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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"

35268 results found.

  1. LIGO/Virgo/KAGRA S250814bg: Identification of a GW compact binary merger candidate possibly associated with GRB 250814A detected by Fermi GBM and Swift BAT
  2. GRB 250813B: VLT X-shooter spectroscopic redshift z = 1.752
  3. GRB 250814A: DDOTI Optical Upper Limit
  4. GRB 250813B: EP-FXT counterpart detection
  5. GRB 250813B: Swift-XRT afterglow detection
  6. GRB 250814A: Swift detection of a burst coincident with a subthreshold GW trigger
  7. GRB 250814A: Fermi GBM Final Real-time Localization
  8. GRB 250813B: SVOM/COLIBRÍ (FM-GFT) optical observations
  9. GRB 250813B: Ondrejov D50 fast decay
  10. GRB 250813B: SVOM detection of a bright long burst (Correction for GCN 41352).
  11. GRB 250813B: Ondrejov D50 optical afterglow detection
  12. GRB 250813B: SVOM detection of a bright long burst
  13. EP250812a: Nickel optical upper limit
  14. GRB 250812A: VLT X-shooter spectroscopic redshift confirmation z = 2.571
  15. GRB 250812A: NTT spectroscopic redshift z = 2.57
  16. GRB 250812A: Swift/UVOT Detection
  17. GRB 250813A: Fermi GBM Final Localization
  18. GRB 250812A: EP-FXT counterpart detection
  19. GRB 250812A: Swift ToO observations
  20. GRB 250807B: Swift-BAT refined analysis
  21. GRB 250812A: Kilonova-Catcher optical afterglow detection
  22. Fermi Gamma-ray Burst Monitor trigger 776705265/250812644 is not a GRB
  23. GRB 250812A: SVOM/COLIBRÍ (FM-GFT) optical observations
  24. GRB 250812A: SVOM/VT optical afterglow confirmation
  25. GRB 250812A: Swift-XRT afterglow detection
  26. GRB 250812A: TRT likely optical counterpart detection
  27. GRB 250812A: SVOM detection of a faint long burst
  28. GRB 250809A: Swift-BAT refined analysis
  29. Fermi Gamma-ray Burst Monitor trigger 776620220/250811660 is not a GRB
  30. GRB 250807A: Swift-BAT refined analysis
  31. GRB 250809A: Swift/UVOT Detection
  32. Corrected Swift-XRT Refined Analysis of GRB 250809A
  33. GRB 250809A: Swift-XRT refined Analysis
  34. GRB 250807B: SVOM/VT optical observation
  35. GRB 250809A: LCOGT Optical Upper Limits
  36. GRB 250702B: Chandra X-ray Detection
  37. Fermi GRB 250808A: Global MASTER-Net observations report
  38. Fermi Gamma-ray Burst Monitor trigger 776449964/250809689 is not a GRB
  39. GRB 250808A: VLT X-shooter candidate counterpart
  40. GRB 250809A: Prompt enhanced Swift-XRT position
  41. GRB 250809A: Swift detection of a gamma ray burst
  42. GRB 250808A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  43. GRB 250808A: Fermi GBM Observation
  44. GRB 250808A: Swift-XRT candidate counterpart detection
  45. GRB 250807A: SVOM/VT optical continued observation
  46. EP-WXT trigger 01709195487: KAIT confirmation of the stellar flare
  47. GRB 250808A: SVOM detection of a long burst
  48. GRB 250808A: Fermi GBM Final Real-time Localization
  49. Konus-Wind detection of GRB 250807A
  50. GRB 250807B: Swift/UVOT Detection
  51. GRB 250807B: Kilonova-Catcher optical afterglow detection
  52. GRB 250807A: Swift/UVOT Detection
  53. GRB 250807A: Swift-XRT refined Analysis
  54. GRB 250807B: VLT/X-Shooter spectroscopic redshift z = 1.522
  55. GRB 250806A: SVOM/MXT refined analysis
  56. GRB 250806A: SVOM/ECLAIRs refined analysis
  57. GRB 250806A: Mondy optical observations, and nearby bright galaxy photometry
  58. GRB 250804B: Insight-HXMT detection
  59. GRB 250807A: SVOM/GRM observation
  60. GRB 250807A: AstroSat CZTI detection of bright long burst
  61. GRB 250807B: Swift-XRT refined Analysis
  62. GRB 250806A: NOT z-band upper limit and host galaxy candidate
  63. GRB 250807B: NTT optical observations
  64. GRB 250807A: SVOM/VT optical observation
  65. EP250806a: Upper limit from Fermi-GBM Observations
  66. GRB 250807B: Enhanced Swift-XRT position
  67. GRB 250807A: Enhanced Swift-XRT position
  68. GRB 250807B: Swift detection of a burst with an optical counterpart.
  69. GRB 250805A: Kilonova-Catcher optical upper limits
  70. GRB 250805A: Swift/UVOT Upper Limits
  71. GRB 250806A: Swift/UVOT U-band detection
  72. GRB 250807A: Swift detection of a burst with an optical counterpart
  73. GRB 250806A: EP-FXT observation
  74. GRB 250806A: J-band upper limit from WINTER
  75. GRB 250805A: Swift-BAT refined analysis
  76. GRB 250806A: KAIT optical upper limit
  77. GRB 250806A: SVOM/VT refined analysis
  78. GRB 250806A: Swift-XRT counterpart detection
  79. GRB 250806A: Kilonova-Catcher optical upper limits
  80. GRB 250806A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  81. GRB 250806A: SVOM/VT optical upper limit
  82. GRB 250806A: SVOM detection of a soft burst
  83. GRB 250805A: SVOM/VT optical counterpart
  84. GRB 250805A: ESO/VLT observations
  85. GRB 250805A: Swift-XRT refined Analysis
  86. GRB 250804B: Swift-XRT observations
  87. GRB 250805A: Enhanced Swift-XRT position
  88. GRB 250804C: AstroSat CZTI detection of a long burst
  89. GRB 250805A: TRT optical upper limits
  90. GRB 250805A: Swift-XRT observations
  91. GRB 250805A: Swift detection of a burst
  92. GRB 250804B: Tiled Swift observations
  93. GRB 250804B: SVOM/GRM observation of a short burst
  94. GRB 250804A: Fermi GBM Final Localization
  95. Fermi Gamma-ray Burst Monitor trigger 775945985/250803856 is not a GRB
  96. GRB 250702B: SMA observations
  97. EP250711a: CrAO and Assy optical observations
  98. GRB 250727A: Swift-XRT afterglow confirmation and refined analysis
  99. LIGO/Virgo/KAGRA S250726ak: Upper limits from Swift/BAT-GUANO
  100. LIGO/Virgo/KAGRA S250725l: Upper limits from Swift/BAT-GUANO

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