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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"

32494 results found.

  1. GRB 250920C: GTC/OSIRIS+ spectroscopic redshift z = 1.40
  2. GRB 250917B: KAIT optical upper limit
  3. GRB 250920A: NuSTAR detection of bright prompt emission
  4. GRB 250920C: GROWTH-India Telescope optical observations
  5. GRB 250920C: Swift-BAT refined analysis
  6. GRB 250920B: Swift-BAT refined analysis
  7. GRB 250916A: FTW optical and NIR observations of the counterpart
  8. GRB 250920C: Swift/UVOT Detection
  9. GRB 250920B: Fermi GBM Observation
  10. GRB 250920A: Fermi GBM Detection
  11. GRB 250920C: Fermi GBM Observation
  12. Swift GRB 250920C: Global MASTER-Net observations report
  13. GRB 250920B: Swift/UVOT Detection
  14. GRB 250920B: FTW optical and NIR observations of the counterpart
  15. GRB 250920C: Optical counterpart detection by LCO
  16. GRB 250920A: SVOM/GRM observation
  17. GRB250920C: LCOGT Optical Detection
  18. GRB 250920B: SVOM/C-GFT optical observations
  19. GRB 250920C: GOTO optical counterpart candidate
  20. GRB 250919A / EP250919a: LCO optical observation
  21. Konus-Wind detection of GRB 250919A
  22. Swift GRB 250920B: Global MASTER-Net observations report
  23. GRB 250919A / EP250919a: Insight-HXMT detection
  24. GRB 250920A: AstroSat CZTI detection
  25. GRB 250919A/EP250919a: SVOM/VT optical observation
  26. GRB 250919A / EP250919a: MASTER bright afterglow detection 24h after GRB time
  27. GRB 250916A: Mondy R-band optical observations
  28. GRB 250919A: Glowbug gamma-ray detection
  29. GRB 250919A: Fermi GBM Observation
  30. Fermi GRB 250918A: Global MASTER-Net observations report
  31. GRB 250919A / EP250919a: NuSTAR detection of bright prompt emission
  32. GRB 250918A: SVOM/GRM observation
  33. GRB 250919A/EP250919A: Swift/UVOT afterglow detection
  34. GRB 250919A: Swift-XRT afterglow detection
  35. GRB 250919A: Fermi-LAT detection
  36. EP250919a/GRB 250919A: Gemini/GMOS-S spectroscopic redshift z = 1.145
  37. GRB 250919A: SVOM/GRM observation of a very bright GRB
  38. EP250919a: Global MASTER-Net observations report
  39. EP250919a: Einstein Probe detection of an X-ray transient
  40. Correction for GCN 41877: EP-WXT ID is 01709243841
  41. GRB 250916A: Fermi GBM Observation
  42. Fermi GRB 250919A: Global MASTER-Net observations report
  43. GRB 250916A: KAIT optical observations
  44. GRB 250917B: VLT/HAWK-I near-infrared observations
  45. GRB 250916A: NuSTAR detection of the prompt emission
  46. GRB 250916A: further SAO RAS optical observations
  47. GRB 250912A: SVOM/ECLAIRs refined analysis
  48. GRB 250917B: Swift-BAT refined analysis
  49. GRB 250917B: Swift/UVOT Upper Limits
  50. GRB 250916A: OSIRIS+/GTC redshift z = 2.015
  51. GRB 250916A: Swift-XRT observations
  52. EP250916a: EP-FXT follow-up observation
  53. GRB 250916A: MAO/AZT-22 optical observations
  54. GRB 250916A: SAO RAS optical observations
  55. GRB 250916A : GIT optical observations
  56. LIGO/Virgo/KAGRA S250917aq: Updated Sky localization
  57. GRB 250916A: Glowbug gamma-ray detection
  58. GRB250917B: WFST optical observations
  59. GRB 250916A: Swift ToO observations
  60. GRB 250917B: Fermi GBM Observation
  61. LIGO/Virgo/KAGRA S250917aq: Identification of a GW compact binary merger candidate
  62. Fermi GRB 250917B: Global MASTER-Net observations report
  63. GRB 250916A: GOTO optical counterpart candidate
  64. GRB 250916A: AstroSat CZTI detection of a bright long burst
  65. GRB 250910A: SVOM/ECLAIRs refined analysis
  66. Fermi GRB 250916A: Global MASTER-Net observations report
  67. EP250827b: VLA Observations
  68. LIGO/Virgo/KAGRA S250818k: HCT optical follow-up
  69. SVOM/sb25091517: Confirmation of a stellar flare by SVOM/VT
  70. SVOM/sb25091517: FRAM-ORM stellar flare - transient observation
  71. GRB 250912A: Swift/BAT-GUANO localization skymap of a possibly short burst
  72. GRB 250912A: SVOM/COLIBRÍ (FM-GFT) optical observations
  73. GRB 250912A: Swift-XRT observations
  74. GRB250912A: VLT/HAWK-I follow-up observations
  75. GRB 250912A: VLT observations
  76. GRB 250912A: Fermi GBM Observation
  77. GRB 250911A: Insight-HXMT detection
  78. GRB 250912A: SVOM/GRM analysis suggests a possible short GRB with extended emission
  79. GRB 250912A:SVOM/VT optical upper limit
  80. GRB 250912A: LCO optical upper limit
  81. Fermi GRB 250912A: Global MASTER-Net observations report
  82. EP250911a: Global MASTER-Net observations report
  83. GRB 250912A: SVOM detection of a burst
  84. EP250908c: tentative VLT/FORS2 redshift z = 2.87
  85. EP250911a: Upper limit from Fermi-GBM Observations
  86. LIGO/Virgo/KAGRA S250912f: Updated Sky localization
  87. GRB 250911A: GECAM-B detection
  88. GRB 250911A: Swift-BAT refined analysis
  89. EP250911a: GTC/OSIRIS+ spectroscopic redshift z = 3.84
  90. LIGO/Virgo/KAGRA S250912f: Identification of a GW compact binary merger candidate
  91. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  92. GRB 250910B: SVOM/GRM observation
  93. EP250911a: SVOM/VT optical observation
  94. GRB 250911A: MASTER optical counterpart observations
  95. EP250911a: SAO RAS optical observations
  96. EP250911a: Swift-XRT observations
  97. EP250911a: Optical detection with Kinder observations
  98. GRB 250911A: Swift/UVOT Detection
  99. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  100. GRB 250910A / EP250910a: SVOM/VT afterglow confirmation

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