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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"

22086 results found.

  1. GRB 250727A: EP-FXT counterpart detection
  2. GRB250727A: SVOM/VT optical upper limit
  3. GRB 250727A: Swift-XRT observations
  4. LIGO/Virgo/KAGRA S250727dc: Identification of a GW compact binary merger candidate
  5. LIGO/Virgo/KAGRA S250727cl: Identification of a GW compact binary merger candidate
  6. LIGO/Virgo/KAGRA S250725j: DECam GW-MMADS candidates
  7. GRB 250727A: SVOM detection of a burst
  8. Swift detection of the Soft Gamma Repeater PSR J1647-4552
  9. LIGO/Virgo/KAGRA S250726ak: Identification of a GW compact binary merger candidate
  10. GRB 250725A: Swift-XRT refined Analysis
  11. LIGO/Virgo/KAGRA S250725j: NED Galaxies in the 3-Initial Localization Volume
  12. GRB 250725A: SVOM/GRM observation
  13. GRB 250725A: Global MASTER-Net: First Optical Synchronous Observatios of Short GRB.
  14. GRB 250725A: Swift/UVOT Upper Limits
  15. GRB 250725A: SVOM/VT optical candidate
  16. LIGO/Virgo/KAGRA S250725l: Identification of a GW compact binary merger candidate
  17. LIGO/Virgo/KAGRA S250725j: Identification of a GW compact binary merger candidate
  18. GRB 250725A: Enhanced Swift-XRT position
  19. GRB 250725A: Swift detection of a burst
  20. EP250702a/GRB250702 B,E,D: MeerKAT radio observations at 3.06 GHz
  21. SVOM J195836+32283 is not a real source
  22. EP250702a/GRB250702 B,D,E: uGMRT Radio detection in 1.26 GHz
  23. SVOM J195836+32283/sb25072103: Liverpool Telescope detection of an extended source
  24. SVOM J195836+32283/sb25072103: Swift XRT/UVOT upper limits
  25. SVOM J195836+32283/sb25072103: NIR observations with WINTER
  26. GRB 250721A: Swift-XRT observations
  27. GRB 250717B: SVOM/GRM observation
  28. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  29. EP250702a/GRB250702B,D,E: SVOM/VT optical upper limit
  30. GRB 250717B: COLIBRÍ optical upper limit
  31. GRB 250717B: Swift-XRT observations
  32. Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
  33. Swift Trigger 1334535: a possible GRB 250718A
  34. GRB 270713A: Kitab and AbAO Optical Observations
  35. GRB 250717B: Swift/BAT-GUANO arcminute localization of a burst
  36. GRB 250716A: Swift-XRT afterglow detection
  37. GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
  38. GRB 250714A: SVOM/GRM observation
  39. EP250702a / GRB 250702B,D,E: Hubble Space Telescope Observations
  40. GRB 250713A: Mephisto optical upper limits
  41. GRB 250713A: SVOM/VT optical upper limit
  42. GRB 250713A: NOT optical upper limits
  43. GRB 250713A: OHP/T193 upper limit
  44. GRB 250713A: SVOM/C-GFT upper limit
  45. GRB 250706B/C: 7DT Follow-up Observations
  46. GRB 250713A: Swift-XRT observations
  47. GRB 250713A: EP-FXT counterpart detection
  48. EP250711a: COLIBRÍ continuous optical observations
  49. GRB 250702F: Swift-BAT refined analysis
  50. GRB 250713A: JinShan optical upper limits
  51. GRB 250713A: SVOM detection of a long burst
  52. GRB 250711A: DDOTI Optical Upper Limit
  53. LIGO/Virgo/KAGRA S250712cd: Identification of a GW compact binary merger candidate
  54. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  55. GRB 250711A: SVOM/GRM observation
  56. EP250711a: NOT optical counterpart candidate
  57. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  58. Fermi GRB 250711A: Global MASTER-Net observations report
  59. EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  60. GRB 250704A: GRANDMA observations
  61. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
  62. GRB 250702B,D,E/EP250702A: JCMT sub-mm observations at 350 GHz
  63. IceCube-250708A: No Candidates from WINTER
  64. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  65. GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz
  66. GRB 250702B,D,E / EP250702a: 10 GHz detection with the VLA
  67. IPN triangulation of GRB 250704B (short/hard, consistent with EP 250704a)
  68. EP250704a/GRB 250704B: 10 GHz VLA detection
  69. IceCube-250706A: No Candidates from WINTER
  70. IPN triangulation of GRB 250706C (consistent with the GRB 250706B)
  71. IceCube-250706A: No Candidates from the Zwicky Transient Facility
  72. LIGO/Virgo/KAGRA S250704ab: Updated Sky localization and EM Bright Classification
  73. EP250704a/GRB250704B : HCT optical and NIR upper limits
  74. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  75. GRB 250702F: radio detection with the VLA
  76. GRB 250706B/C: Fermi-LAT detection
  77. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  78. EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
  79. GRB 250706B: Swift/UVOT Detection
  80. EP250702a/ GRB 250702B: NuSTAR X-ray Observations
  81. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  82. GRB 250702F: GRANDMA observations
  83. GRB 250706B: refined SVOM/MXT data analysis
  84. GRB 250706A: Swift/UVOT Upper Limits
  85. GRB 250706B: REM optical observations
  86. GRB 250706A: REM optical/NIR observations
  87. EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
  88. IceCube-250416A: DDOTI Optical Upper Limit
  89. IceCube-250706A: COLIBRÍ optical upper limits
  90. GRB 250706A: JinShan optical upper limits
  91. GRB 250706A: SAO RAS optical observations
  92. EP250704A: NOWT Detection
  93. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  94. GRB 250706B: iTelescope optical observations
  95. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  96. GRB 250706B: SVOM/VT optical observation
  97. GRB 250706B: TRT bright optical counterpart detection
  98. GRB 250706A: GROWTH-India Telescope optical upper limit
  99. GRB 250706B: SVOM detection of a long burst
  100. GRB 250706A: Swift detection of a burst

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