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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"
  1. GRB 250329A: Fading optical counterpart detection by LCO.
  2. GRB 250328A: SVOM/C-GFT optical upper limit
  3. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  4. GRB 250328A: VLT/HAWK-I near-infrared afterglow candidate
  5. GRB 250329A: VLT/X-shooter redshift z = 2.921
  6. GRB 250329A: SVOM/VT optical counterpart confirmation
  7. GRB 250329A: SVOM detection of a burst
  8. GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
  9. GRB 250327B: J-band observations with WINTER
  10. GRB 250327B: MASTER detection of OT rebrightening
  11. GRB 250327B: LCO optical counterpart detection
  12. GRB 250328A: GWAC-F50A optical upper limit
  13. GRB 250328A: SVOM detection of a burst
  14. FRB 20250316A: FTW optical observations
  15. LIGO/Virgo/KAGRA S250328ae: NED Galaxies in the 4-Update Localization Volume
  16. EP250302a: SPI-ACS/INTEGRAL Upper Limit
  17. GRB 250327B: CrAO and SAO RAS Optical Observations
  18. GRB 250327B: OHP/T193 spectroscopic observations and redshift confirmation
  19. GRB 250327B: further optical observations by LCOGT
  20. EP250315a: Pan-STARRS r and i-band imaging and photometry
  21. GRB 250327b: Liverpool Telescope optical observations
  22. GRB 250322A: GRANDMA/TNOT optical upper limits
  23. LIGO/Virgo/KAGRA S250328ae: Updated Sky localization
  24. GRB 250327A: SVOM/VT upper limits on the XRT position
  25. LIGO/Virgo/KAGRA S250328ae: Identification of a GW compact binary merger candidate
  26. GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  27. GRB 250327B: Las Cumbres optical counterpart detection
  28. GRB 250327B: Swift-XRT detection of the X-ray afterglow
  29. GRB 250327B: 1.6m Mephisto optical observations
  30. GRB 250327B: NOT spectroscopic redshift z = 3.035
  31. GRB 250327A: Swift-XRT refined Analysis
  32. GRB 250327B: GOTO optical counterpart detection
  33. GRB 250327B: SVOM/VT optically bright counterpart
  34. GRB 250327B: SAO RAS optical candidate
  35. GRB 250327B: SVOM detection of a burst
  36. FRB 20250316A: Gemini Imaging and Spectroscopy of the Sub-arcsecond Localization Region of FRB 20250316A
  37. FRB 20250316A: The sub-arcsecond localization of FRB 20250316A using CHIME/FRB Outriggers coincides with reported X-ray counterparts
  38. GRB 250327A: J-band observations with WINTER
  39. GRB 250327A: SVOM/VT optical candidate
  40. FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
  41. GRB 250327A: Fermi GBM observation
  42. Fermi GRB 250327A: Global MASTER-Net observations report
  43. Swift GRB 250327A: Global MASTER-Net observations report
  44. GRB 250327A: DDOTI Optical Observations
  45. GRB 250327A: COLIBRÍ optical upper limit
  46. GRB 250327A: Swift detection of a burst
  47. GRB 250327A: Fermi GBM Final Real-time Localization
  48. Fermi trigger No 764700395: Global MASTER-Net observations report
  49. LIGO/Virgo/KAGRA S250326y: Updated Sky localization
  50. Konus-Wind detection of GRB 250322A (short)
  51. IPN triangulation of GRB 250322B
  52. LIGO/Virgo/KAGRA S250326y: Identification of a GW compact binary merger candidate
  53. EP250321a: Mondy AZT-33IK Continued Optical Observations
  54. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  55. GRB 250322A: third epoch of NOT optical observations
  56. GRB 250322A: Swift-BAT refined analysis
  57. The EP-WXT trigger 01709133021 (designated as EP250324a) is not a real source
  58. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  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. GRB 250322A: Swift/UVOT Upper Limits
  63. EP250324A: COLIBRÍ/DDRAGO Optical Observations
  64. GRB 250322A: VLT/X-shooter redshift confirmation of the putative host galaxy
  65. FRB 250316A: COLIBRÍ/DDRAGO Optical follow up of the X ray source EP J120944.2+585060
  66. GRB 250322B: NuSTAR detection of the prompt emission and regular dips during the burst
  67. GRB 250321B: Swift-XRT observations
  68. GRB 250322A: Swift-XRT refined Analysis
  69. EP250321a: TNOT Observation of Optical Counterpart
  70. FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)
  71. GRB 250322A: Gemini-North redshift of candidate host galaxy
  72. EP250304a: VLT/MUSE spectroscopic observation of its associated supernova SN 2025fhm
  73. SVOM/sb25032302: SVOM detection of a long X-ray transient
  74. GRB 250322A: AstroSat CZTI detection of a short burst
  75. GRB 250322B: AstroSat CZTI detection of a bright long burst
  76. GRB250322A: STEP/T80S optical limits
  77. GRB 250322A: Gemini-South optical observations
  78. GRB 250322A: VLT optical observations
  79. GRB 250322A: VLT near-infrared observations
  80. FRB 250316A: DDOTI Continued Optical Observations
  81. GRB 250322A: NOT optical upper limits
  82. GRB 250322A: Enhanced Swift-XRT position
  83. GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  84. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  85. GRB 250322A: MASTER optical observation
  86. EP250321a: Liverpool Telescope optical follow-up
  87. EP250321a: Mondy AZT-33IK Optical Observations
  88. GRB 250322A: Swift detection of a short burst
  89. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  90. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  91. EP250321a: KAIT optical observations
  92. EP250321A: COLIBRÍ Continuing Optical Observations
  93. GRB 250225B: GECAM-A detection
  94. GRB 250312A: GECAM-A detection
  95. GRB 250321B: Swift ToO observations
  96. EP250321a: WFST optical observations
  97. GRB 250320B: NuSTAR detection of the prompt emission from two broad bursts and preliminary analysis
  98. GRB 250321C: Fermi GBM Final Real-time Localization
  99. GRB 250320A: NuSTAR Detection of the Prompt Emission and Preliminary Results
  100. GRB 250320B: Fermi GBM Observation

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