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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"

28051 results found.

  1. GRB 250807B: Swift/UVOT Detection
  2. GRB 250807B: Kilonova-Catcher optical afterglow detection
  3. IceCube-250804A: Upper limits from a search for additional neutrino events in IceCube
  4. GRB 250807A: Swift/UVOT Detection
  5. GRB 250807A: Swift-XRT refined Analysis
  6. GRB 250806A: SVOM/MXT refined analysis
  7. EP250807a: NTT z-band optical upper limit
  8. GRB 250806A: Mondy optical observations, and nearby bright galaxy photometry
  9. GRB 250807A: SVOM/GRM observation
  10. GRB 250807A: AstroSat CZTI detection of bright long burst
  11. GRB 250807B: Swift-XRT refined Analysis
  12. EP250807a: EP-WXT detection of a fast X-ray transient
  13. EP 250807.979: GOTO optical upper limit
  14. EP250807a: COLIBRÍ optical upper limit
  15. EP250806a: Upper limit from Fermi-GBM Observations
  16. GRB 250807B: Enhanced Swift-XRT position
  17. GRB 250807A: Enhanced Swift-XRT position
  18. IceCube-Cascade 250804A: Upper limits from a search for additional neutrino events in IceCube
  19. GRB 250807B: Swift detection of a burst with an optical counterpart.
  20. GRB 250805A: Kilonova-Catcher optical upper limits
  21. GRB 250805A: Swift/UVOT Upper Limits
  22. GRB 250806A: Swift/UVOT U-band detection
  23. EP250806a: Liverpool telescope optical upper limit
  24. GRB 250807A: Swift detection of a burst with an optical counterpart
  25. EP250802a: EP-FXT follow-up observation
  26. EP250806a: refined analysis of the EP-WXT and EP-FXT observations
  27. EP250806a: SVOM /VT optical candidate
  28. GRB 250806A: J-band upper limit from WINTER
  29. GRB 250805A: Swift-BAT refined analysis
  30. GRB 250806A: KAIT optical upper limit
  31. GRB 250806A: Swift-XRT counterpart detection
  32. EP250806a: COLIBRÍ optical upper limit
  33. GRB 250806A: Kilonova-Catcher optical upper limits
  34. EP250806a: Einstein Probe detection of an X-ray transient
  35. GRB 250806A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  36. GRB 250806A: SVOM/VT optical upper limit
  37. GRB 250806A: SVOM detection of a soft burst
  38. GRB 250805A: SVOM/VT optical counterpart
  39. GRB 250805A: Swift-XRT refined Analysis
  40. GRB 250804B: Swift-XRT observations
  41. GRB 250805A: Enhanced Swift-XRT position
  42. GRB 250805A: TRT optical upper limits
  43. GRB 250805A: Swift-XRT observations
  44. GRB 250804B: SVOM/GRM observation of a short burst
  45. GRB 250804A: Fermi GBM Final Localization
  46. EP250802a: additional Liverpool Telescope upper limits
  47. EP250730a: SVOM/VT optical upper limit
  48. EP250802a: Liverpool Telescope optical upper limits
  49. EP250802a: Global MASTER-Net observations report
  50. EP250802a: GROWTH-India Telescope optical upper limit
  51. LIGO/Virgo/KAGRA S250802dn: Updated Sky localization
  52. LIGO/Virgo/KAGRA S250802dn: Identification of a GW compact binary merger candidate
  53. LIGO/Virgo/KAGRA S250727dc: GRANDMA/OPD observations of AT2025smm
  54. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS candidates
  55. LIGO/Virgo/KAGRA S250725j: GOTO pre-trigger detection of AT2025sib
  56. EP250711a: CrAO and Assy optical observations
  57. LIGO/Virgo/KAGRA S250727dc: DECam DESGW Epoch 1 Candidates
  58. EP250730a: COLIBRÍ optical upper limit
  59. GRB 250727A: Swift-XRT afterglow confirmation and refined analysis
  60. LIGO/Virgo/KAGRA S250725j: DECam DESGW Epoch 1-2 Candidates
  61. LIGO/Virgo/KAGRA S250726ak: Upper limits from Swift/BAT-GUANO
  62. LIGO/Virgo/KAGRA S250725l: Upper limits from Swift/BAT-GUANO
  63. LIGO/Virgo/KAGRA S250727dc: Upper limits from Swift/BAT-GUANO
  64. LIGO/Virgo/KAGRA S250727dc: Swift-XRT observations, 8 X-ray sources
  65. GRB 250727A: EP-FXT follow-up observation
  66. GRB 250725A: PRIME near-infrared observations
  67. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS upper limits of AT 2025smm
  68. LIGO/Virgo/KAGRA S250727dc: PRIME J-band upper limits of AT 2025smm
  69. GRB 250728A: Swift-XRT observations
  70. GRB 250728A: COLIBRÍ optical upper limit
  71. LIGO/Virgo/KAGRA S250727dc: Updated Sky localization
  72. GRB 250728A: Swift/BAT-GUANO arcminute localization of a short burst
  73. LIGO/Virgo/KAGRA S250727cl: Updated Sky localization
  74. GRB 250727A: EP-FXT counterpart detection
  75. GRB 250727A: Swift-XRT observations
  76. LIGO/Virgo/KAGRA S250727dc: Identification of a GW compact binary merger candidate
  77. LIGO/Virgo/KAGRA S250727cl: Identification of a GW compact binary merger candidate
  78. LIGO/Virgo/KAGRA S250725j: DECam GW-MMADS candidates
  79. LIGO/Virgo/KAGRA S250725l: Updated Sky localization
  80. LIGO/Virgo/KAGRA S250726ak: Updated Sky localization
  81. LIGO/Virgo/KAGRA S250726ak: Identification of a GW compact binary merger candidate
  82. GRB 250725A: Swift-XRT refined Analysis
  83. GRB 250725A: Fermi GBM Observation
  84. LIGO/Virgo/KAGRA S250725j: Updated Sky localization
  85. GRB 250725A: Swift-BAT refined analysis
  86. LIGO/Virgo/KAGRA S250725j: NED Galaxies in the 3-Initial Localization Volume
  87. GRB 250725A: SVOM/GRM observation
  88. GRB 250725A: Global MASTER-Net: First Optical Synchronous Observatios of Short GRB.
  89. GRB 250725A: Swift/UVOT Upper Limits
  90. GRB 250725A: Fermi-LAT detection
  91. GRB 250725A: BOOTES-7 early optical detection
  92. GRB 250725A: SVOM/VT optical candidate
  93. GRB 250725A: MASTER-OAFA optical detection of very fast afterglow
  94. LIGO/Virgo/KAGRA S250725l: Identification of a GW compact binary merger candidate
  95. LIGO/Virgo/KAGRA S250725j: Identification of a GW compact binary merger candidate
  96. GRB 250725A: Enhanced Swift-XRT position
  97. GRB 250725A: Swift detection of a burst
  98. Swift GRB 250725A: Global MASTER-Net OT detection
  99. EP250702a/GRB250702 B,E,D: MeerKAT radio observations at 3.06 GHz
  100. SVOM J195836+32283 is not a real source

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