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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"

26167 results found.

  1. GRB 251002A: AbAO optical observations
  2. GRB 251002A: SVOM/COLIBRÍ (FM-GFT) optical observations
  3. GRB 251001C: CALET Gamma-Ray Burst Monitor detection
  4. GRB 251002A: J band observations by SYSU 80cm infrared telescope
  5. GRB 251002A: VLT/X-shooter spectroscopic redshift z = 2.178
  6. GRB 251002A: EP-FXT counterpart detection
  7. GRB 251003A: LCOGT Optical Detection
  8. GRB 251003A: COLIBRÍ optical detection of the fading afterglow
  9. GRB 251003A: Swift detection of a burst
  10. GRB 251003A: Fermi GBM Final Real-time Localization
  11. Swift GRB251003A: Global MASTER-Net observations report
  12. Fermi/SVOM GRB 251002A : MASTER OT earlier detection in 2 polarization filters
  13. GRB 251002A: SAO RAS optical observations
  14. GRB 251002A: ULL-ASTRO-MASTER early detection of the optical afterglow with the LCO 40-cm telescope at Sutherland Observatory
  15. GRB 251002A: FRAM-ORM afterglow detection
  16. GRB 251002A: LCO optical observation
  17. GRB 251002A: SVOM/VT optical observation
  18. GRB 251002A: SVOM detection of a burst
  19. Fermi GRB 251002A: Global MASTER-Net observations report
  20. GRB 251001B: Swift-BAT refined analysis
  21. GRB 251001A: SVOM/GRM observation
  22. GRB 251001A: Insight-HXMT detection
  23. GRB 251001B: Swift/UVOT Detection
  24. GRB 251001B: COLIBRÍ optical observations
  25. GRB 251001B: GTC/OSIRIS+ spectroscopic redshift z = 2.162
  26. GRB 251001B: Swift-XRT refined Analysis
  27. GRB 251001B: SVOM/VT optical observation
  28. GRB 251001B: NOT optical observations
  29. GRB 251001C: Glowbug gamma-ray detection
  30. Swift GRB 251001B: Global MASTER-Net observations report
  31. GRB 251001B: Fermi GBM Observation
  32. GRB 251001B: Further GOTO observations of optical counterpart.
  33. GRB 250930A: Fermi GBM Final Localization
  34. GRB 251001B: LCOGT Optical Observations
  35. GRB 250930A: SVOM/GRM observation
  36. GRB 251001B: TRT optical afterglow detection and potential host galaxy
  37. GRB 251001B: GOTO optical counterpart detection
  38. GRB 251001B: Swift detection of a burst
  39. GRB 251001B: Fermi GBM Final Real-time Localization
  40. GRB 251001A: Fermi GBM Detection
  41. GRB 250910A / EP250910a: VLT limits on the possible associated supernova
  42. GRB 251001A: BALROG localization (Fermi Trigger 780979261 / GRB 251001112)
  43. GRB 251001A: Fermi GBM Final Real-time Localization
  44. LIGO/Virgo/KAGRA S250818k: further MeerKAT monitoring
  45. GRB 250910A / EP250910a: VLT/X-shooter host galaxy redshift z = 0.592
  46. GRB 250925A: MAO/AZT-22 optical observations
  47. Fermi GRB 250929A: Global MASTER-Net observations report
  48. GRB 250929A: Fermi GBM Final Real-time Localization
  49. GRB 250926A: CALET Gamma-Ray Burst Monitor detection
  50. GRB 250925A: Mondy I-band optical observations
  51. GRB 250916A: SVOM/VT optical observation
  52. GRB 250924A: SVOM/GRM observation
  53. GRB 250925A: Swift-XRT refined Analysis
  54. GRB 250926A: Insight-HXMT detection
  55. GRB 250926B: Fermi GBM Final Localization
  56. Fermi trigger No 780609036: Global MASTER-Net observations report
  57. IceCube Alert 250926.52: Global MASTER-Net observations report
  58. GRB 250920C: ULL-ASTRO-MASTER early detection of the optical afterglow with LCO 40-cm telescope at Siding Spring Observatory
  59. GRB 250925A: Swift-BAT refined analysis
  60. GRB 250925A: Mondy and AbAO optical observations
  61. GRB 250925A: COLIBRÍ photometric redshift
  62. GRB 250925A/EP250925a: EP-WXT detection
  63. GRB 250926A: DDOTI Optical Observations and Spatial Coincidence with the Orion Nebula
  64. GRB 250925A : MITSuME Akeno optical upper limits
  65. GRB 250925A: JinShan optical observations
  66. GRB 250925A: 1.5m OSN optical detection and redshift with the 10.4m GTC/OSIRIS+
  67. GRB 250919A / EP250919a: Global MASTER Net before, during and after trigger optical observations
  68. GRB 250925A: COLIBRÍ optical photometry of the afterglow
  69. Fermi GRB 250926A: Global MASTER-Net observations report
  70. GRB 250926A: Fermi GBM Final Real-time Localization
  71. GRB250925A: Liverpool Telescope optical observations
  72. GRB 250925A: NOT optical afterglow candidate
  73. GRB 250925A: Leavitt Observatory optical upper limit
  74. GRB 250924A: Swift-BAT refined analysis
  75. GRB 250925A: GROWTH-India Telescope Upper Limits
  76. GRB 250925A: Swift detection of a burst
  77. Swift GRB 250925A: Global MASTER-Net observations report
  78. GRB 250922A: SVOM/GRM observation
  79. GRB 250924A: 1.6m Mephisto optical upper limits
  80. GRB 250924A: NOT optical observations
  81. GRB 250924A: SVOM/VT optical observation
  82. GRB 250924A: Swift/UVOT Detection
  83. GRB 250924A: Swift-XRT refined Analysis
  84. GRB 250924A: J-band detection with WINTER
  85. GRB 250924A: GROWTH-India Telescope Upper Limits
  86. GRB 250924A: Kilonova-Catcher optical afterglow detection
  87. GRB 250920C: Kilonova-Catcher optical afterglow detection
  88. GRB 250922B: SVOM/GRM observation
  89. GRB 250920C: TRT optical observation
  90. GRB 250924B: Fermi GBM Final Localization
  91. GRB 250924A: COLIBRÍ optical observations
  92. Swift GRB 250924A: Global MASTER-Net observations report
  93. GRB 250919A / EP250919a: further LCO optical observation
  94. GRB 250924A: DDOTI Detection of the Optical Counterpart
  95. GRB 250924A: Swift detection of a burst with an optical counterpart
  96. GRB 250920B: AbAO optical upper limits
  97. GRB 250920C: VLT redshift confirmation z = 1.399
  98. EP250911a: e-MERLIN radio observations
  99. GRB 250920B: CrAO ZTSH optical observations
  100. GRB 250920C: COLIBRÍ optical observations

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