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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"

32492 results found.

  1. GRB 250920A: NuSTAR detection of bright prompt emission
  2. GRB 250920C: GROWTH-India Telescope optical observations
  3. GRB 250920C: Swift-BAT refined analysis
  4. GRB 250920B: Swift-BAT refined analysis
  5. GRB 250916A: FTW optical and NIR observations of the counterpart
  6. GRB 250920C: Swift/UVOT Detection
  7. GRB 250920B: Fermi GBM Observation
  8. GRB 250920A: Fermi GBM Detection
  9. GRB 250920C: Fermi GBM Observation
  10. Swift GRB 250920C: Global MASTER-Net observations report
  11. GRB 250920B: Swift/UVOT Detection
  12. GRB 250920B: FTW optical and NIR observations of the counterpart
  13. GRB 250920C: Optical counterpart detection by LCO
  14. GRB 250920A: SVOM/GRM observation
  15. GRB250920C: LCOGT Optical Detection
  16. GRB 250920B: SVOM/C-GFT optical observations
  17. GRB 250920C: GOTO optical counterpart candidate
  18. GRB 250919A / EP250919a: LCO optical observation
  19. Konus-Wind detection of GRB 250919A
  20. Swift GRB 250920B: Global MASTER-Net observations report
  21. GRB 250919A / EP250919a: Insight-HXMT detection
  22. GRB 250920A: AstroSat CZTI detection
  23. GRB 250919A/EP250919a: SVOM/VT optical observation
  24. GRB 250919A / EP250919a: MASTER bright afterglow detection 24h after GRB time
  25. GRB 250916A: Mondy R-band optical observations
  26. GRB 250919A: Glowbug gamma-ray detection
  27. GRB 250919A: Fermi GBM Observation
  28. Fermi GRB 250918A: Global MASTER-Net observations report
  29. GRB 250919A / EP250919a: NuSTAR detection of bright prompt emission
  30. GRB 250918A: SVOM/GRM observation
  31. GRB 250919A/EP250919A: Swift/UVOT afterglow detection
  32. GRB 250919A: Swift-XRT afterglow detection
  33. GRB 250919A: Fermi-LAT detection
  34. EP250919a/GRB 250919A: Gemini/GMOS-S spectroscopic redshift z = 1.145
  35. GRB 250919A: SVOM/GRM observation of a very bright GRB
  36. EP250919a: Global MASTER-Net observations report
  37. EP250919a: Einstein Probe detection of an X-ray transient
  38. Correction for GCN 41877: EP-WXT ID is 01709243841
  39. GRB 250916A: Fermi GBM Observation
  40. Fermi GRB 250919A: Global MASTER-Net observations report
  41. GRB 250916A: KAIT optical observations
  42. GRB 250917B: VLT/HAWK-I near-infrared observations
  43. GRB 250916A: NuSTAR detection of the prompt emission
  44. GRB 250916A: further SAO RAS optical observations
  45. GRB 250912A: SVOM/ECLAIRs refined analysis
  46. GRB 250917B: Swift-BAT refined analysis
  47. GRB 250917B: Swift/UVOT Upper Limits
  48. GRB 250916A: OSIRIS+/GTC redshift z = 2.015
  49. GRB 250916A: Swift-XRT observations
  50. EP250916a: EP-FXT follow-up observation
  51. GRB 250916A: MAO/AZT-22 optical observations
  52. GRB 250916A: SAO RAS optical observations
  53. GRB 250916A : GIT optical observations
  54. LIGO/Virgo/KAGRA S250917aq: Updated Sky localization
  55. GRB 250916A: Glowbug gamma-ray detection
  56. GRB250917B: WFST optical observations
  57. GRB 250916A: Swift ToO observations
  58. GRB 250917B: Fermi GBM Observation
  59. LIGO/Virgo/KAGRA S250917aq: Identification of a GW compact binary merger candidate
  60. Fermi GRB 250917B: Global MASTER-Net observations report
  61. GRB 250916A: GOTO optical counterpart candidate
  62. GRB 250916A: AstroSat CZTI detection of a bright long burst
  63. GRB 250910A: SVOM/ECLAIRs refined analysis
  64. Fermi GRB 250916A: Global MASTER-Net observations report
  65. EP250827b: VLA Observations
  66. LIGO/Virgo/KAGRA S250818k: HCT optical follow-up
  67. SVOM/sb25091517: Confirmation of a stellar flare by SVOM/VT
  68. SVOM/sb25091517: FRAM-ORM stellar flare - transient observation
  69. GRB 250912A: Swift/BAT-GUANO localization skymap of a possibly short burst
  70. GRB 250912A: SVOM/COLIBRÍ (FM-GFT) optical observations
  71. GRB 250912A: Swift-XRT observations
  72. GRB250912A: VLT/HAWK-I follow-up observations
  73. GRB 250912A: VLT observations
  74. GRB 250912A: Fermi GBM Observation
  75. GRB 250911A: Insight-HXMT detection
  76. GRB 250912A: SVOM/GRM analysis suggests a possible short GRB with extended emission
  77. GRB 250912A:SVOM/VT optical upper limit
  78. GRB 250912A: LCO optical upper limit
  79. Fermi GRB 250912A: Global MASTER-Net observations report
  80. EP250911a: Global MASTER-Net observations report
  81. GRB 250912A: SVOM detection of a burst
  82. EP250908c: tentative VLT/FORS2 redshift z = 2.87
  83. EP250911a: Upper limit from Fermi-GBM Observations
  84. LIGO/Virgo/KAGRA S250912f: Updated Sky localization
  85. GRB 250911A: GECAM-B detection
  86. GRB 250911A: Swift-BAT refined analysis
  87. EP250911a: GTC/OSIRIS+ spectroscopic redshift z = 3.84
  88. LIGO/Virgo/KAGRA S250912f: Identification of a GW compact binary merger candidate
  89. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  90. GRB 250910B: SVOM/GRM observation
  91. EP250911a: SVOM/VT optical observation
  92. GRB 250911A: MASTER optical counterpart observations
  93. EP250911a: SAO RAS optical observations
  94. EP250911a: Swift-XRT observations
  95. EP250911a: Optical detection with Kinder observations
  96. GRB 250911A: Swift/UVOT Detection
  97. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  98. GRB 250910A / EP250910a: SVOM/VT afterglow confirmation
  99. GRB 250909B: Insight-HXMT detection
  100. GRB 250909B: SVOM/GRM observation

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