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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"

27391 results found.

  1. LIGO/Virgo/KAGRA S250726ak: Upper limits from Swift/BAT-GUANO
  2. LIGO/Virgo/KAGRA S250725l: Upper limits from Swift/BAT-GUANO
  3. LIGO/Virgo/KAGRA S250727dc: Upper limits from Swift/BAT-GUANO
  4. LIGO/Virgo/KAGRA S250727dc: Swift-XRT observations, 8 X-ray sources
  5. GRB 250727A: EP-FXT follow-up observation
  6. GRB 250725A: PRIME near-infrared observations
  7. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS upper limits of AT 2025smm
  8. LIGO/Virgo/KAGRA S250727dc: PRIME J-band upper limits of AT 2025smm
  9. GRB 250728A: Swift-XRT observations
  10. GRB 250728A: COLIBRÍ optical upper limit
  11. LIGO/Virgo/KAGRA S250727dc: Updated Sky localization
  12. GRB 250728A: Swift/BAT-GUANO arcminute localization of a short burst
  13. LIGO/Virgo/KAGRA S250727cl: Updated Sky localization
  14. GRB 250727A: EP-FXT counterpart detection
  15. GRB 250727A: Swift-XRT observations
  16. LIGO/Virgo/KAGRA S250727dc: Identification of a GW compact binary merger candidate
  17. LIGO/Virgo/KAGRA S250727cl: Identification of a GW compact binary merger candidate
  18. LIGO/Virgo/KAGRA S250725j: DECam GW-MMADS candidates
  19. LIGO/Virgo/KAGRA S250725l: Updated Sky localization
  20. LIGO/Virgo/KAGRA S250726ak: Updated Sky localization
  21. LIGO/Virgo/KAGRA S250726ak: Identification of a GW compact binary merger candidate
  22. GRB 250725A: Swift-XRT refined Analysis
  23. GRB 250725A: Fermi GBM Observation
  24. LIGO/Virgo/KAGRA S250725j: Updated Sky localization
  25. GRB 250725A: Swift-BAT refined analysis
  26. LIGO/Virgo/KAGRA S250725j: NED Galaxies in the 3-Initial Localization Volume
  27. GRB 250725A: SVOM/GRM observation
  28. GRB 250725A: Global MASTER-Net: First Optical Synchronous Observatios of Short GRB.
  29. GRB 250725A: Swift/UVOT Upper Limits
  30. GRB 250725A: Fermi-LAT detection
  31. GRB 250725A: BOOTES-7 early optical detection
  32. GRB 250725A: SVOM/VT optical candidate
  33. GRB 250725A: MASTER-OAFA optical detection of very fast afterglow
  34. LIGO/Virgo/KAGRA S250725l: Identification of a GW compact binary merger candidate
  35. LIGO/Virgo/KAGRA S250725j: Identification of a GW compact binary merger candidate
  36. GRB 250725A: Enhanced Swift-XRT position
  37. GRB 250725A: Swift detection of a burst
  38. Swift GRB 250725A: Global MASTER-Net OT detection
  39. EP250702a/GRB250702 B,E,D: MeerKAT radio observations at 3.06 GHz
  40. SVOM J195836+32283 is not a real source
  41. EP250702a/GRB250702 B,D,E: uGMRT Radio detection in 1.26 GHz
  42. SVOM J195836+32283/sb25072103: Liverpool Telescope detection of an extended source
  43. GRB 250721A: Fermi GBM Observation
  44. SVOM J195836+32283/sb25072103: NIR observations with WINTER
  45. GRB 250721A: Swift-XRT observations
  46. GRB 250717B: SVOM/GRM observation
  47. LIGO/Virgo/KAGRA S250711q: Updated Sky localization
  48. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  49. GRB 250721A: MAXI/GSC detection
  50. LIGO/Virgo/KAGRA S250720j: Retraction of GW compact binary merger candidate
  51. GRB 250717B: COLIBRÍ optical upper limit
  52. LIGO/Virgo/KAGRA S250711q: Upper limits from Swift/BAT-GUANO
  53. GRB 250717B: Swift-XRT observations
  54. Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
  55. Swift GRB250718.01: Global MASTER-Net observations report
  56. GRB 270713A: Kitab and AbAO Optical Observations
  57. GRB 250717B: Fermi GBM Observation
  58. GRB 250717B: Swift/BAT-GUANO arcminute localization of a burst
  59. GRB 250716A: Swift-XRT afterglow detection
  60. GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
  61. GRB 250716A: Fermi GBM Observation
  62. GRB 250714A: SVOM/GRM observation
  63. EP250702a / GRB 250702B,D,E: Hubble Space Telescope Observations
  64. GRB 250702B,D,E / EP250702a: H.E.S.S. very-high-energy gamma-ray observations
  65. GRB 250713A: Mephisto optical upper limits
  66. GRB 250713A: SVOM/VT optical upper limit
  67. GRB 250713A: NOT optical upper limits
  68. GRB 250713A: OHP/T193 upper limit
  69. GRB 250713A: SVOM/C-GFT upper limit
  70. GRB 250706B/C: 7DT Follow-up Observations
  71. GRB 250713A: Swift-XRT observations
  72. GRB 250713A: EP-FXT counterpart detection
  73. EP250711a: COLIBRÍ continuous optical observations
  74. GRB 250706A: Swift-BAT refined analysis
  75. GRB 250702F: Swift-BAT refined analysis
  76. GRB 250628A: Swift-BAT refined analysis
  77. LIGO/Virgo/KAGRA S250712cd: Updated Sky localization
  78. GRB 250713A: JinShan optical upper limits
  79. GRB 250713A: SVOM detection of a long burst
  80. EP250711a: Global MASTER-Net observations report
  81. GRB 250711A: DDOTI Optical Upper Limit
  82. LIGO/Virgo/KAGRA S250712cd: Identification of a GW compact binary merger candidate
  83. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  84. GRB 250711A: SVOM/GRM observation
  85. EP250711a: NOT optical counterpart candidate
  86. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  87. EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  88. GRB 250704A: GRANDMA observations
  89. GRB 250711A: BALROG localization (Fermi Trigger 773937617 / GRB 250711611)
  90. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
  91. LIGO/Virgo/KAGRA S250629bs: Upper limits from Swift/BAT-GUANO
  92. LIGO/Virgo/KAGRA S250629ae: Upper limits from Swift/BAT-GUANO
  93. IceCube-250708A: No Candidates from WINTER
  94. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  95. GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz
  96. GRB 250702B,D,E / EP250702a: 10 GHz detection with the VLA
  97. IceCube-250708A: Upper limits from a search for additional neutrino events in IceCube
  98. EP-WXT trigger 01709181970. confirmation of a stellar flare by BOOTES-6
  99. EP250704a/GRB 250704B: 10 GHz VLA detection
  100. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 4-Update Localization Volume

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