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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"

24375 results found.

  1. Konus-Wind detection of GRB 250920C
  2. GRB 250920C: KAIT optical observations
  3. GRB 250920C: VLT redshift confirmation z = 1.399
  4. Fermi GRB 250922B: Global MASTER-Net observations report
  5. Fermi trigger No 780156732: Global MASTER-Net observations report
  6. GRB 250922B: Fermi GBM Final Real-time Localization
  7. Konus-Wind detection of GRB 250920B
  8. Konus-Wind detection of GRB 250920A
  9. IPN triangulation of GRB 250920A (long/bright)
  10. Konus-Wind detection of GRB 250911A
  11. GRB 250920C: Swift-XRT refined Analysis
  12. GRB 250922A: Fermi GBM Final Localization
  13. GRB 250920C: SVOM/GRM observation
  14. GRB 250917B: KAIT optical upper limit
  15. GRB 250920A: NuSTAR detection of bright prompt emission
  16. GRB 250920C: Swift-BAT refined analysis
  17. GRB 250920B: Swift-BAT refined analysis
  18. GRB 250920B: Fermi GBM Observation
  19. GRB 250920A: Fermi GBM Detection
  20. GRB 250920C: Fermi GBM Observation
  21. Swift GRB 250920C: Global MASTER-Net observations report
  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. Konus-Wind detection of GRB 250919A
  29. GRB 250920C: Swift detection of a burst
  30. GRB 250920C: Fermi GBM Final Real-time Localization
  31. LIGO/Virgo/KAGRA S250920bq: Coverage and upper limits from MAXI/GSC observations
  32. Swift GRB 250920B: Global MASTER-Net observations report
  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 / EP250919a: MASTER bright afterglow detection 24h after GRB time
  38. GRB 250919A: Fermi GBM Observation
  39. Fermi GRB 250918A: Global MASTER-Net observations report
  40. GRB 250919A / EP250919a: NuSTAR detection of bright prompt emission
  41. GRB 250918A: SVOM/GRM observation
  42. GRB 250919A: Swift-XRT afterglow detection
  43. GRB 250919A: Fermi-LAT detection
  44. EP250919a/GRB 250919A: Gemini/GMOS-S spectroscopic redshift z = 1.145
  45. GRB 250919A: SVOM/GRM observation of a very bright GRB
  46. GRB 250919A: BALROG localization (Fermi Trigger 779934537 / GRB 250919020)
  47. EP250919a: Global MASTER-Net observations report
  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 250916A: KAIT optical observations
  52. GRB 250916A: NuSTAR detection of the prompt emission
  53. GRB 250912A: SVOM/ECLAIRs refined analysis
  54. GRB 250917B: Swift-BAT refined analysis
  55. LIGO/Virgo/KAGRA S250918aw: 1 counterpart neutrino candidate event from an IceCube neutrino search
  56. GRB 250918A: BALROG localization (Fermi Trigger 779891543 / GRB 250918522)
  57. GRB 250918A: Fermi GBM Final Real-time Localization
  58. EP250916a: EP-FXT follow-up observation
  59. LIGO/Virgo/KAGRA S250917aq: Three counterpart neutrino candidates from IceCube neutrino searches
  60. LIGO/Virgo/KAGRA S250917aq: Updated Sky localization
  61. GRB 250916A: Glowbug gamma-ray detection
  62. GRB 250917B: Fermi GBM Observation
  63. GRB 250917B: Swift-XRT observations
  64. LIGO/Virgo/KAGRA S250917aq: Identification of a GW compact binary merger candidate
  65. Fermi GRB 250917B: Global MASTER-Net observations report
  66. GRB 250916A: GOTO optical counterpart candidate
  67. GRB 250917B: Fermi GBM Final Real-time Localization
  68. GRB 250917A: Fermi GBM Final Real-time Localization
  69. The EP-WXT trigger 01709241037 is likely a flaring star
  70. GRB 250916A: AstroSat CZTI detection of a bright long burst
  71. GRB 250910A: SVOM/ECLAIRs refined analysis
  72. Fermi GRB 250916A: Global MASTER-Net observations report
  73. GRB 250916A: Fermi GBM Final Real-time Localization
  74. EP250827b: VLA Observations
  75. LIGO/Virgo/KAGRA S250818k: HCT optical follow-up
  76. SVOM/sb25091517: Confirmation of a stellar flare by SVOM/VT
  77. SVOM/sb25091517: SVOM detection of an X-ray transient
  78. GRB 250912A: Swift/BAT-GUANO localization skymap of a possibly short burst
  79. GRB250912A: VLT/HAWK-I follow-up observations
  80. GRB 250912A: VLT observations
  81. GRB 250912A: Fermi GBM Observation
  82. GRB 250912A: SVOM/GRM analysis suggests a possible short GRB with extended emission
  83. GRB 250912A:SVOM/VT optical upper limit
  84. The EP-WXT trigger 01709240768 is likely a flaring star
  85. Fermi GRB 250912A: Global MASTER-Net observations report
  86. EP250911a: Global MASTER-Net observations report
  87. GRB 250912A: SVOM detection of a burst
  88. GRB 250912A: Fermi GBM Final Real-time Localization
  89. IceCube-Cascade 250911A: Upper limits from a search for additional neutrino events in IceCube
  90. LIGO/Virgo/KAGRA S250912s: 2 counterpart neutrino candidate events from an IceCube neutrino search
  91. EP250908c: tentative VLT/FORS2 redshift z = 2.87
  92. EP250911a: Upper limit from Fermi-GBM Observations
  93. LIGO/Virgo/KAGRA S250912f: Updated Sky localization
  94. GRB 250911A: GECAM-B detection
  95. GRB 250911A: Swift-BAT refined analysis
  96. EP250911a: GTC/OSIRIS+ spectroscopic redshift z = 3.84
  97. LIGO/Virgo/KAGRA S250912f: Identification of a GW compact binary merger candidate
  98. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  99. GRB 250910B: SVOM/GRM observation
  100. EP250911a: SVOM/VT optical observation

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