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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"

23575 results found.

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

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