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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').
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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.

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subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

31730 results found.

  1. GRB 250327B: OHP/T193 spectroscopic observations and redshift confirmation
  2. GRB 250327B: further optical observations by LCOGT
  3. EP250315a: Pan-STARRS r and i-band imaging and photometry
  4. GRB 250327b: Liverpool Telescope optical observations
  5. GRB 250322A: GRANDMA/TNOT optical upper limits
  6. LIGO/Virgo/KAGRA S250328ae: Updated Sky localization
  7. GRB 250327A: SVOM/VT upper limits on the XRT position
  8. LIGO/Virgo/KAGRA S250328ae: Identification of a GW compact binary merger candidate
  9. GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  10. GRB 250327B: Las Cumbres optical counterpart detection
  11. GRB 250327B: Swift-XRT detection of the X-ray afterglow
  12. GRB 250327B: 1.6m Mephisto optical observations
  13. GRB 250327B: NOT spectroscopic redshift z = 3.035
  14. GRB 250327B: GOTO optical counterpart detection
  15. GRB 250327B: SVOM/VT optically bright counterpart
  16. GRB 250327B: SAO RAS optical candidate
  17. FRB 20250316A: Gemini Imaging and Spectroscopy of the Sub-arcsecond Localization Region of FRB 20250316A
  18. GRB 250327A: J-band observations with WINTER
  19. GRB 250327A: SVOM/VT optical candidate
  20. FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
  21. GRB 250327A: Fermi GBM observation
  22. Fermi GRB 250327A: Global MASTER-Net observations report
  23. Swift GRB 250327A: Global MASTER-Net observations report
  24. GRB 250327A: DDOTI Optical Observations
  25. GRB 250327A: COLIBRÍ optical upper limit
  26. GRB 250327A: Swift detection of a burst
  27. LIGO/Virgo/KAGRA S250326y: Updated Sky localization
  28. Konus-Wind detection of GRB 250322A (short)
  29. IPN triangulation of GRB 250322B
  30. LIGO/Virgo/KAGRA S250326y: Identification of a GW compact binary merger candidate
  31. EP250321a: Mondy AZT-33IK Continued Optical Observations
  32. GRB 250322A: third epoch of NOT optical observations
  33. GRB 250322A: Swift-BAT refined analysis
  34. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  35. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  36. GRB 250322A: further NOT optical observations
  37. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  38. GRB 250322A: Swift/UVOT Upper Limits
  39. GRB 250322A: VLT/X-shooter redshift confirmation of the putative host galaxy
  40. FRB 250316A: COLIBRÍ/DDRAGO Optical follow up of the X ray source EP J120944.2+585060
  41. GRB 250322B: NuSTAR detection of the prompt emission and regular dips during the burst
  42. EP250321a: TNOT Observation of Optical Counterpart
  43. FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)
  44. GRB 250322A: Gemini-North redshift of candidate host galaxy
  45. EP250304a: VLT/MUSE spectroscopic observation of its associated supernova SN 2025fhm
  46. GRB 250322A: AstroSat CZTI detection of a short burst
  47. GRB250322A: STEP/T80S optical limits
  48. GRB 250322A: Gemini-South optical observations
  49. GRB 250322A: VLT optical observations
  50. GRB 250322A: VLT near-infrared observations
  51. FRB 250316A: DDOTI Continued Optical Observations
  52. GRB 250322A: NOT optical upper limits
  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: MASTER optical observation
  56. EP250321a: Liverpool Telescope optical follow-up
  57. EP250321a: Mondy AZT-33IK Optical Observations
  58. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  59. EP250321a: KAIT optical observations
  60. EP250321A: COLIBRÍ Continuing Optical Observations
  61. GRB 250225B: GECAM-A detection
  62. GRB 250312A: GECAM-A detection
  63. GRB 250321B: Swift ToO observations
  64. EP250321a: WFST optical observations
  65. GRB 250320B: NuSTAR detection of the prompt emission from two broad bursts and preliminary analysis
  66. GRB 250320A: NuSTAR Detection of the Prompt Emission and Preliminary Results
  67. GRB 250320B: Fermi GBM Observation
  68. EP250321a: Xinglong 216 decaying optical observations
  69. GRB 250321A: Swift-BAT refined analysis
  70. GRB 250320B: Fermi-LAT detection
  71. EP250321a: SVOM/VT optical observation
  72. EP 250321A: Optical counterpart detection by LCO.
  73. EP250321a: Kinder optical follow-up observations
  74. GRB 250321A: Swift/UVOT Upper Limits
  75. GRB 250320B: SVOM/GRM observation of a long burst
  76. EP250321a: LCO optical counterpart detection
  77. EP250321a: Swift-XRT detection of an X-ray source
  78. EP250321A: COLIBRÍ Optical Observations
  79. EP250321a: VLT/X-shooter redshift z = 4.368
  80. GRB 250320B: AstroSat CZTI detection
  81. EP250321a: REM optical/NIR afterglow detection
  82. Fermi GRB 250320B: Global MASTER-Net observations report
  83. EP250321a: TRT optical counterpart detection
  84. EP250321a: Global MASTER-Net observations report
  85. Swift GRB 250321A: Global MASTER-Net observations report
  86. Fermi GRB 250321A: Global MASTER-Net observations report
  87. GRB 250321A: GOTO optical upper limits
  88. GRB 250321A: Swift-XRT localisation
  89. GRB 250314A: Keck/NIRC2 J-band upper limit
  90. EP250226a/GRB 250226A: KAIT optical observations
  91. GRB 250321A: Fermi GBM Observation
  92. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  93. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  94. Fermi GRB 250319B: Global MASTER-Net observations report
  95. GRB 250313A: GRBAlpha detection
  96. LIGO/Virgo/KAGRA S250206dm: LIGHETR followup observations of AT2025azn
  97. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  98. LIGO/Virgo/KAGRA S250319bu: Updated Sky localization
  99. GRB 250314A: ATCA radio upper limits
  100. EP250302a: VLA observations

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