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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 250919A: Glowbug gamma-ray detection
  2. GRB 250919A: Fermi GBM Observation
  3. Fermi GRB 250918A: Global MASTER-Net observations report
  4. GRB 250919A / EP250919a: NuSTAR detection of bright prompt emission
  5. GRB 250918A: SVOM/GRM observation
  6. GRB 250919A/EP250919A: Swift/UVOT afterglow detection
  7. GRB 250919A: Swift-XRT afterglow detection
  8. GRB 250919A: Fermi-LAT detection
  9. EP250919a/GRB 250919A: Gemini/GMOS-S spectroscopic redshift z = 1.145
  10. GRB 250919A: SVOM/GRM observation of a very bright GRB
  11. GRB 250919A: BALROG localization (Fermi Trigger 779934537 / GRB 250919020)
  12. EP250919a: Global MASTER-Net observations report
  13. EP250919a: Einstein Probe detection of an X-ray transient
  14. Correction for GCN 41877: EP-WXT ID is 01709243841
  15. The EP-WXT trigger 01709243841: Las Cumbres discovery of the optical counterpart
  16. GRB 250916A: Fermi GBM Observation
  17. Fermi GRB 250919A: Global MASTER-Net observations report
  18. GRB 250919A: Fermi GBM Final Real-time Localization
  19. GRB 250916A: KAIT optical observations
  20. GRB 250917B: VLT/HAWK-I near-infrared observations
  21. GRB 250916A: NuSTAR detection of the prompt emission
  22. GRB 250916A: further SAO RAS optical observations
  23. GRB 250912A: SVOM/ECLAIRs refined analysis
  24. GRB 250917B: Swift-BAT refined analysis
  25. LIGO/Virgo/KAGRA S250918aw: 1 counterpart neutrino candidate event from an IceCube neutrino search
  26. GRB 250918A: BALROG localization (Fermi Trigger 779891543 / GRB 250918522)
  27. GRB 250918A: Fermi GBM Final Real-time Localization
  28. GRB 250917B: Swift/UVOT Upper Limits
  29. GRB 250916A: OSIRIS+/GTC redshift z = 2.015
  30. GRB 250916A: Swift-XRT observations
  31. EP250916a: EP-FXT follow-up observation
  32. GRB 250916A: MAO/AZT-22 optical observations
  33. GRB 250916A: SAO RAS optical observations
  34. GRB 250916A : GIT optical observations
  35. LIGO/Virgo/KAGRA S250917aq: Three counterpart neutrino candidates from IceCube neutrino searches
  36. LIGO/Virgo/KAGRA S250917aq: Updated Sky localization
  37. GRB 250916A: Glowbug gamma-ray detection
  38. GRB250917B: WFST optical observations
  39. GRB 250916A: Swift ToO observations
  40. GRB 250917B: Fermi GBM Observation
  41. GRB 250917B: Swift-XRT observations
  42. LIGO/Virgo/KAGRA S250917aq: Identification of a GW compact binary merger candidate
  43. Fermi GRB 250917B: Global MASTER-Net observations report
  44. GRB 250917B: Swift detection of a short burst
  45. GRB 250916A: GOTO optical counterpart candidate
  46. GRB 250917B: Fermi GBM Final Real-time Localization
  47. GRB 250917A: Fermi GBM Final Real-time Localization
  48. The EP-WXT trigger 01709241037 is likely a flaring star
  49. GRB 250916A: AstroSat CZTI detection of a bright long burst
  50. GRB 250910A: SVOM/ECLAIRs refined analysis
  51. EP250916a: Einstein Probe detection of an X-ray transient
  52. Fermi GRB 250916A: Global MASTER-Net observations report
  53. GRB 250916A: Fermi GBM Final Real-time Localization
  54. EP250827b: VLA Observations
  55. LIGO/Virgo/KAGRA S250818k: HCT optical follow-up
  56. SVOM/sb25091517: Confirmation of a stellar flare by SVOM/VT
  57. SVOM/sb25091517: FRAM-ORM stellar flare - transient observation
  58. SVOM/sb25091517: SVOM detection of an X-ray transient
  59. GRB 250912A: Swift/BAT-GUANO localization skymap of a possibly short burst
  60. GRB 250912A: SVOM/COLIBRÍ (FM-GFT) optical observations
  61. GRB 250912A: Swift-XRT observations
  62. GRB250912A: VLT/HAWK-I follow-up observations
  63. GRB 250912A: VLT observations
  64. GRB 250912A: Fermi GBM Observation
  65. GRB 250911A: Insight-HXMT detection
  66. GRB 250912A: SVOM/GRM analysis suggests a possible short GRB with extended emission
  67. GRB 250912A:SVOM/VT optical upper limit
  68. GRB 250912A: LCO optical upper limit
  69. The EP-WXT trigger 01709240768 is likely a flaring star
  70. Fermi GRB 250912A: Global MASTER-Net observations report
  71. EP250911a: Global MASTER-Net observations report
  72. GRB 250912A: SVOM detection of a burst
  73. GRB 250912A: Fermi GBM Final Real-time Localization
  74. IceCube-Cascade 250911A: Upper limits from a search for additional neutrino events in IceCube
  75. LIGO/Virgo/KAGRA S250912s: 2 counterpart neutrino candidate events from an IceCube neutrino search
  76. EP250908c: tentative VLT/FORS2 redshift z = 2.87
  77. EP250911a: Upper limit from Fermi-GBM Observations
  78. LIGO/Virgo/KAGRA S250912f: Updated Sky localization
  79. GRB 250911A: GECAM-B detection
  80. GRB 250911A: Swift-BAT refined analysis
  81. EP250911a: GTC/OSIRIS+ spectroscopic redshift z = 3.84
  82. LIGO/Virgo/KAGRA S250912f: Identification of a GW compact binary merger candidate
  83. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  84. GRB 250910B: SVOM/GRM observation
  85. EP250911a: SVOM/VT optical observation
  86. GRB 250911A: MASTER optical counterpart observations
  87. EP250911a: SAO RAS optical observations
  88. GRB 250911A: Swift-XRT refined Analysis
  89. GRB 250910C: Fermi GBM Final Localization Correction
  90. EP250911a: Swift-XRT observations
  91. EP250911a: Optical detection with Kinder observations
  92. GRB 250911A: Swift/UVOT Detection
  93. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  94. GRB 250910A / EP250910a: SVOM/VT afterglow confirmation
  95. GRB 250909B: Insight-HXMT detection
  96. GRB 250909B: SVOM/GRM observation
  97. LIGO/Virgo/KAGRA S250911ac: Updated Sky localization and Source Classification
  98. GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
  99. EP250911a: COLIBRÍ optical observations
  100. LIGO/Virgo/KAGRA S250908y: Updated Sky localization

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