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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

32688 results found.

  1. EP250911a: LCO optical counterpart discovery
  2. EP250910a: Global MASTER-Net observations report
  3. GRB 250404A / EP250404a: spectroscopic redshift at z = 1.88 (correction to GCN 40084)
  4. LIGO/Virgo/KAGRA S250911ac: Identification of a GW compact binary merger candidate
  5. GRB 250903A: SVOM/ECLAIRs refined analysis
  6. GRB 250911A: COLIBRÍ optical counterpart candidate
  7. LIGO/Virgo/KAGRA S250906ca: Updated Sky localization
  8. GRB 250910A / EP250910a: VLT/HAWK-I near-infrared observations
  9. EP250910a/GRB 250910A: EP-WXT detection of a fast X-ray transient
  10. GRB 250910A: SVOM/VT optical upper limit
  11. EP250908C: GROND observation of the fading optical counterpart
  12. GRB 250910A: LCO optical upper limit
  13. GRB 250909A: AstroSat CZTI detection
  14. GRB 250910A: SVOM/MXT possible afterglow detection
  15. GRB 250702B: Late time Chandra observations
  16. EP250908b/EP#01709240653: Swift/UVOT Detection
  17. EP250908c: refined analysis of the EP-WXT and EP-FXT observations
  18. GRB 250907A: CALET Gamma-Ray Burst Monitor detection
  19. EP250908c: SVOM/VT optical observation
  20. EP250908c: VLT/FORS2 optical counterpart identification
  21. EP250908b: SVOM/VT optical candidate (Coordinate supplement for GCN 41758)
  22. EP250908b: SVOM/VT optical candidate
  23. EP250908c: Global MASTER-Net observations report
  24. Fermi GRB 250909A: Global MASTER-Net observations report
  25. LIGO/Virgo/KAGRA S250908y: Identification of a GW compact binary merger candidate
  26. GRB 250905A: Swift-BAT refined analysis
  27. Fermi-LAT Gamma-ray Observations of IceCube-250905A
  28. GRB 250903A: Swift-XRT afterglow detection
  29. LIGO/Virgo/KAGRA S250906ca: Identification of a GW compact binary merger candidate
  30. IceCube-250905A: Upper limits from a search for additional neutrino events in IceCube
  31. EP250905a: Liverpool Telescope i-band upper limits
  32. LIGO/Virgo/KAGRA S250830bp: DECam/SOAR GW-MMADS updates
  33. EP250905b: EP-FXT follow-up observation
  34. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 2 Candidates
  35. EP250905a: Liverpool Telescope observations
  36. EP250905a: refined analysis of the EP-WXT and EP-FXT observations
  37. EP250905b: Global MASTER-Net observations report
  38. EP250905a: FTW one optical and multiple NIR counterpart candidates
  39. EP250905a: JinShan likely optical counterpart detection
  40. GRB 250904A: Swift-BAT refined analysis
  41. GRB 250905A: Swift/UVOT Upper Limits
  42. EP250905a: Global MASTER-Net observations report
  43. GRB 250901A - SVOM/ECLAIRs refined analysis
  44. GRB250904A: Liverpool Telescope upper limits
  45. GRB 250904A: Swift/UVOT Detection
  46. GRB 250903A: Swift/UVOT detection
  47. LIGO/Virgo/KAGRA S250904cv: Updated Sky localization
  48. LIGO/Virgo/KAGRA S250904br: Updated Sky localization
  49. GRB 250905A: KAIT optical upper limit
  50. Swift GRB 250904A: Global MASTER-Net observations report
  51. GRB 250904A: TRT optical counterpart detection
  52. EP250827a and EP250827b: Upper limit from Fermi-GBM Observations
  53. GRB 250902B: CALET Gamma-Ray Burst Monitor detection
  54. EP250827b: Gemini Spectroscopic Confirmation of AT2025wkm as a Ic-BL Supernova
  55. GRB 250902A: CALET Gamma-Ray Burst Monitor detection
  56. LIGO/Virgo/KAGRA S250904ae: Updated Sky localization
  57. GRB 250902A: VZLUSAT-2 detection
  58. LIGO/Virgo/KAGRA S250904cv: Identification of a GW compact binary merger candidate
  59. GRB 250903A: Swift-XRT observations
  60. EP250903a: Swift-XRT observations
  61. EP#01709201209: Swift-XRT observations
  62. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  63. EP-WXT trigger 01709201209: Liverpool Telescope upper limits
  64. GRB 250830C: VZLUSAT-2 detection
  65. EP250903a: refined analysis of the EP-WXT and EP-FXT observations
  66. LIGO/Virgo/KAGRA S250904br: Identification of a GW compact binary merger candidate
  67. GRB 250903A: VLT X-shooter spectroscopic redshift z = 1.590
  68. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  69. GRB 250903A: EP-FXT counterpart detection
  70. GRB 250902A: GECAM-B detection
  71. GRB 250903A: LCO optical observation
  72. GRB 250903A: LCO optical afterglow detection
  73. GRB 250903A: SVOM/VT optical confirmation with VHF data
  74. EP250903a: SVOM/VT optical confirmation
  75. EP250901a: Mondy, Assy and SAO RAS optical limits
  76. Subject GRB 250903A: SVOM/MXT afterglow detection
  77. EP250903a: LCO candidate counterpart discovery
  78. GRB 250903A: TRT optical counterpart detection
  79. GRB 250902B: AstroSat CZTI detection
  80. EP250903a: Global MASTER-Net observations report
  81. EP250903a: TRT optical observations
  82. EP250903a: Einstein Probe detection of an X-ray transient
  83. EP 250827B: Detection of supernova counterpart by LCO.
  84. EP250827b / AT 2025wkm: TRT optical observations
  85. EP250827b: NOT spectroscopic observations and AT 2025wkm classification as a broad-lined type-Ic supernova
  86. EP250827b: continued Liverpool Telescope observations
  87. GRB 250902B: SVOM/GRM observation
  88. EP250827b: SVOM/VT observation of AT 2025wkm
  89. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data
  90. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  91. Fermi GRB 250902B: Global MASTER-Net observations report
  92. Fermi-LAT Gamma-ray Observations of IceCube-250831A
  93. GRB 250902A: Fermi GBM Detection
  94. GRB 250901A: Swift/UVOT Upper Limit
  95. IceCube-250831A: Upper limits from a search for additional neutrino events in IceCube
  96. LIGO/Virgo/KAGRA S250901cb: Updated Sky localization
  97. EP250827b: Liverpool Telescope observations
  98. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  99. GRB 250902A: SVOM/GRM observation
  100. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope

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