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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"

116 results found.

  1. EP250702a/ GRB 250702B: NuSTAR X-ray Observations
  2. Radio observation of GRBs 250702B,C,E / EP250702a with the Allen Telescope Array
  3. GRB 250215A / EP250215A: Encouraging Follow-up Observations of a BdHN I with a Rest-Frame Duration 2.3 s at z=4.61
  4. GRB 221009A: Late-time JWST Observations and Detection of Supernova Emission
  5. GRB 230307A: INTEGRAL upper limit on Hard X-ray afterglow
  6. GRB 230307A: Swift/BAT upper limits on the early afterglow
  7. Konus-Wind detection of GRB 230307A
  8. GRB 230307A: possibly the second highest GRB energy fluence ever identified
  9. GRB 221009A: Continued Swift Observations
  10. GRB 221009A: radio afterglow detection with the EVN
  11. GRB 221009A: MuSCAT3 observations
  12. Optical polarization observation of GRB 221009A
  13. GRB 221009A：DAMPE observed a 34.7 GeV photon at 1.36 hour after the GBM trigger
  14. GRB 221009A: Japanese VLBI Network observation
  15. Correction to GCN 32646 (GRB 221009A (Swift J1913.1+1946): MeerLICHT observations)
  16. GRB 221009A: GRANDMA/Kilonova-Catcher observations
  17. GRB 221009A: Hubble Space Telescope observations
  18. GRB 221009A: Extended Bad Time Intervals for Fermi LAT data
  19. Correction to GCN 32852 (GRB 221009A: SARA-RM 1m Optical Afterglow Detection)
  20. LIGO-Virgo-KAGRA and GEO600 statement on GRB 221009A
  21. GRB 221009A: Further Gemini-South Infrared Observations
  22. GRB 221009A: SARA-RM 1m Optical Afterglow Detection
  23. GRB 221009A: spectroscopic confirmation of SN in LBT spectra
  24. GRB 221009A: Determination of the black holes mass and spin
  25. GRB 221009A: James Webb Space Telescope Observations
  26. GRB 221009A: Analysis of the initial episode using data of GBM/Fermi and SPI-ACS/INTEGRAL
  27. GRB 221009A: optical observations, SN photometric evidence
  28. GRB 221009A: 1.3m DFOT Optical Observations
  29. GRB221009A: LBT optical imaging
  30. GRB 221009A: Peak luminosity of the supernova vs. synchrotron afterglow
  31. Improved IPN localization for GRB 221009A (BepiColombo-MGNS light curve)
  32. GRB 221009A: TNG NIR detection
  33. GRB 221009A: BOAO NIR detections
  34. GRB 221009A X-ray light-curve and the indication of TeV light-curve
  35. GRB 221009A: Spectroscopic detection of emerging SN features
  36. GRB 221009A: Continued LDT Afterglow Monitoring
  37. GRB 221009A: GRANDMA observations
  38. The probability of observing GRB 221009A at z = 0.151
  39. GRB 221009A: Medicina Radio Telescope observations
  40. GRB 221009A: Second epoch of NuSTAR data
  41. GRB 221009A: A type I BdHN of exceptional energetics
  42. GRB 221009A: Faulkes Telescope North continued optical afterglow follow-up
  43. GRB 221009A: continued Assy optical afterglow observations, possible SN evidence
  44. GRB 221009A: LEIA X-ray Afterglow Detection
  45. GRB 221009A: ATCA radio spectrum
  46. GRB 221009A: VLT spectroscopic detection of the host galaxy
  47. GRB 221009A: ATCA detection
  48. GRB 221009A: Armchair Energetics
  49. GRB 221009A: ALMA and ACA detections
  50. GRB 221009A: Fermi LAT data rate effects due to extremely high flux
  51. GRB 221009A: Large Binocular Telescope Observatory optical afterglow detection
  52. GRB 221009A: Pan-STARRS optical photometry
  53. GRB 221009A: VLA detection
  54. MAXI/GSC refined analysis of the bright X-ray afterglow of GRB 221009A/Swift J1913.1+1946
  55. GRB 221009A: continued REM optical/NIR observations and evidence for an achromatic steepening in the afterglow light curve
  56. GRB 221009A: IXPE preliminary upper limits of X-ray polarization
  57. GRB 221009A: OHP optical observations
  58. GRB 221009A: HEBS detection
  59. GRB 221009A: Gemini-South Infrared Afterglow Detection
  60. GRB221009A: Gemini-South Optical Afterglow Detection
  61. GRB 221009A: a 397.7 GeV photon observed by Fermi-LAT at 0.4 day after the GBM trigger
  62. GRB 221009A: Gamma-ray Detection by SIRI-2
  63. GRB 221009A: search for neutrinos with KM3NeT
  64. GRB 221009A: MeerKAT detection
  65. GRB 221009A: Lowell Discovery Telescope Afterglow Detection
  66. GRB221009A: LCOGT Continued Observations - Optical Upper Limits
  67. GRB 221009A/Swift J1913.1+1946: low-frequency ASKAP observations
  68. GRB 221009A: MITSuME Okayama optical observation
  69. GRB 221009A: Sayan observatory 1.6-m telescope observations
  70. GRB 221009A: GMG observation
  71. GRB 221009A/Swift J1913.1+1946: SMA observations
  72. GRB 221009A: COATLI Continued Monitoring of the Afterglow
  73. GRB 221009A/Swift J1913.1+1946: eMERLIN observations
  74. GRB 221009A: NuSTAR Detection
  75. GRB 221009A: NICER follow-up observations
  76. GRB 221009A: LCOGT Optical Afterglow Detection
  77. GRB 221009A: COATLI Detection of the Afterglow
  78. GRB 221009A: planned observation with the Imaging X-ray Polarimetry Explorer (IXPE)
  79. GRB 221009A (Swift J1913.1+1946): Swift-BAT refined analysis
  80. GRB 221009A: 10.4m GTC spectroscopic redshift confirmation
  81. GRB 221009A: Detection by GRBAlpha
  82. GRB 221009A: Sintez-Newton/CrAO optical observations
  83. GRB 221009A: Upper limits from HAWC 8 hours after trigger
  84. Swift/XRT discovery of multiple dust-scattering X-ray rings around GRB 221009A
  85. GRB 221009A (Swift J1913.1+1946): iTelescope optical observation
  86. GRB 221009A: BlackGEM optical observations
  87. LHAASO observed GRB 221009A with more than 5000 VHE photons up to around 18 TeV
  88. GRB 221009A: NOEMA mm detection
  89. GRB 221009A: Continued Swift/XRT observations
  90. GRB 221009A/Swift J1913.1+1946: Assy optical afterglow observation
  91. GRB 221009A/Swift J1913.1+1946: Lick/Nickel telescope optical observations
  92. Konus-Wind detection of GRB 221009A
  93. GRB 221009A: Lulin SLT-40cm optical observations
  94. GRB 221009A: Upper limits from a neutrino search with IceCube
  95. GRB 221009A (Swift J1913.1+1946): Burke-Gaffney Observatory optical observations
  96. GRB221009A/Swift J1913.1+1946: SRG/ART-XC observation
  97. GRB 221009A / Swift J1913.1+1946: GIT detection of the optical afterglow
  98. ​GRB 221009A: Multi-color detection of the optical
  99. GRB 221009A: Fermi-LAT refined analysis
  100. GRB 221009A (Swift J1913.1+1946): AGILE/GRID detection

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