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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"

24368 results found.

  1. LIGO/Virgo/KAGRA S250818k: Properties of the low-significance GW compact binary merger candidate potentially associated with AT 2025ulz
  2. LIGO/Virgo/KAGRA S250818k: Keck I LRIS spectroscopy of ZTF25abjmnps (AT2025ulz)
  3. GRB 250820A: Fermi GBM Final Real-time Localization
  4. GRB 250818B: TRT Optical Observation
  5. Fermi GRB 250816A: Global MASTER-Net observations report
  6. Swift GRB 250818A: Global MASTER-Net observations report
  7. GRB 250818B: NOT optical observations
  8. GRB 250818A: Swift-XRT refined Analysis
  9. GRB 250818B: EP-FXT counterpart detection
  10. GRB 250818A: Swift-BAT refined analysis
  11. GRB 250818C: Fermi GBM Final Real-time Localization
  12. Fermi trigger No 776849714: Global MASTER-Net observations report
  13. GRB 250818B: KAIT optical observations
  14. LIGO/Virgo/KAGRA S250818t: Updated Sky localization
  15. LIGO/Virgo/KAGRA S250818k: Candidates from the Zwicky Transient Facility
  16. GRB 250813B: SVOM/ECLAIRs refined analysis
  17. GRB 250818A: Fermi GBM Observation
  18. LIGO/Virgo/KAGRA S250818k: Coverage and upper limits from MAXI/GSC observations
  19. GRB 250818B: SVOM/VT optical observation
  20. GRB 250818B: Swift-XRT afterglow detection
  21. GRB 250818B: GOTO optical counterpart candidate
  22. GRB 250818B: SVOM detection of a short burst
  23. LIGO/Virgo/KAGRA S250818t: Identification of a GW compact binary merger candidate
  24. GRB 250818A: Fermi GBM Final Real-time Localization
  25. GRB 250816A: SVOM/GRM observation of a short burst
  26. SVOM/sb25081602: detection of a likely X-ray transient
  27. Fermi GRB 250814B: Global MASTER-Net observations report
  28. GRB 250816A: Fermi GBM Final Real-time Localization
  29. GRB 250814A: Swift-BAT refined analysis
  30. GRB 250815A: Fermi GBM Final Localization
  31. GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
  32. GRB 250812A: SVOM/VT optical continued observation
  33. GRB250814A: TRT optical upper limits
  34. GRB 250814B: SVOM/GRM observation
  35. GRB 250814C: SVOM/GRM observation of a short burst
  36. GRB 250813B: SVOM/GRM observation
  37. GRB 250814A: P200/WIRC observations of the afterglow candidate
  38. GRB 250814A: KAIT optical upper limit
  39. GRB 240814A: Fermi GBM Observation
  40. GRB 250813B: Fermi GBM Observation
  41. GRB 250814A: Optical observations with MDM Hiltner 2.4m telescope
  42. Fermi trigger No 776818276: Global MASTER-Net observations report
  43. Swift GRB250814.32: Global MASTER-Net observations report
  44. IceCube-250813A: Upper limits from a search for additional neutrino events in IceCube
  45. GRB 250813B: NOT observations of the optical afterglow
  46. Subject GRB 250813B: SVOM/MXT refined analysis
  47. GRB 250814B: Fermi GBM Final Real-time Localization
  48. LIGO/Virgo/KAGRA S250814bg: Identification of a GW compact binary merger candidate possibly associated with GRB 250814A detected by Fermi GBM and Swift BAT
  49. GRB 250813B: EP-FXT counterpart detection
  50. Fermi-LAT Gamma-ray Observations of IceCube-250813A
  51. GRB 250814A: Fermi GBM Final Real-time Localization
  52. GRB 250813B: SVOM detection of a bright long burst (Correction for GCN 41352).
  53. GRB 250813B: Ondrejov D50 optical afterglow detection
  54. GRB 250813B: SVOM detection of a bright long burst
  55. LIGO/Virgo/KAGRA S250813k: NED Galaxies in the 4-Update Localization Volume
  56. LIGO/Virgo/KAGRA S250813k: Updated Sky localization
  57. EP250812a: Nickel optical upper limit
  58. GRB 250813A: Fermi GBM Final Localization
  59. EP250812a: COLIBRÍ detection of the VT candidate and evidence of flattening
  60. EP250812a: SVOM/VT optical counterpart
  61. IceCube-250813A - IceCube observation of a high-energy neutrino candidate track-like event
  62. IceCube Alert 250813.14: Global MASTER-Net observations report
  63. LIGO/Virgo/KAGRA S250813k: Identification of a GW compact binary merger candidate
  64. GRB 250812A: EP-FXT counterpart detection
  65. GRB 250807B: Swift-BAT refined analysis
  66. EP 250812a: GOTO optical upper limit
  67. GRB 250812A: SVOM/VT optical afterglow confirmation
  68. IceCube-Cascade 250809A: Upper limits from a search for additional neutrino events in IceCube
  69. GRB 250812A: SVOM detection of a faint long burst
  70. GRB 250809A: Swift-BAT refined analysis
  71. Fermi-LAT Gamma-ray Observations of IceCube-250804A
  72. GRB 250807A: Swift-BAT refined analysis
  73. LIGO/Virgo/KAGRA S250810ck: Updated Sky localization and EM Bright Classification
  74. LIGO/Virgo/KAGRA S250810ck: Identification of a GW compact binary merger candidate
  75. GRB 250807B: SVOM/VT optical observation
  76. EP250807a: EP-FXT follow-up observation upper limit
  77. GRB 250809A: LCOGT Optical Upper Limits
  78. GRB 250702B: Chandra X-ray Detection
  79. EP250807a: Global MASTER-Net observations report
  80. Fermi GRB 250808A: Global MASTER-Net observations report
  81. GRB 250809A: Swift detection of a gamma ray burst
  82. GRB 250808A: Fermi GBM Observation
  83. GRB 250807A: SVOM/VT optical continued observation
  84. GRB 250808A: SVOM detection of a long burst
  85. GRB 250808A: Fermi GBM Final Real-time Localization
  86. Konus-Wind detection of GRB 250807A
  87. IceCube-250804A: Upper limits from a search for additional neutrino events in IceCube
  88. GRB 250807A: Swift-XRT refined Analysis
  89. GRB 250806A: SVOM/MXT refined analysis
  90. GRB 250806A: SVOM/ECLAIRs refined analysis
  91. GRB 250807A: SVOM/GRM observation
  92. Swift GRB250807.45: Global MASTER-Net observations report
  93. GRB 250807B: Swift-XRT refined Analysis
  94. GRB 250807A: SVOM/VT optical observation
  95. EP250806a: Upper limit from Fermi-GBM Observations
  96. Swift GRB250807.65: Global MASTER-Net observations report
  97. IceCube-Cascade 250804A: Upper limits from a search for additional neutrino events in IceCube
  98. IceCube Alert 250804.84: Global MASTER-Net observations report
  99. GRB 250806A: EP-FXT observation
  100. EP250806a: Global MASTER-Net observations report

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