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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"

24381 results found.

  1. LIGO/Virgo/KAGRA S250331o: Identification of a GW compact binary merger candidate
  2. Fermi GRB 250330B: Global MASTER-Net observations report
  3. GRB 250330B: Fermi GBM Final Real-time Localization
  4. Fermi GRB 250330A: Global MASTER-Net observations report
  5. GRB 250330A: BOOTES-7 early optical upper limit
  6. GRB 250328A: 1.6m Mephisto optical observations
  7. GRB 250329B: SVOM/COLIBRÍ (F-GFT) optical upper limit
  8. GRB 250330A: Fermi GBM Final Localization
  9. IceCube-250330A - IceCube observation of a high-energy neutrino candidate track-like event
  10. IceCube Alert 250330.35: Global MASTER-Net observations report
  11. GRB 250330A: Prompt Swift-XRT position
  12. GRB 250329B: Swift-XRT afterglow detection
  13. GRB 250330A: Swift detection of a burst
  14. Swift GRB250330.26: Global MASTER-Net observations report
  15. GRB 250328A: A fading optical afterglow confirmed by SVOM/VT
  16. GRB 250329B: SVOM/C-GFT optical upper limit
  17. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 1)
  18. GRB 250329B: SVOM/VT optical upper limit
  19. GRB 250329B: 1.6m Mephisto Optical Upper Limits
  20. LIGO/Virgo/KAGRA S250329fl: 2 counterpart neutrino candidate events from an IceCube neutrino search
  21. GRB250329A: REM optical afterglow detection
  22. GRB 250329B: GWAC-F50A optical upper limit
  23. GRB 250329B: SVOM detection of a faint transient
  24. GRB 250328A: SVOM/VT optical observation
  25. GRB 250329A: VLT/X-shooter redshift z = 2.921
  26. GRB 250329A: SVOM/VT optical counterpart confirmation
  27. GRB 250329A: SVOM detection of a burst
  28. GRB 250327B: MASTER detection of OT rebrightening
  29. GRB 250327B: LCO optical counterpart detection
  30. GRB 250328A: GWAC-F50A optical upper limit
  31. GRB 250328A: SVOM detection of a burst
  32. FRB 20250316A: FTW optical observations
  33. LIGO/Virgo/KAGRA S250328ae: NED Galaxies in the 4-Update Localization Volume
  34. LIGO/Virgo/KAGRA S250328ae: Updated Sky localization
  35. LIGO/Virgo/KAGRA S250328ae: Identification of a GW compact binary merger candidate
  36. GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  37. GRB 250327B: 1.6m Mephisto optical observations
  38. GRB 250327B: GOTO optical counterpart detection
  39. GRB 250327B: SVOM/VT optically bright counterpart
  40. GRB 250327B: SVOM detection of a burst
  41. FRB 20250316A: Gemini Imaging and Spectroscopy of the Sub-arcsecond Localization Region of FRB 20250316A
  42. FRB 20250316A: The sub-arcsecond localization of FRB 20250316A using CHIME/FRB Outriggers coincides with reported X-ray counterparts
  43. GRB 250327A: J-band observations with WINTER
  44. GRB 250327A: SVOM/VT optical candidate
  45. GRB 250327A: Fermi GBM observation
  46. Fermi GRB 250327A: Global MASTER-Net observations report
  47. Swift GRB 250327A: Global MASTER-Net observations report
  48. GRB 250327A: COLIBRÍ optical upper limit
  49. GRB 250327A: Fermi GBM Final Real-time Localization
  50. Fermi trigger No 764700395: Global MASTER-Net observations report
  51. LIGO/Virgo/KAGRA S250326y: Updated Sky localization
  52. Konus-Wind detection of GRB 250322A (short)
  53. IPN triangulation of GRB 250322B
  54. LIGO/Virgo/KAGRA S250326y: Identification of a GW compact binary merger candidate
  55. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  56. GRB 250322A: third epoch of NOT optical observations
  57. GRB 250322A: Swift-BAT refined analysis
  58. The EP-WXT trigger 01709133021 (designated as EP250324a) is not a real source
  59. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  60. GRB 250322A: further NOT optical observations
  61. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  62. EP250324A: COLIBRÍ/DDRAGO Optical Observations
  63. GRB 250322A: VLT/X-shooter redshift confirmation of the putative host galaxy
  64. EP250321a: TNOT Observation of Optical Counterpart
  65. GRB 250322A: Gemini-North redshift of candidate host galaxy
  66. SVOM/sb25032302: SVOM detection of a long X-ray transient
  67. GRB 250322A: Gemini-South optical observations
  68. GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  69. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  70. GRB 250322A: MASTER optical observation
  71. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  72. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  73. GRB 250320B: NuSTAR detection of the prompt emission from two broad bursts and preliminary analysis
  74. GRB 250321C: Fermi GBM Final Real-time Localization
  75. GRB 250320A: NuSTAR Detection of the Prompt Emission and Preliminary Results
  76. GRB 250320B: Fermi GBM Observation
  77. EP250321a: Xinglong 216 decaying optical observations
  78. GRB 250321A: Swift-BAT refined analysis
  79. GRB 250320B: Fermi-LAT detection
  80. GRB 250321B: SVOM detection of a sub-threshold transient event
  81. EP250321a: SVOM/VT optical observation
  82. EP250321A: COLIBRÍ Optical Observations
  83. EP250321a: VLT/X-shooter redshift z = 4.368
  84. EP250321a: REM optical/NIR afterglow detection
  85. Fermi GRB 250320B: Global MASTER-Net observations report
  86. EP250321a: Global MASTER-Net observations report
  87. Swift GRB 250321A: Global MASTER-Net observations report
  88. Fermi GRB 250321A: Global MASTER-Net observations report
  89. EP250226a/GRB 250226A: KAIT optical observations
  90. GRB 250321A: Fermi GBM Observation
  91. GRB 250321A: Swift detection of a burst
  92. GRB 250321A: Fermi GBM Final Real-time Localization
  93. GRB 250320B: Fermi GBM Final Real-time Localization
  94. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  95. GRB 250320A: Fermi GBM Final Real-time Localization
  96. Fermi GRB 250319B: Global MASTER-Net observations report
  97. FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations
  98. GRB 250313A: GRBAlpha detection
  99. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  100. GRB 250319B: Fermi GBM Final Localization

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