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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"

32485 results found.

  1. GRB 250129A: REM optical/NIR afterglow detection
  2. GRB 250129A: OHP/T193 optical and spectroscopy observations
  3. GRB 250129A: Early afterglow detection by LCO.
  4. GRB 250128B: OHP/T193 optical upper limit
  5. Swift GRB 250129A: Global MASTER-Net Slowly evolving LC detection
  6. GRB 250129A: LCO optical observations
  7. GRB 250129A: NOT optical observations and redshift confirmation
  8. GRB 250129A: GOTO optical observations show brightening afterglow
  9. GRB 250129A: VLT/X-shooter redshift of z = 2.151
  10. Swift GRB 250129A: Global MASTER-Net observations report
  11. Fermi GRB 250128B: Global MASTER-Net observations report
  12. GRB 250128B: Fermi GBM Observation
  13. GRB 250128B: GOTO optical upper limit
  14. Swift GRB 250128B: Global MASTER-Net observations report
  15. EP250125a: Upper limits from Swift/BAT-GUANO
  16. GRB 250128B: LCO optical observations
  17. GRB 250127A: Swift-XRT observations
  18. GRB 250127B: DDOTI Upper Limit on the Afterglow
  19. Fermi-LAT Gamma-ray Observations of IceCube-250102A
  20. GRB 250127A: EP-FXT afterglow detection
  21. Fermi GRB 250128A: Global MASTER-Net observations report
  22. GRB 250117A: Fermi GBM Observation
  23. Fermi GRB 250127B: Global MASTER-Net observations report
  24. Fermi-LAT Gamma-ray Observations of IceCube-250101A
  25. GRB 250127A: SVOM/VT upper limit
  26. IPN triangulation of GRB 250119C
  27. GRB 250127A: Swift ToO observations
  28. GRB 250127A: LCO optical upper limit
  29. GRB 241223A: cubesat Avion detection
  30. GRB 250126A: CALET Gamma-Ray Burst Monitor detection
  31. EP250125A: Non-detection from Fermi-GBM Observations
  32. GRB 250126A: MAXI/GSC detection
  33. EP250108a / SN 2025kg: Refined Analysis of EP-WXT Detection
  34. GECAM-A detection of a bright burst from SGR 1E1841-045
  35. GRB 250118A: Fermi GBM Observation
  36. EP250125a: Optical upper limit with Kinder observations
  37. EP250125a: REM optical counterpart detection
  38. GRB 250119C: Fermi GBM Observation
  39. EP250125a: Swift/XRT detection of a fading counterpart
  40. EP250125a: a new X-ray transient detected by Einstein Probe
  41. Konus-Wind detection of a bright burst from SGR 1E1841-045 on 2025 January 23
  42. GRB 250121A: Swift/BAT-GUANO localization skymap of a burst
  43. IPN triangulation of a bright burst from SGR 1E1841-045
  44. GRB 250121A: CALET Gamma-Ray Burst Monitor detection
  45. EP250108a: AbAO, CMO and Terskol optical upper limits
  46. Konus-Wind detection of GRB 250118B
  47. GRB 250121A: Fermi GBM Observation
  48. IPN triangulation of GRB 250118B
  49. Konus-Wind detection of GRB 250119B
  50. IPN triangulation of GRB 250119B
  51. Improved IPN triangulation of GRB 250107C
  52. GRB 250114A: Swift-BAT refined analysis
  53. GRB 250121A: INTEGRAL/SPI-ACS detection
  54. GRB 250121A: Fermi-LAT detection
  55. GRB 250119C: Swift/BAT-GUANO localization skymap of a short burst
  56. GRB 250119B: Swift/BAT-GUANO localization skymap of a long burst
  57. Fermi-LAT Gamma-ray Observations of IceCube-241224A
  58. GRB 250118A: Swift/BAT-GUANO localization skymap of a short burst
  59. GRB 250119B: Fermi GBM Observation
  60. EP250108a/AT2025kg: 1.3m DFOT Optical observations
  61. Konus-Wind detection of GRB 250117A
  62. IPN triangulation of GRB 250117A (short)
  63. ATCA detection of possible radio counterpart to GRB 250114A
  64. EP250108a / SN2025kg: Non-detection from ATCA radio follow-up observations
  65. GRB 250119B: INTEGRAL/SPI-ACS detection
  66. LIGO/Virgo/KAGRA S250119cv: GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  67. EP 250108A: Late-time optical observation by LCO
  68. GRB 250117A: SVOM/GRM observation of a short burst
  69. LIGO/Virgo/KAGRA S250119cv: Updated Sky localization and EM Bright Classification
  70. GRB 250117A: Swift/BAT-GUANO localization skymap of a short burst
  71. EP250108a / SN2025kg: Gemini GMOS-S confirmation of an associated broad-lined SN Ic
  72. LIGO/Virgo/KAGRA S250119cv: Identification of a GW compact binary merger candidate
  73. LIGO/Virgo/KAGRA S250119ag: Updated Sky localization
  74. EP250108a/AT 2025kg: NOT spectroscopy in agreement with SN Ic-BL
  75. EP250108a / AT 2025kg: the kangaroo is hopping, evidence for optical rebrightening
  76. GRB 250117A: GECAM observation of a short burst
  77. LIGO/Virgo/KAGRA S250118dp: Updated Sky localization
  78. LIGO/Virgo/KAGRA S250119ag: Identification of a GW compact binary merger candidate
  79. LIGO/Virgo/KAGRA S250118dp: Identification of a GW compact binary merger candidate
  80. LIGO/Virgo/KAGRA S250118t: Updated Sky localization
  81. LIGO/Virgo/KAGRA S250118az: Identification of a GW compact binary merger candidate
  82. EP250108a / AT2025kg: GMG Optical Observations
  83. LIGO/Virgo/KAGRA S250118t: Identification of a GW compact binary merger candidate
  84. EP250108a / AT2025kg: VLA radio upper limit
  85. Konus-Wind detection of GRB 250116A
  86. GRB 250116A: GECAM-B detection of a long burst
  87. GRB 241217A / EP241217B: radio detection with the VLA
  88. GRB 250116A: INTEGRAL/SPI-ACS and PICsIT detection
  89. GRB 250116A: Fermi-LAT detection
  90. GRB 250114B: Swift-XRT afterglow detection
  91. GRB 250114B: SVOM/VT upper limit
  92. EP250108a: MeerKAT radio upper limit
  93. GRB 250101A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations and rebrightening.
  94. LIGO/Virgo/KAGRA S250114ax: Updated Sky localization
  95. Konus-Wind detection of GRB 250113A
  96. IPN triangulation of GRB 250113A
  97. GRB 250114B: Liverpool Telescope optical upper limit
  98. LIGO/Virgo/KAGRA S250114ax: GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  99. GRB 250114B : MITSuME Akeno optical afterglow candidate detection
  100. GRB 250114A: LCO optical counterpart detection.

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