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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"

23576 results found.

  1. GRB 250330A: Swift detection of a burst
  2. GRB 250328A: A fading optical afterglow confirmed by SVOM/VT
  3. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 1)
  4. GRB 250329B: 1.6m Mephisto Optical Upper Limits
  5. LIGO/Virgo/KAGRA S250329fl: 2 counterpart neutrino candidate events from an IceCube neutrino search
  6. GRB250329A: REM optical afterglow detection
  7. GRB 250329B: GWAC-F50A optical upper limit
  8. GRB 250329B: SVOM detection of a faint transient
  9. GRB 250329A: Swift-XRT afterglow detection
  10. GRB 250328A: SVOM/VT optical observation
  11. GRB 250329A: Fading optical counterpart detection by LCO.
  12. GRB 250328A: SVOM/C-GFT optical upper limit
  13. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  14. GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
  15. GRB 250327B: J-band observations with WINTER
  16. GRB 250327B: LCO optical counterpart detection
  17. GRB 250328A: GWAC-F50A optical upper limit
  18. GRB 250328A: SVOM detection of a burst
  19. LIGO/Virgo/KAGRA S250328ae: NED Galaxies in the 4-Update Localization Volume
  20. EP250302a: SPI-ACS/INTEGRAL Upper Limit
  21. GRB 250327B: OHP/T193 spectroscopic observations and redshift confirmation
  22. GRB 250327B: further optical observations by LCOGT
  23. EP250315a: Pan-STARRS r and i-band imaging and photometry
  24. GRB 250322A: GRANDMA/TNOT optical upper limits
  25. LIGO/Virgo/KAGRA S250328ae: Identification of a GW compact binary merger candidate
  26. GRB 250327B: Las Cumbres optical counterpart detection
  27. GRB 250327B: 1.6m Mephisto optical observations
  28. GRB 250327A: Swift-XRT refined Analysis
  29. GRB 250327B: GOTO optical counterpart detection
  30. GRB 250327B: SAO RAS optical candidate
  31. FRB 20250316A: Gemini Imaging and Spectroscopy of the Sub-arcsecond Localization Region of FRB 20250316A
  32. FRB 20250316A: The sub-arcsecond localization of FRB 20250316A using CHIME/FRB Outriggers coincides with reported X-ray counterparts
  33. GRB 250327A: J-band observations with WINTER
  34. FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
  35. Swift GRB 250327A: Global MASTER-Net observations report
  36. GRB 250327A: DDOTI Optical Observations
  37. GRB 250327A: Swift detection of a burst
  38. Konus-Wind detection of GRB 250322A (short)
  39. LIGO/Virgo/KAGRA S250326y: Identification of a GW compact binary merger candidate
  40. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  41. GRB 250322A: third epoch of NOT optical observations
  42. GRB 250322A: Swift-BAT refined analysis
  43. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  44. GRB 250322A: further NOT optical observations
  45. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  46. GRB 250321B: Swift-XRT observations
  47. GRB 250322A: Swift-XRT refined Analysis
  48. FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)
  49. GRB 250322A: AstroSat CZTI detection of a short burst
  50. GRB 250322B: AstroSat CZTI detection of a bright long burst
  51. GRB250322A: STEP/T80S optical limits
  52. FRB 250316A: DDOTI Continued Optical Observations
  53. GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  54. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  55. GRB 250322A: Swift detection of a short burst
  56. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  57. EP250321a: KAIT optical observations
  58. EP250321A: COLIBRÍ Continuing Optical Observations
  59. GRB 250225B: GECAM-A detection
  60. EP250321a: Xinglong 216 decaying optical observations
  61. GRB 250321A: Swift-BAT refined analysis
  62. GRB 250321A: Swift-XRT refined Analysis
  63. GRB 250320B: Fermi-LAT detection
  64. GRB 250321B: SVOM detection of a sub-threshold transient event
  65. EP 250321A: Optical counterpart detection by LCO.
  66. EP250321a: Kinder optical follow-up observations
  67. EP250321a: LCO optical counterpart detection
  68. EP250321A: COLIBRÍ Optical Observations
  69. EP250321a: REM optical/NIR afterglow detection
  70. EP250321a: BOOTES-5/JGT optical afterglow detection
  71. EP250321a: TRT optical counterpart detection
  72. Fermi GRB 250321A: Global MASTER-Net observations report
  73. GRB 250321A: GOTO optical upper limits
  74. GRB 250314A: Keck/NIRC2 J-band upper limit
  75. EP250226a/GRB 250226A: KAIT optical observations
  76. GRB 250321A: Fermi GBM Observation
  77. GRB 250321A: Swift detection of a burst
  78. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  79. GRB 250313A: GRBAlpha detection
  80. GRB 250317D: EIRSAT-1 GMOD Detection
  81. GRB 250317B: OHP/T193 continued follow-up
  82. GRB 250317C: AstroSat CZTI detection
  83. GRB 250317B: OHP/T193 optical observations
  84. GRB250312A: Swift/UVOT Upper Limits
  85. GRB 250317B: REM optical/NIR observations
  86. GRB 250316A: Swift/UVOT Upper Limits
  87. GRB 250314A: REM optical/NIR upper limits
  88. EP 250317B: Fading optical counterpart detection by LCO
  89. GRB 250316A: Swift-XRT afterglow detection
  90. GRB 250317B: LCO detection of the fading optical afterglow
  91. GRB 250317B: refined SVOM/MXT analysis
  92. GRB 250317B: SVOM/F-GFT (COLIBRÍ) Detection of a Fading Optical Counterpart
  93. GRB 250316A: Swift-XRT observations
  94. The EP-WXT trigger 01709132801 is likely a flaring star
  95. GRB 250315A/EP250315A: Fermi-GBM Sub-Threshold Detection
  96. EP250315a: refined analysis of the EP-WXT and EP-FXT observations
  97. GRB 250314A: Swift/UVOT Upper Limits
  98. GRB 250312B: GRBAlpha detection
  99. EP250315a: optical counterpart candidate detected by Gemini North
  100. EP250315a: Einstein Probe detection of an X-ray transient

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