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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"

45444 results found.

  1. GRB 250127A: CrAO and Terskol optical upper limits
  2. GRB 250129A: Enhanced Swift-XRT position
  3. GRB 250128B: NOT optical upper limit
  4. GRB 250128B: VLT/FORS2 optical observations
  5. GRB 250129A: REM optical/NIR afterglow detection
  6. GRB 250129A: OHP/T193 optical and spectroscopy observations
  7. GRB 250129A: Early afterglow detection by LCO.
  8. GRB 250128B: OHP/T193 optical upper limit
  9. Swift GRB 250129A: Global MASTER-Net Slowly evolving LC detection
  10. GRB 250129A: LCO optical observations
  11. GRB 250129A: NOT optical observations and redshift confirmation
  12. GRB 250129A: GOTO optical observations show brightening afterglow
  13. GRB 250129A: VLT/X-shooter redshift of z = 2.151
  14. Swift GRB 250129A: Global MASTER-Net observations report
  15. GRB 250128B: Enhanced Swift-XRT position
  16. The EP-WXT trigger 01709131085 is likely a flaring star
  17. Fermi GRB 250128B: Global MASTER-Net observations report
  18. GRB 250129A: Swift detection of a burst with an optical counterpart
  19. Swift GRB 250129A: Global MASTER-Net OT detection
  20. GRB 250128B: Swift-XRT refined Analysis
  21. GRB 250128B: Fermi GBM Observation
  22. GRB 250128B: GOTO optical upper limit
  23. Swift GRB 250128B: Global MASTER-Net observations report
  24. EP250125a: Upper limits from Swift/BAT-GUANO
  25. GRB 250128B: LCO optical observations
  26. GRB 250128B: Swift detection of a short burst
  27. GRB 250128B: Fermi GBM Final Real-time Localization
  28. GRB 250127A: Swift-XRT observations
  29. GRB 250127B: DDOTI Upper Limit on the Afterglow
  30. Fermi-LAT Gamma-ray Observations of IceCube-250102A
  31. GRB 250127A: EP-FXT afterglow detection
  32. Fermi GRB 250128A: Global MASTER-Net observations report
  33. GRB 250128A: Fermi GBM Final Real-time Localization
  34. GRB 250117A: Fermi GBM Observation
  35. Fermi GRB 250127B: Global MASTER-Net observations report
  36. Fermi-LAT Gamma-ray Observations of IceCube-250101A
  37. GRB 250127A: SVOM/VT upper limit
  38. GRB 250127B: Fermi GBM Final Real-time Localization
  39. IPN triangulation of GRB 250119C
  40. GRB 250127A: Swift ToO observations
  41. GRB 250127A: LCO optical upper limit
  42. GRB 241223A: cubesat Avion detection
  43. GRB 250127A: SVOM detection of a long burst
  44. GRB 250126A: CALET Gamma-Ray Burst Monitor detection
  45. EP250125A: Non-detection from Fermi-GBM Observations
  46. GRB 250126A: MAXI/GSC detection
  47. EP250108a / SN 2025kg: Refined Analysis of EP-WXT Detection
  48. GRB 250126A: BALROG localization (Fermi Trigger 759560335 / GRB 250126208)
  49. GRB 250126A: Fermi GBM Final Real-time Localization
  50. GECAM-A detection of a bright burst from SGR 1E1841-045
  51. GRB 250118A: Fermi GBM Observation
  52. EP250125a: Optical upper limit with Kinder observations
  53. EP250125a: REM optical counterpart detection
  54. GRB 250119C: Fermi GBM Observation
  55. EP250125a: Swift/XRT detection of a fading counterpart
  56. EP250125a: a new X-ray transient detected by Einstein Probe
  57. EP250125a: Gemini-South optical afterglow discovery and redshift z = 2.89
  58. The EP-WXT trigger 01709130758 is a false trigger
  59. The EP-WXT trigger 01709130758 is a false trigger
  60. Konus-Wind detection of a bright burst from SGR 1E1841-045 on 2025 January 23
  61. GRB 250121A: Swift/BAT-GUANO localization skymap of a burst
  62. IPN triangulation of a bright burst from SGR 1E1841-045
  63. GRB 250121A: CALET Gamma-Ray Burst Monitor detection
  64. EP250108a: AbAO, CMO and Terskol optical upper limits
  65. Konus-Wind detection of GRB 250118B
  66. GRB 250121A: Fermi GBM Observation
  67. IPN triangulation of GRB 250118B
  68. Konus-Wind detection of GRB 250119B
  69. IPN triangulation of GRB 250119B
  70. GRB 250122A: Fermi GBM Final Real-time Localization
  71. Improved IPN triangulation of GRB 250107C
  72. GRB 250114A: Swift-BAT refined analysis
  73. GRB 250121A: INTEGRAL/SPI-ACS detection
  74. GRB 250121A: Fermi-LAT detection
  75. LIGO/Virgo S250119cv: Swift XRT observations, 5 X-ray sources
  76. GRB 250119C: Swift/BAT-GUANO localization skymap of a short burst
  77. GRB 250119B: Swift/BAT-GUANO localization skymap of a long burst
  78. GRB 250121A: Fermi GBM Final Real-time Localization
  79. Fermi-LAT Gamma-ray Observations of IceCube-241224A
  80. GRB 250118A: Swift/BAT-GUANO localization skymap of a short burst
  81. GRB 250119B: Fermi GBM Observation
  82. EP250108a/AT2025kg: 1.3m DFOT Optical observations
  83. Konus-Wind detection of GRB 250117A
  84. IPN triangulation of GRB 250117A (short)
  85. ATCA detection of possible radio counterpart to GRB 250114A
  86. EP250108a / SN2025kg: Non-detection from ATCA radio follow-up observations
  87. GRB 250119B: INTEGRAL/SPI-ACS detection
  88. LIGO/Virgo/KAGRA S250119cv: GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  89. EP 250108A: Late-time optical observation by LCO
  90. GRB 250117A: SVOM/GRM observation of a short burst
  91. LIGO/Virgo/KAGRA S250105bn: 1 counterpart neutrino candidate event from an IceCube neutrino search
  92. LIGO/Virgo/KAGRA S250119cv: Updated NED Galaxies in the Localization Volume
  93. LIGO/Virgo/KAGRA S250119cv: Updated Sky localization and EM Bright Classification
  94. GRB 250119C: Fermi GBM Final Real-time Localization
  95. LIGO/Virgo/KAGRA S250119cv: NED Galaxies in the Localization Volume
  96. GRB 250117A: Swift/BAT-GUANO localization skymap of a short burst
  97. EP250108a / SN2025kg: Gemini GMOS-S confirmation of an associated broad-lined SN Ic
  98. LIGO/Virgo/KAGRA S250119cv: Identification of a GW compact binary merger candidate
  99. LIGO/Virgo/KAGRA S250119ag: Updated Sky localization
  100. EP250108a/AT 2025kg: NOT spectroscopy in agreement with SN Ic-BL

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