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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"

45440 results found.

  1. EP250919a: Einstein Probe detection of an X-ray transient
  2. Correction for GCN 41877: EP-WXT ID is 01709243841
  3. The EP-WXT trigger 01709243841: Las Cumbres discovery of the optical counterpart
  4. GRB 250916A: Fermi GBM Observation
  5. Fermi GRB 250919A: Global MASTER-Net observations report
  6. GRB 250919A: Fermi GBM Final Real-time Localization
  7. GRB 250916A: KAIT optical observations
  8. GRB 250917B: VLT/HAWK-I near-infrared observations
  9. GRB 250916A: NuSTAR detection of the prompt emission
  10. GRB 250916A: further SAO RAS optical observations
  11. GRB 250912A: SVOM/ECLAIRs refined analysis
  12. GRB 250917B: Swift-BAT refined analysis
  13. LIGO/Virgo/KAGRA S250918aw: 1 counterpart neutrino candidate event from an IceCube neutrino search
  14. GRB 250918A: BALROG localization (Fermi Trigger 779891543 / GRB 250918522)
  15. GRB 250918A: Fermi GBM Final Real-time Localization
  16. GRB 250917B: Swift/UVOT Upper Limits
  17. GRB 250916A: OSIRIS+/GTC redshift z = 2.015
  18. GRB 250916A: Swift-XRT observations
  19. EP250916a: EP-FXT follow-up observation
  20. GRB 250916A: MAO/AZT-22 optical observations
  21. GRB 250916A: SAO RAS optical observations
  22. GRB 250916A : GIT optical observations
  23. LIGO/Virgo/KAGRA S250917aq: Three counterpart neutrino candidates from IceCube neutrino searches
  24. LIGO/Virgo/KAGRA S250917aq: Updated Sky localization
  25. GRB 250916A: Glowbug gamma-ray detection
  26. GRB250917B: WFST optical observations
  27. GRB 250916A: Swift ToO observations
  28. GRB 250917B: Fermi GBM Observation
  29. GRB 250917B: Swift-XRT observations
  30. LIGO/Virgo/KAGRA S250917aq: Identification of a GW compact binary merger candidate
  31. Fermi GRB 250917B: Global MASTER-Net observations report
  32. GRB 250917B: Swift detection of a short burst
  33. GRB 250916A: GOTO optical counterpart candidate
  34. GRB 250917B: Fermi GBM Final Real-time Localization
  35. GRB 250917A: Fermi GBM Final Real-time Localization
  36. The EP-WXT trigger 01709241037 is likely a flaring star
  37. GRB 250916A: AstroSat CZTI detection of a bright long burst
  38. GRB 250910A: SVOM/ECLAIRs refined analysis
  39. EP250916a: Einstein Probe detection of an X-ray transient
  40. Fermi GRB 250916A: Global MASTER-Net observations report
  41. GRB 250916A: Fermi GBM Final Real-time Localization
  42. EP250827b: VLA Observations
  43. LIGO/Virgo/KAGRA S250818k: HCT optical follow-up
  44. SVOM/sb25091517: Confirmation of a stellar flare by SVOM/VT
  45. SVOM/sb25091517: FRAM-ORM stellar flare - transient observation
  46. SVOM/sb25091517: SVOM detection of an X-ray transient
  47. GRB 250912A: Swift/BAT-GUANO localization skymap of a possibly short burst
  48. GRB 250912A: SVOM/COLIBRÍ (FM-GFT) optical observations
  49. GRB 250912A: Swift-XRT observations
  50. GRB250912A: VLT/HAWK-I follow-up observations
  51. GRB 250912A: VLT observations
  52. GRB 250912A: Fermi GBM Observation
  53. GRB 250911A: Insight-HXMT detection
  54. GRB 250912A: SVOM/GRM analysis suggests a possible short GRB with extended emission
  55. GRB 250912A:SVOM/VT optical upper limit
  56. GRB 250912A: LCO optical upper limit
  57. The EP-WXT trigger 01709240768 is likely a flaring star
  58. Fermi GRB 250912A: Global MASTER-Net observations report
  59. EP250911a: Global MASTER-Net observations report
  60. GRB 250912A: SVOM detection of a burst
  61. GRB 250912A: Fermi GBM Final Real-time Localization
  62. IceCube-Cascade 250911A: Upper limits from a search for additional neutrino events in IceCube
  63. LIGO/Virgo/KAGRA S250912s: 2 counterpart neutrino candidate events from an IceCube neutrino search
  64. EP250908c: tentative VLT/FORS2 redshift z = 2.87
  65. EP250911a: Upper limit from Fermi-GBM Observations
  66. LIGO/Virgo/KAGRA S250912f: Updated Sky localization
  67. GRB 250911A: GECAM-B detection
  68. GRB 250911A: Swift-BAT refined analysis
  69. EP250911a: GTC/OSIRIS+ spectroscopic redshift z = 3.84
  70. LIGO/Virgo/KAGRA S250912f: Identification of a GW compact binary merger candidate
  71. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  72. GRB 250910B: SVOM/GRM observation
  73. EP250911a: SVOM/VT optical observation
  74. GRB 250911A: MASTER optical counterpart observations
  75. EP250911a: SAO RAS optical observations
  76. GRB 250911A: Swift-XRT refined Analysis
  77. GRB 250910C: Fermi GBM Final Localization Correction
  78. EP250911a: Swift-XRT observations
  79. EP250911a: Optical detection with Kinder observations
  80. GRB 250911A: Swift/UVOT Detection
  81. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  82. GRB 250910A / EP250910a: SVOM/VT afterglow confirmation
  83. GRB 250909B: Insight-HXMT detection
  84. GRB 250909B: SVOM/GRM observation
  85. LIGO/Virgo/KAGRA S250911ac: Updated Sky localization and Source Classification
  86. GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
  87. EP250911a: COLIBRÍ optical observations
  88. LIGO/Virgo/KAGRA S250908y: Updated Sky localization
  89. Fermi GRB 250910B: Global MASTER-Net observations report
  90. EP250911a: LCO optical counterpart discovery
  91. EP250910a: Global MASTER-Net observations report
  92. EP250911a: Einstein Probe detection of an X-ray transient
  93. GRB 250404A / EP250404a: spectroscopic redshift at z = 1.88 (correction to GCN 40084)
  94. LIGO/Virgo/KAGRA S250911ac: Identification of a GW compact binary merger candidate
  95. GRB 250903A: SVOM/ECLAIRs refined analysis
  96. GRB 250911A: Enhanced Swift-XRT position
  97. GRB 250911A: Swift-XRT observations
  98. GRB 250911A: COLIBRÍ optical counterpart candidate
  99. GRB 250911A: Swift detection of a burst
  100. LIGO/Virgo/KAGRA S250906ca: Updated Sky localization

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