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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"

26359 results found.

  1. GRB 250725A: MASTER-OAFA optical detection of very fast afterglow
  2. LIGO/Virgo/KAGRA S250725l: Identification of a GW compact binary merger candidate
  3. LIGO/Virgo/KAGRA S250725j: Identification of a GW compact binary merger candidate
  4. GRB 250725A: Enhanced Swift-XRT position
  5. GRB 250725A: Swift detection of a burst
  6. Swift GRB 250725A: Global MASTER-Net OT detection
  7. EP250702a/GRB250702 B,E,D: MeerKAT radio observations at 3.06 GHz
  8. SVOM J195836+32283 is not a real source
  9. EP250702a/GRB250702 B,D,E: uGMRT Radio detection in 1.26 GHz
  10. SVOM J195836+32283/sb25072103: Liverpool Telescope detection of an extended source
  11. GRB 250721A: Fermi GBM Observation
  12. SVOM J195836+32283/sb25072103: NIR observations with WINTER
  13. GRB 250721A: Swift-XRT observations
  14. GRB 250717B: SVOM/GRM observation
  15. LIGO/Virgo/KAGRA S250711q: Updated Sky localization
  16. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  17. GRB 250721A: MAXI/GSC detection
  18. LIGO/Virgo/KAGRA S250720j: Retraction of GW compact binary merger candidate
  19. GRB 250717B: COLIBRÍ optical upper limit
  20. LIGO/Virgo/KAGRA S250711q: Upper limits from Swift/BAT-GUANO
  21. GRB 250717B: Swift-XRT observations
  22. Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
  23. Swift GRB250718.01: Global MASTER-Net observations report
  24. GRB 270713A: Kitab and AbAO Optical Observations
  25. GRB 250717B: Fermi GBM Observation
  26. GRB 250717B: Swift/BAT-GUANO arcminute localization of a burst
  27. GRB 250716A: Swift-XRT afterglow detection
  28. GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
  29. GRB 250716A: Fermi GBM Observation
  30. GRB 250714A: SVOM/GRM observation
  31. EP250702a / GRB 250702B,D,E: Hubble Space Telescope Observations
  32. GRB 250702B,D,E / EP250702a: H.E.S.S. very-high-energy gamma-ray observations
  33. GRB 250713A: Mephisto optical upper limits
  34. GRB 250713A: SVOM/VT optical upper limit
  35. GRB 250713A: NOT optical upper limits
  36. GRB 250713A: OHP/T193 upper limit
  37. GRB 250713A: SVOM/C-GFT upper limit
  38. GRB 250706B/C: 7DT Follow-up Observations
  39. GRB 250713A: Swift-XRT observations
  40. GRB 250713A: EP-FXT counterpart detection
  41. EP250711a: COLIBRÍ continuous optical observations
  42. GRB 250706A: Swift-BAT refined analysis
  43. GRB 250702F: Swift-BAT refined analysis
  44. GRB 250628A: Swift-BAT refined analysis
  45. LIGO/Virgo/KAGRA S250712cd: Updated Sky localization
  46. GRB 250713A: JinShan optical upper limits
  47. GRB 250713A: SVOM detection of a long burst
  48. EP250711a: Global MASTER-Net observations report
  49. GRB 250711A: DDOTI Optical Upper Limit
  50. LIGO/Virgo/KAGRA S250712cd: Identification of a GW compact binary merger candidate
  51. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  52. GRB 250711A: SVOM/GRM observation
  53. EP250711a: NOT optical counterpart candidate
  54. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  55. EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  56. GRB 250704A: GRANDMA observations
  57. GRB 250711A: BALROG localization (Fermi Trigger 773937617 / GRB 250711611)
  58. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
  59. LIGO/Virgo/KAGRA S250629bs: Upper limits from Swift/BAT-GUANO
  60. LIGO/Virgo/KAGRA S250629ae: Upper limits from Swift/BAT-GUANO
  61. IceCube-250708A: No Candidates from WINTER
  62. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  63. GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz
  64. GRB 250702B,D,E / EP250702a: 10 GHz detection with the VLA
  65. IceCube-250708A: Upper limits from a search for additional neutrino events in IceCube
  66. EP-WXT trigger 01709181970. confirmation of a stellar flare by BOOTES-6
  67. EP250704a/GRB 250704B: 10 GHz VLA detection
  68. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 4-Update Localization Volume
  69. IceCube-250706A: No Candidates from WINTER
  70. IceCube-250706A: No Candidates from the Zwicky Transient Facility
  71. IceCube-250706A: Upper limits from a search for additional neutrino events in IceCube
  72. LIGO/Virgo/KAGRA S250705cb: Updated Sky localization
  73. LIGO/Virgo/KAGRA S250704ab: Updated Sky localization and EM Bright Classification
  74. LIGO/Virgo/KAGRA S250702n: Updated Sky localization
  75. LIGO/Virgo/KAGRA S250701bq: Updated Sky localization
  76. EP250704a/GRB250704B : HCT optical and NIR upper limits
  77. LIGO/Virgo/KAGRA S250701bp: Updated Sky localization
  78. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  79. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  80. GRB 250702F: radio detection with the VLA
  81. IceCube-250706A: EP-FXT follow-up observations
  82. Fermi-LAT Gamma-ray Observations of IceCube-250706A
  83. GRB 250706B/C: Fermi-LAT detection
  84. IceCube-250706A: Global MASTER-Net observations report
  85. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  86. EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
  87. GRB 250706B: Swift/UVOT Detection
  88. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  89. GRB 250702F: GRANDMA observations
  90. GRB 250706A: Swift-XRT refined Analysis
  91. GRB 250706B: refined SVOM/MXT data analysis
  92. GRB 250706A: Swift/UVOT Upper Limits
  93. GRB 250706B: REM optical observations
  94. GRB 250706A: REM optical/NIR observations
  95. EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
  96. IceCube-250416A: DDOTI Optical Upper Limit
  97. IceCube-250706A: COLIBRÍ optical upper limits
  98. GRB 250706A: JinShan optical upper limits
  99. GRB 250706A: SAO RAS optical observations
  100. EP250704A: NOWT Detection

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