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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"

33716 results found.

  1. GRB 251003A: GTC/OSIRIS+ spectroscopic redshift z = 4.412
  2. GRB 251003A: Kilonova-Catcher optical afterglow detection
  3. GRB 251002A: Swift-XRT afterglow detection
  4. GRB 251001B: AbAO optical upper limit
  5. GRB 251002A: Kilonova-Catcher optical afterglow detection
  6. GRB 251002A: AbAO optical observations
  7. GRB 251002A: SVOM/COLIBRÍ (FM-GFT) optical observations
  8. GRB 251001C: CALET Gamma-Ray Burst Monitor detection
  9. GRB 251002A: J band observations by SYSU 80cm infrared telescope
  10. GRB 251002A: OHP/T193 MISTRAL optical afterglow detection
  11. GRB 251002A: VLT/X-shooter spectroscopic redshift z = 2.178
  12. GRB 251002A: EP-FXT counterpart detection
  13. GRB 251003A: LCOGT Optical Detection
  14. GRB 251003A: COLIBRÍ optical detection of the fading afterglow
  15. GRB 251003A: 1.5m OSN afterglow candidate
  16. GRB 251003A: Prompt enhanced Swift-XRT position
  17. GRB 251003A: Swift detection of a burst
  18. GRB 251003A: Fermi GBM Final Real-time Localization
  19. Fermi/SVOM GRB 251002A : MASTER OT earlier detection in 2 polarization filters
  20. GRB 251002A: BOOTES-6 early optical detection
  21. GRB 251002A: SAO RAS optical observations
  22. GRB 251002A: ULL-ASTRO-MASTER early detection of the optical afterglow with the LCO 40-cm telescope at Sutherland Observatory
  23. GRB 251002A: FRAM-ORM afterglow detection
  24. GRB 251002A: LCO optical observation
  25. GRB 251002A: SVOM/VT optical observation
  26. GRB 251002A: SVOM detection of a burst
  27. Fermi GRB 251002A: Global MASTER-Net observations report
  28. GRB 251001B: Swift-BAT refined analysis
  29. GRB 251001A: SVOM/GRM observation
  30. GRB 251001A: Insight-HXMT detection
  31. GRB 251001B: Swift/UVOT Detection
  32. GRB 251001B: COLIBRÍ optical observations
  33. GRB 251001B: GTC/OSIRIS+ spectroscopic redshift z = 2.162
  34. GRB 251001B: Swift-XRT refined Analysis
  35. GRB 251001B: SVOM/VT optical observation
  36. GRB 251001B: NOT optical observations
  37. GRB 251001C: Glowbug gamma-ray detection
  38. Swift GRB 251001B: Global MASTER-Net observations report
  39. GRB 251001B: Fermi GBM Observation
  40. GRB 251001B: Further GOTO observations of optical counterpart.
  41. GRB 251001B: Enhanced Swift-XRT position
  42. GRB 250930A: Fermi GBM Final Localization
  43. GRB 251001B: LCOGT Optical Observations
  44. GRB 250930A: SVOM/GRM observation
  45. GRB 251001B: TRT optical afterglow detection and potential host galaxy
  46. GRB 251001B: GOTO optical counterpart detection
  47. GRB 251001B: Swift detection of a burst
  48. GRB 251001B: Fermi GBM Final Real-time Localization
  49. GRB 251001A: Fermi GBM Detection
  50. GRB 250910A / EP250910a: VLT limits on the possible associated supernova
  51. GRB 251001A: BALROG localization (Fermi Trigger 780979261 / GRB 251001112)
  52. GRB 251001A: Fermi GBM Final Real-time Localization
  53. GRB 250910A / EP250910a: VLT/X-shooter host galaxy redshift z = 0.592
  54. GRB 250925A: MAO/AZT-22 optical observations
  55. Fermi GRB 250929A: Global MASTER-Net observations report
  56. GRB 250929A: Fermi GBM Final Real-time Localization
  57. GRB 250926A: CALET Gamma-Ray Burst Monitor detection
  58. GRB 250925A: Mondy I-band optical observations
  59. GRB 250916A: SVOM/VT optical observation
  60. GRB 250926A: triangulation location with Insight-HXMT/HE and Fermi/GBM
  61. GRB 250924A: SVOM/GRM observation
  62. GRB 250925A: Swift-XRT refined Analysis
  63. GRB 250926A: Insight-HXMT detection
  64. GRB 250926B: Fermi GBM Final Localization
  65. GRB 250920C: ULL-ASTRO-MASTER early detection of the optical afterglow with LCO 40-cm telescope at Siding Spring Observatory
  66. GRB 250926A: AstroSat CZTI detection
  67. GRB 250925A: Swift/UVOT Upper Limits
  68. GRB 250925A: Swift-BAT refined analysis
  69. GRB 250925A: Mondy and AbAO optical observations
  70. GRB 250925A: COLIBRÍ photometric redshift
  71. GRB 250925A: SVOM/GWAC-F60A upper limit
  72. GRB 250925A/EP250925a: EP-WXT detection
  73. GRB 250926A: DDOTI Optical Observations and Spatial Coincidence with the Orion Nebula
  74. GRB 250925A : MITSuME Akeno optical upper limits
  75. GRB 250925A: JinShan optical observations
  76. GRB 250925A: 1.5m OSN optical detection and redshift with the 10.4m GTC/OSIRIS+
  77. GRB 250919A / EP250919a: Global MASTER Net before, during and after trigger optical observations
  78. GRB 250925A: COLIBRÍ optical photometry of the afterglow
  79. Fermi GRB 250926A: Global MASTER-Net observations report
  80. GRB 250926A: Fermi GBM Final Real-time Localization
  81. GRB 250925A: Optical Observations via Virtual Telescope Project, Italy
  82. GRB 250925A: NOT optical afterglow candidate
  83. GRB 250925A: Leavitt Observatory optical upper limit
  84. GRB 250925A: Enhanced Swift-XRT position
  85. GRB 250924A: Swift-BAT refined analysis
  86. GRB 250925A: GROWTH-India Telescope Upper Limits
  87. GRB 250925A: Swift detection of a burst
  88. Swift GRB 250925A: Global MASTER-Net observations report
  89. GRB 250922A: SVOM/GRM observation
  90. GRB 250924A: 1.6m Mephisto optical upper limits
  91. GRB 250924A: SAO RAS optical observations
  92. GRB 250924A: NOT optical observations
  93. GRB 250924A: AstroSat CZTI detection
  94. GRB 250914A: AstroSat CZTI detection
  95. GRB 250920B: AstroSat CZTI detection
  96. GRB 250924A: SVOM/VT optical observation
  97. GRB 250924A: Swift/UVOT Detection
  98. GRB 250924A: Swift-XRT refined Analysis
  99. GRB 250924A: Enhanced Swift-XRT position
  100. GRB 250924A: J-band detection with WINTER

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