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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 250917B: Fermi GBM Final Real-time Localization
  2. GRB 250917A: Fermi GBM Final Real-time Localization
  3. The EP-WXT trigger 01709241037 is likely a flaring star
  4. GRB 250916A: AstroSat CZTI detection of a bright long burst
  5. GRB 250910A: SVOM/ECLAIRs refined analysis
  6. EP250916a: Einstein Probe detection of an X-ray transient
  7. Fermi GRB 250916A: Global MASTER-Net observations report
  8. GRB 250916A: Fermi GBM Final Real-time Localization
  9. EP250827b: VLA Observations
  10. LIGO/Virgo/KAGRA S250818k: HCT optical follow-up
  11. SVOM/sb25091517: Confirmation of a stellar flare by SVOM/VT
  12. SVOM/sb25091517: FRAM-ORM stellar flare - transient observation
  13. SVOM/sb25091517: SVOM detection of an X-ray transient
  14. GRB 250912A: Swift/BAT-GUANO localization skymap of a possibly short burst
  15. GRB 250912A: SVOM/COLIBRÍ (FM-GFT) optical observations
  16. GRB 250912A: Swift-XRT observations
  17. GRB250912A: VLT/HAWK-I follow-up observations
  18. GRB 250912A: VLT observations
  19. GRB 250912A: Fermi GBM Observation
  20. GRB 250911A: Insight-HXMT detection
  21. GRB 250912A: SVOM/GRM analysis suggests a possible short GRB with extended emission
  22. GRB 250912A:SVOM/VT optical upper limit
  23. GRB 250912A: LCO optical upper limit
  24. The EP-WXT trigger 01709240768 is likely a flaring star
  25. Fermi GRB 250912A: Global MASTER-Net observations report
  26. EP250911a: Global MASTER-Net observations report
  27. GRB 250912A: SVOM detection of a burst
  28. GRB 250912A: Fermi GBM Final Real-time Localization
  29. IceCube-Cascade 250911A: Upper limits from a search for additional neutrino events in IceCube
  30. LIGO/Virgo/KAGRA S250912s: 2 counterpart neutrino candidate events from an IceCube neutrino search
  31. EP250908c: tentative VLT/FORS2 redshift z = 2.87
  32. EP250911a: Upper limit from Fermi-GBM Observations
  33. LIGO/Virgo/KAGRA S250912f: Updated Sky localization
  34. GRB 250911A: GECAM-B detection
  35. GRB 250911A: Swift-BAT refined analysis
  36. EP250911a: GTC/OSIRIS+ spectroscopic redshift z = 3.84
  37. LIGO/Virgo/KAGRA S250912f: Identification of a GW compact binary merger candidate
  38. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  39. GRB 250910B: SVOM/GRM observation
  40. EP250911a: SVOM/VT optical observation
  41. GRB 250911A: MASTER optical counterpart observations
  42. EP250911a: SAO RAS optical observations
  43. GRB 250911A: Swift-XRT refined Analysis
  44. GRB 250910C: Fermi GBM Final Localization Correction
  45. EP250911a: Swift-XRT observations
  46. EP250911a: Optical detection with Kinder observations
  47. GRB 250911A: Swift/UVOT Detection
  48. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  49. GRB 250910A / EP250910a: SVOM/VT afterglow confirmation
  50. GRB 250909B: Insight-HXMT detection
  51. GRB 250909B: SVOM/GRM observation
  52. LIGO/Virgo/KAGRA S250911ac: Updated Sky localization and Source Classification
  53. GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
  54. EP250911a: COLIBRÍ optical observations
  55. LIGO/Virgo/KAGRA S250908y: Updated Sky localization
  56. Fermi GRB 250910B: Global MASTER-Net observations report
  57. EP250911a: LCO optical counterpart discovery
  58. EP250910a: Global MASTER-Net observations report
  59. EP250911a: Einstein Probe detection of an X-ray transient
  60. GRB 250404A / EP250404a: spectroscopic redshift at z = 1.88 (correction to GCN 40084)
  61. LIGO/Virgo/KAGRA S250911ac: Identification of a GW compact binary merger candidate
  62. GRB 250903A: SVOM/ECLAIRs refined analysis
  63. GRB 250911A: Enhanced Swift-XRT position
  64. GRB 250911A: Swift-XRT observations
  65. GRB 250911A: COLIBRÍ optical counterpart candidate
  66. GRB 250911A: Swift detection of a burst
  67. LIGO/Virgo/KAGRA S250906ca: Updated Sky localization
  68. GRB 250910B: BALROG localization (Fermi Trigger 779223130 / GRB 250910786)
  69. GRB 250910B: Fermi GBM Final Real-time Localization
  70. GRB 250910A / EP250910a: VLT/HAWK-I near-infrared observations
  71. EP250910a/GRB 250910A: EP-WXT detection of a fast X-ray transient
  72. GRB 250909B: AstroSat CZTI detection of a long burst
  73. GRB 250910A: SVOM/VT optical upper limit
  74. EP250908C: GROND observation of the fading optical counterpart
  75. GRB 250910A: LCO optical upper limit
  76. GRB 250909A: AstroSat CZTI detection
  77. GRB 250910A: SVOM/MXT possible afterglow detection
  78. GRB 250910A: SVOM detection of a faint burst
  79. LIGO/Virgo/KAGRA S250910b: Retraction of GW compact binary merger candidate
  80. GRB 250702B: Late time Chandra observations
  81. EP250908b/EP#01709240653: Swift/UVOT Detection
  82. EP#01709240653: Swift-XRT observations
  83. The EP-WXT trigger 01709240674 is triggered by the known source SS Cyg
  84. EP250908c: refined analysis of the EP-WXT and EP-FXT observations
  85. GRB 250907A: CALET Gamma-Ray Burst Monitor detection
  86. EP250908c: SVOM/VT optical observation
  87. EP250908c: VLT/FORS2 optical counterpart identification
  88. EP250908b: SVOM/VT optical candidate (Coordinate supplement for GCN 41758)
  89. EP250908b: SVOM/VT optical candidate
  90. The EP-WXT trigger EP250908a/01709240652 is not a real source
  91. EP250908c: Global MASTER-Net observations report
  92. Fermi GRB 250909A: Global MASTER-Net observations report
  93. EP250908c: Einstein Probe detection of an X-ray transient
  94. GRB 250909A: Fermi GBM Final Real-time Localization
  95. EP250908b: EP-WXT detection of a fast X-ray transient and EP-FXT observation
  96. EP#01709240652 (possibly EP250908a): FTW optical and NIR observations
  97. LIGO/Virgo/KAGRA S250908y: Identification of a GW compact binary merger candidate
  98. GRB 250907A: GECAM-B detection
  99. GRB 250905A: Swift-BAT refined analysis
  100. Fermi-LAT Gamma-ray Observations of IceCube-250905A

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