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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

28297 results found.

  1. LIGO/Virgo/KAGRA S250725j: GOTO pre-trigger detection of AT2025sib
  2. EP250711a: CrAO and Assy optical observations
  3. LIGO/Virgo/KAGRA S250727dc: DECam DESGW Epoch 1 Candidates
  4. EP250730a: COLIBRÍ optical upper limit
  5. GRB 250727A: Swift-XRT afterglow confirmation and refined analysis
  6. LIGO/Virgo/KAGRA S250725j: DECam DESGW Epoch 1-2 Candidates
  7. LIGO/Virgo/KAGRA S250726ak: Upper limits from Swift/BAT-GUANO
  8. LIGO/Virgo/KAGRA S250725l: Upper limits from Swift/BAT-GUANO
  9. LIGO/Virgo/KAGRA S250727dc: Upper limits from Swift/BAT-GUANO
  10. LIGO/Virgo/KAGRA S250727dc: Swift-XRT observations, 8 X-ray sources
  11. GRB 250727A: EP-FXT follow-up observation
  12. GRB 250725A: PRIME near-infrared observations
  13. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS upper limits of AT 2025smm
  14. LIGO/Virgo/KAGRA S250727dc: PRIME J-band upper limits of AT 2025smm
  15. GRB 250728A: Swift-XRT observations
  16. GRB 250728A: COLIBRÍ optical upper limit
  17. LIGO/Virgo/KAGRA S250727dc: Updated Sky localization
  18. GRB 250728A: Swift/BAT-GUANO arcminute localization of a short burst
  19. LIGO/Virgo/KAGRA S250727cl: Updated Sky localization
  20. GRB 250727A: EP-FXT counterpart detection
  21. GRB 250727A: Swift-XRT observations
  22. LIGO/Virgo/KAGRA S250727dc: Identification of a GW compact binary merger candidate
  23. LIGO/Virgo/KAGRA S250727cl: Identification of a GW compact binary merger candidate
  24. LIGO/Virgo/KAGRA S250725j: DECam GW-MMADS candidates
  25. LIGO/Virgo/KAGRA S250725l: Updated Sky localization
  26. LIGO/Virgo/KAGRA S250726ak: Updated Sky localization
  27. LIGO/Virgo/KAGRA S250726ak: Identification of a GW compact binary merger candidate
  28. GRB 250725A: Swift-XRT refined Analysis
  29. GRB 250725A: Fermi GBM Observation
  30. LIGO/Virgo/KAGRA S250725j: Updated Sky localization
  31. GRB 250725A: Swift-BAT refined analysis
  32. LIGO/Virgo/KAGRA S250725j: NED Galaxies in the 3-Initial Localization Volume
  33. GRB 250725A: SVOM/GRM observation
  34. GRB 250725A: Global MASTER-Net: First Optical Synchronous Observatios of Short GRB.
  35. GRB 250725A: Swift/UVOT Upper Limits
  36. GRB 250725A: Fermi-LAT detection
  37. GRB 250725A: BOOTES-7 early optical detection
  38. GRB 250725A: SVOM/VT optical candidate
  39. GRB 250725A: MASTER-OAFA optical detection of very fast afterglow
  40. LIGO/Virgo/KAGRA S250725l: Identification of a GW compact binary merger candidate
  41. LIGO/Virgo/KAGRA S250725j: Identification of a GW compact binary merger candidate
  42. GRB 250725A: Enhanced Swift-XRT position
  43. GRB 250725A: Swift detection of a burst
  44. Swift GRB 250725A: Global MASTER-Net OT detection
  45. EP250702a/GRB250702 B,E,D: MeerKAT radio observations at 3.06 GHz
  46. SVOM J195836+32283 is not a real source
  47. EP250702a/GRB250702 B,D,E: uGMRT Radio detection in 1.26 GHz
  48. SVOM J195836+32283/sb25072103: Liverpool Telescope detection of an extended source
  49. GRB 250721A: Fermi GBM Observation
  50. SVOM J195836+32283/sb25072103: NIR observations with WINTER
  51. GRB 250721A: Swift-XRT observations
  52. GRB 250717B: SVOM/GRM observation
  53. LIGO/Virgo/KAGRA S250711q: Updated Sky localization
  54. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  55. GRB 250721A: MAXI/GSC detection
  56. LIGO/Virgo/KAGRA S250720j: Retraction of GW compact binary merger candidate
  57. GRB 250717B: COLIBRÍ optical upper limit
  58. LIGO/Virgo/KAGRA S250711q: Upper limits from Swift/BAT-GUANO
  59. GRB 250717B: Swift-XRT observations
  60. Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
  61. Swift GRB250718.01: Global MASTER-Net observations report
  62. GRB 270713A: Kitab and AbAO Optical Observations
  63. GRB 250717B: Fermi GBM Observation
  64. GRB 250717B: Swift/BAT-GUANO arcminute localization of a burst
  65. GRB 250716A: Swift-XRT afterglow detection
  66. GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
  67. GRB 250716A: Fermi GBM Observation
  68. GRB 250714A: SVOM/GRM observation
  69. EP250702a / GRB 250702B,D,E: Hubble Space Telescope Observations
  70. GRB 250702B,D,E / EP250702a: H.E.S.S. very-high-energy gamma-ray observations
  71. GRB 250713A: Mephisto optical upper limits
  72. GRB 250713A: SVOM/VT optical upper limit
  73. GRB 250713A: NOT optical upper limits
  74. GRB 250713A: OHP/T193 upper limit
  75. GRB 250713A: SVOM/C-GFT upper limit
  76. GRB 250706B/C: 7DT Follow-up Observations
  77. GRB 250713A: Swift-XRT observations
  78. GRB 250713A: EP-FXT counterpart detection
  79. EP250711a: COLIBRÍ continuous optical observations
  80. GRB 250706A: Swift-BAT refined analysis
  81. GRB 250702F: Swift-BAT refined analysis
  82. GRB 250628A: Swift-BAT refined analysis
  83. LIGO/Virgo/KAGRA S250712cd: Updated Sky localization
  84. GRB 250713A: JinShan optical upper limits
  85. GRB 250713A: SVOM detection of a long burst
  86. EP250711a: Global MASTER-Net observations report
  87. GRB 250711A: DDOTI Optical Upper Limit
  88. LIGO/Virgo/KAGRA S250712cd: Identification of a GW compact binary merger candidate
  89. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  90. GRB 250711A: SVOM/GRM observation
  91. EP250711a: NOT optical counterpart candidate
  92. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  93. EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  94. GRB 250704A: GRANDMA observations
  95. GRB 250711A: BALROG localization (Fermi Trigger 773937617 / GRB 250711611)
  96. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
  97. LIGO/Virgo/KAGRA S250629bs: Upper limits from Swift/BAT-GUANO
  98. LIGO/Virgo/KAGRA S250629ae: Upper limits from Swift/BAT-GUANO
  99. IceCube-250708A: No Candidates from WINTER
  100. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility

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