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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"

23601 results found.

  1. GRB 250725A: PRIME near-infrared observations
  2. LIGO/Virgo/KAGRA S250727dc: PRIME J-band upper limits of AT 2025smm
  3. GRB 250727A: SVOM/ECLAIRs refined analysis
  4. EP-WXT trigger 01709195487: confirmation of a stellar flare by BOOTES-6 & BOOTES-7
  5. GRB 250728A: COLIBRÍ optical upper limit
  6. LIGO/Virgo/KAGRA S250727dc: Swift-UVOT detection of a new source, AT 2025smm
  7. GRB 250727A: Swift-XRT observations
  8. LIGO/Virgo/KAGRA S250727dc: Identification of a GW compact binary merger candidate
  9. LIGO/Virgo/KAGRA S250727cl: Identification of a GW compact binary merger candidate
  10. GRB 250727A: SVOM detection of a burst
  11. Swift detection of the Soft Gamma Repeater PSR J1647-4552
  12. LIGO/Virgo/KAGRA S250726ak: Identification of a GW compact binary merger candidate
  13. GRB 250725A: Swift-BAT refined analysis
  14. Konus-Wind detection of GRB 250725A
  15. LIGO/Virgo/KAGRA S250725j: NED Galaxies in the 3-Initial Localization Volume
  16. GRB 250725A: BOOTES-7 early optical detection
  17. GRB 250725A: Swift detection of a burst
  18. Swift GRB 250725A: Global MASTER-Net OT detection
  19. GRB 250721A: Fermi GBM Observation
  20. SVOM J195836+32283/sb25072103: NIR observations with WINTER
  21. Swift-BAT trigger 1334535 is not a GRB
  22. GRB 250713A : SVOM/ECLAIRs refined analysis
  23. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  24. GRB 250721A: MAXI/GSC detection
  25. GRB 250717B: COLIBRÍ optical upper limit
  26. Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
  27. Swift Trigger 1334535: a possible GRB 250718A
  28. GRB 250717B: Fermi GBM Observation
  29. Konus-Wind detection of GRB 250716A
  30. GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
  31. GRB 250716A: GOTO tentative optical counterpart candidate
  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: SVOM/C-GFT upper limit
  36. GRB 250713A: Swift-XRT observations
  37. GRB 250713A: EP-FXT counterpart detection
  38. EP250711a: COLIBRÍ continuous optical observations
  39. GRB 250706A: Swift-BAT refined analysis
  40. GRB 250702F: Swift-BAT refined analysis
  41. GRB 250628A: Swift-BAT refined analysis
  42. GRB 250713A: SVOM detection of a long burst
  43. GRB 250711A: DDOTI Optical Upper Limit
  44. LIGO/Virgo/KAGRA S250712cd: Identification of a GW compact binary merger candidate
  45. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  46. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  47. EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  48. GRB 250704A: GRANDMA observations
  49. GRB 250704A: SVOM/ECLAIRs refined analysis
  50. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
  51. IceCube-250708A: No Candidates from WINTER
  52. EP/WXT 01709181970: GOTO observations confirm stellar variability
  53. EP-WXT trigger 01709181970. confirmation of a stellar flare by BOOTES-6
  54. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 4-Update Localization Volume
  55. IceCube-250706A: No Candidates from WINTER
  56. GRB 250704B / EP250704a: VLA radio detection
  57. EP250704a/GRB250704B : HCT optical and NIR upper limits
  58. GRB 250706B/C: Konus-Wind analysis of the prompt emission
  59. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  60. GRB 250704B: CALET Gamma-Ray Burst Monitor detection
  61. GRB 250702F: radio detection with the VLA
  62. GRB 250706B/C: VLT/X-shooter redshift z = 0.942
  63. IceCube-250706A: EP-FXT follow-up observations
  64. GRB 250706B/C: Fermi-LAT detection
  65. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  66. EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
  67. GRB 250706B: Swift/UVOT Detection
  68. GRB 250706C: Konus-Wind detection of a very bright GRB ~1200 s before GRB 250706B
  69. GRB 250702F: GRANDMA observations
  70. GRB 250706B: refined SVOM/MXT data analysis
  71. GRB 250706A: Swift/UVOT Upper Limits
  72. GRB 250706B: REM optical observations
  73. GRB 250706A: REM optical/NIR observations
  74. IceCube-250416A: DDOTI Optical Upper Limit
  75. IceCube-250706A: COLIBRÍ optical upper limits
  76. Swift GRB 250706A: Global MASTER-Net observations report
  77. GRB 250706A: SAO RAS optical observations
  78. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  79. GRB250706B: Swift-XRT counterpart detection
  80. GRB 250706B: iTelescope optical observations
  81. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  82. GRB 250706B: SVOM/VT optical observation
  83. GRB 250706B: TRT bright optical counterpart detection
  84. GRB 250706A: Swift detection of a burst
  85. GRB 250704B: Swift-XRT refined Analysis
  86. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  87. GRB 250703A: EIRSAT-1 GMOD Detection
  88. GRB 250704B: Swift/UVOT Upper Limits
  89. GRB 250704A: Swift/UVOT Detection
  90. Konus-Wind detection of GRB 250703A
  91. IPN triangulation of GRB 250703A
  92. EP250704a/GRB 250704B: GSP observations of the optical counterpart
  93. Konus-Wind detection of short/hard GRB 250704B/ EP250704a
  94. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  95. GRB 250702F: Kilonova-Catcher optical afterglow detection
  96. GRB 250702F: Monte Agliale Observatory optical observations
  97. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  98. EP250704a / GRB 250704B: VLT/X-shooter spectroscopic redshift z = 0.661
  99. EP250704a / GRB 250704B: SAO RAS optical observations
  100. GRBs 250702B,D,E / EP250702a: fast fading, extremely red counterpart

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