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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"

32490 results found.

  1. GRB 250920B: Swift-BAT refined analysis
  2. GRB 250916A: FTW optical and NIR observations of the counterpart
  3. GRB 250920C: Swift/UVOT Detection
  4. GRB 250920B: Fermi GBM Observation
  5. GRB 250920A: Fermi GBM Detection
  6. GRB 250920C: Fermi GBM Observation
  7. Swift GRB 250920C: Global MASTER-Net observations report
  8. GRB 250920B: Swift/UVOT Detection
  9. GRB 250920B: FTW optical and NIR observations of the counterpart
  10. GRB 250920C: Optical counterpart detection by LCO
  11. GRB 250920A: SVOM/GRM observation
  12. GRB250920C: LCOGT Optical Detection
  13. GRB 250920B: SVOM/C-GFT optical observations
  14. GRB 250920C: GOTO optical counterpart candidate
  15. GRB 250919A / EP250919a: LCO optical observation
  16. Konus-Wind detection of GRB 250919A
  17. Swift GRB 250920B: Global MASTER-Net observations report
  18. GRB 250919A / EP250919a: Insight-HXMT detection
  19. GRB 250920A: AstroSat CZTI detection
  20. GRB 250919A/EP250919a: SVOM/VT optical observation
  21. GRB 250919A / EP250919a: MASTER bright afterglow detection 24h after GRB time
  22. GRB 250916A: Mondy R-band optical observations
  23. GRB 250919A: Glowbug gamma-ray detection
  24. GRB 250919A: Fermi GBM Observation
  25. Fermi GRB 250918A: Global MASTER-Net observations report
  26. GRB 250919A / EP250919a: NuSTAR detection of bright prompt emission
  27. GRB 250918A: SVOM/GRM observation
  28. GRB 250919A/EP250919A: Swift/UVOT afterglow detection
  29. GRB 250919A: Swift-XRT afterglow detection
  30. GRB 250919A: Fermi-LAT detection
  31. EP250919a/GRB 250919A: Gemini/GMOS-S spectroscopic redshift z = 1.145
  32. GRB 250919A: SVOM/GRM observation of a very bright GRB
  33. EP250919a: Global MASTER-Net observations report
  34. EP250919a: Einstein Probe detection of an X-ray transient
  35. Correction for GCN 41877: EP-WXT ID is 01709243841
  36. GRB 250916A: Fermi GBM Observation
  37. Fermi GRB 250919A: Global MASTER-Net observations report
  38. GRB 250916A: KAIT optical observations
  39. GRB 250917B: VLT/HAWK-I near-infrared observations
  40. GRB 250916A: NuSTAR detection of the prompt emission
  41. GRB 250916A: further SAO RAS optical observations
  42. GRB 250912A: SVOM/ECLAIRs refined analysis
  43. GRB 250917B: Swift-BAT refined analysis
  44. GRB 250917B: Swift/UVOT Upper Limits
  45. GRB 250916A: OSIRIS+/GTC redshift z = 2.015
  46. GRB 250916A: Swift-XRT observations
  47. EP250916a: EP-FXT follow-up observation
  48. GRB 250916A: MAO/AZT-22 optical observations
  49. GRB 250916A: SAO RAS optical observations
  50. GRB 250916A : GIT optical observations
  51. LIGO/Virgo/KAGRA S250917aq: Updated Sky localization
  52. GRB 250916A: Glowbug gamma-ray detection
  53. GRB250917B: WFST optical observations
  54. GRB 250916A: Swift ToO observations
  55. GRB 250917B: Fermi GBM Observation
  56. LIGO/Virgo/KAGRA S250917aq: Identification of a GW compact binary merger candidate
  57. Fermi GRB 250917B: Global MASTER-Net observations report
  58. GRB 250916A: GOTO optical counterpart candidate
  59. GRB 250916A: AstroSat CZTI detection of a bright long burst
  60. GRB 250910A: SVOM/ECLAIRs refined analysis
  61. Fermi GRB 250916A: Global MASTER-Net observations report
  62. EP250827b: VLA Observations
  63. LIGO/Virgo/KAGRA S250818k: HCT optical follow-up
  64. SVOM/sb25091517: Confirmation of a stellar flare by SVOM/VT
  65. SVOM/sb25091517: FRAM-ORM stellar flare - transient observation
  66. GRB 250912A: Swift/BAT-GUANO localization skymap of a possibly short burst
  67. GRB 250912A: SVOM/COLIBRÍ (FM-GFT) optical observations
  68. GRB 250912A: Swift-XRT observations
  69. GRB250912A: VLT/HAWK-I follow-up observations
  70. GRB 250912A: VLT observations
  71. GRB 250912A: Fermi GBM Observation
  72. GRB 250911A: Insight-HXMT detection
  73. GRB 250912A: SVOM/GRM analysis suggests a possible short GRB with extended emission
  74. GRB 250912A:SVOM/VT optical upper limit
  75. GRB 250912A: LCO optical upper limit
  76. Fermi GRB 250912A: Global MASTER-Net observations report
  77. EP250911a: Global MASTER-Net observations report
  78. GRB 250912A: SVOM detection of a burst
  79. EP250908c: tentative VLT/FORS2 redshift z = 2.87
  80. EP250911a: Upper limit from Fermi-GBM Observations
  81. LIGO/Virgo/KAGRA S250912f: Updated Sky localization
  82. GRB 250911A: GECAM-B detection
  83. GRB 250911A: Swift-BAT refined analysis
  84. EP250911a: GTC/OSIRIS+ spectroscopic redshift z = 3.84
  85. LIGO/Virgo/KAGRA S250912f: Identification of a GW compact binary merger candidate
  86. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  87. GRB 250910B: SVOM/GRM observation
  88. EP250911a: SVOM/VT optical observation
  89. GRB 250911A: MASTER optical counterpart observations
  90. EP250911a: SAO RAS optical observations
  91. EP250911a: Swift-XRT observations
  92. EP250911a: Optical detection with Kinder observations
  93. GRB 250911A: Swift/UVOT Detection
  94. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  95. GRB 250910A / EP250910a: SVOM/VT afterglow confirmation
  96. GRB 250909B: Insight-HXMT detection
  97. GRB 250909B: SVOM/GRM observation
  98. LIGO/Virgo/KAGRA S250911ac: Updated Sky localization and Source Classification
  99. GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
  100. EP250911a: COLIBRÍ optical observations

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