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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"

5057 results found.

  1. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 1 Candidates
  2. EP250901a: Mephisto optical upper limits
  3. EP250901a: Einstein Probe detection of an X-ray transient
  4. GRB 250831A: Swift-XRT counterpart detection
  5. GRB 250830B: MAXI/GSC detection
  6. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  7. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  8. Fermi GRB 250827A: Global MASTER-Net observations report
  9. EP250827a: Global MASTER-Net observations report
  10. Fermi GRB 250824B: Global MASTER-Net observations report
  11. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of SN 2025ulz as a type II supernova
  12. LIGO/Virgo/KAGRA S250818k: COLIBRÍ confirmation of rebrightening of AT2025ulz
  13. GRB 250812A: SVOM/ECLAIRs refined analysis
  14. EP250821a: VLT X-shooter spectroscopic redshift z = 0.577
  15. LIGO/Virgo/KAGRA S250818k: WFST pre-discovery limits and follow-up observations of AT 2025ulz
  16. LIGO/Virgo/KAGRA S250818k: WINTER J-band observations of AT 2025ulz
  17. IPN triangulation of GRB 250814C (short)
  18. GRB 250818B: Liverpool Telescope optical detections
  19. GRB 250818B: Swift/UVOT Detection
  20. GRB 250818B: NOT optical observations
  21. Fermi trigger No 776849714: Global MASTER-Net observations report
  22. GRB 250818B: GOTO optical counterpart candidate
  23. sb25081602: Swift-XRT observations
  24. SVOM/sb25081602: detection of a likely X-ray transient
  25. GRB 250813B: Liverpool Telescope optical upper limits
  26. GRB 250814A: Further COLIBRÍ optical upper limit
  27. GRB 250814A: P200/WIRC observations of the afterglow candidate
  28. Fermi trigger No 776818276: Global MASTER-Net observations report
  29. IceCube-250813A: Upper limits from a search for additional neutrino events in IceCube
  30. Fermi-LAT Gamma-ray Observations of IceCube-250813A
  31. EP250812a: Liverpool Telescope upper limits
  32. EP250812a: SVOM/VT optical counterpart
  33. EP250812a: refined analysis of the EP-WXT and EP-FXT observations
  34. IceCube-250813A - IceCube observation of a high-energy neutrino candidate track-like event
  35. IceCube Alert 250813.14: Global MASTER-Net observations report
  36. EP 250812a: GOTO optical upper limit
  37. EP250812a: Swift-XRT counterpart detection
  38. GRB 250812A: SVOM/VT optical afterglow confirmation
  39. GRB 250812A: SVOM detection of a faint long burst
  40. IceCube-250804A: Upper limits from a search for additional neutrino events in IceCube
  41. GRB 250806A: Mondy optical observations, and nearby bright galaxy photometry
  42. IceCube-Cascade 250804A: Upper limits from a search for additional neutrino events in IceCube
  43. EP250806a: Liverpool telescope optical upper limit
  44. GRB 250807A: Swift detection of a burst with an optical counterpart
  45. EP250802a: additional Liverpool Telescope upper limits
  46. Fermi Gamma-ray Burst Monitor trigger 775945985/250803856 is not a GRB
  47. EP250802a: Liverpool Telescope optical upper limits
  48. EP250802a: Global MASTER-Net observations report
  49. EP250802a: GROWTH-India Telescope optical upper limit
  50. EP250730a: Global MASTER-Net observations report
  51. GRB 250728A: COLIBRÍ optical upper limit
  52. GRB 250727A: Swift-XRT observations
  53. LIGO/Virgo/KAGRA S250727cl: Identification of a GW compact binary merger candidate
  54. GRB 250725A: Swift detection of a burst
  55. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  56. Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
  57. GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
  58. GRB 250717A: Fermi GBM Final Real-time Localization
  59. GRB 250716A: GOTO tentative optical counterpart candidate
  60. Fermi GRB 250716A: Global MASTER-Net observations report
  61. Fermi GRB 250715A: Global MASTER-Net observations report
  62. GRB 250702B,D,E / EP250702a: H.E.S.S. very-high-energy gamma-ray observations
  63. Fermi GRB 250714A: Global MASTER-Net observations report
  64. GRB 250706B/C: 7DT Follow-up Observations
  65. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  66. EP250711a: NOT optical counterpart candidate
  67. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  68. Fermi GRB 250711A: Global MASTER-Net observations report
  69. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
  70. GRB 250702B,D,E / EP250702a: ALMA detection
  71. GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz
  72. GRB 250702B,D,E / EP250702a: 10 GHz detection with the VLA
  73. IPN triangulation of GRB 250704B (short/hard, consistent with EP 250704a)
  74. IceCube-250706A: No Candidates from the Zwicky Transient Facility
  75. GRB 250704B / EP250704a: VLA radio detection
  76. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  77. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  78. GRB 250706B: Swift/UVOT Detection
  79. EP250702a/ GRB 250702B: NuSTAR X-ray Observations
  80. IceCube-250706A: COLIBRÍ optical upper limits
  81. GRB250706B: Swift-XRT counterpart detection
  82. GRB 250706B: iTelescope optical observations
  83. GRB 250706B: TRT bright optical counterpart detection
  84. GRB 250703A: EIRSAT-1 GMOD Detection
  85. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  86. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  87. EP250704a / GRB 250704B: VLT/X-shooter spectroscopic redshift z = 0.661
  88. GRBs 250702B,D,E / EP250702a: fast fading, extremely red counterpart
  89. GRB 250702F: GROWTH-India Telescope optical observations
  90. EP250704a: COLIBRÍ optical counterpart candidate
  91. GRB 250702F: optical photometry from Konkoly
  92. Fermi GRB 250703A: Global MASTER-Net observations report
  93. GRB 250702F: AKO Optical Afterglow Detection
  94. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  95. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  96. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  97. GRB 250702F: TRT Optical Observation
  98. GRB 250703A: DDOTI Optical Upper Limit
  99. EP250702a: Global MASTER-Net observations report
  100. GRB 250702F: DDOTI Optical Observation

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