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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"
  1. GRB 250920A: Fermi GBM Final Localization
  2. GRB 250919A/EP250919a: SVOM/VT optical observation
  3. GRB 250919A / EP250919a: MASTER bright afterglow detection 24h after GRB time
  4. GRB 250916A: Mondy R-band optical observations
  5. GRB 250919A: Glowbug gamma-ray detection
  6. GRB 250919A: Fermi GBM Observation
  7. Fermi GRB 250918A: Global MASTER-Net observations report
  8. GRB 250919A / EP250919a: NuSTAR detection of bright prompt emission
  9. GRB 250918A: SVOM/GRM observation
  10. GRB 250919A/EP250919A: Swift/UVOT afterglow detection
  11. GRB 250919A: Swift-XRT afterglow detection
  12. GRB 250919A: Fermi-LAT detection
  13. EP250919a/GRB 250919A: Gemini/GMOS-S spectroscopic redshift z = 1.145
  14. GRB 250919A: SVOM/GRM observation of a very bright GRB
  15. GRB 250919A: BALROG localization (Fermi Trigger 779934537 / GRB 250919020)
  16. EP250919a: Global MASTER-Net observations report
  17. EP250919a: Einstein Probe detection of an X-ray transient
  18. Correction for GCN 41877: EP-WXT ID is 01709243841
  19. The EP-WXT trigger 01709243841: Las Cumbres discovery of the optical counterpart
  20. GRB 250916A: Fermi GBM Observation
  21. Fermi GRB 250919A: Global MASTER-Net observations report
  22. GRB 250919A: Fermi GBM Final Real-time Localization
  23. GRB 250916A: KAIT optical observations
  24. GRB 250917B: VLT/HAWK-I near-infrared observations
  25. GRB 250916A: NuSTAR detection of the prompt emission
  26. GRB 250916A: further SAO RAS optical observations
  27. GRB 250912A: SVOM/ECLAIRs refined analysis
  28. GRB 250917B: Swift-BAT refined analysis
  29. LIGO/Virgo/KAGRA S250918aw: 1 counterpart neutrino candidate event from an IceCube neutrino search
  30. GRB 250918A: BALROG localization (Fermi Trigger 779891543 / GRB 250918522)
  31. GRB 250918A: Fermi GBM Final Real-time Localization
  32. GRB 250917B: Swift/UVOT Upper Limits
  33. GRB 250916A: OSIRIS+/GTC redshift z = 2.015
  34. GRB 250916A: Swift-XRT observations
  35. EP250916a: EP-FXT follow-up observation
  36. GRB 250916A: MAO/AZT-22 optical observations
  37. GRB 250916A: SAO RAS optical observations
  38. GRB 250916A : GIT optical observations
  39. LIGO/Virgo/KAGRA S250917aq: Three counterpart neutrino candidates from IceCube neutrino searches
  40. LIGO/Virgo/KAGRA S250917aq: Updated Sky localization
  41. GRB 250916A: Glowbug gamma-ray detection
  42. GRB250917B: WFST optical observations
  43. GRB 250916A: Swift ToO observations
  44. GRB 250917B: Fermi GBM Observation
  45. GRB 250917B: Swift-XRT observations
  46. LIGO/Virgo/KAGRA S250917aq: Identification of a GW compact binary merger candidate
  47. Fermi GRB 250917B: Global MASTER-Net observations report
  48. GRB 250917B: Swift detection of a short burst
  49. GRB 250916A: GOTO optical counterpart candidate
  50. GRB 250917B: Fermi GBM Final Real-time Localization
  51. GRB 250917A: Fermi GBM Final Real-time Localization
  52. The EP-WXT trigger 01709241037 is likely a flaring star
  53. GRB 250916A: AstroSat CZTI detection of a bright long burst
  54. GRB 250910A: SVOM/ECLAIRs refined analysis
  55. EP250916a: Einstein Probe detection of an X-ray transient
  56. Fermi GRB 250916A: Global MASTER-Net observations report
  57. GRB 250916A: Fermi GBM Final Real-time Localization
  58. EP250827b: VLA Observations
  59. LIGO/Virgo/KAGRA S250818k: HCT optical follow-up
  60. SVOM/sb25091517: Confirmation of a stellar flare by SVOM/VT
  61. SVOM/sb25091517: FRAM-ORM stellar flare - transient observation
  62. SVOM/sb25091517: SVOM detection of an X-ray transient
  63. GRB 250912A: Swift/BAT-GUANO localization skymap of a possibly short burst
  64. GRB 250912A: SVOM/COLIBRÍ (FM-GFT) optical observations
  65. GRB 250912A: Swift-XRT observations
  66. GRB250912A: VLT/HAWK-I follow-up observations
  67. GRB 250912A: VLT observations
  68. GRB 250912A: Fermi GBM Observation
  69. GRB 250911A: Insight-HXMT detection
  70. GRB 250912A: SVOM/GRM analysis suggests a possible short GRB with extended emission
  71. GRB 250912A:SVOM/VT optical upper limit
  72. GRB 250912A: LCO optical upper limit
  73. The EP-WXT trigger 01709240768 is likely a flaring star
  74. Fermi GRB 250912A: Global MASTER-Net observations report
  75. EP250911a: Global MASTER-Net observations report
  76. GRB 250912A: SVOM detection of a burst
  77. GRB 250912A: Fermi GBM Final Real-time Localization
  78. IceCube-Cascade 250911A: Upper limits from a search for additional neutrino events in IceCube
  79. LIGO/Virgo/KAGRA S250912s: 2 counterpart neutrino candidate events from an IceCube neutrino search
  80. EP250908c: tentative VLT/FORS2 redshift z = 2.87
  81. EP250911a: Upper limit from Fermi-GBM Observations
  82. LIGO/Virgo/KAGRA S250912f: Updated Sky localization
  83. GRB 250911A: GECAM-B detection
  84. GRB 250911A: Swift-BAT refined analysis
  85. EP250911a: GTC/OSIRIS+ spectroscopic redshift z = 3.84
  86. LIGO/Virgo/KAGRA S250912f: Identification of a GW compact binary merger candidate
  87. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  88. GRB 250910B: SVOM/GRM observation
  89. EP250911a: SVOM/VT optical observation
  90. GRB 250911A: MASTER optical counterpart observations
  91. EP250911a: SAO RAS optical observations
  92. GRB 250911A: Swift-XRT refined Analysis
  93. GRB 250910C: Fermi GBM Final Localization Correction
  94. EP250911a: Swift-XRT observations
  95. EP250911a: Optical detection with Kinder observations
  96. GRB 250911A: Swift/UVOT Detection
  97. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  98. GRB 250910A / EP250910a: SVOM/VT afterglow confirmation
  99. GRB 250909B: Insight-HXMT detection
  100. GRB 250909B: SVOM/GRM observation

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