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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"

45694 results found.

  1. EP detected a brightening of LMXB 1ES 1735-26.9
  2. GRB 250905A: KAIT optical upper limit
  3. GRB 250905A: Swift detection of a burst
  4. Swift GRB250905.09: Global MASTER-Net observations report
  5. Swift GRB 250904A: Global MASTER-Net observations report
  6. GRB 250904A: Enhanced Swift-XRT position
  7. IceCube-Cascade 250903A: Upper limits from a search for additional neutrino events in IceCube
  8. GRB 250904A: TRT optical counterpart detection
  9. EP250827a and EP250827b: Upper limit from Fermi-GBM Observations
  10. GRB 250902B: CALET Gamma-Ray Burst Monitor detection
  11. GRB 250904A: Prompt enhanced Swift-XRT position
  12. EP250827b: Gemini Spectroscopic Confirmation of AT2025wkm as a Ic-BL Supernova
  13. GRB 250904A: Swift detection of a burst
  14. GRB 250902A: CALET Gamma-Ray Burst Monitor detection
  15. LIGO/Virgo/KAGRA S250904ae: Updated Sky localization
  16. GRB 250902A: VZLUSAT-2 detection
  17. LIGO/Virgo/KAGRA S250904cv: Identification of a GW compact binary merger candidate
  18. GRB 250903A: Swift-XRT observations
  19. EP250903a: Swift-XRT observations
  20. EP#01709201209: Swift-XRT observations
  21. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  22. EP-WXT trigger 01709201209: Liverpool Telescope upper limits
  23. GRB 250830C: VZLUSAT-2 detection
  24. EP250903a: refined analysis of the EP-WXT and EP-FXT observations
  25. LIGO/Virgo/KAGRA S250904br: Identification of a GW compact binary merger candidate
  26. GRB 250903A: VLT X-shooter spectroscopic redshift z = 1.590
  27. The EP-WXT trigger 01709201209 is likely a flaring star
  28. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  29. GRB 250903A: EP-FXT counterpart detection
  30. GRB 250902A: GECAM-B detection
  31. GRB 250903A: LCO optical observation
  32. GRB 250903A: LCO optical afterglow detection
  33. GRB 250903A: SVOM/VT optical confirmation with VHF data
  34. EP250903a: SVOM/VT optical confirmation
  35. EP250901a: Mondy, Assy and SAO RAS optical limits
  36. Subject GRB 250903A: SVOM/MXT afterglow detection
  37. EP250903a: LCO candidate counterpart discovery
  38. GRB 250903A: TRT optical counterpart detection
  39. GRB 250902B: AstroSat CZTI detection
  40. GRB 250903A: SVOM detection of a burst
  41. EP250903a: Global MASTER-Net observations report
  42. EP250903a: TRT optical observations
  43. EP250903a: Einstein Probe detection of an X-ray transient
  44. EP 250827B: Detection of supernova counterpart by LCO.
  45. EP/WXT01709201159: GOTO optical follow-up
  46. EP250827b / AT 2025wkm: TRT optical observations
  47. EP250827b: NOT spectroscopic observations and AT 2025wkm classification as a broad-lined type-Ic supernova
  48. EP250827b: continued Liverpool Telescope observations
  49. GRB 250902B: SVOM/GRM observation
  50. EP250827b: SVOM/VT observation of AT 2025wkm
  51. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data
  52. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  53. Fermi GRB 250902B: Global MASTER-Net observations report
  54. Fermi-LAT Gamma-ray Observations of IceCube-250831A
  55. GRB 250902A: Fermi GBM Detection
  56. GRB 250901A: Swift/UVOT Upper Limit
  57. GRB 250902B: Fermi GBM Final Real-time Localization
  58. IceCube-250831A: Upper limits from a search for additional neutrino events in IceCube
  59. GRB 250830B: Swift-XRT afterglow detection
  60. LIGO/Virgo/KAGRA S250902av: 1 counterpart neutrino candidate event from an IceCube neutrino search
  61. LIGO/Virgo/KAGRA S250901cb: Updated Sky localization
  62. EP250827b: Liverpool Telescope observations
  63. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  64. GRB 250902A: SVOM/GRM observation
  65. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  66. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  67. GRB 250901A: EP-FXT follow-up observation
  68. GRB 250901A: NOT optical observations
  69. GRB 250902A: Fermi GBM Final Real-time Localization
  70. IceCube-Cascade 250828A: Upper limits from a search for additional neutrino events in IceCube
  71. GRB 250901A: SVOM/VT optical afterglow with VHF data
  72. GRB 250901A: Swift-XRT afterglow detection
  73. EP250901a: Swift-XRT observations
  74. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  75. GRB 250901A: LCO optical upper limit
  76. EP250827b: Swift observations of AT 2025wkm
  77. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 1 Candidates
  78. EP250827b: Gemini Spectroscopy of AT 2025wkm
  79. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  80. EP250831a: NOT optical observations and tentative afterglow candidate
  81. EP250827b: FTW Observations of AT 2025wkm
  82. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  83. GRB 250901A: SVOM detection of a burst
  84. GRB 250831B: SVOM/GRM observation
  85. GRB 250830C: Insight-HXMT detection
  86. EP250901a: Mephisto optical upper limits
  87. GRB 250830C: GECAM-B detection
  88. EP250901a: Global MASTER-Net observations report
  89. GRB 250830C: AstroSat CZTI detection of a long burst
  90. EP250901a: Einstein Probe detection of an X-ray transient
  91. LIGO/Virgo/KAGRA S250830m: Updated Sky localization
  92. EP250831a: EP-FXT follow-up observation
  93. EP250831a: Swift-XRT observations
  94. LIGO/Virgo/KAGRA S250831cc: Coverage and upper limits from MAXI/GSC observations
  95. IceCube Alert 250831.75: Global MASTER-Net observations report
  96. EP250831a: Global MASTER-Net observations report
  97. IceCube-250831A - IceCube observation of a high-energy neutrino candidate track-like event
  98. EP250831a: EP-WXT detection of a fast X-ray transient
  99. GRB 250831A (SVOM trigger sb25083102) is likely an outburst from star G 272-61
  100. GRB 250831A: Swift-XRT counterpart detection

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