Kilonova-Catcher optical afterglow detection
  8. GRB 251201B: Swift/UVOT Detection
  9. GRB 251130B: Glowbug gamma-ray detection
  10. GRB 251201B: GECAM-B observation of a long burst
  11. GRB 251122A/EP251122a: CrAO ZTSh optical observations
  12. EP251202a / GRB 251202A: LCO r- and i-band optical detection
  13. GRB 251202A: GOTO optical afterglow detection
  14. EP251202a/GRB 251202A: refined analysis of the EP-WXT observations
  15. GRB 251201A: GECAM-B observation of a burst
  16. GRB 251126A: SAO RAS optical marginal detection
  17. GRB 251202A: Swift-XRT afterglow detection
  18. EP251129a/GRB 251129A: NOWT Detection
  19. GRB 251126A: SVOM/VT optical observation
  20. EP251202a / GRB 251202A: NOT spectroscopic redshift z = 2.785
  21. Fermi GRB 251202A: Global MASTER-Net observations report
  22. EP251202a/GRB 251202A: Einstein Probe detection of an X-ray transient
  23. GRB 251201B: Swift-XRT refined Analysis
  24. GRB 251202A: Fermi GBM Final Real-time Localization
  25. GRB 251201A: SVOM/GRM observation of a burst
  26. GRB 251201B: SVOM/VT optical fading
  27. Swift GRB 251201B : MASTER optical counterpart detection
  28. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  29. Swift GRB 251201B: Global MASTER-Net observations report
  30. GRB 251201B: Enhanced Swift-XRT position
  31. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  32. GRB 251130B: AstroSat CZTI detection
  33. GRB 251201B: Swift detection of a burst with an optical counterpart
  34. GRB 251201B: Fermi GBM Final Real-time Localization
  35. EP251130a: Mondy optical observations
  36. EP251130a: SAO RAS optical observations
  37. EP251130a: KAIT optical observations
  38. GRB 251201A: MAXI/GSC detection
  39. Fermi GRB 251130B: Global MASTER-Net observations report
  40. GRB 251127A: SVOM/GRM observation
  41. GRB 251130B: Fermi GBM Final Localization Correction
  42. GRB 251130B: Fermi GBM Final Real-time Localization
  43. EP251129a/GRB 251129A: EP-FXT follow-up observations
  44. GRB 251130A: Fermi GBM Final Real-time Localization
  45. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  46. GRB 251129A / EP251129a: OSN and CAHA optical follow-up
  47. GRB 251128A: AstroSat CZTI detection
  48. GRB 251129A / EP251129a: SAO RAS optical observations
  49. GRB 251126A: SAO RAS optical observations
  50. GRB 251128A: GECAM-B detection
  51. GRB 251128A: SVOM/GRM observation of a long burst
  52. GRB 251128A: Insight-HXMT/HE detection
  53. SVOM GRB 251129A : MASTER optical counterpart detection
  54. GRB 251129A: Swift-XRT afterglow detection
  55. GRB 251129A: Swift ToO observations
  56. GRB 251129A / EP251129a: SVOM/VT optical fading
  57. GRB 251129A: Optical Observations via Virtual Telescope Project, Italy
  58. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  59. GRB 251129A: Correction to the position of the optical counterpar
  60. GRB 251129A: SVOM/VT optical counterpart confirmation with VHF data
  61. GRB 251128A: Fermi GBM Observation
  62. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  63. GRB 251129A: SVOM detection of a burst
  64. GRB 251129A: SVOM detection of a burst
  65. GRB 251126A: Swift-BAT refined analysis
  66. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  67. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  68. Fermi GRB 251128A: Global MASTER-Net observations report
  69. GRB 251127A: Glowbug gamma-ray detection
  70. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  71. GRB 251126A: further SAO RAS optical observations
  72. GRB 250702B: detection of the compact radio counterpart 139 days after the burst
  73. GRB 251126A NUTTelA-TAO Early Measurements
  74. GRB251126A: MAO/AZT-22 optical observations
  75. GRB 251128A: Fermi GBM Final Real-time Localization
  76. GRB251126A: Continued optical observation from 1.3m DFOT
  77. GRB 251126A: Swift/UVOT Detection
  78. GRB 251126A: Mondy and SAO RAS optical observations
  79. GRB 251126A: Swift-XRT refined Analysis
  80. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  81. GRB 251126A: NOT optical observations
  82. GRB 251126A: 1.3m DFOT optical afterglow detection
  83. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  84. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  85. GRB 251125B: GECAM-B detection
  86. Fermi GRB 251127A: Global MASTER-Net observations report
  87. GRB 251127A: Fermi GBM Final Real-time Localization
  88. GRB 251126A: Enhanced Swift-XRT position
  89. GRB 251126A: Kilonova-Catcher optical afterglow detection
  90. GRB 251126A: Asiago i-band detection
  91. GRB 251126A: Nanshan/HMT optical afterglow detection
  92. Swift GRB 251126A: Global MASTER-Net observations report
  93. GRB 251121A: Fermi GBM Observation
  94. GRB 251126A: Prompt enhanced Swift-XRT position
  95. GRB 251126A: GIT discovery of the likely optical afterglow
  96. GRB 251126A: Swift detection of a burst
  97. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  98. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  99. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  100. Fermi GRB 251125B: Global MASTER-Net observations report

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