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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"

45435 results found.

  1. LIGO/Virgo/KAGRA S250726ak: Updated Sky localization
  2. The EP-WXT trigger 01709195487 is likely a flaring star
  3. Swift detection of the Soft Gamma Repeater PSR J1647-4552
  4. LIGO/Virgo/KAGRA S250726ak: Identification of a GW compact binary merger candidate
  5. GRB 250725A: Swift-XRT refined Analysis
  6. GRB 250725A: Fermi GBM Observation
  7. LIGO/Virgo/KAGRA S250725j: Updated Sky localization
  8. GRB 250725A: Swift-BAT refined analysis
  9. Konus-Wind detection of GRB 250725A
  10. LIGO/Virgo/KAGRA S250725j: NED Galaxies in the 3-Initial Localization Volume
  11. GRB 250725A: SVOM/GRM observation
  12. GRB 250725A: Global MASTER-Net: First Optical Synchronous Observatios of Short GRB.
  13. GRB 250725A: Swift/UVOT Upper Limits
  14. GRB 250725A: Fermi-LAT detection
  15. GRB 250725A: VLT/FORS2 spectroscopic redshift z = 5.26
  16. GRB 250725A: BOOTES-7 early optical detection
  17. GRB 250725A: SVOM/VT optical candidate
  18. GRB 250725A: MASTER-OAFA optical detection of very fast afterglow
  19. LIGO/Virgo/KAGRA S250725l: Identification of a GW compact binary merger candidate (duplicate submission)
  20. LIGO/Virgo/KAGRA S250725l: Identification of a GW compact binary merger candidate
  21. LIGO/Virgo/KAGRA S250725j: Identification of a GW compact binary merger candidate
  22. GRB 250725A: Enhanced Swift-XRT position
  23. GRB 250725A: Swift detection of a burst
  24. Swift GRB 250725A: Global MASTER-Net OT detection
  25. GRB 250725A: Fermi GBM Final Real-time Localization
  26. Fermi GRB 250725A: Global MASTER-Net observations report
  27. Swift GRB 250725A: Global MASTER-Net observations report
  28. EP250702a/GRB250702 B,E,D: MeerKAT radio observations at 3.06 GHz
  29. SVOM J195836+32283 is not a real source
  30. EP250702a/GRB250702 B,D,E: uGMRT Radio detection in 1.26 GHz
  31. SVOM J195836+32283/sb25072103: Second VT observation
  32. SVOM J195836+32283/sb25072103: Liverpool Telescope detection of an extended source
  33. GRB 250723B: Fermi GBM Final Real-time Localization
  34. GRB 250721A: Fermi GBM Observation
  35. GRB 250723A: Fermi GBM Final Real-time Localization
  36. SVOM J195836+32283/sb25072103: Swift XRT/UVOT upper limits
  37. SVOM J195836+32283/sb25072103: NIR observations with WINTER
  38. Swift-BAT trigger 1334535 is not a GRB
  39. GRB 250721A: Swift-XRT observations
  40. GRB 250722A: Fermi GBM Final Real-time Localization
  41. GRB 250713A : SVOM/ECLAIRs refined analysis
  42. GRB 250717B: SVOM/GRM observation
  43. LIGO/Virgo/KAGRA S250711q: Updated Sky localization
  44. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  45. GRB 250721A: Tiled Swift observations
  46. GRB 250721A: MAXI/GSC detection
  47. GRB 250721A: Fermi GBM Final Localization
  48. GRB 250720B: Fermi GBM Final Localization Correction
  49. GRB 250720A: Fermi GBM Final Localization
  50. Fermi trigger No 774730635: Global MASTER-Net observations report
  51. LIGO/Virgo/KAGRA S250720j: Retraction of GW compact binary merger candidate
  52. Fermi Gamma-ray Burst Monitor trigger 774670514/250720094 is not a GRB
  53. EP250702a/GRB250702B,D,E: SVOM/VT optical upper limit
  54. GRB 250717B: COLIBRÍ optical upper limit
  55. LIGO/Virgo/KAGRA S250711q: Upper limits from Swift/BAT-GUANO
  56. GRB 250717B: Swift-XRT observations
  57. GRB 250718B: Fermi GBM Final Localization Correction
  58. GRB 250718B: Fermi GBM Final Real-time Localization
  59. Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
  60. Swift Trigger 1334535: a possible GRB 250718A
  61. Swift GRB250718.01: Global MASTER-Net observations report
  62. GRB 250717B: Swift ToO observations
  63. GRB 270713A: Kitab and AbAO Optical Observations
  64. GRB 250717B: Fermi GBM Observation
  65. GRB 250717B: Swift/BAT-GUANO arcminute localization of a burst
  66. Konus-Wind detection of GRB 250716A
  67. GRB 250716A: Swift-XRT afterglow detection
  68. GRB 250717B: Fermi GBM Final Real-time Localization
  69. GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
  70. GRB 250717A: Fermi GBM Final Real-time Localization
  71. GRB 250716A: Swift ToO observations
  72. GRB 250716A: GOTO tentative optical counterpart candidate
  73. GRB 250716A: Fermi GBM Observation
  74. GRB 250714A: SVOM/GRM observation
  75. Fermi GRB 250716A: Global MASTER-Net observations report
  76. GRB 250716A: Fermi GBM Final Real-time Localization
  77. Fermi GRB 250715A: Global MASTER-Net observations report
  78. GRB 250715A: Fermi GBM Final Real-time Localization
  79. EP250702a / GRB 250702B,D,E: Hubble Space Telescope Observations
  80. GRB 250702B,D,E / EP250702a: H.E.S.S. very-high-energy gamma-ray observations
  81. GRB 250713A: Mephisto optical upper limits
  82. Fermi GRB 250714A: Global MASTER-Net observations report
  83. GRB 250713A: SVOM/VT optical upper limit
  84. GRB 250713A: NOT optical upper limits
  85. GRB 250713A: OHP/T193 upper limit
  86. GRB 250713A: SVOM/C-GFT upper limit
  87. GRB 250714A: Fermi GBM Final Real-time Localization
  88. GRB 250706B/C: 7DT Follow-up Observations
  89. GRB 250713A: Swift-XRT observations
  90. GRB 250713A: EP-FXT counterpart detection
  91. EP250711a: COLIBRÍ continuous optical observations
  92. GRB 250706A: Swift-BAT refined analysis
  93. GRB 250702F: Swift-BAT refined analysis
  94. GRB 250628A: Swift-BAT refined analysis
  95. LIGO/Virgo/KAGRA S250712cd: Updated Sky localization
  96. GRB 250713A: JinShan optical upper limits
  97. GRB 250713A: SVOM detection of a long burst
  98. EP250711a: Global MASTER-Net observations report
  99. GRB 250711A: DDOTI Optical Upper Limit
  100. LIGO/Virgo/KAGRA S250712cd: Identification of a GW compact binary merger candidate

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