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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"

11394 results found.

  1. The EP-WXT trigger 01709198251 is likely a flaring star
  2. LIGO/Virgo/KAGRA S250802dn: Identification of a GW compact binary merger candidate
  3. The EP-WXT trigger 01709198202 is likely a flaring star
  4. EP250711a: CrAO and Assy optical observations
  5. EP250730a: Einstein Probe detection of an X-ray transient
  6. LIGO/Virgo/KAGRA S250726ak: Upper limits from Swift/BAT-GUANO
  7. LIGO/Virgo/KAGRA S250725l: Upper limits from Swift/BAT-GUANO
  8. LIGO/Virgo/KAGRA S250727dc: Upper limits from Swift/BAT-GUANO
  9. GRB 250725A: AstroSat CZTI detection
  10. Fermi trigger No 775387550: Global MASTER-Net observations report
  11. GRB 250727A: Swift-XRT observations
  12. LIGO/Virgo/KAGRA S250727dc: Identification of a GW compact binary merger candidate
  13. LIGO/Virgo/KAGRA S250727cl: Identification of a GW compact binary merger candidate
  14. The EP-WXT trigger 01709195487 is likely a flaring star
  15. Swift detection of the Soft Gamma Repeater PSR J1647-4552
  16. GRB 250725A: Swift-XRT refined Analysis
  17. Konus-Wind detection of GRB 250725A
  18. LIGO/Virgo/KAGRA S250725j: NED Galaxies in the 3-Initial Localization Volume
  19. GRB 250725A: Fermi-LAT detection
  20. LIGO/Virgo/KAGRA S250725l: Identification of a GW compact binary merger candidate
  21. GRB 250725A: Swift detection of a burst
  22. Fermi GRB 250725A: Global MASTER-Net observations report
  23. Swift GRB 250725A: Global MASTER-Net observations report
  24. SVOM J195836+32283/sb25072103: Swift XRT/UVOT upper limits
  25. SVOM J195836+32283/sb25072103: NIR observations with WINTER
  26. GRB 250717B: SVOM/GRM observation
  27. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  28. GRB 250721A: MAXI/GSC detection
  29. GRB 250720B: Fermi GBM Final Localization Correction
  30. GRB 250720A: Fermi GBM Final Localization
  31. Fermi trigger No 774730635: Global MASTER-Net observations report
  32. Fermi Gamma-ray Burst Monitor trigger 774670514/250720094 is not a GRB
  33. LIGO/Virgo/KAGRA S250711q: Upper limits from Swift/BAT-GUANO
  34. GRB 270713A: Kitab and AbAO Optical Observations
  35. Konus-Wind detection of GRB 250716A
  36. GRB 250716A: Swift-XRT afterglow detection
  37. Fermi GRB 250716A: Global MASTER-Net observations report
  38. GRB 250713A: SVOM/C-GFT upper limit
  39. GRB 250713A: Swift-XRT observations
  40. EP250711a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  41. Fermi GRB 250711A: Global MASTER-Net observations report
  42. EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  43. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
  44. GRB 250702B,D,E/EP250702A: JCMT sub-mm observations at 350 GHz
  45. LIGO/Virgo/KAGRA S250629bs: Upper limits from Swift/BAT-GUANO
  46. LIGO/Virgo/KAGRA S250629ae: Upper limits from Swift/BAT-GUANO
  47. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 4-Update Localization Volume
  48. GRB 250704B / EP250704a: VLA radio detection
  49. GRB 250706B/C: Konus-Wind analysis of the prompt emission
  50. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  51. Fermi-LAT Gamma-ray Observations of IceCube-250706A
  52. GRB 250706B/C: Fermi-LAT detection
  53. IceCube-250706A: Global MASTER-Net observations report
  54. EP250702a/ GRB 250702B: NuSTAR X-ray Observations
  55. GRB 250706C: Konus-Wind detection of a very bright GRB ~1200 s before GRB 250706B
  56. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  57. GRB 250706B: refined SVOM/MXT data analysis
  58. GRB 250706A: SAO RAS optical observations
  59. GRB250706B: Swift-XRT counterpart detection
  60. GRB 250706B: iTelescope optical observations
  61. GRB 250706B: SVOM detection of a long burst
  62. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  63. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  64. Konus-Wind detection of GRB 250703A
  65. EP250704a/GRB 250704B: GSP observations of the optical counterpart
  66. Konus-Wind detection of short/hard GRB 250704B/ EP250704a
  67. EP250704a/GRB 250704B VLT/HAWK-I NIR afterglow detection
  68. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 3-Initial Localization Volume
  69. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  70. EP250704a / GRB250704B: Swift-XRT counterpart detection
  71. GRB 250704A: Swift-XRT afterglow detection
  72. Konus-Wind detection of GRB 250702F
  73. EP250704a: COLIBRÍ optical counterpart candidate
  74. EP250704a: Einstein Probe detection of an X-ray transient
  75. LIGO/Virgo/KAGRA S250704ab: Coverage and upper limits from MAXI/GSC observations
  76. GRB 250704A: SVOM detection of a burst
  77. Fermi GRB 250703A: Global MASTER-Net observations report
  78. GRB 250702F: Swift-XRT refined Analysis
  79. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  80. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  81. GRBs 250702B,C,D,E / EP250702a: Konus-Wind detection of a hard X-ray transient activity
  82. EP250702a: Global MASTER-Net observations report
  83. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  84. Fermi GRB 250702C: Global MASTER-Net observations report
  85. Konus-Wind detection of GRB 250627A
  86. LIGO/Virgo/KAGRA S250701bp: Identification of a GW compact binary merger candidate
  87. Fermi Gamma-ray Burst Monitor trigger 772838080/250628885 is not a GRB
  88. GRB 250628B: Swift-XRT observations
  89. GRB 250628A: REM optical/NIR upper limits
  90. GRB 250628B: SVOM detection of a long burst
  91. GRB 250628A: Swift-XRT refined Analysis
  92. Fermi GRB 250626A: Global MASTER-Net observations report
  93. GRB 250628A: Swift detection of a burst
  94. GRB 250625A: Leavitt Observatory afterglow detection
  95. GRB 250625A: ABObservatory afterglow detection
  96. GRB 250625A: OHP/T193 optical detection
  97. GRB 250625A: Fermi-LAT detection
  98. GRB 250625A: Swift-XRT refined Analysis
  99. Swift GRB 250625A: Global MASTER-Net observations report
  100. GRB 250620B: Fermi GBM Observation

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