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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"

23607 results found.

  1. GRB 250818B: Swift/UVOT Detection
  2. GRB 250818B: optical afterglow detection with Lesedi (GOTO25fzq)
  3. GRB 250818B: TRT Optical Observation
  4. GRB 250818B: SAO RAS optical observations
  5. GRB 250818A: Swift-BAT refined analysis
  6. Fermi trigger No 776849714: Global MASTER-Net observations report
  7. GRB 250818B: KAIT optical observations
  8. GRB 250818A: Swift/UVOT Upper Limits
  9. LIGO/Virgo/KAGRA S250818k: Candidates from the Zwicky Transient Facility
  10. GRB 250813B: SVOM/ECLAIRs refined analysis
  11. LIGO/Virgo/KAGRA S250818k: Coverage and upper limits from MAXI/GSC observations
  12. GRB 250814A: Further GRAWITA TNG NIR observations
  13. GRB 250818B: Swift-XRT afterglow detection
  14. GRB 250818B: GOTO optical counterpart candidate
  15. GRB 250818A: Swift detection of a burst
  16. sb25081602: Swift-XRT observations
  17. Fermi GRB 250814B: Global MASTER-Net observations report
  18. GRB 250814A: Swift-BAT refined analysis
  19. GRB 250815A: Fermi GBM Final Localization
  20. GRB 250813B: Liverpool Telescope optical upper limits
  21. GRB 250814A: Further COLIBRÍ optical upper limit
  22. GRB 250814A: GRAWITA TNG NIR observations
  23. GRB 250812A: SVOM/VT optical continued observation
  24. GRB250814A: TRT optical upper limits
  25. LIGO/Virgo/KAGRA S250813k: Swift XRT observations, 2 X-ray sources
  26. GRB 250813B: SVOM/GRM observation
  27. GRB 250814A: possible optical afterglow candidate at Spanish observatories
  28. GRB 250814A: KAIT optical upper limit
  29. GRB 250814A: Swift-XRT refined Analysis
  30. GRB 250813B: Fermi GBM Observation
  31. GRB 250814A: Optical observations with MDM Hiltner 2.4m telescope
  32. Swift GRB250814.32: Global MASTER-Net observations report
  33. GRB 250814A: J-band upper limit from WINTER
  34. Subject GRB 250813B: SVOM/MXT refined analysis
  35. GRB 250814A: COLIBRÍ optical upper limit
  36. GRB 250813A: AstroSat CZTI detection
  37. LIGO/Virgo/KAGRA S250814bg: Identification of a GW compact binary merger candidate possibly associated with GRB 250814A detected by Fermi GBM and Swift BAT
  38. GRB 250814A: DDOTI Optical Upper Limit
  39. GRB 250814A: Swift detection of a burst coincident with a subthreshold GW trigger
  40. GRB 250813B: SVOM/COLIBRÍ (FM-GFT) optical observations
  41. GRB 250813B: Ondrejov D50 fast decay
  42. GRB 250813B: Ondrejov D50 optical afterglow detection
  43. LIGO/Virgo/KAGRA S250813k: NED Galaxies in the 4-Update Localization Volume
  44. EP250812a: Nickel optical upper limit
  45. GRB 250812A: VLT X-shooter spectroscopic redshift confirmation z = 2.571
  46. GRB 250812A: NTT spectroscopic redshift z = 2.57
  47. GRB250812a: STEP/T80S Indication of slow decay of afterglow
  48. EP250812a: NOT, NTT, and GS observations
  49. GRB 250812A: Swift/UVOT Detection
  50. EP250812a: COLIBRÍ detection of the VT candidate and evidence of flattening
  51. LIGO/Virgo/KAGRA S250813k: Identification of a GW compact binary merger candidate
  52. GRB 250812A: EP-FXT counterpart detection
  53. GRB 250807B: Swift-BAT refined analysis
  54. EP 250812a: GOTO optical upper limit
  55. GRB 250812A: Kilonova-Catcher optical afterglow detection
  56. EP250812a: Swift-XRT counterpart detection
  57. GRB 250812A: SVOM/COLIBRÍ (FM-GFT) optical observations
  58. EP250812a: Einstein Probe detection of an X-ray transient
  59. GRB 250812A: SVOM/VT optical afterglow confirmation
  60. GRB 250812A: TRT likely optical counterpart detection
  61. GRB 250809A: Swift-BAT refined analysis
  62. GRB 250807A: Swift-BAT refined analysis
  63. GRB 250809A: Swift/UVOT Detection
  64. GRB 250702B: Chandra X-ray Detection
  65. GRB 250808A: VLT X-shooter candidate counterpart
  66. GRB 250809A: Swift detection of a gamma ray burst
  67. GRB 250808A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  68. GRB 250808A: Swift-XRT candidate counterpart detection
  69. EP-WXT trigger 01709195487: KAIT confirmation of the stellar flare
  70. Konus-Wind detection of GRB 250807A
  71. GRB 250807B: Kilonova-Catcher optical afterglow detection
  72. GRB 250807B: VLT/X-Shooter spectroscopic redshift z = 1.522
  73. GRB 250806A: SVOM/MXT refined analysis
  74. GRB 250807A: AstroSat CZTI detection of bright long burst
  75. GRB 250807B: Swift-XRT refined Analysis
  76. GRB 250807B: NTT optical observations
  77. EP 250807.979: GOTO optical upper limit
  78. EP250807a: COLIBRÍ optical upper limit
  79. EP250806a: Upper limit from Fermi-GBM Observations
  80. GRB 250807B: Swift detection of a burst with an optical counterpart.
  81. GRB 250805A: Kilonova-Catcher optical upper limits
  82. GRB 250805A: Swift/UVOT Upper Limits
  83. EP#01709198415/EP250806a: Swift-XRT observations
  84. EP250806a: Earlier Detection of the VT Candidate by COLIBRÍ and LS
  85. GRB 250806A: J-band upper limit from WINTER
  86. GRB 250805A: Swift-BAT refined analysis
  87. GRB 250806A: KAIT optical upper limit
  88. EP250806a: COLIBRÍ optical upper limit
  89. GRB 250806A: Kilonova-Catcher optical upper limits
  90. GRB 250806A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  91. GRB 250805A: ESO/VLT observations
  92. GRB 250805A: Swift-XRT refined Analysis
  93. GRB 250804B: Swift-XRT observations
  94. GRB 250804C: AstroSat CZTI detection of a long burst
  95. GRB 250805A: TRT optical upper limits
  96. GRB 250805A: Swift detection of a burst
  97. EP250802a: Global MASTER-Net observations report
  98. LIGO/Virgo/KAGRA S250802dn: Identification of a GW compact binary merger candidate
  99. LIGO/Virgo/KAGRA S250727dc: GRANDMA/OPD observations of AT2025smm
  100. GRB 250702B: SMA observations

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