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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 250916A: Fermi GBM Observation
  2. Fermi GRB 250919A: Global MASTER-Net observations report
  3. GRB 250919A: Fermi GBM Final Real-time Localization
  4. GRB 250916A: KAIT optical observations
  5. GRB 250917B: VLT/HAWK-I near-infrared observations
  6. GRB 250916A: NuSTAR detection of the prompt emission
  7. GRB 250916A: further SAO RAS optical observations
  8. GRB 250912A: SVOM/ECLAIRs refined analysis
  9. GRB 250917B: Swift-BAT refined analysis
  10. LIGO/Virgo/KAGRA S250918aw: 1 counterpart neutrino candidate event from an IceCube neutrino search
  11. GRB 250918A: BALROG localization (Fermi Trigger 779891543 / GRB 250918522)
  12. GRB 250918A: Fermi GBM Final Real-time Localization
  13. GRB 250917B: Swift/UVOT Upper Limits
  14. GRB 250916A: OSIRIS+/GTC redshift z = 2.015
  15. GRB 250916A: Swift-XRT observations
  16. EP250916a: EP-FXT follow-up observation
  17. GRB 250916A: MAO/AZT-22 optical observations
  18. GRB 250916A: SAO RAS optical observations
  19. GRB 250916A : GIT optical observations
  20. LIGO/Virgo/KAGRA S250917aq: Three counterpart neutrino candidates from IceCube neutrino searches
  21. LIGO/Virgo/KAGRA S250917aq: Updated Sky localization
  22. GRB 250916A: Glowbug gamma-ray detection
  23. GRB250917B: WFST optical observations
  24. GRB 250916A: Swift ToO observations
  25. GRB 250917B: Fermi GBM Observation
  26. GRB 250917B: Swift-XRT observations
  27. LIGO/Virgo/KAGRA S250917aq: Identification of a GW compact binary merger candidate
  28. Fermi GRB 250917B: Global MASTER-Net observations report
  29. GRB 250917B: Swift detection of a short burst
  30. GRB 250916A: GOTO optical counterpart candidate
  31. GRB 250917B: Fermi GBM Final Real-time Localization
  32. GRB 250917A: Fermi GBM Final Real-time Localization
  33. The EP-WXT trigger 01709241037 is likely a flaring star
  34. GRB 250916A: AstroSat CZTI detection of a bright long burst
  35. GRB 250910A: SVOM/ECLAIRs refined analysis
  36. EP250916a: Einstein Probe detection of an X-ray transient
  37. Fermi GRB 250916A: Global MASTER-Net observations report
  38. GRB 250916A: Fermi GBM Final Real-time Localization
  39. EP250827b: VLA Observations
  40. LIGO/Virgo/KAGRA S250818k: HCT optical follow-up
  41. SVOM/sb25091517: Confirmation of a stellar flare by SVOM/VT
  42. SVOM/sb25091517: FRAM-ORM stellar flare - transient observation
  43. SVOM/sb25091517: SVOM detection of an X-ray transient
  44. GRB 250912A: Swift/BAT-GUANO localization skymap of a possibly short burst
  45. GRB 250912A: SVOM/COLIBRÍ (FM-GFT) optical observations
  46. GRB 250912A: Swift-XRT observations
  47. GRB250912A: VLT/HAWK-I follow-up observations
  48. GRB 250912A: VLT observations
  49. GRB 250912A: Fermi GBM Observation
  50. GRB 250911A: Insight-HXMT detection
  51. GRB 250912A: SVOM/GRM analysis suggests a possible short GRB with extended emission
  52. GRB 250912A:SVOM/VT optical upper limit
  53. GRB 250912A: LCO optical upper limit
  54. The EP-WXT trigger 01709240768 is likely a flaring star
  55. Fermi GRB 250912A: Global MASTER-Net observations report
  56. EP250911a: Global MASTER-Net observations report
  57. GRB 250912A: SVOM detection of a burst
  58. GRB 250912A: Fermi GBM Final Real-time Localization
  59. IceCube-Cascade 250911A: Upper limits from a search for additional neutrino events in IceCube
  60. LIGO/Virgo/KAGRA S250912s: 2 counterpart neutrino candidate events from an IceCube neutrino search
  61. EP250908c: tentative VLT/FORS2 redshift z = 2.87
  62. EP250911a: Upper limit from Fermi-GBM Observations
  63. LIGO/Virgo/KAGRA S250912f: Updated Sky localization
  64. GRB 250911A: GECAM-B detection
  65. GRB 250911A: Swift-BAT refined analysis
  66. EP250911a: GTC/OSIRIS+ spectroscopic redshift z = 3.84
  67. LIGO/Virgo/KAGRA S250912f: Identification of a GW compact binary merger candidate
  68. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  69. GRB 250910B: SVOM/GRM observation
  70. EP250911a: SVOM/VT optical observation
  71. GRB 250911A: MASTER optical counterpart observations
  72. EP250911a: SAO RAS optical observations
  73. GRB 250911A: Swift-XRT refined Analysis
  74. GRB 250910C: Fermi GBM Final Localization Correction
  75. EP250911a: Swift-XRT observations
  76. EP250911a: Optical detection with Kinder observations
  77. GRB 250911A: Swift/UVOT Detection
  78. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  79. GRB 250910A / EP250910a: SVOM/VT afterglow confirmation
  80. GRB 250909B: Insight-HXMT detection
  81. GRB 250909B: SVOM/GRM observation
  82. LIGO/Virgo/KAGRA S250911ac: Updated Sky localization and Source Classification
  83. GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
  84. EP250911a: COLIBRÍ optical observations
  85. LIGO/Virgo/KAGRA S250908y: Updated Sky localization
  86. Fermi GRB 250910B: Global MASTER-Net observations report
  87. EP250911a: LCO optical counterpart discovery
  88. EP250910a: Global MASTER-Net observations report
  89. EP250911a: Einstein Probe detection of an X-ray transient
  90. GRB 250404A / EP250404a: spectroscopic redshift at z = 1.88 (correction to GCN 40084)
  91. LIGO/Virgo/KAGRA S250911ac: Identification of a GW compact binary merger candidate
  92. GRB 250903A: SVOM/ECLAIRs refined analysis
  93. GRB 250911A: Enhanced Swift-XRT position
  94. GRB 250911A: Swift-XRT observations
  95. GRB 250911A: COLIBRÍ optical counterpart candidate
  96. GRB 250911A: Swift detection of a burst
  97. LIGO/Virgo/KAGRA S250906ca: Updated Sky localization
  98. GRB 250910B: BALROG localization (Fermi Trigger 779223130 / GRB 250910786)
  99. GRB 250910B: Fermi GBM Final Real-time Localization
  100. GRB 250910A / EP250910a: VLT/HAWK-I near-infrared observations

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