Recently, some of LIGO’s detchar experts investigated the connection between Tomte glitches from Gravity Spy and the bias voltage on a particular circuit. You can read the full alog of this investigation here. Below is a summary written by TJ Massinger, one of the detchar experts who does a lot of work with Gravity Spy data!
During recent commissioning work at the LIGO Livingston Observatory, it was noticed that glitches were occurring while the bias voltage on a circuit (an electrostatic actuator) was adjusted. Inspection of these glitches using the same time-frequency visualization that Gravity Spy uses showed that they looked qualitatively similar to glitches classified by users as the “tomte” class.
Using the GravitySpy classifier, it was found that these recent glitches are also classified as tomte glitches. To quantify the similarity of the bias voltage glitches to the tomte glitches seen in the second observing run (O2), GravitySpy was used to gather a collection of previously identified tomte glitches in O2 with parameters similar to those seen when adjusting the bias voltage. Upon comparing these populations, their time- and frequency-domain morphology was found to be nearly identical, suggesting that the population of tomte glitches in O2 might be understood by continuing to investigate the glitches that occur when adjusting bias voltages.
Hello Gravity Spiers!
At long last and after much demand, we have added audio examples of what the Gravity Spy glitches sound like to our field guide! As many of you may know, the frequencies of gravitational waves (and frequencies of glitches) detectable by LIGO are similar to the frequencies of sound (i.e. the pitches) that humans can hear. Therefore, LIGO scientists oftentimes convert our signals to sound!* The MP3s are embedded directly into the field guide, so you should be able to play them straight from there.
Some glitch categories may be hard to distinguish above the background noise, whereas others you should hear quite distinctly. Either way, having a good set of headphones will help hear the subtle features of the glitches better.
Big thanks to our LIGO collaborator Derek Davis for putting together these glitch sounds! Head on over to the Gravity Spy field guide to take a listen to the sounds of glitches!
-Mike / the GSpy team
*There are a few changes done to the data that make the sounds easier to hear. Other than the standard whitening and band-passing, for the glitches in our field guide we also linearly shift the frequency up by 60Hz to make the sounds (especially the low frequency glitches) more in our audible range. Also, a filter that can be described as an “inverse A-weighting” filter is utilized. The basic idea of this filter is to account for the fact that our ears are less sensitive to particularly low and high frequencies. Since the drop off starts around 200 Hz, this affects a decent number of glitches. By increasing the loudness of these lower frequencies, we make it so that features of similar intensity in an omega scan are ideally heard equally loud, no matter their frequency.
Hello Gravity Spy team,
As you may have heard, the LIGO and Virgo detector network has found its first triple-coincident signal! This signal, GW170814, is a binary black hole inspiral, with the masses of the two colliding black holes at about 25 and 30 times the mass of the Sun. Virgo’s observation of this event, and the relative time delay of receiving the signals between the 3 detectors, GREATLY improves our ability to pinpoint the location of the event on the sky, which will help our electromagnetic partners to possibly find a coincident signal with their telescopes. You can find the full paper of this discovery here.
Take a look at the spectrogram from the Virgo detector below? See the signal? If you’re looking at the bright thing just right of center, you’re actually looking at a glitch that occurred right after the signal! Soon, we will be adding data from the Virgo interferometer to the Gravity Spy project, so we can help to better the sensitivity of this instrument, just like what Gravity Spy has been doing for the two LIGO instruments.
Also, we have finally figured out and updated our statistics page with the correct retirement information! Take a gander at our progress here.
-Mike & the Gravity Spy team
Hi Gravity Spiers,
Today we announced the detection of the third confidently-observed gravitational wave event – GW170104. It was detected on January 4 2017, as the name suggests! It’s the most distant black hole merger detected to date.
We have a surprise waiting for you on the Gravity Spy project, try doing a few classifications and see if you can find the event for yourself…
Dear Gravity Spiers,
Gravity Spy has recently hit a new milestone – over one million classifications! Thank you for all your hard work so far – we are humbled by you continued enthusiasm. All these classifications have helped uncover new glitch classes in the data from LIGO’s first observing run, and have bolstered the labeled datasets that we use to train machine learning algorithms.
Now for some more good news! LIGO started its second observing run at the end of 2016 and is still collecting data and searching for more gravitational-wave events. We are happy to announce that we have added the data from this observing run (O2) and the preceding engineering run (ER10) to the Gravity Spy project. As the detector has evolved a great deal over the past year, we expect many new types of glitches in this dataset. Furthermore, we will now upload new glitches to the project every few days as LIGO records them, so there should be no shortage of data to look through! Your classifications and analysis will be a massive help to LIGO scientists, and help us to uncover even more of the gravitational-wave universe.
You may also notice that we’ve added two new categories to choose from – ‘1080 Line’ and ‘1400 Ripple’. As we find more prominent glitches in O2, we’ll add more glitch options to choose from.
All the best,
-Mike and the GSpy Team
Hi GSpy users,
At LIGO Hanford we recently discovered that some of the telephones in the large experimental areas of LIGO were accidentally left switched on during a a couple of weeks of O2 data collection up to December 13 when they were switched off. At least once these phones rang and the ringtone made loud sounds (glitches) show up in microphones but also in the gravitational-wave channel data. Attached is an O2-preview of what this glitch will look like in GravitySpy data. We am worried that there might be other times in the data set for O1 and O2 when a phone at one of the sites was on. We would be very interested to learn whether any of you have seen glitches similar to this in the GravitySpy data set so far?
For more information, see this LIGO Hanford logbook post, including wave files, https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=32503.