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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"

24753 results found.

  1. GRB 250320C : SVOM detection of a burst through offline search
  2. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  3. GRB 250330A: VLT/FORS2 Afterglow Detection
  4. GRB20250327B: 45th Parallel Observatory upper limit
  5. GRB 250328A: Swift/UVOT Detection
  6. GRB 250328A: Swift-XRT refined Analysis
  7. Fermi-LAT gamma-ray observations of IceCube-250330A
  8. SVOM/sb25033102 is a false trigger
  9. GRB 250330A: Fermi GBM Observation
  10. GRB 250331C: COLIBRÍ/DDRAGO optical upper limit
  11. GRB 250331B: COLIBRÍ/DDRAGO optical upper limit
  12. GRB 250331C: Swift detection of a burst
  13. GRB 250331B: Swift detection of a burst
  14. GRB 250331A: MAXI/GSC detection
  15. SVOM/sb25033102: SVOM detection of an X-ray transient
  16. LIGO/Virgo/KAGRA S250331o: Identification of a GW compact binary merger candidate
  17. GRB 250330A: Swift/UVOT Upper Limits
  18. GRB 250330A: Swift-XRT afterglow detection
  19. GRB 250328A: 1.6m Mephisto optical observations
  20. GRB 250329B: SVOM/COLIBRÍ (F-GFT) optical upper limit
  21. GRB 250330A: VLT/FORS2 Optical Observations
  22. GRB 250329B: Swift-XRT afterglow detection
  23. GRB 250330A: Swift detection of a burst
  24. GRB 250329B: SVOM/C-GFT optical upper limit
  25. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 1)
  26. GRB 250329B: SVOM/VT optical upper limit
  27. GRB 250327B: SVOM/COLIBRÍ (F-GFT) Further Observations
  28. GRB 250329B: 1.6m Mephisto Optical Upper Limits
  29. LIGO/Virgo/KAGRA S250329fl: 2 counterpart neutrino candidate events from an IceCube neutrino search
  30. GRB250329A: REM optical afterglow detection
  31. GRB 250329A: Swift-XRT afterglow detection
  32. GRB 250328A: SVOM/VT optical observation
  33. GRB 250329A: Fading optical counterpart detection by LCO.
  34. GRB 250328A: SVOM/C-GFT optical upper limit
  35. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  36. GRB 250329A: SVOM/VT optical counterpart confirmation
  37. GRB 250329A: SVOM detection of a burst
  38. GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
  39. GRB 250327B: J-band observations with WINTER
  40. GRB 250327B: LCO optical counterpart detection
  41. GRB 250328A: SVOM detection of a burst
  42. LIGO/Virgo/KAGRA S250328ae: NED Galaxies in the 4-Update Localization Volume
  43. EP250302a: SPI-ACS/INTEGRAL Upper Limit
  44. GRB 250327B: CrAO and SAO RAS Optical Observations
  45. GRB 250327b: Liverpool Telescope optical observations
  46. GRB 250322A: GRANDMA/TNOT optical upper limits
  47. LIGO/Virgo/KAGRA S250328ae: Updated Sky localization
  48. GRB 250327A: SVOM/VT upper limits on the XRT position
  49. LIGO/Virgo/KAGRA S250328ae: Identification of a GW compact binary merger candidate
  50. GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  51. GRB 250327B: Las Cumbres optical counterpart detection
  52. GRB 250327B: Swift-XRT detection of the X-ray afterglow
  53. GRB 250327B: 1.6m Mephisto optical observations
  54. GRB 250327A: Swift-XRT refined Analysis
  55. GRB 250327B: SVOM/VT optically bright counterpart
  56. GRB 250327B: SAO RAS optical candidate
  57. GRB 250327B: SVOM detection of a burst
  58. FRB 20250316A: Gemini Imaging and Spectroscopy of the Sub-arcsecond Localization Region of FRB 20250316A
  59. FRB 20250316A: The sub-arcsecond localization of FRB 20250316A using CHIME/FRB Outriggers coincides with reported X-ray counterparts
  60. GRB 250327A: J-band observations with WINTER
  61. GRB 250327A: SVOM/VT optical candidate
  62. FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
  63. GRB 250327A: DDOTI Optical Observations
  64. GRB 250327A: COLIBRÍ optical upper limit
  65. LIGO/Virgo/KAGRA S250326y: Updated Sky localization
  66. IPN triangulation of GRB 250322B
  67. LIGO/Virgo/KAGRA S250326y: Identification of a GW compact binary merger candidate
  68. EP250321a: Mondy AZT-33IK Continued Optical Observations
  69. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  70. GRB 250322A: third epoch of NOT optical observations
  71. GRB 250322A: Swift-BAT refined analysis
  72. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  73. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  74. GRB 250322A: further NOT optical observations
  75. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  76. GRB 250322A: Swift/UVOT Upper Limits
  77. EP250324A: COLIBRÍ/DDRAGO Optical Observations
  78. FRB 250316A: COLIBRÍ/DDRAGO Optical follow up of the X ray source EP J120944.2+585060
  79. GRB 250322B: NuSTAR detection of the prompt emission and regular dips during the burst
  80. GRB 250321B: Swift-XRT observations
  81. GRB 250322A: Swift-XRT refined Analysis
  82. EP250321a: TNOT Observation of Optical Counterpart
  83. FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)
  84. SVOM/sb25032302: SVOM detection of a long X-ray transient
  85. GRB 250322B: AstroSat CZTI detection of a bright long burst
  86. GRB 250322A: VLT optical observations
  87. GRB 250322A: VLT near-infrared observations
  88. FRB 250316A: DDOTI Continued Optical Observations
  89. GRB 250322A: NOT optical upper limits
  90. GRB 250322A: Enhanced Swift-XRT position
  91. GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  92. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  93. EP250321a: Liverpool Telescope optical follow-up
  94. EP250321a: Mondy AZT-33IK Optical Observations
  95. GRB 250322A: Swift detection of a short burst
  96. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  97. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  98. EP250321A: COLIBRÍ Continuing Optical Observations
  99. EP250321a: WFST optical observations
  100. GRB 250320B: NuSTAR detection of the prompt emission from two broad bursts and preliminary analysis

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