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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"

26164 results found.

  1. Fermi trigger No 780156732: Global MASTER-Net observations report
  2. GRB 250922B: Fermi GBM Final Real-time Localization
  3. IPN triangulation of GRB 250920A (long/bright)
  4. GRB 250916A: Swift/UVOT Detection
  5. GRB 250920C: Swift-XRT refined Analysis
  6. GRB 250922A: Fermi GBM Final Localization
  7. GRB 250920B: Kitab-ISON optical upper limit
  8. GRB 250920C: SVOM/GRM observation
  9. GRB 250920C: GTC/OSIRIS+ spectroscopic redshift z = 1.40
  10. GRB 250920C: GROWTH-India Telescope optical observations
  11. GRB 250920C: Swift-BAT refined analysis
  12. GRB 250920B: Swift-BAT refined analysis
  13. GRB 250916A: FTW optical and NIR observations of the counterpart
  14. GRB 250920C: Swift/UVOT Detection
  15. GRB 250920B: Fermi GBM Observation
  16. GRB 250920A: Fermi GBM Detection
  17. GRB 250920C: Fermi GBM Observation
  18. Swift GRB 250920C: Global MASTER-Net observations report
  19. GRB 250920B: Swift/UVOT Detection
  20. GRB 250920B: FTW optical and NIR observations of the counterpart
  21. GRB 250920C: Optical counterpart detection by LCO
  22. GRB 250920A: SVOM/GRM observation
  23. GRB250920C: LCOGT Optical Detection
  24. GRB 250920B: Swift-XRT refined Analysis
  25. GRB 250920B: SVOM/C-GFT optical observations
  26. GRB 250920C: GOTO optical counterpart candidate
  27. GRB 250919A / EP250919a: LCO optical observation
  28. GRB 250920C: Swift detection of a burst
  29. GRB 250920C: Fermi GBM Final Real-time Localization
  30. LIGO/Virgo/KAGRA S250920bq: Coverage and upper limits from MAXI/GSC observations
  31. Swift GRB 250920B: Global MASTER-Net observations report
  32. GRB 250920B: Swift detection of a burst with a bright optical counterpart.
  33. GRB 250920B: Fermi GBM Final Real-time Localization
  34. GRB 250920A: BALROG localization (Fermi Trigger 780029651 / GRB 250920121)
  35. GRB 250920A: Fermi GBM Final Localization
  36. GRB 250919A/EP250919a: SVOM/VT optical observation
  37. GRB 250919A: Fermi GBM Observation
  38. Fermi GRB 250918A: Global MASTER-Net observations report
  39. GRB 250918A: SVOM/GRM observation
  40. GRB 250919A: Swift-XRT afterglow detection
  41. GRB 250919A: Fermi-LAT detection
  42. GRB 250919A: SVOM/GRM observation of a very bright GRB
  43. GRB 250919A: BALROG localization (Fermi Trigger 779934537 / GRB 250919020)
  44. EP250919a: Global MASTER-Net observations report
  45. EP250919a: Einstein Probe detection of an X-ray transient
  46. Correction for GCN 41877: EP-WXT ID is 01709243841
  47. The EP-WXT trigger 01709243841: Las Cumbres discovery of the optical counterpart
  48. GRB 250916A: Fermi GBM Observation
  49. Fermi GRB 250919A: Global MASTER-Net observations report
  50. GRB 250919A: Fermi GBM Final Real-time Localization
  51. GRB 250917B: VLT/HAWK-I near-infrared observations
  52. GRB 250912A: SVOM/ECLAIRs refined analysis
  53. GRB 250917B: Swift-BAT refined analysis
  54. LIGO/Virgo/KAGRA S250918aw: 1 counterpart neutrino candidate event from an IceCube neutrino search
  55. GRB 250918A: BALROG localization (Fermi Trigger 779891543 / GRB 250918522)
  56. GRB 250918A: Fermi GBM Final Real-time Localization
  57. GRB 250917B: Swift/UVOT Upper Limits
  58. EP250916a: EP-FXT follow-up observation
  59. GRB 250916A : GIT optical observations
  60. LIGO/Virgo/KAGRA S250917aq: Three counterpart neutrino candidates from IceCube neutrino searches
  61. GRB 250916A: Glowbug gamma-ray detection
  62. GRB 250917B: Fermi GBM Observation
  63. Fermi GRB 250917B: Global MASTER-Net observations report
  64. GRB 250917B: Swift detection of a short burst
  65. GRB 250916A: GOTO optical counterpart candidate
  66. GRB 250917B: Fermi GBM Final Real-time Localization
  67. GRB 250917A: Fermi GBM Final Real-time Localization
  68. The EP-WXT trigger 01709241037 is likely a flaring star
  69. GRB 250910A: SVOM/ECLAIRs refined analysis
  70. EP250916a: Einstein Probe detection of an X-ray transient
  71. Fermi GRB 250916A: Global MASTER-Net observations report
  72. GRB 250916A: Fermi GBM Final Real-time Localization
  73. LIGO/Virgo/KAGRA S250818k: HCT optical follow-up
  74. SVOM/sb25091517: Confirmation of a stellar flare by SVOM/VT
  75. SVOM/sb25091517: FRAM-ORM stellar flare - transient observation
  76. SVOM/sb25091517: SVOM detection of an X-ray transient
  77. GRB 250912A: Swift/BAT-GUANO localization skymap of a possibly short burst
  78. GRB 250912A: SVOM/COLIBRÍ (FM-GFT) optical observations
  79. GRB 250912A: Swift-XRT observations
  80. GRB250912A: VLT/HAWK-I follow-up observations
  81. GRB 250912A: VLT observations
  82. GRB 250912A: Fermi GBM Observation
  83. GRB 250912A: SVOM/GRM analysis suggests a possible short GRB with extended emission
  84. GRB 250912A:SVOM/VT optical upper limit
  85. GRB 250912A: LCO optical upper limit
  86. The EP-WXT trigger 01709240768 is likely a flaring star
  87. Fermi GRB 250912A: Global MASTER-Net observations report
  88. EP250911a: Global MASTER-Net observations report
  89. GRB 250912A: SVOM detection of a burst
  90. GRB 250912A: Fermi GBM Final Real-time Localization
  91. LIGO/Virgo/KAGRA S250912s: 2 counterpart neutrino candidate events from an IceCube neutrino search
  92. EP250908c: tentative VLT/FORS2 redshift z = 2.87
  93. EP250911a: Upper limit from Fermi-GBM Observations
  94. GRB 250911A: GECAM-B detection
  95. GRB 250911A: Swift-BAT refined analysis
  96. EP250911a: GTC/OSIRIS+ spectroscopic redshift z = 3.84
  97. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  98. GRB 250910B: SVOM/GRM observation
  99. EP250911a: SVOM/VT optical observation
  100. GRB 250911A: Swift-XRT refined Analysis

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