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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: Swift-XRT afterglow detection
  2. GRB 250919A: Fermi-LAT detection
  3. EP250919a/GRB 250919A: Gemini/GMOS-S spectroscopic redshift z = 1.145
  4. GRB 250919A: SVOM/GRM observation of a very bright GRB
  5. GRB 250919A: BALROG localization (Fermi Trigger 779934537 / GRB 250919020)
  6. EP250919a: Global MASTER-Net observations report
  7. EP250919a: Einstein Probe detection of an X-ray transient
  8. Correction for GCN 41877: EP-WXT ID is 01709243841
  9. The EP-WXT trigger 01709243841: Las Cumbres discovery of the optical counterpart
  10. GRB 250916A: Fermi GBM Observation
  11. Fermi GRB 250919A: Global MASTER-Net observations report
  12. GRB 250919A: Fermi GBM Final Real-time Localization
  13. GRB 250916A: KAIT optical observations
  14. GRB 250917B: VLT/HAWK-I near-infrared observations
  15. GRB 250916A: NuSTAR detection of the prompt emission
  16. GRB 250916A: further SAO RAS optical observations
  17. GRB 250912A: SVOM/ECLAIRs refined analysis
  18. GRB 250917B: Swift-BAT refined analysis
  19. LIGO/Virgo/KAGRA S250918aw: 1 counterpart neutrino candidate event from an IceCube neutrino search
  20. GRB 250918A: BALROG localization (Fermi Trigger 779891543 / GRB 250918522)
  21. GRB 250918A: Fermi GBM Final Real-time Localization
  22. GRB 250917B: Swift/UVOT Upper Limits
  23. GRB 250916A: OSIRIS+/GTC redshift z = 2.015
  24. GRB 250916A: Swift-XRT observations
  25. EP250916a: EP-FXT follow-up observation
  26. GRB 250916A: MAO/AZT-22 optical observations
  27. GRB 250916A: SAO RAS optical observations
  28. GRB 250916A : GIT optical observations
  29. LIGO/Virgo/KAGRA S250917aq: Three counterpart neutrino candidates from IceCube neutrino searches
  30. LIGO/Virgo/KAGRA S250917aq: Updated Sky localization
  31. GRB 250916A: Glowbug gamma-ray detection
  32. GRB250917B: WFST optical observations
  33. GRB 250916A: Swift ToO observations
  34. GRB 250917B: Fermi GBM Observation
  35. GRB 250917B: Swift-XRT observations
  36. LIGO/Virgo/KAGRA S250917aq: Identification of a GW compact binary merger candidate
  37. Fermi GRB 250917B: Global MASTER-Net observations report
  38. GRB 250917B: Swift detection of a short burst
  39. GRB 250916A: GOTO optical counterpart candidate
  40. GRB 250917B: Fermi GBM Final Real-time Localization
  41. GRB 250917A: Fermi GBM Final Real-time Localization
  42. The EP-WXT trigger 01709241037 is likely a flaring star
  43. GRB 250916A: AstroSat CZTI detection of a bright long burst
  44. GRB 250910A: SVOM/ECLAIRs refined analysis
  45. EP250916a: Einstein Probe detection of an X-ray transient
  46. Fermi GRB 250916A: Global MASTER-Net observations report
  47. GRB 250916A: Fermi GBM Final Real-time Localization
  48. EP250827b: VLA Observations
  49. LIGO/Virgo/KAGRA S250818k: HCT optical follow-up
  50. SVOM/sb25091517: Confirmation of a stellar flare by SVOM/VT
  51. SVOM/sb25091517: FRAM-ORM stellar flare - transient observation
  52. SVOM/sb25091517: SVOM detection of an X-ray transient
  53. GRB 250912A: Swift/BAT-GUANO localization skymap of a possibly short burst
  54. GRB 250912A: SVOM/COLIBRÍ (FM-GFT) optical observations
  55. GRB 250912A: Swift-XRT observations
  56. GRB250912A: VLT/HAWK-I follow-up observations
  57. GRB 250912A: VLT observations
  58. GRB 250912A: Fermi GBM Observation
  59. GRB 250911A: Insight-HXMT detection
  60. GRB 250912A: SVOM/GRM analysis suggests a possible short GRB with extended emission
  61. GRB 250912A:SVOM/VT optical upper limit
  62. GRB 250912A: LCO optical upper limit
  63. The EP-WXT trigger 01709240768 is likely a flaring star
  64. Fermi GRB 250912A: Global MASTER-Net observations report
  65. EP250911a: Global MASTER-Net observations report
  66. GRB 250912A: SVOM detection of a burst
  67. GRB 250912A: Fermi GBM Final Real-time Localization
  68. IceCube-Cascade 250911A: Upper limits from a search for additional neutrino events in IceCube
  69. LIGO/Virgo/KAGRA S250912s: 2 counterpart neutrino candidate events from an IceCube neutrino search
  70. EP250908c: tentative VLT/FORS2 redshift z = 2.87
  71. EP250911a: Upper limit from Fermi-GBM Observations
  72. LIGO/Virgo/KAGRA S250912f: Updated Sky localization
  73. GRB 250911A: GECAM-B detection
  74. GRB 250911A: Swift-BAT refined analysis
  75. EP250911a: GTC/OSIRIS+ spectroscopic redshift z = 3.84
  76. LIGO/Virgo/KAGRA S250912f: Identification of a GW compact binary merger candidate
  77. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  78. GRB 250910B: SVOM/GRM observation
  79. EP250911a: SVOM/VT optical observation
  80. GRB 250911A: MASTER optical counterpart observations
  81. EP250911a: SAO RAS optical observations
  82. GRB 250911A: Swift-XRT refined Analysis
  83. GRB 250910C: Fermi GBM Final Localization Correction
  84. EP250911a: Swift-XRT observations
  85. EP250911a: Optical detection with Kinder observations
  86. GRB 250911A: Swift/UVOT Detection
  87. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  88. GRB 250910A / EP250910a: SVOM/VT afterglow confirmation
  89. GRB 250909B: Insight-HXMT detection
  90. GRB 250909B: SVOM/GRM observation
  91. LIGO/Virgo/KAGRA S250911ac: Updated Sky localization and Source Classification
  92. GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
  93. EP250911a: COLIBRÍ optical observations
  94. LIGO/Virgo/KAGRA S250908y: Updated Sky localization
  95. Fermi GRB 250910B: Global MASTER-Net observations report
  96. EP250911a: LCO optical counterpart discovery
  97. EP250910a: Global MASTER-Net observations report
  98. EP250911a: Einstein Probe detection of an X-ray transient
  99. GRB 250404A / EP250404a: spectroscopic redshift at z = 1.88 (correction to GCN 40084)
  100. LIGO/Virgo/KAGRA S250911ac: Identification of a GW compact binary merger candidate

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