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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"

19824 results found.

  1. GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
  2. GRB 250327B: J-band observations with WINTER
  3. GRB 250327B: LCO optical counterpart detection
  4. LIGO/Virgo/KAGRA S250328ae: NED Galaxies in the 4-Update Localization Volume
  5. EP250302a: SPI-ACS/INTEGRAL Upper Limit
  6. GRB 250327B: CrAO and SAO RAS Optical Observations
  7. EP250315a: Pan-STARRS r and i-band imaging and photometry
  8. GRB 250327b: Liverpool Telescope optical observations
  9. GRB 250322A: GRANDMA/TNOT optical upper limits
  10. GRB 250327A: SVOM/VT upper limits on the XRT position
  11. LIGO/Virgo/KAGRA S250328ae: Identification of a GW compact binary merger candidate
  12. GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  13. GRB 250327B: Las Cumbres optical counterpart detection
  14. GRB 250327B: 1.6m Mephisto optical observations
  15. GRB 250327B: NOT spectroscopic redshift z = 3.035
  16. GRB 250327B: SVOM/VT optically bright counterpart
  17. GRB 250327B: SAO RAS optical candidate
  18. GRB 250327B: SVOM detection of a burst
  19. GRB 250327A: J-band observations with WINTER
  20. GRB 250327A: SVOM/VT optical candidate
  21. FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
  22. GRB 250327A: DDOTI Optical Observations
  23. GRB 250327A: COLIBRÍ optical upper limit
  24. IPN triangulation of GRB 250322B
  25. LIGO/Virgo/KAGRA S250326y: Identification of a GW compact binary merger candidate
  26. EP250321a: Mondy AZT-33IK Continued Optical Observations
  27. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  28. GRB 250322A: third epoch of NOT optical observations
  29. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  30. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  31. GRB 250322A: further NOT optical observations
  32. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  33. GRB 250322A: Swift/UVOT Upper Limits
  34. EP250324A: COLIBRÍ/DDRAGO Optical Observations
  35. FRB 250316A: COLIBRÍ/DDRAGO Optical follow up of the X ray source EP J120944.2+585060
  36. GRB 250321B: Swift-XRT observations
  37. EP250321a: TNOT Observation of Optical Counterpart
  38. FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)
  39. GRB 250322A: VLT optical observations
  40. GRB 250322A: VLT near-infrared observations
  41. FRB 250316A: DDOTI Continued Optical Observations
  42. GRB 250322A: NOT optical upper limits
  43. GRB 250322A: Enhanced Swift-XRT position
  44. GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  45. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  46. EP250321a: Liverpool Telescope optical follow-up
  47. EP250321a: Mondy AZT-33IK Optical Observations
  48. GRB 250322A: Swift detection of a short burst
  49. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  50. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  51. EP250321a: KAIT optical observations
  52. EP250321A: COLIBRÍ Continuing Optical Observations
  53. EP250321a: WFST optical observations
  54. EP250321a: Xinglong 216 decaying optical observations
  55. GRB 250321A: Swift-XRT refined Analysis
  56. EP 250321A: Optical counterpart detection by LCO.
  57. EP250321a: Kinder optical follow-up observations
  58. GRB 250321A: Swift/UVOT Upper Limits
  59. GRB 250320B: SVOM/GRM observation of a long burst
  60. EP250321a: LCO optical counterpart detection
  61. EP250321A: COLIBRÍ Optical Observations
  62. GRB 250320B: AstroSat CZTI detection
  63. EP250321a: REM optical/NIR afterglow detection
  64. EP250321a: TRT optical counterpart detection
  65. EP250321a: Einstein Probe detection of an X-ray transient
  66. GRB 250321A: GOTO optical upper limits
  67. GRB 250314A: Keck/NIRC2 J-band upper limit
  68. EP250226a/GRB 250226A: KAIT optical observations
  69. GRB 250321A: Swift detection of a burst
  70. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  71. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  72. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  73. EP250302a: VLA observations
  74. LIGO/Virgo/KAGRA S250319bu: Identification of a GW compact binary merger candidate
  75. GRB 250317C: SVOM/GRM observation of a long burst
  76. GRB 250317B: Leavitt Observatory optical upper limit
  77. GRB 250317B: Mondy AZT-33IK Optical Observations
  78. GRB 250317B: NOT optical observations suggest an optical plateau phase
  79. GRB 250317B: OHP/T193 optical observations
  80. GRB250312A: Swift/UVOT Upper Limits
  81. GRB 250317B: REM optical/NIR observations
  82. GRB 250316A: Swift/UVOT Upper Limits
  83. GRB 250314A: REM optical/NIR upper limits
  84. GRB 250316A: AbAO AS-32 Optical Upper Limit
  85. EP 250317B: Fading optical counterpart detection by LCO
  86. GRB 250316A: Swift-XRT afterglow detection
  87. GRB 250317B: LCO detection of the fading optical afterglow
  88. GRB 250317B: SVOM/VT detection of an optical candidate from VHF data
  89. GRB 250317B: SVOM/F-GFT (COLIBRÍ) Detection of a Fading Optical Counterpart
  90. GRB 250317B: SVOM detection of a burst / correction to GRB name of GCN 39752
  91. GRB 250317B: SVOM detection of a burst
  92. EP250315a: refined analysis of the EP-WXT and EP-FXT observations
  93. GRB 250314A: Swift/UVOT Upper Limits
  94. GRB 250314A: Swift XRT Detection
  95. EP250315a: optical counterpart candidate detected by Gemini North
  96. GRB 250314A: VLT/X-shooter dropout, redshift z ~ 7.3
  97. EP250315a: Einstein Probe detection of an X-ray transient
  98. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  99. SVOM/MXT upper limit on GRB 250314A
  100. GRB 250314A: SVOM/VT upper limit

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