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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"

32510 results found.

  1. GRB 250920C: NIR observations with WINTER
  2. GRB 250920B: NIR observations with WINTER
  3. GRB 250920C: PRIME near-infrared detection
  4. Konus-Wind detection of GRB 250920B
  5. Konus-Wind detection of GRB 250920A
  6. IPN triangulation of GRB 250920A (long/bright)
  7. Konus-Wind detection of GRB 250911A
  8. GRB 250916A: Swift/UVOT Detection
  9. GRB 250920B: Glowbug gamma-ray detection
  10. GRB 250916A: CrAO ZTSh R-band optical observations
  11. GRB 250916A: SAO RAS Zeiss-1000 optical observations
  12. GRB 250920B: Asiago optical observations
  13. GRB 250920B: Kitab-ISON optical upper limit
  14. GRB 250917B: Mondy and Zeiss-1000 SAO RAS optical observations, optical observations, afterglow candidate
  15. GRB 250920C: SVOM/GRM observation
  16. GRB 250920C: GTC/OSIRIS+ spectroscopic redshift z = 1.40
  17. GRB 250917B: KAIT optical upper limit
  18. GRB 250920A: NuSTAR detection of bright prompt emission
  19. GRB 250920C: GROWTH-India Telescope optical observations
  20. GRB 250920C: Swift-BAT refined analysis
  21. GRB 250920B: Swift-BAT refined analysis
  22. GRB 250916A: FTW optical and NIR observations of the counterpart
  23. GRB 250920C: Swift/UVOT Detection
  24. GRB 250920B: Fermi GBM Observation
  25. GRB 250920A: Fermi GBM Detection
  26. GRB 250920C: Fermi GBM Observation
  27. Swift GRB 250920C: Global MASTER-Net observations report
  28. GRB 250920B: Swift/UVOT Detection
  29. GRB 250920B: FTW optical and NIR observations of the counterpart
  30. GRB 250920C: Optical counterpart detection by LCO
  31. GRB 250920A: SVOM/GRM observation
  32. GRB250920C: LCOGT Optical Detection
  33. GRB 250920B: SVOM/C-GFT optical observations
  34. GRB 250920C: GOTO optical counterpart candidate
  35. GRB 250919A / EP250919a: LCO optical observation
  36. Konus-Wind detection of GRB 250919A
  37. Swift GRB 250920B: Global MASTER-Net observations report
  38. GRB 250919A / EP250919a: Insight-HXMT detection
  39. GRB 250920A: AstroSat CZTI detection
  40. GRB 250919A/EP250919a: SVOM/VT optical observation
  41. GRB 250919A / EP250919a: MASTER bright afterglow detection 24h after GRB time
  42. GRB 250916A: Mondy R-band optical observations
  43. GRB 250919A: Glowbug gamma-ray detection
  44. GRB 250919A: Fermi GBM Observation
  45. Fermi GRB 250918A: Global MASTER-Net observations report
  46. GRB 250919A / EP250919a: NuSTAR detection of bright prompt emission
  47. GRB 250918A: SVOM/GRM observation
  48. GRB 250919A/EP250919A: Swift/UVOT afterglow detection
  49. GRB 250919A: Swift-XRT afterglow detection
  50. GRB 250919A: Fermi-LAT detection
  51. EP250919a/GRB 250919A: Gemini/GMOS-S spectroscopic redshift z = 1.145
  52. GRB 250919A: SVOM/GRM observation of a very bright GRB
  53. EP250919a: Global MASTER-Net observations report
  54. EP250919a: Einstein Probe detection of an X-ray transient
  55. Correction for GCN 41877: EP-WXT ID is 01709243841
  56. GRB 250916A: Fermi GBM Observation
  57. Fermi GRB 250919A: Global MASTER-Net observations report
  58. GRB 250916A: KAIT optical observations
  59. GRB 250917B: VLT/HAWK-I near-infrared observations
  60. GRB 250916A: NuSTAR detection of the prompt emission
  61. GRB 250916A: further SAO RAS optical observations
  62. GRB 250912A: SVOM/ECLAIRs refined analysis
  63. GRB 250917B: Swift-BAT refined analysis
  64. GRB 250917B: Swift/UVOT Upper Limits
  65. GRB 250916A: OSIRIS+/GTC redshift z = 2.015
  66. GRB 250916A: Swift-XRT observations
  67. EP250916a: EP-FXT follow-up observation
  68. GRB 250916A: MAO/AZT-22 optical observations
  69. GRB 250916A: SAO RAS optical observations
  70. GRB 250916A : GIT optical observations
  71. LIGO/Virgo/KAGRA S250917aq: Updated Sky localization
  72. GRB 250916A: Glowbug gamma-ray detection
  73. GRB250917B: WFST optical observations
  74. GRB 250916A: Swift ToO observations
  75. GRB 250917B: Fermi GBM Observation
  76. LIGO/Virgo/KAGRA S250917aq: Identification of a GW compact binary merger candidate
  77. Fermi GRB 250917B: Global MASTER-Net observations report
  78. GRB 250916A: GOTO optical counterpart candidate
  79. GRB 250916A: AstroSat CZTI detection of a bright long burst
  80. GRB 250910A: SVOM/ECLAIRs refined analysis
  81. Fermi GRB 250916A: Global MASTER-Net observations report
  82. EP250827b: VLA Observations
  83. LIGO/Virgo/KAGRA S250818k: HCT optical follow-up
  84. SVOM/sb25091517: Confirmation of a stellar flare by SVOM/VT
  85. SVOM/sb25091517: FRAM-ORM stellar flare - transient observation
  86. GRB 250912A: Swift/BAT-GUANO localization skymap of a possibly short burst
  87. GRB 250912A: SVOM/COLIBRÍ (FM-GFT) optical observations
  88. GRB 250912A: Swift-XRT observations
  89. GRB250912A: VLT/HAWK-I follow-up observations
  90. GRB 250912A: VLT observations
  91. GRB 250912A: Fermi GBM Observation
  92. GRB 250911A: Insight-HXMT detection
  93. GRB 250912A: SVOM/GRM analysis suggests a possible short GRB with extended emission
  94. GRB 250912A:SVOM/VT optical upper limit
  95. GRB 250912A: LCO optical upper limit
  96. Fermi GRB 250912A: Global MASTER-Net observations report
  97. EP250911a: Global MASTER-Net observations report
  98. GRB 250912A: SVOM detection of a burst
  99. EP250908c: tentative VLT/FORS2 redshift z = 2.87
  100. EP250911a: Upper limit from Fermi-GBM Observations

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