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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"

20815 results found.

  1. GRB 250129A: Skynet optical observations
  2. GRB 250128B: Gemini-North optical extended source detection
  3. The EP-WXT trigger 01709131085: KAIT confirmation of the stellar flare
  4. GRB 250128B: TNG optical upper limit
  5. GRB 250129A: Swift/UVOT Detection
  6. GRB 250128B: VLT/HAWKI near-infrared observations
  7. GRB 250127A: CrAO and Terskol optical upper limits
  8. GRB 250129A: Enhanced Swift-XRT position
  9. GRB 250128B: NOT optical upper limit
  10. GRB 250128B: VLT/FORS2 optical observations
  11. GRB 250129A: REM optical/NIR afterglow detection
  12. GRB 250129A: OHP/T193 optical and spectroscopy observations
  13. GRB 250129A: Early afterglow detection by LCO.
  14. GRB 250128B: OHP/T193 optical upper limit
  15. GRB 250129A: LCO optical observations
  16. GRB 250128B: Enhanced Swift-XRT position
  17. GRB 250129A: Swift detection of a burst with an optical counterpart
  18. GRB 250128B: Swift-XRT refined Analysis
  19. GRB 250128B: GOTO optical upper limit
  20. Swift GRB 250128B: Global MASTER-Net observations report
  21. GRB 250128B: LCO optical observations
  22. GRB 250128B: Swift detection of a short burst
  23. GRB 250127A: Swift-XRT observations
  24. GRB 250127B: DDOTI Upper Limit on the Afterglow
  25. Fermi GRB 250128A: Global MASTER-Net observations report
  26. GRB 250127A: SVOM/VT upper limit
  27. IPN triangulation of GRB 250119C
  28. GRB 250127A: LCO optical upper limit
  29. GRB 241223A: cubesat Avion detection
  30. EP250125a: Optical upper limit with Kinder observations
  31. EP250125a: REM optical counterpart detection
  32. EP250125a: Swift/XRT detection of a fading counterpart
  33. EP250125a: a new X-ray transient detected by Einstein Probe
  34. EP250125a: Gemini-South optical afterglow discovery and redshift z = 2.89
  35. GRB 250121A: Swift/BAT-GUANO localization skymap of a burst
  36. EP250108a: AbAO, CMO and Terskol optical upper limits
  37. Konus-Wind detection of GRB 250118B
  38. IPN triangulation of GRB 250118B
  39. Konus-Wind detection of GRB 250119B
  40. IPN triangulation of GRB 250119B
  41. Improved IPN triangulation of GRB 250107C
  42. LIGO/Virgo S250119cv: Swift XRT observations, 5 X-ray sources
  43. GRB 250119C: Swift/BAT-GUANO localization skymap of a short burst
  44. GRB 250119B: Swift/BAT-GUANO localization skymap of a long burst
  45. Fermi-LAT Gamma-ray Observations of IceCube-241224A
  46. GRB 250118A: Swift/BAT-GUANO localization skymap of a short burst
  47. EP250108a/AT2025kg: 1.3m DFOT Optical observations
  48. Konus-Wind detection of GRB 250117A
  49. IPN triangulation of GRB 250117A (short)
  50. LIGO/Virgo/KAGRA S250119cv: GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  51. EP 250108A: Late-time optical observation by LCO
  52. LIGO/Virgo/KAGRA S250105bn: 1 counterpart neutrino candidate event from an IceCube neutrino search
  53. LIGO/Virgo/KAGRA S250119cv: Updated Sky localization and EM Bright Classification
  54. LIGO/Virgo/KAGRA S250119cv: NED Galaxies in the Localization Volume
  55. GRB 250117A: Swift/BAT-GUANO localization skymap of a short burst
  56. LIGO/Virgo/KAGRA S250119cv: Identification of a GW compact binary merger candidate
  57. LIGO/Virgo/KAGRA S250119ag: Identification of a GW compact binary merger candidate
  58. LIGO/Virgo/KAGRA S250118dp: Identification of a GW compact binary merger candidate
  59. LIGO/Virgo/KAGRA S250118az: Identification of a GW compact binary merger candidate
  60. EP250108a / AT2025kg: GMG Optical Observations
  61. LIGO/Virgo/KAGRA S250118t: Identification of a GW compact binary merger candidate
  62. EP250108a / AT2025kg: VLA radio upper limit
  63. Konus-Wind detection of GRB 250116A
  64. GRB 241217A / EP241217B: radio detection with the VLA
  65. GRB 250114B: Swift-XRT afterglow detection
  66. GRB 250114B: SVOM/VT upper limit
  67. EP250108a: MeerKAT radio upper limit
  68. GRB 250101A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations and rebrightening.
  69. IPN triangulation of GRB 250113A
  70. GRB 250114B: Liverpool Telescope optical upper limit
  71. LIGO/Virgo/KAGRA S250114ax: GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  72. GRB 250114B : MITSuME Akeno optical afterglow candidate detection
  73. GRB 250114B: Swift-XRT observations
  74. GRB 250114A: LCO optical counterpart detection.
  75. GRB 250114B: OHP/T193 optical upper limit
  76. GRB 250114A: GRANDMA/TAROT optical afterglow detection
  77. GRB 250114A: Swift-XRT refined Analysis
  78. GRB 250114A: LCOGT optical afterglow i-band detection
  79. GRB 250114B : GIT optical upper limit
  80. EP250111a: SAO RAS optical upper limit
  81. LIGO/Virgo/KAGRA S250114ax: NED Galaxies in the Localization Volume
  82. GRB 250114A: Enhanced Swift-XRT position
  83. GRB 250113A: INTEGRAL/SPI-ACS detection
  84. GRB 250114A: REM detection of the optical and NIR counterpart
  85. LIGO/Virgo/KAGRA S250114ax: Identification of a GW compact binary merger candidate
  86. GRB 250114A: LCO optical observations
  87. GRB 250114A: TRT optical observations
  88. GRB 250114A: Swift detection of a burst with an optical counterpart
  89. GRB 250101A: Terskol Zeiss-2000 optical observations
  90. EP250108a / AT 2025kg: SAO RAS optical observations
  91. EP241021a: SMA radio observation
  92. GRB 250113A: SVOM/GRM observation of a long burst
  93. EP250109b: optical upper limits with the Liverpool Telescope
  94. GRB 250106A: Swift-XRT afterglow detection
  95. EP250111a: KAIT optical observations
  96. GRB 250109A / EP250109a: Mephisto optical upper limits
  97. EP250108a: Mephisto detection
  98. EP250111a: Mondy optical observation
  99. EP250108a / AT 2025kg: LCO optical observations
  100. EP250108a / AT 2025kg: Swift UVOT detections

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