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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"

23151 results found.

  1. GRB 250812A: SVOM/COLIBRÍ (FM-GFT) optical observations
  2. EP250812a: Einstein Probe detection of an X-ray transient
  3. GRB 250812A: SVOM/VT optical afterglow confirmation
  4. GRB 250812A: TRT likely optical counterpart detection
  5. GRB 250809A: Swift-BAT refined analysis
  6. GRB 250807A: Swift-BAT refined analysis
  7. GRB 250809A: Swift/UVOT Detection
  8. GRB 250702B: Chandra X-ray Detection
  9. GRB 250808A: VLT X-shooter candidate counterpart
  10. GRB 250809A: Swift detection of a gamma ray burst
  11. GRB 250808A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  12. GRB 250808A: Swift-XRT candidate counterpart detection
  13. EP-WXT trigger 01709195487: KAIT confirmation of the stellar flare
  14. Konus-Wind detection of GRB 250807A
  15. GRB 250807B: Kilonova-Catcher optical afterglow detection
  16. GRB 250807B: VLT/X-Shooter spectroscopic redshift z = 1.522
  17. GRB 250806A: SVOM/MXT refined analysis
  18. GRB 250807A: AstroSat CZTI detection of bright long burst
  19. GRB 250807B: Swift-XRT refined Analysis
  20. GRB 250807B: NTT optical observations
  21. EP 250807.979: GOTO optical upper limit
  22. EP250807a: COLIBRÍ optical upper limit
  23. EP250806a: Upper limit from Fermi-GBM Observations
  24. GRB 250807B: Swift detection of a burst with an optical counterpart.
  25. GRB 250805A: Kilonova-Catcher optical upper limits
  26. GRB 250805A: Swift/UVOT Upper Limits
  27. EP#01709198415/EP250806a: Swift-XRT observations
  28. EP250806a: Earlier Detection of the VT Candidate by COLIBRÍ and LS
  29. GRB 250806A: J-band upper limit from WINTER
  30. GRB 250805A: Swift-BAT refined analysis
  31. GRB 250806A: KAIT optical upper limit
  32. EP250806a: COLIBRÍ optical upper limit
  33. GRB 250806A: Kilonova-Catcher optical upper limits
  34. GRB 250806A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  35. GRB 250805A: ESO/VLT observations
  36. GRB 250805A: Swift-XRT refined Analysis
  37. GRB 250804B: Swift-XRT observations
  38. GRB 250804C: AstroSat CZTI detection of a long burst
  39. GRB 250805A: TRT optical upper limits
  40. GRB 250805A: Swift detection of a burst
  41. EP250802a: Global MASTER-Net observations report
  42. LIGO/Virgo/KAGRA S250802dn: Identification of a GW compact binary merger candidate
  43. LIGO/Virgo/KAGRA S250727dc: GRANDMA/OPD observations of AT2025smm
  44. GRB 250702B: SMA observations
  45. LIGO/Virgo/KAGRA S250725j: GOTO pre-trigger detection of AT2025sib
  46. LIGO/Virgo/KAGRA S250727dc: DECam DESGW Epoch 1 Candidates
  47. EP250730a: COLIBRÍ optical upper limit
  48. LIGO/Virgo/KAGRA S250727dc: Swift-UVOT follow up of AT 2025smm
  49. LIGO/Virgo/KAGRA S250727dc: Swift-XRT observations, 8 X-ray sources
  50. GRB 250725A: AstroSat CZTI detection
  51. GRB 250725A: PRIME near-infrared observations
  52. LIGO/Virgo/KAGRA S250727dc: PRIME J-band upper limits of AT 2025smm
  53. GRB 250727A: SVOM/ECLAIRs refined analysis
  54. EP-WXT trigger 01709195487: confirmation of a stellar flare by BOOTES-6 & BOOTES-7
  55. GRB 250728A: COLIBRÍ optical upper limit
  56. LIGO/Virgo/KAGRA S250727dc: Swift-UVOT detection of a new source, AT 2025smm
  57. GRB 250727A: Swift-XRT observations
  58. LIGO/Virgo/KAGRA S250727dc: Identification of a GW compact binary merger candidate
  59. LIGO/Virgo/KAGRA S250727cl: Identification of a GW compact binary merger candidate
  60. GRB 250727A: SVOM detection of a burst
  61. Swift detection of the Soft Gamma Repeater PSR J1647-4552
  62. LIGO/Virgo/KAGRA S250726ak: Identification of a GW compact binary merger candidate
  63. GRB 250725A: Swift-BAT refined analysis
  64. Konus-Wind detection of GRB 250725A
  65. LIGO/Virgo/KAGRA S250725j: NED Galaxies in the 3-Initial Localization Volume
  66. GRB 250725A: BOOTES-7 early optical detection
  67. GRB 250725A: Swift detection of a burst
  68. Swift GRB 250725A: Global MASTER-Net OT detection
  69. GRB 250721A: Fermi GBM Observation
  70. SVOM J195836+32283/sb25072103: NIR observations with WINTER
  71. Swift-BAT trigger 1334535 is not a GRB
  72. GRB 250713A : SVOM/ECLAIRs refined analysis
  73. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  74. GRB 250721A: MAXI/GSC detection
  75. GRB 250717B: COLIBRÍ optical upper limit
  76. Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
  77. Swift Trigger 1334535: a possible GRB 250718A
  78. GRB 250717B: Fermi GBM Observation
  79. Konus-Wind detection of GRB 250716A
  80. GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
  81. GRB 250716A: GOTO tentative optical counterpart candidate
  82. GRB 250702B,D,E / EP250702a: H.E.S.S. very-high-energy gamma-ray observations
  83. GRB 250713A: Mephisto optical upper limits
  84. GRB 250713A: SVOM/VT optical upper limit
  85. GRB 250713A: SVOM/C-GFT upper limit
  86. GRB 250713A: Swift-XRT observations
  87. GRB 250713A: EP-FXT counterpart detection
  88. EP250711a: COLIBRÍ continuous optical observations
  89. GRB 250706A: Swift-BAT refined analysis
  90. GRB 250702F: Swift-BAT refined analysis
  91. GRB 250628A: Swift-BAT refined analysis
  92. GRB 250713A: SVOM detection of a long burst
  93. GRB 250711A: DDOTI Optical Upper Limit
  94. LIGO/Virgo/KAGRA S250712cd: Identification of a GW compact binary merger candidate
  95. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  96. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  97. EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  98. GRB 250704A: GRANDMA observations
  99. GRB 250704A: SVOM/ECLAIRs refined analysis
  100. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate

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