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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"

24373 results found.

  1. GRB 250920C: VLT redshift confirmation z = 1.399
  2. Fermi GRB 250922B: Global MASTER-Net observations report
  3. Fermi trigger No 780156732: Global MASTER-Net observations report
  4. GRB 250922B: Fermi GBM Final Real-time Localization
  5. Konus-Wind detection of GRB 250920B
  6. Konus-Wind detection of GRB 250920A
  7. IPN triangulation of GRB 250920A (long/bright)
  8. Konus-Wind detection of GRB 250911A
  9. GRB 250920C: Swift-XRT refined Analysis
  10. GRB 250922A: Fermi GBM Final Localization
  11. GRB 250920C: SVOM/GRM observation
  12. GRB 250917B: KAIT optical upper limit
  13. GRB 250920A: NuSTAR detection of bright prompt emission
  14. GRB 250920C: Swift-BAT refined analysis
  15. GRB 250920B: Swift-BAT refined analysis
  16. GRB 250920B: Fermi GBM Observation
  17. GRB 250920A: Fermi GBM Detection
  18. GRB 250920C: Fermi GBM Observation
  19. Swift GRB 250920C: Global MASTER-Net observations report
  20. GRB 250920A: SVOM/GRM observation
  21. GRB250920C: LCOGT Optical Detection
  22. GRB 250920B: Swift-XRT refined Analysis
  23. GRB 250920B: SVOM/C-GFT optical observations
  24. GRB 250920C: GOTO optical counterpart candidate
  25. GRB 250919A / EP250919a: LCO optical observation
  26. Konus-Wind detection of GRB 250919A
  27. GRB 250920C: Swift detection of a burst
  28. GRB 250920C: Fermi GBM Final Real-time Localization
  29. LIGO/Virgo/KAGRA S250920bq: Coverage and upper limits from MAXI/GSC observations
  30. Swift GRB 250920B: Global MASTER-Net observations report
  31. GRB 250920B: Fermi GBM Final Real-time Localization
  32. GRB 250920A: BALROG localization (Fermi Trigger 780029651 / GRB 250920121)
  33. GRB 250920A: Fermi GBM Final Localization
  34. GRB 250919A/EP250919a: SVOM/VT optical observation
  35. GRB 250919A / EP250919a: MASTER bright afterglow detection 24h after GRB time
  36. GRB 250919A: Fermi GBM Observation
  37. Fermi GRB 250918A: Global MASTER-Net observations report
  38. GRB 250919A / EP250919a: NuSTAR detection of bright prompt emission
  39. GRB 250918A: SVOM/GRM observation
  40. GRB 250919A: Swift-XRT afterglow detection
  41. GRB 250919A: Fermi-LAT detection
  42. EP250919a/GRB 250919A: Gemini/GMOS-S spectroscopic redshift z = 1.145
  43. GRB 250919A: SVOM/GRM observation of a very bright GRB
  44. GRB 250919A: BALROG localization (Fermi Trigger 779934537 / GRB 250919020)
  45. EP250919a: Global MASTER-Net observations report
  46. GRB 250916A: Fermi GBM Observation
  47. Fermi GRB 250919A: Global MASTER-Net observations report
  48. GRB 250919A: Fermi GBM Final Real-time Localization
  49. GRB 250916A: KAIT optical observations
  50. GRB 250916A: NuSTAR detection of the prompt emission
  51. GRB 250912A: SVOM/ECLAIRs refined analysis
  52. GRB 250917B: Swift-BAT refined analysis
  53. LIGO/Virgo/KAGRA S250918aw: 1 counterpart neutrino candidate event from an IceCube neutrino search
  54. GRB 250918A: BALROG localization (Fermi Trigger 779891543 / GRB 250918522)
  55. GRB 250918A: Fermi GBM Final Real-time Localization
  56. EP250916a: EP-FXT follow-up observation
  57. LIGO/Virgo/KAGRA S250917aq: Three counterpart neutrino candidates from IceCube neutrino searches
  58. LIGO/Virgo/KAGRA S250917aq: Updated Sky localization
  59. GRB 250916A: Glowbug gamma-ray detection
  60. GRB 250917B: Fermi GBM Observation
  61. GRB 250917B: Swift-XRT observations
  62. LIGO/Virgo/KAGRA S250917aq: Identification of a GW compact binary merger candidate
  63. Fermi GRB 250917B: Global MASTER-Net observations report
  64. GRB 250916A: GOTO optical counterpart candidate
  65. GRB 250917B: Fermi GBM Final Real-time Localization
  66. GRB 250917A: Fermi GBM Final Real-time Localization
  67. The EP-WXT trigger 01709241037 is likely a flaring star
  68. GRB 250916A: AstroSat CZTI detection of a bright long burst
  69. GRB 250910A: SVOM/ECLAIRs refined analysis
  70. Fermi GRB 250916A: Global MASTER-Net observations report
  71. GRB 250916A: Fermi GBM Final Real-time Localization
  72. EP250827b: VLA Observations
  73. LIGO/Virgo/KAGRA S250818k: HCT optical follow-up
  74. SVOM/sb25091517: Confirmation of a stellar flare by SVOM/VT
  75. SVOM/sb25091517: SVOM detection of an X-ray transient
  76. GRB 250912A: Swift/BAT-GUANO localization skymap of a possibly short burst
  77. GRB250912A: VLT/HAWK-I follow-up observations
  78. GRB 250912A: VLT observations
  79. GRB 250912A: Fermi GBM Observation
  80. GRB 250912A: SVOM/GRM analysis suggests a possible short GRB with extended emission
  81. GRB 250912A:SVOM/VT optical upper limit
  82. The EP-WXT trigger 01709240768 is likely a flaring star
  83. Fermi GRB 250912A: Global MASTER-Net observations report
  84. EP250911a: Global MASTER-Net observations report
  85. GRB 250912A: SVOM detection of a burst
  86. GRB 250912A: Fermi GBM Final Real-time Localization
  87. IceCube-Cascade 250911A: Upper limits from a search for additional neutrino events in IceCube
  88. LIGO/Virgo/KAGRA S250912s: 2 counterpart neutrino candidate events from an IceCube neutrino search
  89. EP250908c: tentative VLT/FORS2 redshift z = 2.87
  90. EP250911a: Upper limit from Fermi-GBM Observations
  91. LIGO/Virgo/KAGRA S250912f: Updated Sky localization
  92. GRB 250911A: GECAM-B detection
  93. GRB 250911A: Swift-BAT refined analysis
  94. EP250911a: GTC/OSIRIS+ spectroscopic redshift z = 3.84
  95. LIGO/Virgo/KAGRA S250912f: Identification of a GW compact binary merger candidate
  96. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  97. GRB 250910B: SVOM/GRM observation
  98. EP250911a: SVOM/VT optical observation
  99. GRB 250910C: Fermi GBM Final Localization Correction
  100. GRB 250910A / EP250910a: Swift-XRT afterglow detection

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