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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"

20525 results found.

  1. GRB 250813A: AstroSat CZTI detection
  2. LIGO/Virgo/KAGRA S250814bg: Identification of a GW compact binary merger candidate possibly associated with GRB 250814A detected by Fermi GBM and Swift BAT
  3. GRB 250813B: VLT X-shooter spectroscopic redshift z = 1.752
  4. GRB 250814A: DDOTI Optical Upper Limit
  5. Fermi-LAT Gamma-ray Observations of IceCube-250813A
  6. GRB 250814A: Swift detection of a burst coincident with a subthreshold GW trigger
  7. GRB 250813B: SVOM/COLIBRÍ (FM-GFT) optical observations
  8. GRB 250813B: SVOM detection of a bright long burst (Correction for GCN 41352).
  9. GRB 250813B: SVOM detection of a bright long burst
  10. LIGO/Virgo/KAGRA S250813k: NED Galaxies in the 4-Update Localization Volume
  11. EP250812a: Nickel optical upper limit
  12. EP250812a: NOT, NTT, and GS observations
  13. GRB 250812A: Swift/UVOT Detection
  14. EP250812a: COLIBRÍ detection of the VT candidate and evidence of flattening
  15. EP250812a: Liverpool Telescope upper limits
  16. EP250812a: refined analysis of the EP-WXT and EP-FXT observations
  17. LIGO/Virgo/KAGRA S250813k: Identification of a GW compact binary merger candidate
  18. EP 250812a: GOTO optical upper limit
  19. GRB 250812A: Kilonova-Catcher optical afterglow detection
  20. EP250812a: Swift-XRT counterpart detection
  21. GRB 250812A: SVOM/COLIBRÍ (FM-GFT) optical observations
  22. EP250812a: Einstein Probe detection of an X-ray transient
  23. GRB 250812A: Swift-XRT afterglow detection
  24. GRB 250812A: TRT likely optical counterpart detection
  25. IceCube-Cascade 250809A: Upper limits from a search for additional neutrino events in IceCube
  26. Fermi-LAT Gamma-ray Observations of IceCube-250804A
  27. GRB 250809A: Swift/UVOT Detection
  28. GRB 250809A: Swift-XRT refined Analysis
  29. GRB 250809A: LCOGT Optical Upper Limits
  30. GRB 250808A: VLT X-shooter candidate counterpart
  31. GRB 250809A: Swift detection of a gamma ray burst
  32. GRB 250808A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  33. Konus-Wind detection of GRB 250807A
  34. GRB 250807B: Swift/UVOT Detection
  35. GRB 250807B: Kilonova-Catcher optical afterglow detection
  36. IceCube-250804A: Upper limits from a search for additional neutrino events in IceCube
  37. GRB 250807A: Swift/UVOT Detection
  38. GRB 250807B: VLT/X-Shooter spectroscopic redshift z = 1.522
  39. GRB 250806A: SVOM/ECLAIRs refined analysis
  40. EP250807a: NTT z-band optical upper limit
  41. GRB 250806A: Mondy optical observations, and nearby bright galaxy photometry
  42. GRB 250807A: SVOM/GRM observation
  43. GRB 250807A: AstroSat CZTI detection of bright long burst
  44. EP250807a: EP-WXT detection of a fast X-ray transient
  45. EP 250807.979: GOTO optical upper limit
  46. EP250807a: COLIBRÍ optical upper limit
  47. GRB 250807B: Enhanced Swift-XRT position
  48. GRB 250807A: Enhanced Swift-XRT position
  49. IceCube-Cascade 250804A: Upper limits from a search for additional neutrino events in IceCube
  50. GRB 250807B: Swift detection of a burst with an optical counterpart.
  51. GRB 250805A: Kilonova-Catcher optical upper limits
  52. GRB 250805A: Swift/UVOT Upper Limits
  53. GRB 250806A: Swift/UVOT U-band detection
  54. EP250806a: Liverpool telescope optical upper limit
  55. GRB 250807A: Swift detection of a burst with an optical counterpart
  56. GRB 250806A: EP-FXT observation
  57. EP250806a: refined analysis of the EP-WXT and EP-FXT observations
  58. EP250806a: SVOM /VT optical candidate
  59. GRB 250806A: J-band upper limit from WINTER
  60. GRB 250806A: KAIT optical upper limit
  61. EP250806a: COLIBRÍ optical upper limit
  62. GRB 250806A: Kilonova-Catcher optical upper limits
  63. EP250806a: Einstein Probe detection of an X-ray transient
  64. GRB 250806A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  65. GRB 250806A: SVOM/VT optical upper limit
  66. GRB 250806A: SVOM detection of a soft burst
  67. GRB 250805A: SVOM/VT optical counterpart
  68. GRB 250805A: Enhanced Swift-XRT position
  69. GRB 250805A: TRT optical upper limits
  70. GRB 250805A: Swift-XRT observations
  71. GRB 250804B: SVOM/GRM observation of a short burst
  72. EP250802a: additional Liverpool Telescope upper limits
  73. EP250730a: SVOM/VT optical upper limit
  74. EP250802a: Liverpool Telescope optical upper limits
  75. EP250802a: GROWTH-India Telescope optical upper limit
  76. EP250802a: Einstein Probe detection of an X-ray transient
  77. LIGO/Virgo/KAGRA S250802dn: Identification of a GW compact binary merger candidate
  78. LIGO/Virgo/KAGRA S250727dc: GRANDMA/OPD observations of AT2025smm
  79. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS candidates
  80. LIGO/Virgo/KAGRA S250725j: GOTO pre-trigger detection of AT2025sib
  81. EP250711a: CrAO and Assy optical observations
  82. LIGO/Virgo/KAGRA S250727dc: DECam DESGW Epoch 1 Candidates
  83. EP250730a: COLIBRÍ optical upper limit
  84. GRB 250727A: Swift-XRT afterglow confirmation and refined analysis
  85. EP250730a: Einstein Probe detection of an X-ray transient
  86. LIGO/Virgo/KAGRA S250727dc: Swift-XRT observations, 8 X-ray sources
  87. GRB 250725A: PRIME near-infrared observations
  88. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS upper limits of AT 2025smm
  89. LIGO/Virgo/KAGRA S250727dc: PRIME J-band upper limits of AT 2025smm
  90. GRB 250727A: SVOM/ECLAIRs refined analysis
  91. GRB 250728A: COLIBRÍ optical upper limit
  92. LIGO/Virgo/KAGRA S250727dc: Identification of a GW compact binary merger candidate
  93. LIGO/Virgo/KAGRA S250727cl: Identification of a GW compact binary merger candidate
  94. LIGO/Virgo/KAGRA S250725j: DECam GW-MMADS candidates
  95. LIGO/Virgo/KAGRA S250726ak: Identification of a GW compact binary merger candidate
  96. GRB 250725A: SVOM/GRM observation
  97. GRB 250725A: Global MASTER-Net: First Optical Synchronous Observatios of Short GRB.
  98. GRB 250725A: Swift/UVOT Upper Limits
  99. GRB 250725A: SVOM/VT optical candidate
  100. LIGO/Virgo/KAGRA S250725l: Identification of a GW compact binary merger candidate

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