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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"

27083 results found.

  1. sb25081602: Swift-XRT observations
  2. GRB 250816A: SVOM/GRM observation of a short burst
  3. SVOM/sb25081602: detection of a likely X-ray transient
  4. Fermi GRB 250814B: Global MASTER-Net observations report
  5. GRB 250816A: Fermi GBM Final Real-time Localization
  6. GRB 250814A: Swift-BAT refined analysis
  7. GRB 250815A: Fermi GBM Final Localization
  8. GRB 250813B: Liverpool Telescope optical upper limits
  9. GRB 250814A: Further COLIBRÍ optical upper limit
  10. GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
  11. GRB 250814A: GRAWITA TNG NIR observations
  12. GRB 250812A: SVOM/VT optical continued observation
  13. GRB 250814A: Mondy optical observations of the candidate counterpart to LVK S250814bg
  14. GRB250814A: TRT optical upper limits
  15. GRB 250814B: SVOM/GRM observation
  16. GRB 250814C: SVOM/GRM observation of a short burst
  17. LIGO/Virgo/KAGRA S250813k: Swift XRT observations, 2 X-ray sources
  18. GRB 250813B: SVOM/GRM observation
  19. GRB 250814A: P200/WIRC observations of the afterglow candidate
  20. GRB 250814A: possible optical afterglow candidate at Spanish observatories
  21. GRB 250814A: Swift-XRT refined Analysis
  22. GRB 240814A: Fermi GBM Observation
  23. GRB 250814A: Possible afterglow candidate from P200/WIRC
  24. GRB 250813B: Fermi GBM Observation
  25. GRB 250814A: Optical observations with MDM Hiltner 2.4m telescope
  26. Fermi trigger No 776818276: Global MASTER-Net observations report
  27. Swift GRB250814.32: Global MASTER-Net observations report
  28. GRB 250814A: J-band upper limit from WINTER
  29. GRB 250813B: NOT observations of the optical afterglow
  30. GRB 250813B: SVOM/VT optical observations
  31. Subject GRB 250813B: SVOM/MXT refined analysis
  32. GRB 250814A: COLIBRÍ optical upper limit
  33. GRB 250814B: Fermi GBM Final Real-time Localization
  34. LIGO/Virgo/KAGRA S250814bg: Identification of a GW compact binary merger candidate possibly associated with GRB 250814A detected by Fermi GBM and Swift BAT
  35. GRB 250813B: VLT X-shooter spectroscopic redshift z = 1.752
  36. GRB 250814A: DDOTI Optical Upper Limit
  37. GRB 250813B: EP-FXT counterpart detection
  38. GRB 250813B: Swift-XRT afterglow detection
  39. GRB 250814A: Swift detection of a burst coincident with a subthreshold GW trigger
  40. GRB 250814A: Fermi GBM Final Real-time Localization
  41. GRB 250813B: SVOM/COLIBRÍ (FM-GFT) optical observations
  42. GRB 250813B: Ondrejov D50 fast decay
  43. GRB 250813B: SVOM detection of a bright long burst (Correction for GCN 41352).
  44. GRB 250813B: SVOM detection of a bright long burst
  45. EP250812a: Nickel optical upper limit
  46. GRB 250812A: VLT X-shooter spectroscopic redshift confirmation z = 2.571
  47. GRB 250812A: NTT spectroscopic redshift z = 2.57
  48. GRB250812a: STEP/T80S Indication of slow decay of afterglow
  49. EP250812a: NOT, NTT, and GS observations
  50. GRB 250812A: Swift/UVOT Detection
  51. GRB 250813A: Fermi GBM Final Localization
  52. EP250812a: COLIBRÍ detection of the VT candidate and evidence of flattening
  53. EP250812a: Liverpool Telescope upper limits
  54. EP250812a: SVOM/VT optical counterpart
  55. EP250812a: refined analysis of the EP-WXT and EP-FXT observations
  56. IceCube Alert 250813.14: Global MASTER-Net observations report
  57. GRB 250812A: EP-FXT counterpart detection
  58. GRB 250807B: Swift-BAT refined analysis
  59. EP 250812a: GOTO optical upper limit
  60. GRB 250812A: Kilonova-Catcher optical afterglow detection
  61. EP250812a: Swift-XRT counterpart detection
  62. Fermi Gamma-ray Burst Monitor trigger 776705265/250812644 is not a GRB
  63. GRB 250812A: SVOM/COLIBRÍ (FM-GFT) optical observations
  64. EP250812a: Einstein Probe detection of an X-ray transient
  65. GRB 250812A: SVOM/VT optical afterglow confirmation
  66. GRB 250812A: TRT likely optical counterpart detection
  67. GRB 250812A: SVOM detection of a faint long burst
  68. GRB 250809A: Swift-BAT refined analysis
  69. Fermi Gamma-ray Burst Monitor trigger 776620220/250811660 is not a GRB
  70. GRB 250807A: Swift-BAT refined analysis
  71. GRB 250809A: Swift/UVOT Detection
  72. Corrected Swift-XRT Refined Analysis of GRB 250809A
  73. GRB 250809A: Swift-XRT refined Analysis
  74. GRB 250807B: SVOM/VT optical observation
  75. EP250807a: EP-FXT follow-up observation upper limit
  76. GRB 250809A: LCOGT Optical Upper Limits
  77. GRB 250702B: Chandra X-ray Detection
  78. EP250807a: Global MASTER-Net observations report
  79. Fermi GRB 250808A: Global MASTER-Net observations report
  80. Fermi Gamma-ray Burst Monitor trigger 776449964/250809689 is not a GRB
  81. GRB 250808A: VLT X-shooter candidate counterpart
  82. GRB 250809A: Swift detection of a gamma ray burst
  83. GRB 250808A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  84. GRB 250808A: Fermi GBM Observation
  85. GRB 250808A: Swift-XRT candidate counterpart detection
  86. GRB 250807A: SVOM/VT optical continued observation
  87. EP-WXT trigger 01709195487: KAIT confirmation of the stellar flare
  88. GRB 250808A: SVOM detection of a long burst
  89. GRB 250808A: Fermi GBM Final Real-time Localization
  90. GRB 250807B: Swift/UVOT Detection
  91. GRB 250807B: Kilonova-Catcher optical afterglow detection
  92. GRB 250807A: Swift/UVOT Detection
  93. GRB 250807A: Swift-XRT refined Analysis
  94. GRB 250807B: VLT/X-Shooter spectroscopic redshift z = 1.522
  95. GRB 250806A: SVOM/MXT refined analysis
  96. GRB 250806A: SVOM/ECLAIRs refined analysis
  97. EP250807a: NTT z-band optical upper limit
  98. GRB 250806A: Mondy optical observations, and nearby bright galaxy photometry
  99. GRB 250807A: SVOM/GRM observation
  100. Swift GRB250807.45: Global MASTER-Net observations report

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